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reference designIS31LT3957 | Demoboard IS31LT3957-ZLS4-EBSEPIC

ISSI IS31LT3957 | Demoboard IS31LT3957-ZLS4-EBSEPIC

HIGH VOLTAGE LED LIGHTING CONTROLLER WITH FAULT PROTECTION

Overview

TopologySEPIC Buck-Boost Topology
Input voltage5-75 V
Switching frequency100-1000 kHz
IC revisionB

Description

The IS31LT3957 is a current mode PWM controller designed to drive a low side external NMOS FET for wide input/output voltage range and high LED current applications. An external resistor senses the high side output current of the LED string. A high side sense is the most flexible current sensing scheme, since it functions in either boost or buck-boost mode configurations. The controller can be configured with an external resistor to operate between 100kHz~1MHz frequency resulting in small external inductor and capacitors while maintaining high efficiency. A single capacitor is all that is required to set the spread spectrum dither frequency to reduce the radiated peak emission and optimize the system EMI performance.

Features

  • Wide high voltage input range: 5V to 75V
  • Supports boost, buck-boost, SEPIC and buck topology
  • ±2% output current accuracy
  • Adjustable operating frequency range of 100kHz~1MHz
  • Programmable soft start to avoid inrush current
  • Fixed under voltage lockout threshold
  • EMI reduction capabilities
  • Programmable spread spectrum function
  • Operating frequency synchronization with external clock source
  • Supports either analog or PWM dimming
  • Fault protection with reporting:
  • VCC under voltage lockout (not reported)
  • Programmable output over voltage protection
  • Output short circuit protection
  • RT/SYNC pin short protection
  • VDD pin short protection
  • VDD under voltage lockout (not reported)
  • Over temperature protection

Typical applications

  • General high power LED, Architecture lighting, Motorcycle headlight, Exit Signs and Emergency Lighting

More information

Parts approved by ISSI

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Order Code
Data­sheet
Simu­lation
Downloads
Status
Product series
L1(µH)
L2(µH)
IR(A)
IR 2(A)
ISAT(A)
RDC1 typ(Ω)
RDC2 typ(Ω)
RDC1 max(Ω)
RDC2 max(Ω)
fres(MHz)
Type
SamplesAvailability & Sample
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744870100
SPECWE-DD SMT Shielded Coupled Inductor, 10 µH, 10 µH
Simu­lation
Availability
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Downloads9 files

Status
ActiveProduction is active. Expected lifetime: >10 years.
iProduction is active. Expected lifetime: >10 years.
Product seriesWE-DD SMT Shielded Coupled Inductor
Inductance 110 µH
Inductance 210 µH
Rated Current2.7 A
Rated Current 22.7 A
Saturation Current7 A
DC Resistance 10.038 Ω
DC Resistance 20.038 Ω
DC Resistance 10.044 Ω
DC Resistance 20.044 Ω
Self Resonant Frequency18 MHz
TypeCrossed 
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