LT1510/LT1510-5 Constant-Voltage/ Constant-Current Battery Charger FEATURES n Charges NiCd, NiMH and Lithium-Ion Batteries –– plest, most efficient solution to fast-charge modern re- Only One 1/ W Resistor Is Needed to Program chargeable batteries including lithium-ion (Li-Ion), nickel- 10 Charging Current metal-hydride (NiMH)* and nickel-cadmium (NiCd)* that n High Efficiency Current Mode PWM with 1.5A require constant-current and/or constant-voltage charg- Internal Switch and Sense Resistor ing. The internal switch is capable of delivering 1.5A DC n 3% Typical Charging Current Accuracy current (2A peak current). The 0.1W onboard current n Precision 0.5% Voltage Reference for Voltage sense resistor makes the charging current programming Mode Charging or Overvoltage Protection very simple. One resistor (or a programming current from n Current Sensing Can Be at Either Terminal of a DAC) is required to set the full charging current (1.5A) to the Battery within 5% accuracy. The LT1510 with 0.5% reference n Low Reverse Battery Drain Current: 3m A voltage accuracy meets the critical constant-voltage charg- n Charging Current Soft Start ing requirement for lithium cells. n Shutdown Control The LT1510 can charge batteries ranging from 2V to 20V. n 500kHz Version Uses Small Inductor Ground sensing of current is not required and the battery’s negative terminal can be tied directly to ground. A saturat- APPLICATIOUNS ing switch running at 200kHz (500kHz for LT1510-5) gives high charging efficiency and small inductor size. A block- n Chargers for NiCd, NiMH and Lithium Batteries ing diode is not required between the chip and the battery n Step-Down Switching Regulator with Precision because the chip goes into sleep mode and drains only 3m A Adjustable Current Limit when the wall adaptor is unplugged. Soft start and shutdown features are also provided. The LT1510 is available in a 16-pin DESCRIPTIOUN fused lead power SO package with a thermal resistance of 50(cid:176) C/W, an 8-pin SO and a 16-pin PDIP. With switching frequency as high as 500kHz, The LT®1510 , LTC and LT are registered trademarks of Linear Technology Corporation. current mode PWM battery charger is the smallest, sim- * NiCd and NiMH batteries require charge termination circuitry (not shown in Figure 1). TYPICAL APPLICATIONUS D3(cid:13) 0.2C21m(cid:13)F MBRMD11(cid:13)20T3 MBRMD31(cid:13)20T3 8.2V TO 20V 0.2C21m(cid:13)F 1ND518(cid:13)19 SW(cid:13) VCC(cid:13) + 1N5819 11V TO 28V SW(cid:13) VCC(cid:13) + C10INm*F(cid:13) –+ C10INm*F(cid:13) –+ BOOST(cid:13) PROG(cid:13) L110*m*H(cid:13) DM2M(cid:13)BD914L BGONODLS(cid:13)TT1(cid:13)510P-5ROVGC(cid:13)(cid:13) 0.11mmFF300W 6.19k L313*m*H(cid:13) D1N2(cid:13)914 GND(cid:13)LT1510 VC(cid:13) 0.11mmFF310k0W 3.83k 1k OVP OVP SENSE BAT + SENSE BAT + + COUT(cid:13) 4.2V + 2C2OmUFT***(cid:13) 4.2V Q3†(cid:13) 2T2AmNFT(cid:13) + VQN3†2(cid:13)222 2N7002 4.2V R3(cid:13) N(cid:9)OTE: COMPLETE LITHIUM-ION CHARGER, NO TERMINATION REQUIRED(cid:13) R3(cid:13) 240k(cid:13) 70.6k(cid:13) 0.25% * ** (cid:13)(cid:13) TCOOKILINTR OORN MICASR TCPO3N-1 C0E0R, 1A0MµIHC, S2U.2RmFmAC HEE MIGOHUTN (T0(cid:13).8A CHARGING CURRENT)(cid:13) 0.25% N(cid:9)OTE: COMPLETE LITHIUM-ION CHARGER, NO TERMINATION REQUIRED(cid:13) R4(cid:13) (cid:13) COILTRONICS TP1 SERIES, 10µH, 1.8mm HEIGHT (<0.5A CHARGING CURRENT)(cid:13) R1040(cid:13)k(cid:13) (cid:9) *(cid:9)TOKIN OR MARCON CERAMIC SURFACE MOUNT(cid:13) 100.205k%(cid:13) ** * (cid:13) PANASONIC EEFCD1B220(cid:9) (cid:13) 0.25% (cid:9)**(cid:9)COILTRONICS CTX33-2 (cid:9) (cid:13) 1510 F02 † OPTIONAL, SEE APPLICATIONS INFORMATION 1510 F01 (cid:9) †(cid:9)OPTIONAL, SEE APPLICATIONS INFORMATION Figure 1. 500kHz Smallest Li-Ion Cell Phone Charger (0.8A) Figure 2. Charging Lithium Batteries (Efficiency at 1.3A > 87%) 1

LT1510/LT1510-5 ABSOLUTE WMAXIWMUWM RATINUGS Supply Voltage (V )............................................ 30V Operating Ambient Temperature Range MAX Switch Voltage with Respect to GND...................... –3V Commercial.............................................0(cid:176) C to 70(cid:176) C Boost Pin Voltage with Respect to V ................... 30V Extended Commercial (Note 7)........... –40(cid:176) C to 85(cid:176) C CC Boost Pin Voltage with Respect to GND ................. –5V Industrial (Note 8).............................. –40(cid:176) C to 85(cid:176) C V , PROG, OVP Pin Voltage...................................... 8V Operating Junction Temperature Range C I (Average)........................................................ 1.5A LT1510C (Note 7)............................. –40(cid:176) C to 125(cid:176) C BAT Switch Current (Peak)............................................... 2A LT1510I............................................ –40(cid:176) C to 125(cid:176) C Storage Temperature Range................. –65(cid:176) C to 150(cid:176) C Lead Temperature (Soldering, 10 sec)..................300(cid:176) C PACKAGE/ORDER IUNFORWMATIOUN ORDER PART ORDER PART TOP VIEW TOP VIEW TOP VIEW NUMBER NUMBER SW(cid:13) 1(cid:13) 8(cid:13) VCC(cid:13) **GND(cid:13) 1(cid:13) 16(cid:13) GND**(cid:13) **GND(cid:13) 1(cid:13) 16(cid:13) GND**(cid:13) BOOST(cid:13) 2(cid:13) 7(cid:13) PROG(cid:13) SW(cid:13) 2(cid:13) 15(cid:13) VCC2(cid:13) LT1510CGN SW(cid:13) 2(cid:13) 15(cid:13) VCC2(cid:13) LT1510CN GND(cid:13) 3(cid:13) 6(cid:13) VC(cid:13) BOOST(cid:13) 3(cid:13) 14(cid:13) VCC1(cid:13) LT1510IGN BOOST(cid:13) 3(cid:13) 14(cid:13) VCC1(cid:13) LT1510CS SENSE 4 5(cid:13) BAT GND(cid:13) 4(cid:13) 13(cid:13) PROG(cid:13) LT1510-5CGN GND(cid:13) 4(cid:13) 13(cid:13) PROG(cid:13) LT1510IN (cid:13) OVP(cid:13) 5(cid:13) 12(cid:13) VC(cid:13) LT1510-5IGN OVP(cid:13) 5(cid:13) 12(cid:13) VC(cid:13) LT1510IS S8 PACKAGE(cid:13) 8-LEAD PLASTIC SO NC(cid:13) 6(cid:13) 11(cid:13) NC(cid:13) SENSE(cid:13) 6(cid:13) 11(cid:13) BAT(cid:13) TJMAX = 125(cid:176)C, q JA = 125(cid:176)C/W SENSE(cid:13) 7(cid:13) 10(cid:13) BAT(cid:13) GND(cid:13) 7(cid:13) 10(cid:13) GND(cid:13) **GND 8(cid:13) 9(cid:13) GND** **GND 8(cid:13) 9(cid:13) GND** ORDER PART (cid:13) (cid:13) (cid:13) (cid:13) GN PACKAGE (0.015 IN)(cid:13) N PACKAGE(cid:13) S PACKAGE*(cid:13) NUMBER 16-LEAD PLASTIC SSOP GN PART 16-LEAD PDIP 16-LEAD PLASTIC SO LT1510CS8 TJMAX = 125(cid:176)C, q JA = 75(cid:176)C/W MARKING TTJJMMAAXX == 112255(cid:176)(cid:176)CC,, qq JJAA == 7550(cid:176)(cid:176)CC//WW ((NS))* LT1510IS8 **FOUR CORNER PINS ARE FUSED TO 1510 INTERNAL DIE ATTACH PADDLE FOR 1510I * VCC1 AND VCC2 SHOULD BE CONNECTED HEAT SINKING. CONNECT THESE FOUR TOGETHER CLOSE TO THE PINS. S8 PART MARKING PINS TO EXPANDED PC LANDS FOR 15105 **FOUR CORNER PINS ARE FUSED TO PROPER HEAT SINKING. 15105I INTERNAL DIE ATTACH PADDLE FOR 1510 HEAT SINKING. CONNECT THESE FOUR PINS TO EXPANDED PC LANDS FOR 1510I PROPER HEAT SINKING. Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS V = 16V, V = 8V, V (maximum operating V ) = 28V, no load on any outputs, unless otherwise noted. (Notes 7, 8) CC BAT MAX CC PARAMETER CONDITIONS MIN TYP MAX UNITS Overall Supply Current V = 2.7V, V £ 20V l 2.90 4.3 mA PROG CC V = 2.7V, 20V < V £ V l 2.91 4.5 mA PROG CC MAX DC Battery Current, I (Note 1) 8V £ V £ 25V, 0V £ V £ 20V, T < 0(cid:176) C l 0.91 1.09 A BAT CC BAT J R = 4.93k l 0.93 1.0 1.07 A PROG R = 3.28k (Note 4) l 1.35 1.5 1.65 A PROG R = 49.3k l 75 100 125 mA PROG T < 0(cid:176) C l 70 130 mA J V = 28V, V = 20V CC BAT R = 4.93k l 0.93 1.0 1.07 A PROG R = 49.3k l 75 100 125 mA PROG 2

LT1510/LT1510-5 ELECTRICAL CHARACTERISTICS V = 16V, V = 8V, V (maximum operating V ) = 28V, no load on any outputs, unless otherwise noted. CC BAT MAX CC PARAMETER CONDITIONS MIN TYP MAX UNITS Overall Minimum Input Operating Voltage Undervoltage Lockout l 6.2 7 7.8 V Reverse Current from Battery (When V Is Not V £ 20V, 0(cid:176) C £ T £ 70(cid:176) C l 3 15 m A CC BAT J Connected, V Is Floating) SW Boost Pin Current V – V £ 20V l 0.10 20 m A CC BOOST 20V < V – V £ 28V l 0.25 30 m A CC BOOST 2V £ V – V £ 8V (Switch ON) l 6 11 mA BOOST CC 8V < V – V £ 25V (Switch ON) l 8 14 mA BOOST CC Switch Switch ON Resistance V = 10V CC I = 1.5A, V – V ‡ 2V (Note 4) l 0.3 0.5 W SW BOOST SW I = 1A, V – V < 2V (Unboosted) l 2.0 W SW BOOST SW D I /D I During Switch ON V = 24V, I £ 1A 20 35 mA/A BOOST SW BOOST SW Switch OFF Leakage Current V = 0V, V £ 20V l 2 100 m A SW CC 20V < V £ 28V l 4 200 m A CC Maximum V with Switch ON l V – 2 V BAT CC Minimum I for Switch ON 2 4 20 m A PROG Minimum I for Switch OFF at V £ 1V l 1 2.4 mA PROG PROG Current Sense Amplifier Inputs (SENSE, BAT) Sense Resistance (R ) 0.08 0.12 W S1 Total Resistance from SENSE to BAT (Note 3) 0.2 0.25 W BAT Bias Current (Note 5) V < 0.3V –200 –375 m A C V > 0.6V 700 1300 m A C Input Common Mode Limit (Low) l –0.25 V Input Common Mode Limit (High) l V – 2 V CC Reference Reference Voltage (Note 1) S8 Package R = 4.93k, Measured at PROG Pin l 2.415 2.465 2.515 V PROG Reference Voltage (Note 2) 16-Pin R = 3.28k, Measured at OVP with 2.453 2.465 2.477 V PROG VA Supplying I and Switch OFF PROG Reference Voltage Tolerance, 16-Pin Only 8V £ V £ 28V, 0(cid:176) C £ T £ 70(cid:176) C l 2.446 2.465 2.480 V CC J 8V £ V £ 28V, 0(cid:176) C £ T £ 125(cid:176) C l 2.441 2.489 V CC J 8V £ V £ 28V, T < 0(cid:176) C l 2.430 2.489 V CC J Oscillator Switching Frequency LT1510 180 200 220 kHz LT1510-5 440 500 550 kHz Switching Frequency Tolerance All Conditions of V , Temperature, LT1510 l 170 200 230 kHz CC LT1510, T < 0(cid:176) C l 160 230 kHz J LT1510-5 l 425 500 575 kHz LT1510-5, T < 0(cid:176) C l 400 575 kHz J Maximum Duty Cycle LT1510 l 87 % LT1510, T = 25(cid:176) C (Note 8) 90 93 % A LT1510-5 (Note 9) l 77 81 % 3

LT1510/LT1510-5 ELECTRICAL CHARACTERISTICS V = 16V, V = 8V, V (maximum operating V ) = 28V, no load on any outputs, unless otherwise noted. CC BAT MAX CC PARAMETER CONDITIONS MIN TYP MAX UNITS Current Amplifier (CA2) Transconductance V = 1V, I = – 1m A 150 250 550 m mho C VC Maximum V for Switch OFF l 0.6 V C I Current (Out of Pin) V ‡ 0.6V 100 m A VC C V < 0.45V 3 mA C Voltage Amplifier (VA), 16-Pin Only Transconductance (Note 2) Output Current from 100m A to 500m A 0.5 1.2 2.5 mho Output Source Current, V = 10V V = V = V + 10mV 1.3 mA CC PROG OVP REF OVP Input Bias Current At 0.75mA VA Output Current l 50 150 nA The l denotes specifications which apply over the specified Note 7: Commercial grade device specifications are guaranteed over the temperature range. 0(cid:176) C to 70(cid:176) C temperature range. In addition, commercial grade device Note 1: Tested with Test Circuit 1. specifications are assured over the –40(cid:176) C to 85(cid:176) C temperature range by Note 2: Tested with Test Circuit 2. design or correlation, but are not production tested. Note 3: Sense resistor R and package bond wires. Maximum allowable ambient temperature may be limited by power S1 Note 4: Applies to 16-pin only. 8-pin packages are guaranteed but not dissipation. Parts may not necessarily be operated simultaneously at tested at –40(cid:176) C. maximum power dissipation and maximum ambient temperature. Note 5: Current (» 700m A) flows into the pins during normal operation and Temperature rise calculations must be done as shown in the Applications Information section to ensure that maximum junction temperature does also when an external shutdown signal on the V pin is greater than 0.3V. Current decreases to » 200m A and flows out of tChe pins when external not exceed the 125(cid:176) C limit. With high power dissipation, maximum ambient temperature may be less than 70(cid:176) C. shutdown holds the V pin below 0.3V. Current drops to near zero when C input voltage collapses. See external Shutdown in Applications Information Note 8: Industrial grade device specifications are guaranteed over the section. –40(cid:176) C to 85(cid:176) C temperature range. Note 6: A linear interpolation can be used for reference voltage Note 9: 91% maximum duty cycle is guaranteed by design if VBAT or VX specification between 0(cid:176) C and –40(cid:176) C. (see Figure 8 in Application Information) is kept between 3V and 5V. Note 10: V = 4.2V. BAT TYPICAL PERFORWMANUCE CHARACTERISTICS Thermally Limited Maximum Thermally Limited Maximum Thermally Limited Maximum Charging Current, 8-Pin SO Charging Current, 16-Pin SO Charging Current, 16-Pin GN 1.3(cid:13) 1.5(cid:13) 1.5(cid:13) (q JA=125°C/W)(cid:13) NT (A) 1.1(cid:13) TTAJMMAAXX==16205°°CC(cid:13) NT (A) 1.3(cid:13) 4V B8VA TBTAETRTYERY NT (A) 1.3(cid:13) RRE 4V BATTERY RRE 12V BATTERY RRE 4V BATTERY U U U G C 0.9(cid:13) G C 1.1(cid:13) G C 1.1(cid:13) HARGIN 0.7(cid:13) 8V BATTERY HARGIN 0.9(cid:13) 16V BATTERY HARGIN 0.9(cid:13) 8V BATTERY C C C M M M MAXIMU 0.5(cid:13) 12V BAT1T6EVR YBATTERY MAXIMU 0.7(cid:13) (TTqAJJMMAAA=XX5==016°2C05°/W°CC(cid:13))(cid:13) MAXIMU 0.7(cid:13) TqTAJJMAM A=AXX 8 ==0 °16C20/5°WC°C(cid:13)(cid:13) 12V B1A6TVT EBRAYTTERY 0.3 0.5 0.5 0 5 10 15 20 25 0 5 10 15 20 25 0 5 10 15 20 25 INPUT VOLTAGE (V) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 1510 G12 1510 G13 LT1510 • TPC14 4

LT1510/LT1510-5 TYPICAL PERFORWMANUCE CHARACTERISTICS Switching Frequency vs Efficiency of Figure 2 Circuit I vs Duty Cycle Temperature CC 100(cid:13) 8(cid:13) 210(cid:13) 98(cid:13) VCC = 15V (EXCLUDING DISSIPATION(cid:13) VCC = 16V ON INPUT DIODE D3)(cid:13) 7(cid:13) 205(cid:13) 96(cid:13) VBAT = 8.4V 6(cid:13) 94(cid:13) EFFICIENCY (%) 99882086(cid:13)(cid:13)(cid:13)(cid:13) I (mA)CC 543(cid:13)(cid:13)(cid:13) 0°C25°C 125°C FREQUENCY (kHz)211099050(cid:13)(cid:13)(cid:13) 2(cid:13) 84(cid:13) 185(cid:13) 1(cid:13) 82(cid:13) 80 0 180 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 0 10 20 30 40 50 60 70 80 –20 0 20 40 60 80 100 120 140 IBAT (A) DUTY CYCLE (%) TEMPERATURE (°C) 1510 G01 1510 G04 1510 G05 I vs V V Line Regulation I vs D V (Voltage Amplifier) CC CC REF VA OVP 7.0(cid:13) 0.003(cid:13) 4(cid:13) MAXIMUM DUTY CYCLE 6.5(cid:13) 0°C 0.002(cid:13) 3(cid:13) 25°C 0.001(cid:13) I (mA)CC 65..05(cid:13)(cid:13) 125°C ∆V (V)REF 0(cid:13) ALL TEMPERATURES V (mV)OVP 2(cid:13) 125°C ∆ –0.001(cid:13) 1(cid:13) 5.0(cid:13) –0.002(cid:13) 25°C 4.5 –0.003 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 VCC (V) VCC (V) IVA (mA) 1510 G03 1510 G02 1510 G08 Maximum Duty Cycle V Pin Characteristic PROG Pin Characteristic C 98(cid:13) –1.20(cid:13) 6 –1.08(cid:13) 97(cid:13) –0.96(cid:13) 96(cid:13) –0.84(cid:13) 125°C %) 95(cid:13) –0.72(cid:13) CYCLE ( 94(cid:13) (mA)C––00..6408(cid:13)(cid:13) (mA)OG 0 25°C UTY 93(cid:13) IV–0.36(cid:13) IPR D 92(cid:13) –0.24(cid:13) –0.12(cid:13) 91(cid:13) 0(cid:13) 90 0.12 –6 0 20 40 60 80 100 120 140 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 1 2 3(cid:13) 4 5 TEMPERATURE (°C) VC (V) VPROG (V) 1510 G09 1510 G10 1510 G11 5

LT1510/LT1510-5 TYPICAL PERFORWMANUCE CHARACTERISTICS Switch Current vs Boost Current Reference Voltage vs V vs BOOST vs Boost Voltage Temperature Maximum Duty Cycle 50(cid:13) 2.470(cid:13) 96(cid:13) 45(cid:13) VCC = 16V 95(cid:13) 2.468(cid:13) BOOST CURRENT (mA) 433221050505(cid:13)(cid:13)(cid:13)(cid:13)(cid:13)(cid:13) VBOOST = 213888VVV(cid:13)(cid:13) EFERENCE VOLTAGE (V) 222...444666642(cid:13)(cid:13)(cid:13) XIMUM DUTY CYCLE (%) 999998432109(cid:13)(cid:13)(cid:13)(cid:13)(cid:13)(cid:13) R A 10(cid:13) M 88(cid:13) 2.460(cid:13) 5(cid:13) 87(cid:13) 0(cid:13) 2.458 86 0 0.2 0.4 0.6 0.8 1.0 1.(cid:13)2 1.4 1.6 1.8 2.0 0 25 50 75 100 125 150 2 4 6 8 10 12 14 16 18 20 22 (cid:13) SWITCH CURRENT (A) TEMPERATURE (°C) VBOOST (V) 1510 G07 1510 G14 LT1510 • TPC15 PIUN FUUNCTIOUNS GND: Ground Pin. BAT: Current Amplifier CA1 Input. SW: Switch Output. The Schottky catch diode must be PROG: This pin is for programming the charging current placed with very short lead length in close proximity to SW and for system loop compensation. During normal opera- pin and GND. tion, V stays close to 2.465V. If it is shorted to GND PROG the switching will stop. When a microprocessor-controlled V : Supply for the Chip. For good bypass, a low ESR CC DAC is used to program charging current, it must be capacitor of 10m F or higher is required, with the lead length capable of sinking current at a compliance up to 2.465V. kept to a minimum. V should be between 8V and 28V CC and at least 2V higher than V for V less than 10V, and V : This is the control signal of the inner loop of the current BAT BAT C 2.5V higher than V for V greater than 10V. Under- mode PWM. Switching starts at 0.7V and higher V BAT BAT C voltage lockout starts and switching stops when V goes corresponds to higher charging current in normal opera- CC below 7V. Note that there is a parasitic diode inside from tion. A capacitor of at least 0.1m F to GND filters out noise SW pin to V pin. Do not force V below SW by more and controls the rate of soft start. To shut down switching, CC CC than 0.7V with battery present. All V pins should be pull this pin low. Typical output current is 30m A. CC shorted together close to the pins. OVP: This is the input to the amplifier VA with a threshold BOOST: This pin is used to bootstrap and drive the switch of 2.465V. Typical input current is about 50nA into pin. For power NPN transistor to a low on-voltage for low power charging lithium-ion batteries, VA monitors the battery dissipation. In normal operation, V = V + V voltage and reduces charging current when battery volt- BOOST CC BAT when switch is on. Maximum allowable V is 55V. age reaches the preset value. If it is not used, the OVP pin BOOST should be grounded. SENSE: Current Amplifier CA1 Input. Sensing can be at either terminal of the battery. Note that current sense resistor R (0.08W ) is between Sense and BAT pins. S1 6

LT1510/LT1510-5 BLOCK DIAGRAWM 200kHz(cid:13) + OSCILLATOR VCC 0.7V SHUTDOWN + – S BOOST VSW VCC – QSW R R + SW + – 1.5V GND PWM SCLOOMPPEE(cid:13)NSATION B1 IPROG + SENSE VBAT – C1 + R2 + CA1 IBAT RS1 R1(cid:13) IPROG(cid:13)= 500m A/A – BAT 1k IBAT R3 + 0VP – VA VC CA2 – V2.R4E6F5(cid:13)V 60k + VREF gm = 0.64W PROG RPROG (cid:13)C= H((IAPRRGOGIN)(G)2 0C0U0R)(cid:13)RENT IBAT(cid:13) 1510 BD CPROG IPROG = 2.465V(cid:13) (2000) RPROG TEST CIRC(cid:13)UITS (cid:13) Test Circuit 1 LT1510 + SENSE IBAT – CA1 RS1 VC CA2 – BAT + 1k + 0.047m F 60k + 56m F VBAT VREF PROG 0.22m F 3.3k RPROG + LT1006 LT1010 2N3055 1k – + 1k » 0.65V 20k 1510 TC01 7

LT1510/LT1510-5 TEST CIRC(cid:13)UITS (cid:13) Test Circuit 2 LT1510 OVP + VA – PROG VREF IPROG 10k 10k – LT1013 + + 0.47m F RPROG 2.465V 1510 TC02 OPERATIOU The LT1510 is a current mode PWM step-down (buck) level shift resistors R2 and R3, forming the current mode switcher. The battery DC charging current is programmed inner loop. The Boost pin drives the switch NPN Q into SW by a resistor R (or a DAC output current) at the PROG saturation and reduces power loss. For batteries like PROG pin (see Block Diagram). Amplifier CA1 converts the lithium-ion that require both constant-current and con- charging current through R to a much lower current stant-voltage charging, the 0.5%, 2.465V reference and S1 I (500m A/A) fed into the PROG pin. Amplifier CA2 the amplifier VA reduce the charging current when battery PROG compares the output of CA1 with the programmed current voltage reaches the preset level. For NiMH and NiCd, VA and drives the PWM loop to force them to be equal. High can be used for overvoltage protection. When input volt- DC accuracy is achieved with averaging capacitor C . age is not present, the charger goes into low current (3m A PROG Note that I has both AC and DC components. I typically) sleep mode as input drops down to 0.7V below PROG PROG goes through R1 and generates a ramp signal that is fed to battery voltage. To shut down the charger, simply pull the the PWM control comparator C1 through buffer B1 and V pin low with a transistor. C APPLICATIOUNS INUFORWMATIOUN Application Note 68, the LT1510 design manual, contains tantalum capacitors such as the AVX TPS and Sprague more in depth appications examples. 593D series have high ripple current rating in a relatively small surface mount package, but caution must be used Input and Output Capacitors when tantalum capacitors are used for input bypass. High input surge currents can be created when the adapter is In the chargers in Figures 1 and 2 on the first page of this hot-plugged to the charger and solid tantalum capacitors data sheet, the input capacitor C is assumed to absorb all IN have a known failure mechanism when subjected to very input switching ripple current in the converter, so it must high turn-on surge currents. Highest possible voltage have adequate ripple current rating. Worst-case RMS rating on the capacitor will minimize problems. Consult with ripple current will be equal to one half of output charging the manufacturer before use. Alternatives include new high current. Actual capacitance value is not critical. Solid 8

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN capacity ceramic capacitor (5m F to 10m F) from Tokin or deliver full power to the load when the input voltage is still United Chemi-Con/MARCON, et al., and the old standby, well below its final value. If the adapter is current limited, aluminum electrolytic, which will require more microfarads it cannot deliver full power at reduced output voltages and to achieve adequate ripple rating. OS-CON can also be used. the possibility exists for a quasi “latch” state where the adapter output stays in a current limited state at reduced The output capacitor C is also assumed to absorb OUT output voltage. For instance, if maximum charger plus output switching current ripple. The general formula for computer load power is 20W, a 24V adapter might be capacitor current is: current limited at 1A. If adapter voltage is less than (20W/1A ( )(cid:230) (cid:246) (cid:86) = 20V) when full power is drawn, the adapter voltage will be (cid:48).(cid:50)(cid:57) (cid:86) (cid:231) (cid:49)- (cid:66)(cid:65)(cid:84)(cid:247) (cid:66)(cid:65)(cid:84) Ł (cid:86) ł sucked down by the constant 20W load until it reaches a (cid:73) = ( )( ) (cid:67)(cid:67) (cid:82)(cid:77)(cid:83) lower stable state where the switching regulators can no (cid:76)(cid:49) (cid:102) longer supply full load. This situation can be prevented by For example, with V = 16V, V = 8.4V, L1 = 30m H and utilizing undevoltage lockout, set higher than the minimum CC BAT adapter voltage where full power can be achieved. f = 200kHz, I = 0.2A. RMS A fixed undervoltage lockout of 7V is built into the V pin. EMI considerations usually make it desirable to minimize CC Internal lockout is performed by clamping the V pin low. ripple current in the battery leads, and beads or inductors C The V pin is released from its clamped state when the V may be added to increase battery impedance at the 200kHz C CC pin rises above 7V. The charger will start delivering current switching frequency. Switching ripple current splits be- about 2ms after V is released, as set by the 0.1m F at V tween the battery and the output capacitor depending on C C pin. Higher lockout voltage can be implemented with a the ESR of the output capacitor and the battery impedance. If the ESR of C is 0.2W and the battery impedance is Zener diode (see Figure 3 circuit). OUT raised to 4W with a bead of inductor, only 5% of the current ripple will flow in the battery. VIN VZ D1(cid:13) VCC Soft Start 1N4001 VC LT1510 The LT1510 is soft started by the 0.1m F capacitor on V C 2k GND pin. On start-up, V pin voltage will rise quickly to 0.5V, C then ramp at a rate set by the internal 45m A pull-up current 1510 F03 and the external capacitor. Battery charging current starts Figure 3. Undervoltage Lockout ramping up when V voltage reaches 0.7V and full current C is achieved with VC at 1.1V. With a 0.1m F capacitor, time to The lockout voltage will be VIN = VZ + 1V. reach full charge current is about 3ms and it is assumed For example, for a 24V adapter to start charging at 22V , that input voltage to the charger will reach full value in less IN choose V = 21V. When V is less than 22V, D1 keeps V than 3ms. Capacitance can be increased up to 0.47m F if Z IN C low and charger off. longer input start-up times are needed. In any switching regulator, conventional timer-based soft Charging Current Programming starting can be defeated if the input voltage rises much The basic formula for charging current is (see Block slower than the time-out period. This happens because the Diagram): switching regulators in the battery charger and the com- puter power supply are typically supplying a fixed amount ( )( ) (cid:230) (cid:50).(cid:52)(cid:54)(cid:53)(cid:86)(cid:246) ( ) of power to the load. If input voltage comes up slowly (cid:73) = (cid:73) (cid:50)(cid:48)(cid:48)(cid:48) =(cid:231) (cid:247) (cid:50)(cid:48)(cid:48)(cid:48) (cid:66)(cid:65)(cid:84) (cid:80)(cid:82)(cid:79)(cid:71) Ł (cid:82) ł compared to the soft start time, the regulators will try to (cid:80)(cid:82)(cid:79)(cid:71) 9

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN where R is the total resistance from PROG pin to even this low current drain. A 47k resistor from adapter PROG ground. output to ground should be added if Q3 is used to ensure that the gate is pulled to ground. For example, 1A charging current is needed. With divider current set at 25m A, R4 = 2.465/25m A = 100k ( )( ) (cid:50).(cid:52)(cid:54)(cid:53)(cid:86) (cid:50)(cid:48)(cid:48)(cid:48) and, (cid:82)(cid:80)(cid:82)(cid:79)(cid:71)= =(cid:52).(cid:57)(cid:51)(cid:107) ( )( ) ( ) (cid:49)(cid:65) (cid:82)(cid:52) (cid:86) - (cid:50).(cid:52)(cid:54)(cid:53) (cid:49)(cid:48)(cid:48)(cid:107) (cid:56).(cid:52)- (cid:50).(cid:52)(cid:54)(cid:53) (cid:66)(cid:65)(cid:84) (cid:82)(cid:51)= ( )= ( ) Charging current can also be programmed by pulse width (cid:50).(cid:52)(cid:54)(cid:53)+(cid:82)(cid:52) (cid:48).(cid:48)(cid:53)m (cid:65) (cid:50).(cid:52)(cid:54)(cid:53)+(cid:49)(cid:48)(cid:48)(cid:107) (cid:48).(cid:48)m(cid:53) (cid:65) modulating I with a switch Q1 to R at a frequency PROG PROG higher than a few kHz (Figure 4). Charging current will be (cid:32)(cid:32)(cid:32)(cid:32)=(cid:50)(cid:52)(cid:48)(cid:107) proportional to the duty cycle of the switch with full current Lithium-ion batteries typically require float voltage accu- at 100% duty cycle. racy of 1% to 2%. Accuracy of the LT1510 OVP voltage is When a microprocessor DAC output is used to control – 0.5% at 25(cid:176) C and – 1% over full temperature. This leads charging current, it must be capable of sinking current to the possibility that very accurate (0.1%) resistors might at a compliance up to 2.5V if connected directly to the be needed for R3 and R4. Actually, the temperature of the PROG pin. LT1510 will rarely exceed 50(cid:176) C in float mode because charging currents have tapered off to a low level, so 0.25% LT1510 resistors will normally provide the required level of overall accuracy. PROG 300Ω External Shutdown RPROG(cid:13) CPROG(cid:13) 4.64k 1µF The LT1510 can be externally shut down by pulling the V C 5V Q1(cid:13) pin low with an open drain MOSFET, such as VN2222. The 0V VN2222 PWM VC pin should be pulled below 0.8V at room temperature IBAT = (DC)(1A) 1510 F04 to ensure shutdown. This threshold decreases at about 2mV/(cid:176) C. A diode connected between the MOSFET drain Figure 4. PWM Current Programming and the V pin will still ensure the shutdown state over all C temperatures, but it results in slightly different conditions Lithium-Ion Charging as outlined below. The circuit in Figure 2 uses the 16-pin LT1510 to charge If the V pin is held below threshold, but above » 0.4V, the C lithium-ion batteries at a constant 1.3A until battery volt- current flowing into the BAT pin will remain at about age reaches a limit set by R3 and R4. The charger will then 700m A. Pulling the V pin below 0.4V will cause the current C automatically go into a constant-voltage mode with cur- to drop to » 200m A and reverse, flowing out of the BAT pin. rent decreasing to zero over time as the battery reaches full Although these currents are low, the long term effect may charge. This is the normal regimen for lithium-ion charg- need to be considered if the charger is held in a shutdown ing, with the charger holding the battery at “float” voltage state for very long periods of time, with the charger input indefinitely. In this case no external sensing of full charge voltage remaining. Removing the charger input voltage is needed. causes all currents to drop to near zero. Current through the R3/R4 divider is set at a compromise If it is acceptable to have 200m A flowing into the battery value of 25m A to minimize battery drain when the charger while the charger is in shutdown, simply pull the V pin C is off and to avoid large errors due to the 50nA bias current directly to ground with the external MOSFET. The resistor of the OVP pin. Q3 can be added if it is desired to eliminate divider used to sense battery voltage will pull current out 10

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN of the battery, canceling part or all of the 200m A. Note that period, after which the LT1510 can be shut down by if net current is into the battery and the battery is removed, pulling the V pin low with an open collector or drain. C the charger output voltage will float high, to near input Some external means must be used to detect the need for voltage. This could be a problem when reinserting the additional charging if needed, or the charger may be battery, if the resulting output capacitor/battery surge turned on periodically to complete a short float-voltage current is high enough to damage either the battery or the cycle. capacitor. Current trip level is determined by the battery voltage, R1 If net current into the battery must be less than zero in through R3, and the internal LT1510 sense resistor shutdown, there are several options. Increasing divider (» 0.18W pin-to-pin). D2 generates hysteresis in the trip current to 300m A - 400m A will ensure that net battery level to avoid multiple comparator transitions. current is less than zero. For long term storage conditions however, the divider may need to be disconnected with a Nickel-Cadmium and Nickel-Metal-Hydride Charging MOSFET switch as shown in Figures 2 and 5. A second The circuit in Figure 6 uses the 8-pin LT1510 to charge option is to connect a 1N914 diode in series with the NiCd or NiMH batteries up to 12V with charging currents MOSFET drain. This will limit how far the V pin will be pulled C of 0.5A when Q1 is on and 50mA when Q1 is off. down, and current (» 700m A) will flow into the BAT pin, and therefore out of the battery. This is not usually a problem D3(cid:13) C1(cid:13) D1(cid:13) unless the charger will remain in the shutdown state with 0.22m F 1N5819 1N5819 SW(cid:13) VCC(cid:13) + input power applied for very long periods of time. 1C0INm*F(cid:13) WALL(cid:13) ADAPTER Removing input power to the charger will cause the BAT BOOST(cid:13) PROG(cid:13) pin current to drop to near zero, with only the divider L313*m *H(cid:13) D2(cid:13) LT1510 1m F300W 10R01k(cid:13) current remaining as a small drain on the battery. Even that current can be eliminated with a switch as shown in 1N914 GND(cid:13) VC(cid:13) 0.1m F 1k R112k(cid:13) Q1(cid:13) Figures 2 and 5. IBAT VN2222(cid:13) (cid:13) SENSE BAT + + ON: IBAT = 0.5A(cid:13) COUT(cid:13) 2V TO(cid:13) OFF: IBAT = 0.05A(cid:13) + VBAT (cid:9)(cid:9)(cid:9) *(cid:9)STOUKRIFNA COER MMOAURNCTO(cid:13)N CERAMIC(cid:13) 2T2AmNFT(cid:13) 20V (cid:13) R3(cid:13) 4.2V (cid:9)**(cid:9)COILTRONICS CTX33-2 1510 F05.5 12k – R5(cid:13) + Figure 6. Charging NiMH or NiCd Batteries 220k LT1510 Q3(cid:13) 4.2V (Efficiency at 0.5A » 90%) VN2222 – OVP VIN R4(cid:13) 4.99k(cid:13) For a 2-level charger, R1 and R2 are found from: 0.25% 1510 F05 ( )( ) (cid:50)(cid:48)(cid:48)(cid:48) (cid:50).(cid:52)(cid:54)(cid:53) Figure 5. Disconnecting Voltage Divider (cid:73) = (cid:66)(cid:65)(cid:84) (cid:82) (cid:80)(cid:82)(cid:79)(cid:71) Some battery manufacturers recommend termination of ( )( ) ( )( ) constant-voltage float mode after charging current has (cid:50).(cid:52)(cid:54)(cid:53) (cid:50)(cid:48)(cid:48)(cid:48) (cid:50).(cid:52)(cid:54)(cid:53) (cid:50)(cid:48)(cid:48)(cid:48) (cid:82)(cid:49)= (cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:82)(cid:50)= dropped below a specified level (typically 50mA to 100mA) (cid:73) (cid:73) - (cid:73) (cid:76)(cid:79)(cid:87) (cid:72)(cid:73) (cid:76)(cid:79)(cid:87) and a further time-out period of 30 minutes to 90 minutes has elapsed. This may extend the life of the battery, so All battery chargers with fast-charge rates require some check with manufacturers for details. The circuit in Figure means to detect full charge state in the battery to terminate 7 will detect when charging current has dropped below the high charging current. NiCd batteries are typically 75mA. This logic signal is used to initiate a time-out charged at high current until temperature rise or battery 11

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN BAT 0.18W ADAPTER(cid:13) SENSE OUTPUT 3.3V OR 5V INTERNAL(cid:13) R1*(cid:13) C1(cid:13) D1(cid:13) SENSE(cid:13) 1.6k 0.1m F 1N4148 R4(cid:13) RESISTOR LT1510 3 – 8 470k 7 NEGATIVE EDGE(cid:13) LT1011 TO TIMER GND 2 + 4 R2(cid:13) D2(cid:13) 1 560k 1N4148 R3(cid:13) * TRIP CURRENT = R1(VBAT)(cid:13) 430k (R2 + R3)(0.18W ) 1510 F06 Figure 7. Current Comparator for Initiating Float Time-Out voltage decrease is detected as an indication of near full battery and 1.1A for a 4.2V battery. This assumes a 60(cid:176) C charge. The charging current is then reduced to a much maximum ambient temperature. The 16-pin SO, with a lower value and maintained as a constant trickle charge. thermal resistance of 50(cid:176) C/W, can provide a full 1.5A An intermediate “top off” current may be used for a fixed charging current in many situations. The 16-pin PDIP falls time period to reduce 100% charge time. between these extremes. Graphs are shown in the Typical Performance Characteristics section. NiMH batteries are similar in chemistry to NiCd but have two differences related to charging. First, the inflection ( )( ) ( ) characteristic in battery voltage as full charge is ap- (cid:80) = (cid:51).(cid:53)(cid:109)(cid:65) (cid:86) +(cid:49).(cid:53)(cid:109)(cid:65) (cid:86) (cid:66)(cid:73)(cid:65)(cid:83) (cid:73)(cid:78) (cid:66)(cid:65)(cid:84) proached is not nearly as pronounced. This makes it more ( ) (cid:50) difficult to use dV/dt as an indicator of full charge, and (cid:86) [ ( )( )] (cid:66)(cid:65)(cid:84) change of temperature is more often used with a tempera- (cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)+ (cid:55).(cid:53)(cid:109)(cid:65)+ (cid:48).(cid:48)(cid:49)(cid:50) (cid:73) (cid:66)(cid:65)(cid:84) (cid:86) ture sensor in the battery pack. Secondly, constant trickle (cid:73)(cid:78) ( )( ) (cid:230) (cid:246) charge may not be recommended. Instead, a moderate (cid:73) (cid:86) (cid:50)(cid:231) (cid:49)+ (cid:86)(cid:66)(cid:65)(cid:84)(cid:247) level of current is used on a pulse basis (» 1% to 5% duty (cid:66)(cid:65)(cid:84) (cid:66)(cid:65)(cid:84) Ł (cid:51)(cid:48) ł (cid:80) = ( ) cycle) with the time-averaged value substituting for a (cid:68)(cid:82)(cid:73)(cid:86)(cid:69)(cid:82) (cid:53)(cid:53) (cid:86) (cid:73)(cid:78) constant low trickle. ( ) ( )( ) (cid:50) (cid:73) (cid:82) (cid:86) ( )( )( )( ) Thermal Calculations (cid:80) = (cid:66)(cid:65)(cid:84) (cid:83)(cid:87) (cid:66)(cid:65)(cid:84) + (cid:116) (cid:86) (cid:73) (cid:102) (cid:83)(cid:87) (cid:79)(cid:76) (cid:73)(cid:78) (cid:66)(cid:65)(cid:84) (cid:86) If the LT1510 is used for charging currents above 0.4A, a (cid:73)(cid:78) ( )( ) thermal calculation should be done to ensure that junction (cid:80) = (cid:48)..(cid:49)(cid:56)W (cid:73) (cid:50) temperature will not exceed 125(cid:176) C. Power dissipation in (cid:83)(cid:69)(cid:78)(cid:83)(cid:69) (cid:66)(cid:65)(cid:84) the IC is caused by bias and driver current, switch resis- tance, switch transition losses and the current sense R = Switch ON resistance » 0.35W SW resistor. The following equations show that maximum t = Effective switch overlap time » 10ns OL practical charging current for the 8-pin SO package f = 200kHz (500kHz for LT1510-5) (125(cid:176) C/W thermal resistance) is about 0.8A for an 8.4V 12

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN Example: V = 15V, V = 8.4V, I = 1.2A; The average I required is: IN BAT BAT VX ( )( ) ( ) (cid:80) = (cid:51).(cid:53)(cid:109)(cid:65) (cid:49)(cid:53) +(cid:49).(cid:53)(cid:109)(cid:65) (cid:56).(cid:52) (cid:80) (cid:48).(cid:48)(cid:52)(cid:53)(cid:87) (cid:66)(cid:73)(cid:65)(cid:83) (cid:68)(cid:82)(cid:73)(cid:86)(cid:69)(cid:82) = =(cid:49)(cid:52)(cid:109)(cid:65) ( ) (cid:86) (cid:51).(cid:51)(cid:86) (cid:50) (cid:88) (cid:56).(cid:52) [ ( )( )] Total board area becomes an important factor when the + (cid:55).(cid:53)(cid:109)(cid:65)+ (cid:48).(cid:48)(cid:49)(cid:50) (cid:49).(cid:50) =(cid:48).(cid:49)(cid:55)(cid:87) (cid:49)(cid:53) area of the board drops below about 20 square inches. The ( )( )(cid:50)(cid:230) (cid:56).(cid:52)(cid:246) graph in Figure 9 shows thermal resistance vs board area (cid:49).(cid:50) (cid:56).(cid:52) (cid:231) (cid:49)+ (cid:247) for 2-layer and 4-layer boards. Note that 4-layer boards Ł (cid:51)(cid:48)ł (cid:80) = ( ) =(cid:48).(cid:49)(cid:51)(cid:87) have significantly lower thermal resistance, but both types (cid:68)(cid:82)(cid:73)(cid:86)(cid:69)(cid:82) (cid:53)(cid:53) (cid:49)(cid:53) show a rapid increase for reduced board areas. Figure 10 ( ) ( )( ) shows actual measured lead temperature for chargers (cid:50) (cid:49)(cid:46)(cid:50) (cid:48)(cid:46)(cid:51)(cid:53) (cid:56)(cid:46)(cid:52) operating at full current. Battery voltage and input voltage (cid:80) = + (cid:83)(cid:87) will affect device power dissipation, so the data sheet (cid:49)(cid:53) (cid:230) - (cid:57)(cid:246) ( )( )( ) power calculations must be used to extrapolate these (cid:49)(cid:48)(cid:183)(cid:49)(cid:48) (cid:49)(cid:53) (cid:49)(cid:46)(cid:50) (cid:50)(cid:48)(cid:48)(cid:107)(cid:72)(cid:122) Ł ł readings to other situations. (cid:32)(cid:32)(cid:32)(cid:32)(cid:32)(cid:32)= (cid:48)(cid:46)(cid:50)(cid:56)+(cid:48)(cid:46)(cid:48)(cid:52)=(cid:48)(cid:46)(cid:51)(cid:50)(cid:87) Vias should be used to connect board layers together. ( )( )(cid:50) Planes under the charger area can be cut away from the (cid:80) = (cid:48)(cid:46)(cid:49)(cid:56) (cid:49)(cid:46)(cid:50) =(cid:48)(cid:46)(cid:50)(cid:54)(cid:87) (cid:83)(cid:69)(cid:78)(cid:83)(cid:69) rest of the board and connected with vias to form both a Total power in the IC is: SW 0.17 + 0.13 + 0.32+ 0.26 = 0.88W C1 LT1510 Temperature rise will be (0.88W)(50(cid:176) C/W) = 44(cid:176) C. This L1 BOOST D2 assumes that the LT1510 is properly heat sunk by con- SENSE necting the four fused ground pins to the expanded traces VX + 1510 F07 and that the PC board has a backside or internal plane for IVX 10m F heat spreading. The P term can be reduced by connecting the boost Figure 8 DRIVER diode D2 (see Figures 2 and 6 circuits) to a lower system voltage (lower than V ) instead of V (see Figure 8). 60(cid:13) BAT BAT Then, 55(cid:13) W) ((cid:73)(cid:66)(cid:65)(cid:84))((cid:86)(cid:66)(cid:65)(cid:84))((cid:86)(cid:88))(cid:230)Ł(cid:231) (cid:49)+ (cid:51)(cid:86)(cid:48)(cid:88)(cid:246)ł(cid:247) °STANCE (C/ 5405(cid:13)(cid:13) 2-LAYER BOARD (cid:80)(cid:68)(cid:82)(cid:73)(cid:86)(cid:69)(cid:82) = ( ) (cid:13)RESI 40(cid:13) 4-LAYER BOARD (cid:53)(cid:53) (cid:86) L (cid:73)(cid:78) A M 35(cid:13) R E For example, V = 3.3V, TH S16, MEASURED FROM AIR AMBIENT(cid:13) X 30(cid:13) TO DIE USING COPPER LANDS AS (cid:13) SHOWN ON DATA SHEET ((cid:49).(cid:50)(cid:65))((cid:56).(cid:52)(cid:86))((cid:51).(cid:51)(cid:86))(cid:230)Ł(cid:231) (cid:49)+ (cid:51)(cid:51).(cid:51)(cid:48)(cid:86)(cid:246)ł(cid:247) 250 5 10BOAR1D5 ARE2A0 (IN22)5 30 35 (cid:80) = ( ) =(cid:48).(cid:48)(cid:52)(cid:53)(cid:87) 1510 F08 (cid:68)(cid:82)(cid:73)(cid:86)(cid:69)(cid:82) (cid:53)(cid:53) (cid:49)(cid:53)(cid:86) Figure 9. LT1510 Thermal Resistance 13

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN 90(cid:13) event of an input short. The body diode of Q2 creates the NOTE: PEAK DIE TEMPERATURE WILL BE(cid:13) 80(cid:13) ABOUT 10°C HIGHER THAN LEAD TEMPER-(cid:13) necessary pumping action to keep the gate of Q1 low ATURE AT 1.3A CHARGING CURRENT C) during normal operation (see Figure 11). °RE ( 70(cid:13) 2-LAYER BOARD TU 60(cid:13) Q1 RA VIN + (cid:13)E MP 50(cid:13) 4-LAYER BOARD E AD T 40(cid:13) ICHRG = 1.3A(cid:13) SW VCC LE 30(cid:13) VVVIBBNAO TO= S=1T 68 =V.4 (cid:13)VVB(cid:13)AT(cid:13) RX(cid:13) Q2 D1 L1 C3 BOOLSTT1510 20 TA = 25°C 50k D2 0 5 10 15 20 25 30 35 SENSE BOARD AREA (IN2) 1510 F09 VX(cid:13) BAT 3V TO 6V CX(cid:13) Figure 10. LT1510 Lead temperature 10m F VBAT Q1: Si4435DY(cid:13) + low thermal resistance system and to act as a ground Q2: TP0610L HIGH DUTY CYCLE(cid:13) plane for reduced EMI. CONNECTION 1510 F10 Figure 11. Replacing the Input Diode Higher Duty Cycle for the LT1510 Battery Charger Maximum duty cycle for the LT1510 is typically 90% but Layout Considerations this may be too low for some applications. For example, if Switch rise and fall times are under 10ns for maximum an 18V – 3% adapter is used to charge ten NiMH cells, the efficiency. To prevent radiation, the catch diode, SW pin charger must put out 15V maximum. A total of 1.6V is lost and input bypass capacitor leads should be kept as short in the input diode, switch resistance, inductor resistance as possible. A ground plane should be used under the and parasitics so the required duty cycle is 15/16.4 = switching circuitry to prevent interplane coupling and to 91.4%. As it turns out, duty cycle can be extended to 93% act as a thermal spreading path. All ground pins should be by restricting boost voltage to 5V instead of using V as BAT connected to expand traces for low thermal resistance. is normally done. This lower boost voltage V (see Figure X The fast-switching high current ground path including the 8) also reduces power dissipation in the LT1510, so it is a switch, catch diode and input capacitor should be kept win-win decision. very short. Catch diode and input capacitor should be close to the chip and terminated to the same point. This Even Lower Dropout path contains nanosecond rise and fall times with several For even lower dropout and/or reducing heat on the board, amps of current. The other paths contain only DC and /or the input diode D3 (Figures 2 and 6) should be replaced 200kHz triwave and are less critical. Figure 13 shows with a FET. It is pretty straightforward to connect a critical path layout. Figure 12 indicates the high speed, P-channel FET across the input diode and connect its gate high current switching path. to the battery so that the FET commutates off when the SWITCH NODE input goes low. The problem is that the gate must be L1 pumped low so that the FET is fully turned on even when VBAT the input is only a volt or two above the battery voltage. HIGH(cid:13) Also there is a turn off speed issue. The FET should turn off FREQUENCY(cid:13) VIN CIN CIRCULATING(cid:13) COUT BAT instantly when the input is dead shorted to avoid large PATH current surges form the battery back through the charger into the FET. Gate capacitance slows turn off, so a small P-FET (Q2) discharges the gate capacitance quickly in the 1510 F12 Figure 12. High Speed Switching Path 14

LT1510/LT1510-5 APPLICATIOUNS INUFORWMATIOUN GND LT1510 D1 GND(cid:13) GND(cid:13) CIN SW(cid:13) VCC2(cid:13) BOOST(cid:13) VCC1(cid:13) GND(cid:13) PROG(cid:13) OVP(cid:13) VC(cid:13) L1 SENSE(cid:13) BAT(cid:13) GND(cid:13) GND(cid:13) GND GND 1510 F11 Figure 13. Critical Electrical and Thermal Path Layer PACKAGE DESCRIPTIOUN Dimensions in inches (millimeters) unless otherwise noted. GN Package 0.189 – 0.196*(cid:13) 16-Lead Plastic SSOP (Narrow 0.150) (4.801 – 4.978) (LTC DWG # 05-08-1641) 16 15141312 1110 9 0(0.0.3185 –– 00..1000)4(cid:13)(cid:13)· 45(cid:176) (01..035531 –– 01..076498(cid:13)) (00..010042 –– 00..024099(cid:13)) 0.229 – 0.244(cid:13) 0.150 – 0.157**(cid:13) 0.0075 – 0.0098(cid:13) 0° – 8° T(cid:13)YP (5.817 – 6.198) (3.810 – 3.988) (0.191 – 0.249) 0.016 – 0.050(cid:13) 0.008 – 0.012(cid:13) 0.025(cid:13) (0.406 – 1.270) (0.203 – 0.305) (0.635)(cid:13) BSC 1 2 3 4 5 6 7 8 (cid:9) *(cid:9)DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH(cid:13) (cid:9)(cid:9) SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE(cid:13) GN16 (SSOP) 0895 (cid:9) **(cid:9)DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD(cid:13) (cid:9)(cid:9) FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE N Package 16-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.770*(cid:13) 0.300 – 0.325(cid:13) 0.130 – 0.005(cid:13) 0.045 – 0.065(cid:13) (19.558)(cid:13) (7.620 – 8.255) (3.302 – 0.127) (1.143 – 1.651) MAX 16 15 14 13 12 11 10 9 0.015(cid:13) (0.381)(cid:13) MIN 0.065(cid:13) 0.255 – 0.015*(cid:13) 0.009 – 0.015(cid:13) (1.651)(cid:13) (6.477 – 0.381) (0.229 – 0.381) TYP +0.025(cid:13) (0.325–0.015) 0.125(cid:13) 0.005(cid:13) 0.018 – 0.003(cid:13) 1 2 3 4 5 6 7 8 8.255–+00..633851(cid:13) (3M.1I7N5)(cid:13) 0.1(00M0.1 I–2N 70).(cid:13)010(cid:13) *THES(0E. 4D5I7M –E N0S.0IO76N)S DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.(cid:13) (2.540 – 0.254) MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) N16 0695 S8 Package 0.189 – 0.197*(cid:13) 8-Lead Plastic Small Outline (Narrow 0.150) (4.801 – 5.004) (LTC DWG # 05-08-1610) 8 7 6 5 (00..021504 –– 00..052008(cid:13))· 45(cid:176) 0.053 – 0.069(cid:13) (05..272981 –– 06..214947(cid:13)) (1.346 – 1.752) 0.004 – 0.010(cid:13) 0.150 – 0.157**(cid:13) 0.008 – 0.010(cid:13) (0.203 – 0.254) 0°– 8° TYP (0.101 – 0.254) (3.810 – 3.988) 0.016 – 0.050(cid:13) 0.014 – 0.019(cid:13) 0.050(cid:13) 0.406 – 1.270 (0.355 – 0.483) (1.270) BSC 1 2 3 4 *(cid:13)DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE(cid:13) SO8 0695 **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE(cid:13) (cid:13) (cid:13) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 15 However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

LT1510/LT1510-5 TYPICAL APPLICATIONU Adjustable Voltage Regulator with Precision Adjustable Current Limit LT1510 0.22m F 1N5819 SW(cid:13) VCC2 + V18INV(cid:13) TO 25V VCC1 100m F BOOST PROG 30m H 1k RPROG(cid:13) GND VC 0.01m F 4.93k 1N914 OVP 0.1m F POT(cid:13) 1m F 100k(cid:13) SENSE BAT VOUT(cid:13) (cid:13) + 2.5V TO 15V(cid:13) POT(cid:13) 500m F CURRENT LIMIT LEVEL(cid:13) 5k(cid:13) 50mA TO 1A ( ) (cid:13) 2.465V(cid:13) CURRENT LIMIT LEVEL = (2000) 1k RPROG 1510 TA01 PACKAGE DESCRIPTIOUN Dimensions in inches (millimeters) unless otherwise noted. S Package 16-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.386 – 0.394*(cid:13) (9.804 – 10.008) 16 15 14 13 12 11 10 9 0.004 – 0.010(cid:13) (00..021504 –– 00..052008(cid:13))· 45(cid:176) (01..035436 –– 01..076592(cid:13)) (0.101 – 0.254) 0.150 – 0.157**(cid:13) (3.810 – 3.988) 0.008 – 0.010(cid:13) 0.228 – 0.244(cid:13) (0.203 – 0.254) 0° – 8° TYP (5.791 – 6.197) 0.016 – 0.050(cid:13) 0.014 – 0.019(cid:13) 0.050(cid:13) 1 2 3 4 5 6 7 8 (0.355 – 0.483) (1.270)(cid:13) 0.406 – 1.270 TYP S16 0695 *(cid:13)DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH (cid:13) (cid:13)SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE(cid:13) **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD (cid:13) FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE(cid:13) (cid:13) (cid:13) RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC®1325 Microprocessor-Controlled Battery Management Can Charge, Discharge and Gas Gauge NiCd, NiMH and Pb-Acid System Batteries with Software Charging Profiles LT1372/LT1377 500kHz/1MHz Step-Up Switching Regulators High Frequency, Small Inductor, High Efficiency Switchers, 1.5A Switch LT1373 250kHz Step-Up Switching Regulator High Efficiency, Low Quiescent Current, 1.5A Switch LT1376 500kHz Step-Down Switching Regulator High Frequency, Small Inductor, High Efficiency Switcher, 1.5A Switch LT1511 3A Constant-Voltage/Constant-Current Battery Charger High Efficiency, Minimal External Components to Fast Charge Lithium, NiMH and NiCd Batteries LT1512 SEPIC Battery Charger V Can Be Higher or Lower Than Battery Voltage IN 16 Linear Technology Corporation 1510fc LT/GP 1197 REV C 4K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 l (408) 432-1900 FAX: (408) 434-0507 l TELEX: 499-3977 l www.linear-tech.com ª LINEAR TECHNOLOGY CORPORATION 1995