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LINEAR TECHNOLOGY LT1676 User Guide

Summary

This high-efficiency step-down switching regulator is engineered for robust power conversion, handling exceptionally wide input voltages up to 60V. Featuring advanced True Current Mode Control and Adaptive Switch Drive, it ensures consistent performance across both heavy loads and light load conditions. Ideal for demanding sectors such as automotive DC/DC converters, telecommunications equipment, and battery charging systems. The documentation provides comprehensive details on electrical specifications, operating modes, package options, and typical application circuits for reliable integration.

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LT1676

Wide Input Range, High Efficiency, Step-Down Switching Regulator

FEATURES DESCRIPTIO Wide Input Range: 7.4V to 60V The LT®1676 is a wide input range, high efficiency Buck 700m A Peak Switch Current Rating (step-down) switching regulator. The monolithic die in- Adaptive Switch Drive Maintains Efficiency at High cludes all oscillator, control and protection circuitry. The Load Without Pulse Skipping at Light Load part can accept input voltages as high as 60V and contains True Current Mode Control an output switch rated at 700m A peak current. Current 100k Hz Fixed Operating Frequency mode control offers excellent dynamic input supply rejec- Synchronizable to 250k Hz tion and short-circuit protection. Low Supply Current in Shutdown: 30µA

The LT1676 contains several features to enhance effi-

Available in 8-Pin SO and PDIP Packages

ciency. The internal control circuitry is normally powered via the VCC pin, thereby minimizing power drawn directly APPLICATIO S from the VIN supply (see Applications Information). The action of the LT1676 switch circuitry is also load depen-

Automotive DC/DC Converters

dent. At medium to high loads, the output switch circuitry

Telecom 48V Step-Down Converters

EF FI CI EN CY maintains high rise time for good efficiency. At light loads,

Cellular Phone Battery Charger Accessories

rise time is deliberately reduced to avoid pulse skipping

IEEE 1394 Step-Down Converters

behavior. The available SO-8 package and 100k Hz switching fre- quency allow for minimal PC board area requirements. , LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATIO VIN Efficiency vs VIN and ILOAD 8V TO 50V

VIN SHDN VCC

MBR160 36.5k

LT1676

FB SYNC VC

2200p F VIN = 12V

VIN = 24V

GND 22k 100p F

VIN = 36V VIN = 48V

*65T #30 ON MAGNETICS 1676 F01

MPP #55030

ILOAD (m A)

1676 TA01

Figure 1

Page Summary Contents For LINEAR TECHNOLOGY LT1676 User Guide

Page 1 LT1676 Wide Input Range, High Efficiency, Step-Down Switching Regulator FEATURES DESCRIPTIO Wide Input Range: 7.4V to 60V The LT®1676 is a wide input range, high efficiency Buck 700m A Peak Switch Cur...
Page 2 LT1676 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Supply Voltage 60V ORDER PART TOP VIEW Switch Voltage 60V NUMBER SHDN, SYNC Pin Voltage 7V SHDN VC LT1676CN8 VCC Pin Voltage 30V VCC ...
Page 3 IN PU VO LT AG (V LT1676 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 48V, VSW open, VCC...
Page 4 IN OL TA GE (V SW IT CH IN FR EQ UE NC (k Hz SH DN IN OL TA GE (m V) LT1676 TYPICAL PERFORMANCE CHARACTERISTICS SHDN Pin Shutdown Threshold SHDN Pin Input Current SHDN Pin Lockout Thresholds vs Temper...
Page 5 LT1676 PIN FUNCTIONS SHDN (Pin 1): When pulled below the shutdown mode short as possible to minimize electromagnetic radiation threshold, nominally 0.30V, this pin turns off the regula- and voltage sp...
Page 6 LT1676 BLOCK DIAGRA VCC VIN5 R1 RSENSE SHDN BIAS SWDR SWON SYNC LOGICOSC BOOST SWOFF VSW BOOST COMP FB VTH BOOST SWOFF Q5 1676 BD OPERATIO The LT1676 is a current mode switching regulator IC that Outp...
Page 7 LT1676 OPERATIO Please refer to the High d V/dt Mode Timing Diagram. A threshold reference, VTH. (Remember that in a current typical oscillator cycle is as follows: The logic section first mode switch...
Page 8 LT1676 APPLICATIONS INFORMATION Once the inductance value is decided, inductor peak internal switch will ramp up VIN current into the diode in an current rating and resistance need to be considered. H...
Page 9 LT1676 APPLICATIONS INFORMATION which tantalum capacitors are generally unavailable. Rela- t ON(MIN). When combined with the large ratio of VIN to tively bulky “high frequency” aluminum electrolytic t...
Page 10 LT1676 APPLICATIONS INFORMATION oscillator frequency during short-circuit conditions can Power loss internal to the LT1676 related to actual output then maintain control with the effective minimum ON ...
Page 11 LT1676 APPLICATIONS INFORMATION frequency resonance problems, proper layout of the com- i.e., SHDN, SYNC, VC and FB. This can cause erratic ponents connected to the IC is essential, especially the ope...
Page 12 LT1676 TYPICAL APPLICATIONS VIN 12V TO 48V VIN SHDN VCC VSW 5V C1 L1 +D1 C2 0m A to 500m A 39µF LT1676 220µH 100µF 100p F MBRS1100 36.5k SYNC VC 22k 5% VIN = 12V VIN = 24V C1: PANASONIC HFQ FOR 3.3V V...
Page 13 LT1676 TYPICAL APPLICATIONS Micropower Undervoltage Lockout A possible way to improve light load efficiency is in Burst Mode operation. Certain applications may require very low current drain when in ...
Page 14 LT1676 TYPICAL APPLICATIONS to maintain proper short-circuit protection. Transistors Minimum Size Inductor Application Q1, Q2 and resistor R7 form a high VIN, low quiescent Figure 4a employs power pat...
Page 15 LT1676 TYPICAL APPLICATIONS VIN SYNC VCC 10M VOUT Q1 LT1676 PN2484 FB Q2 VCSHDN C1: PANASONIC HFQ 39µF AT 63V OUTA INA+ C2: AVX D CASE 100µF 10V INB– TPSD107M010R0080 U2 R5 D1: MOTOROLA 100V, 1A, LTC1...
Page 16 LT1676 TYPICAL APPLICATION Minimum Inductor Size Application VIN 12V TO 48V VIN SHDN VCC C5 VSW 5V 100p F L1 C2 0m A to 150m A LT1676 FB VCSYNC 1676 TA02 C1: PANASONIC HFQ D1: MOTOROLA 100V, 1A, SMD S...

Manual Details

Brand Linear
Pages 16
File Size 140.15 KB
Published June 01, 2026
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Frequently Asked Questions

What is the wide input voltage range for this regulator?

The LT1676 supports a very wide input range, accommodating voltages from 7.4V up to 60V.

How does the unit maintain high efficiency under varying load conditions?

It uses an Adaptive Switch Drive that maintains high efficiency at medium/high loads and keeps it stable at light loads to prevent pulse skipping.

What is the minimum current draw when operating in shutdown mode?

The supply current consumed in shutdown mode is very low, specified at 30µA.

Does the unit offer synchronizable operation?

Yes, the switching frequency can be synchronized (SYNC pin) up to a range of 130 kHz to 250 kHz.