LM5146 datasheet(16/55 Pages) TI

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8 Detailed Description

8.1 Overview

The LM5146 is a 100-V synchronous buck controller with all of the functions necessary to implement a high-

efficiency step-down power supply. The output voltage range is from 0.8 V to 60 V. The voltage-mode control

architecture uses input feedforward for excellent line transient response over a wide VIN range. Voltage-mode

control supports the wide duty cycle range for high input voltage and low dropout applications as well as when

a high-voltage conversion ratio (for example, 10-to-1) is required. Current sensing for cycle-by-cycle current limit

can be implemented with either the low-side FET RDS(on) or a current sense resistor. The operating frequency

is programmable from 100 kHz to 1 MHz. The LM5146 drives external high-side and low-side NMOS power

switches with robust 7.5-V gate drivers suitable for standard threshold MOSFETs. Adaptive dead-time control

between the high-side and low-side drivers minimizes body diode conduction during switching transitions. An

external bias supply can be connected to the VCC pin to improve efficiency in high-voltage applications. A

user-selectable diode emulation feature enables DCM operation for improved efficiency and lower dissipation at

light-load conditions.

8.2 Functional Block Diagram

VIN

VCC

BST

PGND

AGND

ILIM

ERROR

AMP

VCC

UVLO

7.5 V LDO

REGULATOR

SS/TRK

COMP

PWM

COMPARATOR

0.8 V

THERMAL

SHUTDOWN

ENABLE

LOGIC

OSCILLATOR &

FEEDFORWARD

RAMP

GENERATOR

EN/UVLO

0.4 V

HYSTERESIS

1.2 V

STANDBY

SHUTDOWN

CLK

SYNCOUT

kFF*VIN

VCC ENABLE

PWM

LOGIC

SYNCIN

SUPERVISORY

COMPARATORS

PGOOD

0.8 V + 8%

VCC

CURRENT LIMIT

COMPARATOR

7.5 V

FPWM

ILIM

LEVEL

SHIFT

ADAPTIVE

DEADTIME

DELAY

COMP

CLAMP

MODULATOR

0.8 V - 8%

25 µs

delay

5 µs

FILTER

STANDBY

PEAK

DETECT

FILTER

OCP

115 mV

RAMP

kFF*VIN + 0.3 V

0.3 V

BST_UV

VSW +

VBST-UV

³1´

VVCC-UV

DRIVER

RDS(on) or

Shunt Sensing

HICCUP

COUNTERS

CLK

CLAMP

ZERO CROSS

DETECTION

LM5146

SNVSBV0A – JUNE 2021 – REVISED JUNE 2021

www.ti.com

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