Datasheet LT3740 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Wide Operating Range, Valley Mode, No RSENSE Synchronous Step-Down Controller |
| Pages / Page | 20 / 1 — FEATURES. DESCRIPTION. Wide VIN Range: 2.2V to 22V. Internal Boost … |
| File Format / Size | PDF / 244 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide VIN Range: 2.2V to 22V. Internal Boost Provides 6V Gate Drive. For VIN Down to 2.2V
Model Line for this Datasheet
Text Version of Document
LT3740 Wide Operating Range, Valley Mode, No RSENSE™ Synchronous Step-Down Controller
FEATURES DESCRIPTION
n
Wide VIN Range: 2.2V to 22V
The LT®3740 is a synchronous step-down switching n
Internal Boost Provides 6V Gate Drive
regulator controller that drives N-channel power MOSFET
For VIN Down to 2.2V
stages. The controller uses valley current mode architecture n
No Sensing Resistor Required
to achieve very low duty cycles with excellent transient n
Dual N-Channel MOSFET Synchronous Drive
response without requiring a sense resistor. n Valley Current Mode Control The LT3740 includes an internal step-up converter to n Optimized for High Step-Down Ratio provide a bias 7.8V higher than the input voltage for the n Power Good Output Voltage Monitor drive. This enables the part to work from an input voltage n 0.8V Reference as low as 2.2V. n Three Pin-Selected Current Limit Levels n Constant Switching Frequency: 300kHz The XREF pin is an external reference input that allows the n Programmable Soft-Start user to override the internal 0.8V feedback reference with n Output Voltage Tracking any lower value, allowing full control of the output voltage n Available in 16-Pin 5mm × 3mm DFN during operation, output voltage tracking or soft-start. The LT3740 has three current limit levels that can be
APPLICATIONS
chosen by connecting the RANGE pin to ground, open, and input respectively. n Notebook and Palmtop Computers, PDA L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. n Portable Instruments No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Distributed Power Systems
TYPICAL APPLICATION High Effi ciency Step-Down Converter Effi ciency vs Load Current
VIN 94 3V to 12V 22μH LT3740 1μF SWB BGDP 10μF 92 V V IN = 5V V BIAS IN = 3V IN 90 1Ω M1 SHDN TGATE HAT2168H 0.9μH 88 1Ω VOUT SW 1.8V 15k 10A 86 VIN = 12V XREF SN+ D1 EFFICIENCY (%) 100μF 1Ω M2 B320A 84 s 3 BGATE 0.22μF HAT2165H 82 39pF VOUT = 1.8V 15k SN– 80 V 105k C 0 2 4 6 PGND 8 10 20k LOAD CURRENT (A) RANGE GND FB 3740 TA01b 1nF 22pF 80.6k 3740 TA01a 3740fc 1
FEATURES DESCRIPTION
n
Wide VIN Range: 2.2V to 22V
The LT®3740 is a synchronous step-down switching n
Internal Boost Provides 6V Gate Drive
regulator controller that drives N-channel power MOSFET
For VIN Down to 2.2V
stages. The controller uses valley current mode architecture n
No Sensing Resistor Required
to achieve very low duty cycles with excellent transient n
Dual N-Channel MOSFET Synchronous Drive
response without requiring a sense resistor. n Valley Current Mode Control The LT3740 includes an internal step-up converter to n Optimized for High Step-Down Ratio provide a bias 7.8V higher than the input voltage for the n Power Good Output Voltage Monitor drive. This enables the part to work from an input voltage n 0.8V Reference as low as 2.2V. n Three Pin-Selected Current Limit Levels n Constant Switching Frequency: 300kHz The XREF pin is an external reference input that allows the n Programmable Soft-Start user to override the internal 0.8V feedback reference with n Output Voltage Tracking any lower value, allowing full control of the output voltage n Available in 16-Pin 5mm × 3mm DFN during operation, output voltage tracking or soft-start. The LT3740 has three current limit levels that can be
APPLICATIONS
chosen by connecting the RANGE pin to ground, open, and input respectively. n Notebook and Palmtop Computers, PDA L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. n Portable Instruments No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Distributed Power Systems
TYPICAL APPLICATION High Effi ciency Step-Down Converter Effi ciency vs Load Current
VIN 94 3V to 12V 22μH LT3740 1μF SWB BGDP 10μF 92 V V IN = 5V V BIAS IN = 3V IN 90 1Ω M1 SHDN TGATE HAT2168H 0.9μH 88 1Ω VOUT SW 1.8V 15k 10A 86 VIN = 12V XREF SN+ D1 EFFICIENCY (%) 100μF 1Ω M2 B320A 84 s 3 BGATE 0.22μF HAT2165H 82 39pF VOUT = 1.8V 15k SN– 80 V 105k C 0 2 4 6 PGND 8 10 20k LOAD CURRENT (A) RANGE GND FB 3740 TA01b 1nF 22pF 80.6k 3740 TA01a 3740fc 1
