MP4571

– 60V, 1A, SYNCHRONOUS STEP-DOWN CONVERTER

MP4571 Rev. 1.1

www.MonolithicPower.com

28

2/22/2023

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VIN

EN

IN

R4

2.8M

Ω

R5

8

12

6V

Zener

Figure 6: Adjustable UVLO Using EN Divider

when EN Falls

The UVLO threshold can be calculated with

Equation (13) and Equation (14) when EN is

rising or falling, respectively:

EN_RISING

RISING

V

1.8M//R5

R4

(1

INUV



+

=

)

(13)

EN_FALLING

FALLING

V

2.8M//R5

R4

(1

INUV



+

=

)

(14)

Where VEN_RISING = 1.45V, VEN_FALLING = 1.12V.

When choosing R4, ensure it is big enough to

limit the current flowing into EN pin below 100µA.

BST Resistor and Capacitor

A resistor in series with the BST capacitor (RBST)

can reduce the SW rising rate and voltage spikes.

This enhances EMI performance and reduces

voltage stress at a high VIN. A higher resistance

is

better

for

SW

spike

reduction,

but

compromises efficiency. To make a tradeoff

between EMI and efficiency, it is recommended

to keep RBST below 20Ω. It is also recommended

for the BST capacitor to be between 0.1µF and

1μF.