171010601 查看數據表（PDF） - Wurth Elektronik GmbH & Co. KG, Germany.

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171010601

MagI3C Power Module VDRM – Variable Step Down Regulator Module

Wurth Elektronik GmbH & Co. KG, Germany. 

WPMDM1500602 / 171050601

MagI3C Power Module

VDRM – Variable Step Down Regulator Module

Step 6 Optional: Select the under voltage lockout divider

For applications not requiring precision under voltage lockout (UVLO), the EN input may be left open. An internal 2MΩ pull-

up resistor (RENint) is connected from EN pin to VIN. It will always enable the module. In such case, the internal UVLO occurs

typically at 4.3V (VIN rising). In applications with separate supervisory circuits, the EN pin can be directly interfaced to a logic

source. In the case of sequencing supplies, the divider is connected to a rail that becomes active earlier in the power-up

cycle than the MagI³C power module output rail. Enable provides a precise 1.279V threshold to allow for direct logic drive or

connection to a voltage divider from a higher enable voltage such as VIN (see figure below, left). Additionally there is

switched offset current (IEN, 21µA typ.) allowing programmable hysteresis.

The function of the enable divider is to allow the designer to choose an input voltage below which the circuit will be disabled.

This implements the feature of programmable UVLO. The two resistors should be chosen based on the following ratio:

RENT

RENB

=

(VVUEVNLO)

–1

(16)

where VEN is the EN threshold trip point (1.279V, see “Electrical specifications” on page 5). Equation (16) neglects the

internal pull-up resistor but it is nevertheless a good approximation.

The rising threshold of the UVLO at the input voltage can be calculated as follows:

VIN(rising)=

VEN∙

(1+

(RENT‖RENint))

RENB

(17)

An additional hysteresis can be introduced by connecting the resistor RENH (see picture below, right). The falling threshold is

therefore defined as:

VIN(falling) = VIN(rising) - IEN ∙[RENT‖RENint‖(RENH+RENB)]

(18)

A zener clamp diode might be required in order to prevent the EN input voltage from exceeding its maximum absolute rating

value (6V, see “Absolute maximum ratings” on page 4).

For example, selecting RENB = 12.7kΩ and RENT = 42.2kΩ would result in a rising UVLO threshold of 5.46V. This divider

however presents 8.33V to the input when the input voltage reaches its maximum value (36V), exceeding the 6V mentioned

above. A midpoint 5.1V zener clamp should be used in this case to allow the application to cover the full 6V to 36V range of

operation (see figure below, right).

VIN

5V INT

RENT

RENint

2MΩ

21µA

EN

RUN

RENB

1.27 9V

VIN

5V INT

RENT

RENint

2MΩ

21µA

RENH EN

RUN

5.1V

RENB

1.279V

we-online.com

© July 2018

Basic external UVLO divider

External UVLO circuit with programmable

hysteresis and EN pin voltage clamp

Würth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 2.0

29/56

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