LM5145 datasheet(17/55 Pages) TI

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8.3 Feature Description

8.3.1 Input Range (VIN)

The LM5146 operational input voltage range is from 5.5 V to 100 V. The device is intended for step-down

conversions from 12-V, 24-V, 48-V, 60-V, and 72-V unregulated, semiregulated, and fully-regulated supply rails.

The application circuit in Figure 8-1 shows all the necessary components to implement an LM5146-based

wide-VIN step-down regulator using a single supply. The LM5146 uses an internal LDO subregulator to provide a

7.5-V VCC bias rail for the gate drive and control circuits (assuming the input voltage is higher than 7.5 V plus

the necessary subregulator dropout specification).

BST

PGND

SS/TRK

COMP

AGND

VIN

VOUT

LM5146

OUT

SYNC

GND

SYNCOUT

SYNCIN

EN/UVLO

VIN

ILIM

PGOOD

SYNC

out

VCC

OUT

ILIM

VCC

BST

UV2

UV1

FB2

FB1

op onal

ILIM

Figure 8-1. Schematic Diagram for VIN Operating Range of 5.5 V to 100 V

In high-voltage applications, take extra care to ensure the VIN pin does not exceed the absolute maximum

voltage rating of 100 V during line or load transient events. Voltage ringing on the VIN pin that exceeds the

values in the Absolute Maximum Ratings can damage the IC. Use high-quality ceramic input capacitors to

minimize ringing. An RC filter from the input rail to the VIN pin (for example, 4.7 Ω and 0.1 µF) provides

supplementary filtering at the VIN pin.

8.3.2 Output Voltage Setpoint and Accuracy (FB)

The reference voltage at the FB pin is set at 0.8 V with a feedback system accuracy over the full junction

temperature range of ±1%. Junction temperature range for the device is –40°C to +150°C. While dependent

on switching frequency and load current requirements, the LM5146 is generally capable of providing an output

voltage in the range of 0.8 V to a maximum of 60 V or slightly less than VIN, whichever is lower. The DC output

voltage setpoint during normal operation is set by the feedback resistor network, RFB1 and RFB2, connected to

the output.

8.3.3 High-Voltage Bias Supply Regulator (VCC)

The LM5146 contains an internal high-voltage VCC regulator that provides a bias supply for the PWM controller

and its gate drivers for the external MOSFETs. The input pin (VIN) can be connected directly to an input voltage

source up to 100 V. The output of the VCC regulator is set to 7.5 V. However, when the input voltage is below

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LM5146

SNVSBV0A – JUNE 2021 – REVISED JUNE 2021

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