LT1300 Micropower High Efficiency 3.3/5V Step-Up DC/DC Converter FEATURES DESCRIPTIOUN n Up to 220mA Output Current at 5V from 2V Supply The LT1300 is a micropower step-up DC/DC converter that n Supply Voltage as Low as 1.8V utilizes Burst Mode™ operation. The device can deliver 5V n Up to 88% Efficiency or 3.3V from a two-cell battery input. It features program- n Small Inductor –10m H mable 5V or 3.3V output via a logic-controlled input, no- n 120m A Quiescent Current load quiescent current of 120m A and a shutdown pin which n Shutdown to 10m A reduces supply current to 10m A. The on-chip power switch n Programmable 3.3V or 5V Output has a low 170mV saturation voltage at a switch current of n I Pin Programs Peak Switch Current 1A, a four-fold reduction over prior designs. A 155kHz LIM n Low V Switch: 170mV at 1A Typical internal oscillator allows the use of extremely small sur- CESAT n Uses Inexpensive Surface Mount Inductors face mount inductors and capacitors. Operation is guaran- n 8-Lead DIP or SOIC Package teed at 1.8V input. This allows more energy to be extracted APPLICATIOUNS from the battery increasing operating life. The ILIM pin can be used to program peak switch current with a single n Palmtop Computers resistor allowing the use of less expensive and smaller n Portable Instruments inductors and capacitors in lighter load applications. The n Bar-Code Scanners LT1300 is available in an 8-lead SOIC package, minimizing n DC/DC Converter Module Replacements board space requirements. For a 5V/12V Selectable Out- n Battery Backup Supplies put Converter see the LT1301. For increased output cur- n Personal Digital Assistants rent see the LT1302. n PCMCIA Cards Burst Mode is a trademark of Linear Technology Corporation. TYPICAL APPLICATIONUS N Two-Cell to 3.3V/5V Step-Up Converter 5V Output Efficiency L1(cid:13) 10µH D1 5V/3.3V(cid:13) 90 OUTPUT 6 7 5V/3.3V(cid:13) 2 VIN SW 4 88 VIN = 4.0V 2· (cid:13) + SELECT SELECT SENSE 86 ACAEL(cid:13) L SC1H01U0(cid:13)TµDFOWN 3 SHDN LT1300 ILIM (cid:13)5 N/C +C1(cid:13) 010(cid:13) µF(cid:13) ENCY (%) 8824 VVIINN == 32..05VV CI PGND GND FI 80 VIN = 2.0V F E 8 1 78 76 L1 =COILCRAFT DO1608-103 LT1300 TA1 OR SUMIDA CD54-100 74 C1 =AVX TPSD107M010R0100 1 10 100 500 OR SANYO OS-CON 16SA100M LOAD CURRENT (mA) D1 =MBRS130LT3 LT1300 TA2 OR 1N5817 1

LT1300 ABSOLUTE WMAXIWMUWM RATINUGS PACKAGE/ORDER IUNFORWMATIOUN V Voltage .............................................................. 10V IN ORDER PART TOP VIEW SW1 Voltage............................................................ 20V NUMBER Sense Voltage.......................................................... 10V GND(cid:13) 1(cid:13) 8(cid:13) PGND(cid:13) SHUTDOWN Voltage................................................ 10V SEL(cid:13) 2(cid:13) 7(cid:13) SW(cid:13) LT1300CN8 SELECT Voltage....................................................... 10V SHDN(cid:13) 3(cid:13) 6(cid:13) VIN(cid:13) LT1300CS8 I Voltage ............................................................ 0.5V SENSE 4 5(cid:13) ILIM LIM (cid:13) Maximum Power Dissipation.............................500mW N8 PACKAGE(cid:13) S8 PACKAGE(cid:13) S8 PART MARKING Operating Temperature Range.....................0(cid:176) C to 70(cid:176) C 8-LEAD PLASTIC DIP(cid:13) 8-LEAD PLASTIC SOIC (cid:13) (cid:13) Storage Temperature Range................. –65(cid:176) C to 150(cid:176) C Lead Temperature (Soldering, 10 sec)..................300(cid:176) C TJMAX = 100(cid:176)C, q JA = 150(cid:176)C/W 1300 Consult factory for Industrial grade parts. ELECTRICAL CHARACTERISTICS T = 25(cid:176) C, V = 2V unless otherwise noted. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Quiescent Current V = 0.5V, V = 5V, V = 5.5V l 120 200 m A Q SHDN SEL SENSE V = 1.8V l 7 15 m A SHDN V Input Voltage Range 1.8 V IN l 2.0 V V Output Sense Voltage V = 5V l 4.80 5.0 5.20 V OUT SEL V = 0V l 3.15 3.3 3.45 V SEL Output Referred V = 5V (Note 1) l 22 50 mV SEL Comparator Hysteresis V = 0V (Note 1) l 14 35 mV SEL Oscillator Frequency Current Limit not Asserted. See Test Circuit. 120 155 185 kHz Oscillator TC 0.2 %/(cid:176) C DC Maximum Duty Cycle 75 86 95 % t Switch On Time Current Limit not Asserted. 5.6 m s ON Output Line Regulation 1.8V < V < 6V l 0.06 0.15 %/V IN V Switch Saturation Voltage I = 700mA l 130 200 mV CESAT SW Switch Leakage Current V = 5V, Switch Off l 0.1 10 m A SW Peak Switch Current I Floating (See Typical Application) 0.75 1.0 1.25 A LIM (Internal Trip Point) I Grounded 0.4 A LIM V Shutdown Pin High l 1.8 V SHDNH V Shutdown Pin Low 0.5 V SHDNL V Select Pin High l 1.5 V SELH V Select Pin Low l 0.8 V SELL I Shutdown Pin Bias Current V = 5V l 9 20 m A SHDN SHDN V = 2V l 3 m A SHDN V = 0V l 0.1 1 m A SHDN I Select Pin Bias Current 0V < V < 5V l 1 3 m A SEL SEL The l denotes specifications which apply over the 0(cid:176) C to 70(cid:176) C Note 1: Hysteresis specified is DC. Output ripple may be higher if temperature range. output capacitance is insufficient or capacitor ESR is excessive. See applications section. 2

LT1300 TYPICAL PERFORWMANUCE CHARACTERISTICS Total Quiescent Current Efficiency No-Load Battery Current in Shutdown 88 170 80 VOUT = 3.3V(cid:13) 86 L = 10µH 165 84 VOUT = 5V 70 160 CIENCY (%) 78878026 VIN = 3V VIN = 2V.I5NV = 2V CURRENT (µA) 111554505 VOUT = 3.3V + I (µA)VINSENSE 456000 EFFI 7742 INPUT 114305 + ISHDN 3200 70 130 I 10 68 125 66 120 0 1 10 100 1000 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 0 1 2 3 4 5 6 7 8 LOAD CURRENT (mA) INPUT VOLTAGE (V) INPUT VOLTAGE (V) LT1300 G1 LT1300 G2 LT1300 G3 Maximum Output Current Shutdown Pin Bias Current V vs I vs Input Voltage CESAT SW 20 250 700 18 TA = 25°C 225 600 IVLOIMUT F =L O5AVT,(cid:13)ING WN CURRENT (µA) 111128046 (mV)CESAT211110705205005 T CURRENT (mA) 345000000 DCOO3LI3L =1C 62R-2A2µ2FHT3(cid:13)(cid:13) LCD OO=I1 L16C00µR8HA-1(cid:13)F0T3(cid:13) O V U D P UT 6 75 UT 200 H O S 4 50 100 2 25 0 0 0 0 1 2 3 4 5 6 7 8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.5 2 2.5 3 3.5 4 4.5 SHUTDOWN VOLTAGE (V) SWITCH CURRENT (A) INPUT VOLTAGE (V) LT1300 G4 LT1300 G5 LT1300 G6 Maximum Output Current Transient Response vs Input Voltage V = 2V, V = 5V Startup Response IN OUT 900 800 VILOIMUT F =L O3A.3TVIN(cid:13) G 100mVV/DOUIVT VOUT 700 AC COUPLED 1V/DIV mA) 600 NT ( 500 L = 10µH ILOAD200mA VSHDN RE 0 10V/DIV R U 400 C AD 300 200m s/DIV 500m s/DIV LO LT1300 G8 VOUT = 5V LT1300 G9 200 RLOAD = 20W 100 0 1.5 (cid:13) 2 (cid:13) 2.5 (cid:13) 3 (cid:13) 3.5 INPUT VOLTAGE (V) LT1300 G7 3

LT1300 PIUN FUUNCTIOUNS GND (Pin 1): Signal Ground. V (Pin 6): Supply Pin. Must be bypassed with a large IN value electrolytic to ground. A 0.1m F ceramic capacitor Sel (Pin 2): Output Select. When tied to V or V IN OUT close to the pin may be needed in some cases. converter regulates at 5V. When grounded converter regulates at 3.3V. SW (Pin 7): Switch Pin. Connect inductor and diode here. Keep layout short and direct to minimize electronic radia- SHDN (Pin 3): Shutdown. Pull high to effect shutdown. Tie tion. to ground for normal operation. PGND (Pin 8): Power Ground. Tie to signal ground (pin 1) Sense (Pin 4): “Output” Pin. under the package. Bypass capacitor from V should be IN ILIM (Pin 5): Float for 1A switch current limit. Tie to ground tied directly to the pin. for approximately 400mA. A resistor between I and LIM ground sets peak current to some intermediate value (see Figure 5). BLOCK DIAGRAWM VIN L1 D1 VOUT + + C1 C2(cid:13) (cid:13) SENSE VIN SW 4 2 7 18mV A2 CURRENT (cid:13) R1(cid:13) COMPARATOR + 3W 500k (cid:13) 73R02W(cid:13) – A1(cid:13) OFF COMPARATOR + 1.25V(cid:13) ENABLE OSCILLATOR(cid:13) REFERENCE 155kHZ A3 DRIVER Q2(cid:13) Q1(cid:13) 144k – 1x 160x 161k BIAS Q3 8.5k GND SELECT SHUTDOWN ILIM PGND 1 2 3 5 8 LT1300 F1 Figure 1. 4

LT1300 TEST CIRC(cid:13)UITS Oscillator Test Circuit 5V 2V 100W VIN IL SEL SW fOUT 100µF LT1300 SENSE SHDN GND PGND OPERATIOUN Operation of the LT1300 is best understood by referring to the Block Diagram in Figure 1. When A1’s negative input, TRACE A 500mA/DIV related to the Sense pin voltage by the appropriate resis- ILIM PIN OPEN tor-divider ratio, is higher that the 1.25V reference voltage, A1’s output is low. A2, A3 and the oscillator are turned off, drawing no current. Only the reference and A1 consume TRACE B 500mA/DIV current, typically 120m A. When the voltage at A1’s nega- ILIM PIN GROUNDED tive input decreases below 1.25V, overcoming A1’s 6mV hysteresis, A1’s output goes high, enabling the oscillator, 20m s/DIV LT1300 F2 current comparator A2, and driver A3. Quiescent current Figure 2. Switch Pin Current With I Floating or Grounded LIM increases to 2mA as the device prepares for high current reduced by tying the I pin to ground, causing 15m A to LIM switching. Q1 then turns on in a controlled saturation for flow through R2 into Q3’s collector. Q3’s current causes (nominally) 5.3m s or until current comparator A2 trips, a 10.4mV drop in R2 so that only an additional 7.6mV is whichever comes first. After a fixed off-time of (nominally) required across R1 to turn off the switch. This corre- 1.2m s, Q1 turns on again. The LT1300’s switching causes sponds to a 400mA switch current as shown in Figure 2, current to alternately build up in L1 and dump into capaci- trace B. The reduced peak switch current reduces I2R tor C2 via D1, increasing the output voltage. When the loses in Q1, L1, C1 and D1. Efficiency can be increased by output is high enough to cause A1’s output to go to low, doing this provided that the accompanying reduction in switching action ceases. C2 is left to supply current to the full load output current is acceptable. Lower peak currents load until V decreases enough to force A1’s output OUT also extend alkaline battery life due to the alkaline cell’s high, and the entire cycle repeats. high internal impedance. Typical operating waveforms are If switch current reaches 1A, causing A2 to trip, switch on- shown in Figure 3. time is reduced and off-time increases slightly. This allows continuous mode operation during bursts. Current com- VOUT 20mV/DIV parator A2 monitors the voltage across 3W resistor R1 AC COUPLED which is directly related to inductor L1’s current. Q2’s collector current is set by the emitter-area ratio to 0.6% VSW 5V/DIV of Q1’s collector current. When R1’s voltage drop exceeds 18mV, corresponding to 1A inductor current, A2’s output ISW goes high, truncating the on-time portion of the oscillator IA/DIV cycle and increasing off-time to about 2m s as shown in 20m S/DIV LT1300 F2 Figure 2, trace A. This programmed peak current can be Figure 3. Burst Mode Operation in Action 5

LT1300 APPLICATIOUNS INUFORWMATIOUN Output Voltage Selection L1(cid:13) 10µH D1 The LT1300 can be selected to 3.3V or 5V under logic control or fixed at either by tying SELECT to ground or V IN VIN SW respectively. It is permissible to tie SELECT to a voltage 5V/3.3V(cid:13) SELECT SENSE + OUTPUT higher than V as long as it does not exceed 10V. C1(cid:13) IN 100µF LT1300 Efficiency in 3.3V mode will be slightly less that in 5V mode + due to the fact that the diode drop is a greater percentage SHDN ILIM C1020(cid:13) µF(cid:13) of 3.3V than 5V. Since the bipolar switch in the LT1300 PGND GND (cid:13) R1(cid:13) C3(cid:13) gets its base drive from V , no reduction in switch 1M 0.1µF(cid:13) IN (cid:13) efficiency occurs when in 3.3V mode. When V exceeds IN the programmed output voltage the output will follow the input. This is characteristic of the simple step-up or Figure 4. Addition of R1 and C3 Limit Input Current at Startup “boost” converter topology. A circuit example that pro- vides a regulated output with an input voltage above or below the output (called a buck-boost or SEPIC) is shown in the Typical Applications section. VOUT 2VDIV Shutdown IBATTERY The converter can be turned off by pulling SHDN (pin 3) 500mA/DIV high. Quiescent current drops to 10m A in this condition. Bias current of 3m A to 5m A flows into the pin (at 2.5V input). VSHDN 10V/DIV It is recommended that SHDN not be left floating. Tie the 500m s/DIV pin to ground if the feature is not used. REP RATE = 1Hz LT1300 F5 I Function Figure 5. Startup Waveforms using Soft-Start Circuitry LIM I = 100mA, V = 5V LOAD OUT The LT1300’s current limit (I ) pin can be used for soft LIM start. Upon start-up, switching regulators require maxi- mum current from the supply. The high currents flowing 1100 1.6V £ VIN £ 5V can create IR drops along supply and ground lines and 1000 are especially demanding on alkaline batteries. By in- A)900 stalling an R1 and C3 as shown in Figure 4, the switch m current in the LT1300 is limited to 400mA until the 15m A ENT (800 R flowing out of the I pin charges up the 0.1m F capaci- UR700 LIM C tor. Input current is held to under 500mA while the CH 600 T WI output voltage ramps up to 5V as shown in Figure 5. The S500 1Meg resistor provides a discharge path for the capacitor 400 without appreciably decreasing peak switch current. When 300 the full capability of the LT1300 is not required, peak 100 1k 10k 100k 1M RLIM (W ) current can be reduced by changing the value of R3 as LT1300 F1B shown in Figure 6. With R3 = 0, switch current is limited Figure 6. Peak Switch Current vs. R LIM to approximately 400mA. 6

LT1300 APPLICATIOUNS INUFORWMATIOUN Table 1. Recommended Inductors EFFICIENCY 2.5VIN, 5VOUT COMPONENT PART NUMBER VENDOR L (m H) DCR (W ) I PIN 50mA LOAD 200mA LOAD HEIGHT (mm) PHONE NUMBER LIM DO1608-103 Coilcraft 10 0.11 Float 83 83 3.5 (708) 639–6400 DO3316-223 Coilcraft 22 0.050 Float 85 85 5.5 DO1608-223 Coilcraft 22 0.31 Ground 85 — 3.5 CTX10-1 Coiltronics 10 0.038 Float 85 85 4.2 (407) 241–7876 CTX20-1 Coiltronics 20 0.175 Ground 86 — 4.2 LQH3C2204K0M00 Murata-Frie 22 0.7 Ground 81 — 2.0 (404) 436–1300 CD54-100M Sumida 10 0.11 Float 85 85 4.5 (708) 956–0666 CDRH62-220M Sumida 22 0.38 Ground 84 — 3.0 CDRH62-100M Sumida 10 0.17 Float 81 82 3.0 GA10-102K Gowanda 10 0.038 Float 85 86 6.6 Through-Hole (716) 532–2234 Inductor Selection Table 2. Recommended Capacitors For full output power, the inductor should have a satura- VENDOR SERIES TYPE PHONE# tion current rating of 1.25A for worst-case current limit, AVX TPS Surface Mount (803)448–9411 although it is acceptable to bias an inductor 20% or more Sanyo OS-CON Through-Hole (619) 661–6835 into saturation. Smaller inductors can be used in conjunc- Panasonic HFQ Through-Hole (201) 348–5200 tion with the I pin. Efficiency is significantly affected by LIM inductor DCR. For best efficiency limit the DCR to 0.03W Diode Selection or less. Toroidal types are preferred in some cases due to Best performance is obtained with a Schottky rectifier their closed design and inherent EMI/RFI superiority. diode such as the 1N5817. Phillips Components makes Recommended inductors are listed in Table 1. this in surface mount as the PRLL5817. Motorola makes the MBRS130LT3 which is slightly better and also in Capacitor Selection surface mount. For lower output power a 1N4148 can be Low ESR capacitors are required for both input and output used although efficiency will suffer substantially. of the LT1300. ESR directly affects ripple voltage and Layout Considerations efficiency. For surface mount applications AVX TPS series tantalum capacitors are recommended. These have been The LT1300 is a high speed, high current device. The input specially designed for SMPS and have low ESR along with capacitor must be no more than 0.2" from V (pin 6) and IN high surge current ratings. For through-hole application ground. Connect the PGND and GND (pins 8 and 1) Sanyo OS-CON capacitors offer extremely low ESR in a together under the package. Place the inductor adjacent to small size. Again, if peak switch current is reduced using SW (pin 7) and make the switch pin trace as short as the I pin, capacitor requirements can be relaxed and possible. This keeps radiated noise to a minimum. LIM smaller, higher ESR units can be used. Low frequency output ripple can be reduced by adding multiple output capacitors. If capacitance is reduced, output ripple will increase. Suggested capacitor sources are listed in Table 2. Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 7 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.

LT1300 TYPICAL APPLICATIONUS N Four-Cell to 5V/3.3V Up-Down Converter LCD Contrast Supply C2**(cid:13) CONTRAST (cid:13) 2.5V £ VIN £ 8V 2L71µ*H(cid:13) 1+00µF VIN(cid:13) T1 VMOAUXTIM –U4MV TFOR O–2M9 V1. 81V2m SAU(cid:13)PPLY (cid:13) 1.8V TO 6V 4 (77% EFFICIENT)(cid:13) 20mA MAXIMUM FROM (cid:13) N/C 3V SUPPLY (83% EFFICIENT) 7 1 3 4·(cid:13) ILIM VIN L227*µ(cid:13)H 1N5817 150K 22µF(cid:13) ACAEL(cid:13)L + C1**(cid:13) 5V/3.3V SELECT SW 10 82 +35V 100µF LT1300 (cid:13) 5V/3.3V(cid:13) SHUTDOWN SHDN SENSE 220mA(cid:13) 9 1N5819 80% EFFICIENT GND PGND + C3**(cid:13) 100µF VIN SW N/C SENSE SHDN SHUTDOWN + *L1, L2 = GOWANDA GA20-272K(cid:13) 100µF LT1300 COILCRAFT DO3316-273K(cid:13) SUMIDA CD73-270K(cid:13) N/C SELECT ILIM **C1, C2, C3 = SANYO OS-CON 16SA100M LT1300 TA3 PGND GND 12K Step-Up Converter with Automatic Output Disconnect + T1 = DALE LPE-5047-AO45 (605) 665-9301 12K 2.2µF 470W PWM IN(cid:13) 1L01µ*H(cid:13) 1N5817 2N4403 CMOS0% D RTIOV E1 000V% T(cid:13)O 5V LT1300 TA6 5V, 200mA + 2·(cid:13) SELECT VIN 100µF AA(cid:13) SHUTDOWN SHDN SW CELL + 100µF LT1300 (cid:13) NC ILIM SENSE GND PGND 0.1µF *SUMIDA CD54-100LC (cid:13) LT1300 TA5 COILCRAFT DO3316-223 PACKAGE DESCRIPTIOUN Dimensions in inches (millimeters) unless otherwise noted. 0.400(cid:13) (10.160)(cid:13) 0.300 – 0.320(cid:13) 0.045 – 0.065(cid:13) 0.130 ± 0.005(cid:13) MAX (7.620 – 8.128) (1.143 – 1.651) (3.302 ± 0.127) 8 7 6 5 N8 Package 0.065(cid:13) 8-Lead Plastic DIP (1.651)(cid:13) 0.250 ± 0.010(cid:13) 0.009 – 0.015(cid:13) TYP (6.350 ± 0.254)(cid:13) (0.229 – 0.381) 0.125(cid:13) (cid:13) (3.175)(cid:13) 0.020(cid:13) (0.325–+00..002155)(cid:13) (01..014453 ±± 00..031851(cid:13)) MI(cid:13)N(cid:13) (0M.5I0N8)(cid:13) 1 2 3 4 +0.635(cid:13) 8.255–0.381 0.100 ± 0.010(cid:13) 0.018 ± 0.003(cid:13) N8 0392 (2.540 ± 0.254) (0.457 ± 0.076) 0.189 – 0.197*(cid:13) (4.801 – 5.004) 0.010 – 0.020(cid:13)· 45(cid:176) 0.053 – 0.069(cid:13) 8 7 6 5 (0.254 – 0.508) (1.346 – 1.752) 0.004 – 0.010(cid:13) 0.008 – 0.010(cid:13) S8 Package (0.203 – 0.254) 0°– 8° TYP (0.101 – 0.254) 8-Lead Plastic S0IC 0.228 – 0.244(cid:13) 0.150 – 0. 0.016 – 0.050(cid:13) 0.014 – 0.019(cid:13) 0.050(cid:13) (5.791 – 6.197) (3.810 – 3. 0.406 – 1.270 (0.355 – 0.483) (1.270)(cid:13) BSC *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.(cid:13) (cid:9)(cid:9)MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 1 2 3 4 SO8 0294 8 Linear Technology Corporation LT/GP 0394 10K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 l F AX: (408) 434-0507 l TELEX: 499-3977 ª LINEAR TECHNOLOGY CORPORATION 1994