Datasheet LT3685 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | 36V, 2A, 2.4MHz Step-Down Switching Regulator |
| Pages / Page | 24 / 1 — FEATURES. DESCRIPTION. Wide Input Range:. Operation From 3.6V to 36V. … |
| File Format / Size | PDF / 282 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Range:. Operation From 3.6V to 36V. Overvoltage Lockout Protects Circuit through. 60V. Transients
Model Line for this Datasheet
Text Version of Document
LT3685 36V, 2A, 2.4MHz Step-Down Switching Regulator
FEATURES DESCRIPTION
■
Wide Input Range:
The LT®3685 is an adjustable frequency (200kHz to 2.4MHz)
Operation From 3.6V to 36V
monolithic step-down switching regulator that accepts
Overvoltage Lockout Protects Circuit through
input voltages up to 38V operating and 60V maximum. An
60V Transients
internal overvoltage protection circuit turns off the power ■
2A Maximum Output Current
switch when VIN is above 38V typical (36V minimum) which ■
Adjustable Switching Frequency: 200kHz to 2.4MHz
then allows the part to safely withstand 60V transients. A ■
Low Shutdown Current: IQ < 1μA
high effi ciency 0.25 switch is included on the die along ■
Integrated Boost Diode
with a boost Schottky diode and the necessary oscillator, ■
Synchronizable Between 250kHz to 2MHz
control, and logic circuitry. Current mode topology is ■ Power Good Flag used for fast transient response and good loop stability. ■ Saturating Switch Design: 0.25 On-Resistance The LT3685’s high operating frequency allows the use of ■ 0.790V Feedback Reference Voltage small, low cost inductors and ceramic capacitors result- ■ Output Voltage: 0.79V to 20V ing in low output ripple while keeping total solution size ■ Soft-Start Capability to a minimum. The low current shutdown mode reduces ■ Small 10-Pin Thermally Enhanced MSOP and input supply current to less than 1μA while a resistor and (3mm × 3mm) DFN Packages capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good fl ag signals when
APPLICATIONS
VOUT reaches 89% of the programmed output voltage. The LT3685 is available in 10-Pin MSOP and 3mm × 3mm DFN ■ Automotive Battery Regulation packages with exposed pads for low thermal resistance. ■ Set Top Box ■ Distributed Supply Regulation , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other ■ Industrial Supplies trademarks are the property of their respective owners. ■ Wall Transformer Regulation
TYPICAL APPLICATION 3.3V Step-Down Converter Effi ciency
V 100 IN VOUT 4.5V TO 36V 3.3V TRANSIENT 2A V V OUT = 5V IN BD TO 60V 90 OFF ON RUN/SS BOOST VOUT = 3.3V 0.47μF 80 14k 4.7μH V LT3685 SW C 4.7μF 70 RT 470pF EFFICIENCY (%) PG 60 316k 40.2k SYNC V FB IN = 12V GND L = 5.6μH F = 800 kHz 100k 22μF 50 0 0.5 1.0 1.5 2 LOAD CURRENT (A) 3685 TA01 3685 TA01b 3685fb 1
FEATURES DESCRIPTION
■
Wide Input Range:
The LT®3685 is an adjustable frequency (200kHz to 2.4MHz)
Operation From 3.6V to 36V
monolithic step-down switching regulator that accepts
Overvoltage Lockout Protects Circuit through
input voltages up to 38V operating and 60V maximum. An
60V Transients
internal overvoltage protection circuit turns off the power ■
2A Maximum Output Current
switch when VIN is above 38V typical (36V minimum) which ■
Adjustable Switching Frequency: 200kHz to 2.4MHz
then allows the part to safely withstand 60V transients. A ■
Low Shutdown Current: IQ < 1μA
high effi ciency 0.25 switch is included on the die along ■
Integrated Boost Diode
with a boost Schottky diode and the necessary oscillator, ■
Synchronizable Between 250kHz to 2MHz
control, and logic circuitry. Current mode topology is ■ Power Good Flag used for fast transient response and good loop stability. ■ Saturating Switch Design: 0.25 On-Resistance The LT3685’s high operating frequency allows the use of ■ 0.790V Feedback Reference Voltage small, low cost inductors and ceramic capacitors result- ■ Output Voltage: 0.79V to 20V ing in low output ripple while keeping total solution size ■ Soft-Start Capability to a minimum. The low current shutdown mode reduces ■ Small 10-Pin Thermally Enhanced MSOP and input supply current to less than 1μA while a resistor and (3mm × 3mm) DFN Packages capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good fl ag signals when
APPLICATIONS
VOUT reaches 89% of the programmed output voltage. The LT3685 is available in 10-Pin MSOP and 3mm × 3mm DFN ■ Automotive Battery Regulation packages with exposed pads for low thermal resistance. ■ Set Top Box ■ Distributed Supply Regulation , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. All other ■ Industrial Supplies trademarks are the property of their respective owners. ■ Wall Transformer Regulation
TYPICAL APPLICATION 3.3V Step-Down Converter Effi ciency
V 100 IN VOUT 4.5V TO 36V 3.3V TRANSIENT 2A V V OUT = 5V IN BD TO 60V 90 OFF ON RUN/SS BOOST VOUT = 3.3V 0.47μF 80 14k 4.7μH V LT3685 SW C 4.7μF 70 RT 470pF EFFICIENCY (%) PG 60 316k 40.2k SYNC V FB IN = 12V GND L = 5.6μH F = 800 kHz 100k 22μF 50 0 0.5 1.0 1.5 2 LOAD CURRENT (A) 3685 TA01 3685 TA01b 3685fb 1
