LTBBV

LT3462 LINER

Document overview

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Technical content

n Integrated Schottky Rectifier n Fixed Frequency 1.2MHz/2.7MHz Operation n Very Low Noise: 1mVP-P Output Ripple n Low VCESAT Switch: 270mV at 250mA n –5V at 100mA from 5V Input n –12V at 30mA from 3.3V Input n Low Input Bias Current GND Based FB Input n Low Impedance (40Ω ) 1.265V Reference Output n High Output Voltage: Up to – 38V n Wide Input Range: 2.5V to 16V n Uses Tiny Surface Mount Components n Low Shutdown Current: <10µA n Low Profile (1mm) SOT-23 (ThinSOT TM ) Package n CCD Bias n LCD Bias n GaAs FET Bias n General Purpose Negative Voltage Supply Inverting 1.2MHz/2.7MHz DC/DC Converters with Integrated Schottky in ThinSOT The LT 3462/LT3462A are general purpose fixed fre- quency current mode inverting DC/DC converters. Both devices feature an integrated Schottky and a low V CESAT switch allowing a small converter footprint and lower parts cost. The LT3462 switches at 1.2MHz while the LT3462A switches at 2.7MHz. These high speeds enable the use of tiny, low cost and low height capacitors and inductors. The LT3462/LT3462A operate in a dual inductor inverting topology that filters both the input and output currents. Very low output voltage ripple approaching 1mV P-P can be achieved when ceramic capacitors are used. Fixed fre- quency switching ensures a clean output free from low frequency noise typically present with charge pump solu- tions. The 40V switch allows a V IN to VOUT differential of up to 38V for dual inductor topologies. Both devices provide a low impedance 1.265V reference output to supply the feedback resistor network. A ground referenced, high impedance FB input allows high feedback resistor values without compromising output accuracy. The LT3462/LT3462A are available in a 6-lead SOT-23 package. , LTC and LT are registered trademarks of Linear Technology Corporation. 5V to –5V, 100mA Inverting DC/DC Converter Efficiency ThinSOT is a trademark of Linear Technology Corporation LOAD CURRENT (mA) EFFICIENCY (%)

3462 TA01b

VIN = 3.3V VIN = 5V TA = 25°C VIN 22µH 22µH 267k 68.1k 10µF 22pF 1µF 1µF VOUT –5V 100mA VIN SW FB SDREF GND LT3462A

3462 TA01

D

ABSOLUTE AXI U RATI GSW WW U PACKAGE/ORDER I FOR ATIOUU W (Note 1) ELECTRICAL CHARACTERISTICSThe l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C, VIN = 3V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Operating Voltage 2.5 V Maximum Operating Voltage 16 V SDREF Voltage 10 µA > ISDREF ≥ –80µA l 1.245 1.265 1.285 V FB Pin Bias Current (Note 2) 15 50 nA SDREF Minus FB Voltage 10 µA > ISDREF ≥ –80µA l 1.235 1.263 1.285 V Error Amp Offset Voltage –12 12 mV SDREF Reference Source Current SDREF >1.2V l 120 180 µA Supply Current FB = –0.05V, Not Switching 2.9 3.6 mA SDREF = 0V, FB = Open, VIN = 5V 6.5 10 µA SDREF Line Regulation 0.007 %/V Switching Frequency (LT3462) l 0.8 1.2 1.6 MHz Switching Frequency (LT3462A) l 2.0 2.7 3.5 MHz Maximum Duty Cycle (LT3462) l 90 % Maximum Duty Cycle (LT3462A) l 77 % Switch Current Limit 300 420 mA Switch VCESAT ISW = 250mA 270 350 mV Switch Leakage Current V SW = 5V 0.01 1 µA Rectifier Leakage Current V D = –40V 0.03 4 µA Rectifier Forward Drop I SCHOTTKY = 250mA 800 1100 mV SDREF Voltage Low l 0.20 V SDREF Off-State Pull-Up Current 123 µA SDREF Turn-Off Current –300 –200 µA Consult LTC Marketing for parts specified with wider operating temperature ranges. ORDER PART NUMBER S6 PART MARKING LTBBV LTBGB LT3462ES6 LT3462AES6 TJMAX = 125°C θJA = 150°C ON BOARD OVER GROUND PLANE θJC = 120°C/W Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Current flows out of the pin. Note 3: The LT3462E is guaranteed to meet specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls.

6 VIN

4 SDREF

TEMPERATURE (°C) SDREF MINUS FB (V) 1.29 1.28 1.27 1.26 1.25 1.24 1.23

3462 G03

DUTY CYCLE (%) CURRENT LIMIT (mA) 9080604020

3462 G02

3462 G05 3462 G06

TEMPERATURE (°C) –40 FREQUENCY (MHz) 1.6 1.5 1.4 1.3 1.2 1.1 1.0 20 60

3462 G01

–20 0 40 80 100 TEMPERATURE (°C) FREQUENCY (MHz)

3462 G04

3.2 3.0 2.8 2.6 2.4 2.2 2.0 TA = 25°C SUPPLY VOLTAGE (V) QUIESCENT CURRENT (µA) 1648 1 2 TA = 25°C FB = N/C TEMPERATURE (°C) FB BIAS CURRENT (nA) 80 10040 60200–40 –20 –10 –15 –20 –25 –30 –35 –40 –45 –50 –40 20 60–20 0 40 80 100 –40 20 60–20 0 40 80 100 TA = 25°C LT3462 LT3462A TYPICAL PERFOR A CE CHARACTERISTICSUW Oscillator Frequency (LT3462) Current Limit SDREF Minus FB Pin Voltage Oscillator Frequency (LT3462A) FB Bias Current Quiescent Current in Shutdown Mode UUUPI FU CTIO S SW (Pin 1): Switch Pin. Connect to external inductor L1 and positive terminal of transfer cap. GND (Pin 2): Ground. Tie directly to local ground plane. FB (Pin 3): Feedback Pin. Connect resistive divider tap here. Set R1 according to R1 = R2 • (V OUT/1.265V). In shutdown, a proprietary shutdown bias current cancella- tion circuit allows the internal 3 µA source to pull up the SDREF pin, even with residual negative voltage on VOUT. SDREF (Pin 4): Dual Function Shutdown and 1.265V Reference Output Pin. Pull to GND with external N-FET to turn regulator off. Turn-off pull-down and a 2 µA internal source will pull SDREF up to turn-on the regulator. At turn- on, a 180µA internal source pulls the pin to the regulation voltage. The SDREF pin can supply up to 80µA at 1.265V to bias the feedback resistor divider. An optional soft-start circuit capacitor connects from this pin to –VOUT. D (Pin 5): Anode Terminal of Integrated Schottky Diode. Connect to negative terminal of transfer cap and external inductor L2. VIN (Pin 6): Input Supply Pin. Must be locally bypassed.

Figure 1. Block Diagram

3462 F02

cycle, the SR latch is set, turning on the power switch Q1. of the difference between the feedback voltage and GND. components connected to the LT3462. current to external resistor R1 while VOUT is lower than FB. exceed 10µA by the amount of current flowing in R1.

3462 F03

is the capacitance between SW and D. Table 3. Inrush Peak Current inductors will be acceptable for most applications. Figure 2. Suggested Layout severely with applied voltage and at temperature limits. and be placed as close as possible to the LT3462/LT3462A.

Li+ to –8V Supply –12V Efficiency LOAD CURRENT (mA) EFFICIENCY (%)

3462 TA02b

TA = 25°C VIN = 3.3V 3.3V to –12V with Soft-Start Circuit VIN 3.3V 47µH 47µH 267k 27.4k 2.2µF CS1 100nF 22nF 15pFC1 4.7µF 1µF V OUT –12V 30mA VIN SW FB SDREF GND LT3462 C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R EMK212BJ105MG C3: TAIYO YUDEN EMK316BJ225 L1, L2: MURATA LQH32CN470

3462 TA02a

D VIN 2.7V TO 4.2V L1A 22µH L1B 22µH 267k 42.2k 4.7µF 15pFC1 4.7µF 1µF V OUT –8V VIN SW FB SDREF GND LT3462 C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R EMK212BJ105MG C3: TAIYO YUDEN LMK316BJ475 L1: SUMIDA CLS62-220 OR 2X MURATA LQH32CN330

3462 TA03a

D LOAD CURRENT (mA) EFFICIENCY (%)

3462 TA03b

TA = 25°C VIN = 3.3V –8V Efficiency 2ms/DIV IIN 100mA/DIV OFF VOUT 10V/DIV

3462 TA02c

VOUT Reaches –12V in 750µs; Input Current Peaks at 300mA without CS1 VOUT Reaches –12V in 7.5ms; Input Current Peaks at 125mA with CS1 = 100nF 2ms/DIV IIN 50mA/DIV OFF VOUT 10V/DIV

3462 TA02d

(Reference LTC DWG # 05-08-1636) 1.50 – 1.75 (NOTE 4)2.80 BSC 0.30 – 0.45

6 PLCS (NOTE 3)

DATUM ‘A’ 0.09 – 0.20 (NOTE 3) S6 TSOT-23 0302

2.90 BSC

(NOTE 4)

0.95 BSC

1.90 BSC

0.80 – 0.90

1.00 MAX

0.01 – 0.100.20 BSC 0.30 – 0.50 REF PIN ONE ID NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193

3.85 MAX

0.62 MAX 0.95 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 1.4 MIN2.62 REF

1.22 REF

Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 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. TYPICAL APPLICATIO SU VIN 2.7V TO 4.2V L1A 10µH L1B 10µH 267k 42.2k 4.7µF 22pFC1 1µF 1µF V OUT –8V 35mA VIN SW FB SDREF GND LT3462A C1: TAIYO YUDEN JMK107BJ105MA C2: TAIYO YUDEN EMK212BJ105MA C3: TAIYO YUDEN LMK316BJ475 L1: WURTH 50310057-100

3462 TA04a

D VIN 22µH 22µH 267k 68.1k 10µF 22pFC1 1µF 1µF V OUT –5V 100mA VIN SW FB SDREF GND LT3462A C1: TAIYO YUDEN JMK107BJ105MA C2: TAIYO YUDEN EMK212BJ105MA C3: MURATA GRM219R60J106KE19B L1, L2: MURATA LQH32CN220

3462 TA05a

D 5V to –5V Supply (LT3462A)3.3V to –8V (LT3462A) Switching Waveform 200ns/DIV VOUT 1mV/DIV AC COUPLED VSW 10V/DIV

3462 TA05b

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com  LINEAR TECHNOLOGY CORPORATION 2004 LT/TP 0304 1K • PRINTED IN USA RELATED PARTS TYPICAL APPLICATIO SU 12V to –36V DC/DC Converter VIN 12V 47µH 432k 15k 1µF 50V 5pF 1µF 0.47µF V OUT –36V 36mA VIN SW FB SDREF GND LT3462 C1: TAIYO YUDEN X5R EMK212BJ105 C2: MURATA GRM42-6X7R474K50 C3: MURATA GRM42-6X7R474K50 ×2 D1: CENTRAL CMSH5-4-LTN L1: MURATA LQH32CN470

3462 TA06a

D 100nF –36V Efficiency LOAD CURRENT (mA) EFFICIENCY (%)

3462 TA06b

TA = 25°C VIN = 12V PART NUMBER DESCRIPTION COMMENTS LT1617/LT1617-1 350mA/100mA (I SW) High Efficiency V IN: 1.2V to 15V, VOUT(MAX) = –34V, IQ = 20µA, ISD <1µA Micropower Inverting DC/DC Converter ThinSOT Package LT1931/LT1931A 1A (I SW), 1.2MHz/2.2MHz, High Efficiency V IN: 2.6V to 16V, VOUT(MAX) = –34V, IQ = 5.8mA, ISD <1µA Micropower Inverting DC/DC Converter ThinSOT Package LT1945 Dual Output, Boost/Inverter, 350mA (I SW), Constant V IN: 1.2V to 15V, VOUT(MAX) = ±34V, IQ = 40µA, ISD <1µA, Off-Time, High Efficiency Step-Up DC/DC Converter MS10 Package Step-Up DC/DC Converter MS8 Package LT3463 Dual Output, Boost/Inverter, 250mA (I SW), Constant V IN: 2.3V to 15V, VOUT(MAX) = ±40V, IQ = 40µA, ISD <1µA Off-Time, High Efficiency Step-Up DC/DC Converter DFN Package with Integrated Schottky Diodes LT3464 85mA (I SW), High Efficiency Step-Up DC/DC Converter V IN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD <1µA with Integrated Schottky and PNP Disconnect ThinSOT Package