LM5032MTCSLASHNOPB datasheet(19/34 Pages) TI

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UVLO

LM5032

1.25V

20 2A

Max. Duty

Cycle Limiter

VPWR

Shutdown

Control

UVLO

LM5032

1.25V

20 2A

Max. Duty

Cycle Limiter

VPWR

Enable VCC Regulator

and Output Drivers

R2 =

1.25 x R1

VPWR - 1.25

VCC

8V - 15V

LM5032

VIN

8V-15V

Start-up

Voltage

LM5032

www.ti.com

SNVS344B – MARCH 2005 – REVISED DECEMBER 2014

Application Information (continued)

Figure 21. Bypassing the Internal Start-up Regulator

8.1.3 UVLO

The under-voltage lockout threshold (UVLO) is internally set at 1.25V at the UVLO pin. With two external

resistors as shown in Figure 22, the LM5032 is enabled when VPWR exceeds the programmed threshold voltage.

When VPWR is above the threshold, the internal 20 µA current source is enabled to raise the voltage at the UVLO

pin, providing hysteresis. R1 and R2 are determined from the following equations:

R1 = VHYS/20 µA

(3)

(4)

where VHYS is the desired UVLO hysteresis at VPWR, and VPWR in the second equation is the turn-on voltage. For

example, if the LM5032 is to be enabled when VPWR reaches 20V, and disabled when VPWR is decreased to 17V,

R1 calculates to 150 k

Ω, and R2 calculates to 10 kΩ. The voltage at UVLO should not exceed 6V at any time.

Figure 22. UVLO Circuit

The LM5032 can be remotely shutdown by taking the UVLO pin below 1.25V with an external open collector or

open drain device, as shown in Figure 23. The outputs, and the VCC regulator, are disabled, and the LM5032

enters a low power mode. To shut down one regulator without affecting the other, see the Soft-start section.

Figure 23. Shutdown Control

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