LT1615/LT1615-1 DC/DC Converters - Analog Devices

1 LT1615/LT1615-1 . Micropower Step-Up DC/DC Converters in ThinSOT. U. FEATURES DESCRIPTIO. Low Quiescent current : The LT 1615/LT1615-1 are micropower step-up DC/DC . 20 A in Active Mode Converters in a 5-lead low profile (1mm) ThinSOT pack- <1 A in Shutdown Mode age. The LT1615 is designed for higher power systems Operates with VIN as Low as 1V with a 350mA current limit and an input voltage range of Low VCESAT Switch: 250mV at 300mA to 15V, whereas the LT1615-1 is intended for lower Uses Small Surface Mount Components power and single-cell applications with a 100mA current High Output Voltage: Up to 34V limit and an extended input voltage range of 1V to 15V.

2 Low Profile (1mm) ThinSOTTM Package Otherwise, the two Devices are functionally equivalent. Both Devices feature a quiescent current of only 20 A at no U load, which further reduces to A in shutdown. A. APPLICATIO S current limited, fixed off-time control scheme conserves LCD Bias operating current , resulting in high efficiency over a broad Handheld Computers range of load current . The 36V switch allows high voltage Battery Backup outputs up to 34V to be easily generated in a simple boost Digital Cameras topology without the use of costly transformers. The LT1615's low off-time of 400ns permits the use of tiny, low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications.

3 , LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. U. TYPICAL APPLICATIO. 1-Cell Li-Ion to 20V Converter for LCD Bias Efficiency 85. L1. D1. 10 H. VIN 20V 80. TO 12mA VIN = 75. R1. EFFICIENCY (%). VIN SW VIN = 2M 70 VIN = LT1615 C2. 1 F. SHDN FB 65. C1 GND R2. F 130k 60. C1: TAIYO YUDEN LMK316BJ475 1615/-1 TA01. 55. C2: TAIYO YUDEN TMK316BJ105. D1: MOTOROLA MBR0530 50. L1: MURATA LQH3C100K24 1 3 10 30. LOAD current (mA). 1615/-1 TA01a sn16151 16151fas 1. LT1615/LT1615-1 . W W W U U W U. ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO. (Note 1). ORDER PART. VIN, SHDN Voltage.

4 15V NUMBER. SW Voltage .. 36V. TOP VIEW LT1615ES5. FB Voltage ..VIN. LT1615ES5-1. current into FB Pin .. 1mA SW 1 5 VIN. GND 2 LT1615IS5. Junction Temperature .. 125 C. FB 3 4 SHDN LT1615IS5-1. Operating Temperature Range (Note 2) .. 40 C to 85 C. Storage Temperature Range .. 65 C to 150 C S5 PACKAGE. S5 PART MARKING. 5-LEAD PLASTIC SOT-23. Lead Temperature (Soldering, 10 sec).. 300 C. TJMAX = 125 C, JA = 256 C/W LTIZ. LTKH. LTXZ. LTBHT. Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C.

5 VIN = , VSHDN = unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS. Minimum Input Voltage LT1615-1 V. LT1615 V. Quiescent current Not Switching 20 30 A. VSHDN = 0V 1 A. FB Comparator Trip Point V. FB Comparator Hysteresis 8 mV. Output Voltage Line Regulation < VIN < 12V %/V. FB Pin Bias current (Note 3) VFB = 30 80 nA. Switch Off Time VFB > 1V 400 ns VFB < s Switch VCESAT ISW = 70mA (LT1615-1) 85 120 mV. ISW = 300mA (LT1615) 250 350 mV. Switch current Limit LT1615-1 75 100 125 mA. LT1615 300 350 400 mA. SHDN Pin current VSHDN = 2 3 A. VSHDN = 5V 8 12 A. SHDN Input Voltage High V. SHDN Input Voltage Low V. Switch Leakage current Switch Off, VSW = 5V 5 A.

6 Note 1: Absolute Maximum Ratings are those values beyond which the life characterization and correlation with statistical process controls. The of a device may be impaired. LT1615I/LT1615I-1 is guaranteed to meet performance specifications over Note 2: The LT1615E and LT1615E-1 are guaranteed to meet performance the 40 C to 85 C operating temperature range. specifications from 0 C to 70 C. Specifications over the Note 3: Bias current flows into the FB pin. 40 C to 85 C operating temperature range are assured by design, sn16151 16151fas 2. LT1615/LT1615-1 . U W. TYPICAL PERFOR A CE CHARACTERISTICS. Switch Saturation Voltage Feedback Pin Voltage and (VCESAT) Bias current Quiescent current 50 25.

7 VFB = NOT SWITCHING. 40 23. QUIESCENT current ( A). FEEDBACK VOLTAGE (V). SWITCH VOLTAGE (V). VOLTAGE. BIAS current (nA). ISWITCH = 500mA. 30 21. VIN = 12V. current 20 19. ISWITCH = 300mA. VIN = 10 17. 0 15. 50 25 0 25 50 75 100 50 25 0 25 50 75 100 50 25 0 25 50 75 100. TEMPERATURE ( C) TEMPERATURE ( C) TEMPERATURE ( C). 1615/-1 G01 1615/-1 G02 1615/-1 G03. Switch Off Time Switch current Limit Shutdown Pin current 550 400 25. VIN = 12V. 350. 500. SHUTDOWN PIN current ( A). VIN = 20. 300 LT1615. SWITCH OFF TIME (ns). PEAK current (mA). 450. 250 15. VIN = 400 200. 25 C. VIN = 12V 10. 150 100 C. 350 LT1615-1 VIN = 12V. 100. VIN = 5. 300. 50. 250 0 0.

8 50 25 0 25 50 75 100 50 25 0 25 50 75 100 0 5 10 15. TEMPERATURE ( C) TEMPERATURE ( C) SHUTDOWN PIN VOLTAGE (V). 1615/-1 G04 1615/-1 G05 1615/-1 G03. U U U. PI FU CTIO S. SW (Pin 1): Switch Pin. This is the collector of the internal SHDN (Pin 4): Shutdown Pin. Tie this pin to or higher NPN power switch. Minimize the metal trace area con- to enable the device. Tie below to turn off the device. nected to this pin to minimize EMI. VIN (Pin 5): Input Supply Pin. Bypass this pin with a GND (Pin 2): Ground. Tie this pin directly to the local capacitor as close to the device as possible. ground plane. FB (Pin 3): Feedback Pin. Set the output voltage by selecting values for R1 and R2 (see Figure 1): V.

9 R1 = R2 OUT 1 .. sn16151 16151fas 3. LT1615/LT1615-1 . W. BLOCK DIAGRA. D1. L1. VIN VOUT. C1 VIN SHDN SW C2. 5 4 1. R5 R6. 40k 40k A1. +. ENABLE. VOUT.. R1. (EXTERNAL) FB Q1. 3 Q2 400ns Q3. X10 ONE-SHOT. R2 DRIVER. (EXTERNAL) R3 RESET. 30k +. R4. 140k . A2. 42mV*. GND. 2. 1615/-1 BD. * 12mV FOR LT1615-1. Figure 1. LT1615 Block Diagram U. OPERATIO. The LT1615 uses a constant off-time control scheme to current ramps back up to 350mA, then A2 resets the one- provide high efficiencies over a wide range of output shot, again allowing L1 to deliver current to the output. current . Operation can be best understood by referring to This switching action continues until the output voltage is the block diagram in Figure 1.

10 Q1 and Q2 along with R3 and charged up (until the FB pin reaches ), then A1 turns R4 form a bandgap reference used to regulate the output off the internal circuitry and the cycle repeats. The LT1615. voltage. When the voltage at the FB pin is slightly above contains additional circuitry to provide protection during , comparator A1 disables most of the internal cir- start-up and under short-circuit conditions. When the FB. cuitry. Output current is then provided by capacitor C2, pin voltage is less than approximately 600mV, the switch which slowly discharges until the voltage at the FB pin off-time is increased to s and the current limit is drops below the lower hysteresis point of A1 (typical reduced to around 250mA (70% of its normal value).)