Datasheet LT3972 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | 33V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75μA Quiescent Current |
| Pages / Page | 24 / 1 — FEATURES. DESCRIPTION. Wide Input Range:. Operation from 3.6V to 33V. … |
| File Format / Size | PDF / 346 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Range:. Operation from 3.6V to 33V. Overvoltage Lockout Protects Circuits
Model Line for this Datasheet
Text Version of Document
LT3972 33V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75µA Quiescent Current
FEATURES DESCRIPTION
■
Wide Input Range:
The LT®3972 is an adjustable frequency (200kHz to 2.4MHz)
Operation from 3.6V to 33V
monolithic buck switching regulator that accepts input
Overvoltage Lockout Protects Circuits
voltages up to 33V (62V maximum). A high effi ciency
Through 62V Transients
95mΩ switch is included on the die along with a boost ■
3.5A Maximum Output Current
Schottky diode and the necessary oscillator, control and ■
Low Ripple (<15mVP-P) Burst Mode
®
Operation:
logic circuitry. Current mode topology is used for fast
IQ = 75μA at 12VIN to 3.3VOUT
transient response and good loop stability. Low ripple ■
Adjustable Switching Frequency: 200kHz to 2.4MHz
Burst Mode operation maintains high effi ciency at low ■
Low Shutdown Current: IQ < 1μA
output currents while keeping output ripple below 15mV ■
Integrated Boost Diode
in a typical application. In addition, the LT3972 can fur- ■
Synchronizable Between 250kHz to 2MHz
ther enhance low output current effi ciency by drawing ■ Power Good Flag bias current from the output when VOUT is above 3V. ■ Saturating Switch Design: 95mΩ On-Resistance Shutdown reduces input supply current to less than 1μA ■ Output Voltage: 0.79V to 30V while a resistor and capacitor on the RUN/SS pin provide a ■ Thermal Protection controlled output voltage ramp (soft-start). A power good ■ Soft-Start Capability fl ag signals when VOUT reaches 91% of the programmed ■ Small 10-Pin Thermally Enhanced MSOP and output voltage. The LT3972 is available in 10-pin MSOP (3mm × 3mm) DFN Packages and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.
APPLICATIONS
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their ■ Automotive Battery Regulation respective owners. ■ Distributed Supply Regulation ■ Industrial Supplies ■ Wall Transformer Regulation
TYPICAL APPLICATION 5V Step-Down Converter Effi ciency
V V OUT 100 IN 5V 6.3V TO 33V 3.5A TRANSIENT VIN = 12V V TO 62V IN BD 90 OFF ON RUN/SS BOOST VIN = 30V 80 V 0.47μF IN = 24V 15k 4.7μH V LT3972 SW C 10μF 70 RT EFFICIENCY (%) 680pF PG 60 536k VOUT = 5V 63.4k SYNC FB L = 4.7μH GND f = 600kHz 100k 47μF 50 0 0.5 1 1.5 2 2.5 3 3.5 OUTPUT CURRENT (A) 3972 TA01 3972 TA01a 3972fa 1
FEATURES DESCRIPTION
■
Wide Input Range:
The LT®3972 is an adjustable frequency (200kHz to 2.4MHz)
Operation from 3.6V to 33V
monolithic buck switching regulator that accepts input
Overvoltage Lockout Protects Circuits
voltages up to 33V (62V maximum). A high effi ciency
Through 62V Transients
95mΩ switch is included on the die along with a boost ■
3.5A Maximum Output Current
Schottky diode and the necessary oscillator, control and ■
Low Ripple (<15mVP-P) Burst Mode
®
Operation:
logic circuitry. Current mode topology is used for fast
IQ = 75μA at 12VIN to 3.3VOUT
transient response and good loop stability. Low ripple ■
Adjustable Switching Frequency: 200kHz to 2.4MHz
Burst Mode operation maintains high effi ciency at low ■
Low Shutdown Current: IQ < 1μA
output currents while keeping output ripple below 15mV ■
Integrated Boost Diode
in a typical application. In addition, the LT3972 can fur- ■
Synchronizable Between 250kHz to 2MHz
ther enhance low output current effi ciency by drawing ■ Power Good Flag bias current from the output when VOUT is above 3V. ■ Saturating Switch Design: 95mΩ On-Resistance Shutdown reduces input supply current to less than 1μA ■ Output Voltage: 0.79V to 30V while a resistor and capacitor on the RUN/SS pin provide a ■ Thermal Protection controlled output voltage ramp (soft-start). A power good ■ Soft-Start Capability fl ag signals when VOUT reaches 91% of the programmed ■ Small 10-Pin Thermally Enhanced MSOP and output voltage. The LT3972 is available in 10-pin MSOP (3mm × 3mm) DFN Packages and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.
APPLICATIONS
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their ■ Automotive Battery Regulation respective owners. ■ Distributed Supply Regulation ■ Industrial Supplies ■ Wall Transformer Regulation
TYPICAL APPLICATION 5V Step-Down Converter Effi ciency
V V OUT 100 IN 5V 6.3V TO 33V 3.5A TRANSIENT VIN = 12V V TO 62V IN BD 90 OFF ON RUN/SS BOOST VIN = 30V 80 V 0.47μF IN = 24V 15k 4.7μH V LT3972 SW C 10μF 70 RT EFFICIENCY (%) 680pF PG 60 536k VOUT = 5V 63.4k SYNC FB L = 4.7μH GND f = 600kHz 100k 47μF 50 0 0.5 1 1.5 2 2.5 3 3.5 OUTPUT CURRENT (A) 3972 TA01 3972 TA01a 3972fa 1
