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LINEAR TECHNOLOGY LT3972 Data Sheet manual instructions

Summary

The LT3972 is a high-efficiency, adjustable frequency step-down (buck) switching regulator designed for demanding power supply applications. It provides reliable voltage conversion across a wide input range (3.6V to 33V), featuring low ripple (<15mV) and integrated protections like soft-start and thermal management. Ideal for industrial and distributed power systems, this highly compact regulator includes advanced features such as burst mode control and an integrated boost diode. The technical manual provides comprehensive details on electrical specifications, package configuration, and typical application circuits to facilitate precise system integration.

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LT3972

33V, 3.5A, 2.4MHz

Step-Down Switching Regulator with 75µA Quiescent Current DESCRIPTION FEATURES

■ Wide Input Range: The LT®3972 is an adjustable frequency (200k Hz to 2.4MHz) Operation from 3.6V to 33V monolithic buck switching regulator that accepts input Over-Voltage 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 (<15m VP-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: 200k Hz to 2.4MHz Burst Mode operation maintains high effi ciency at low ■ Low Shutdown Current: IQ < 1μA output currents while keeping output ripple below 15m V ■ Integrated Boost Diode in a typical application. In addition, the LT3972 can fur- ■ Synchronizable Between 250k Hz 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

EF FI CI EN CY

■ 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

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation.

■ Automotive Battery Regulation All other trademarks are the property of their respective owners.

■ Distributed Supply Regulation

■ Industrial Supplies

■ Wall Transformer Regulation

TYPICAL APPLICATION

5V Step-Down Converter Effi ciency

6.3V TO 33V

3.5A VIN = 12V

TRANSIENT

TO 62V VIN BD

RUN/SS BOOST VIN = 30V

OFF ON

VIN = 24V

VC LT3972 SW

PG VOUT = 5V

63.4k SYNC FB

GND f = 600k Hz

OUTPUT CURRENT (A)

3680 TA01a

3680 TA01

Page Summary Contents For LINEAR TECHNOLOGY LT3972 Data Sheet manual instructions

Page 1 LT3972 33V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75µA Quiescent Current DESCRIPTION FEATURES ■ Wide Input Range: The LT®3972 is an adjustable frequency (200k Hz to 2.4MHz) Operation from 3....
Page 2 LT3972 ABSOLUTE MAXIMUM RATINGS (Note 1) VIN, RUN/SS Voltage (Note 5) ...................................62V Operating Junction Temperature Range (Note 2) BOOST Pin Voltage ..............................
Page 3 LT3972 ELECTRICAL CHARACTERISTICS The ● denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at TA = 25°C. VIN = 10V, VRUN/SS = 10V, VBOOST ...
Page 4 EF FI CI EN CY LT3972 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C unless otherwise noted. Effi ciency Effi ciency Effi ciency VIN = 12V VIN = 12V 2.5 VIN = 30V VIN = 30V VIN = 24V 2.0 VIN = 24V IT I...
Page 5 IT IM IT FR z) LT3972 TA = 25°C unless otherwise noted. TYPICAL PERFORMANCE CHARACTERISTICS Switch Voltage Drop Boost Pin Current Feedback Voltage IT IN k H z) /S IN SWITCH CURRENT (A) SWITCH CURRENT ...
Page 6 LT3972 TA = 25°C unless otherwise noted. TYPICAL PERFORMANCE CHARACTERISTICS Error Amp Output Current Minimum Input Voltage Minimum Input Voltage 3.0 IN VOUT = 3.3V VOUT = 5V –30 4.5 TA = 25 °C 2.5 TA...
Page 7 LT3972 PIN FUNCTIONS BD (Pin 1): This pin connects to the anode of the boost SYNC (Pin 6): This is the external clock synchronization Schottky diode. BD also supplies current to the internal input. Gr...
Page 8 LT3972 OPERATION The LT3972 is a constant frequency, current mode step- to generate a voltage at the BOOST pin that is higher than down regulator. An oscillator, with frequency set by RT, the input su...
Page 9 LT3972 APPLICATIONS INFORMATION FB Resistor Network where VIN is the typical input voltage, VOUT is the output voltage, VD is the catch diode drop (~0.5V) and VSW is the The output voltage is programm...
Page 10 LT3972 APPLICATIONS INFORMATION the ripple current is: +– VIN MAX SW( ΔIL = 0.4(IOUT(MAX)) SW ON MIN where IOUT(MAX) is the maximum output load current. To where VIN(MAX) is the maximum operating inpu...
Page 11 LT3972 APPLICATIONS INFORMATION Table 1. Inductor Vendors Step-down regulators draw current from the input sup- VENDOR URL PART SERIES TYPE ply in pulses with very fast rise and fall times. The input ...
Page 12 LT3972 APPLICATIONS INFORMATION Table 2. Capacitor Vendors VENDOR PHONE URL PART SERIES COMMANDS Panasonic (714) 373-7366 www.panasonic.com Ceramic, Polymer, EEF Series Tantalum Kemet (864) 963-6300 w...
Page 13 LT3972 APPLICATIONS INFORMATION Frequency Compensation well as long as the value of the inductor is not too high and the loop crossover frequency is much lower than the The LT3972 uses current mode co...
Page 14 LT3972 APPLICATIONS INFORMATION Low-Ripple Burst Mode and Pulse-Skip Mode that the LT3972 will enter full frequency standard PWM operation at a lower output load current than when in Burst The LT3972 ...
Page 15 LT3972 APPLICATIONS INFORMATION VOUT 6.0 BD 5.5 TO START BOOST (WORST CASE) VIN VIN LT3972 C3 SW 4.7μF GND 4.0 TO RUN 3.5 3.0 VOUT = 3.3V TA = 25°C (5a) For VOUT &gt; 2.8V 2.5 L = 8.2μH f = 700k Hz 2....
Page 16 LT3972 APPLICATIONS INFORMATION plications or in battery backup systems where a battery or some other supply is diode OR-ed with the LT3972’s RUN 1A/DIV output. If the VIN pin is allowed to fl oat and...
Page 17 LT3972 APPLICATIONS INFORMATION traces will shield them from the SW and BOOST nodes. The Exposed Pad on the bottom of the package must be soldered to ground so that the pad acts as a heat sink. To kee...
Page 18 LT3972 APPLICATIONS INFORMATION voltage at the VIN pin of the LT3972 can ring to twice the to ambient can be reduced to JA = 35°C/W or less. With nominal input voltage, possibly exceeding the LT3972’s...
Page 19 LT3972 TYPICAL APPLICATIONS 3.3V Step-Down Converter 4.4V TO 33V TRANSIENT VIN BD TO 62V ON OFF RUN/SS BOOST VC SW LT3972 63.4k SYNC f = 600k Hz 3680 TA03 D: ON SEMI MBRA340 L: NEC MPLC0730L3R3 2.5V S...
Page 20 LT3972 TYPICAL APPLICATIONS 5V, 2MHz Step-Down Converter VIN VOUT 8.6V TO 22V 5V TRANSIENT 2.5A TO 62V VIN BD ON OFF RUN/SS BOOST VC SW LT3972 SYNC FB f = 2MHz 3680 TA05 D: ON SEMI MBRA340 L: NEC MPLC...
Page 21 LT3972 TYPICAL APPLICATIONS 1.8V Step-Down Converter VIN 1.8V 3.5V TO 27V 3.5A VIN BD ON OFF RUN/SS BOOST VC SW LT3972 SYNC FB f = 500k Hz 3680 TA08 D: ON SEMI MBRA340 L: NEC MPLC0730L3R3
Page 22 LT3972 PACKAGE DESCRIPTION DD Package 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699) 0.05 (2 SIDES)2.15 PACKAGE OUTLINE 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND ...
Page 23 LT3972 PACKAGE DESCRIPTION MSE Package 10-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1664 Rev B) BOTTOM VIEW OF EXPOSED PAD OPTION TYP BSC (NOTE 3) RECOMMENDED SOLDER PAD LAYOUT (NO...
Page 24 LT3972 TYPICAL APPLICATION 1.2V Step-Down Converter VIN 1.2V 3.6V TO 27V 3.5A VIN BD ON OFF RUN/SS BOOST VC SW LT3972 78.7k FB f = 500k Hz 3680 TA09 D: ON SEMI MBRA340 L: NEC MPLC0730L3R3 RELATED PART...

Manual Details

Brand Linear
Pages 24
File Size 287.51 KB
Published June 16, 2026
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Frequently Asked Questions

What is the specified junction temperature operating range?

The operational junction temperature range for these components is –40°C to 125°C.

How does the device signal successful power-up and voltage stability?

It features a Power Good flag, which signals when the output voltage reaches 91% of the programmed OUT voltage.

What are the key benefits of using Burst Mode operation?

Burst Mode maintains high efficiency at low output currents while ensuring minimum output ripple below 15mV.