MCP2025-330ESLASHP datasheet(9/36 Pages) MICROCHIP

9 / 36 page

 2012 Microchip Technology Inc.

DS22306A-page 9

MCP2025

FIGURE 1-7:

VOLTAGE REGULATOR OUTPUT ON OVER CURRENT SITUATION

1.5

Optional External Protection

1.5.1

REVERSE BATTERY PROTECTION

An external reverse-battery-blocking diode should be

used to provide polarity protection (see Figure 1-9).

1.5.2

TRANSIENT VOLTAGE

PROTECTION (LOAD DUMP)

An external 43V transient suppressor (TVS) diode,

between VBB and ground, with a transient protection

resistor (RTP) in series with the battery supply and the

VBB pin protects the device from power transients and

ESD events greater than 43V (see Figure 1-9). The

maximum value for the RTP protection resistor depends

upon two parameters: the minimum voltage the part will

start at, and the impacts of this RTP resistor on the VBB

value, thus on the Bus recessive level and slopes.

This leads to a set of three equations to fulfill.

Equation 1-1 provides a max RTP value, according to

the minimum battery voltage the user wants the part to

start with.

Equation 1-2 provides a max RTP value according to

the maximum error on the recessive level, thus VBB,

since the part uses VBB as the reference value for the

recessive level.

Equation 1-3 provides a max RTP value according to

the maximum relative variation the user can accept on

the slope when IREG varies.

Since both Equation 1-1 and Equation 1-2 must be ful-

filled, the maximum allowed value for RTP is the

smaller of the two values found when solving

Equation 1-1 and Equation 1-2.

Usually, Equation 1-1 gives the higher constraint

(smaller value) for RTP as shown in the example where

VBATmin is 8V.

However, the user needs to verify that the value found

in Equation 1-1 also satisfies Equation 1-2 and

Equation 1-3.

While this protection is optional, it should be

considered as good engineering practice.

Note 1:

IREG less than ILIM, regulator on

After IREG exceeds ILIM, voltage regulator output will be reduced until

voltage regulator shutdown voltage VSD is reached.

VSD

(1)

(2)

ILIM

IREG

VREG

VREG-NOM

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