MCP2050 datasheet(14/40 Pages) MICROCHIP

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MCP2050

DS20002299C-page 14

 2012-2014 Microchip Technology Inc.

FIGURE 1-10:

VOLTAGE REGULATOR OUTPUT ON OVER CURRENT SITUATION

1.6

Optional External Protection

1.6.1

REVERSE BATTERY PROTECTION

An external reverse-battery-blocking diode should be

used to provide polarity protection (see Figure 1-12).

1.6.2

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 1-12). The

maximum value for the RTP protection resistor depends

on 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 1-2 provides a max RTP value according to

the minimum battery voltage the user wants the part to

start at.

Equation 1-3 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 1-4 provides a max RTP value according to

the maximum relative variation the user can accept on

the slope when IREG varies.

Since both Equation 1-2 and Equation 1-3 must be

fulfilled, the maximum allowed value for RTP is thus the

smaller of the two values found when solving

Equation 1-2 and Equation 1-3.

Usually Equation 1-2 gives the higher constraint

(smaller value) for RTP as shown in the following

example where VBATmin is 8V.

However, the user needs to check that the value found

with Equation 1-2 also fulfills Equation 1-3 and

Equation 1-4.

While this protection is optional, it should be

considered as good engineering practice.

Note 1:

IREG less than lLIM, regulator on.

After IREG exceeds lLIM, the voltage regulator output will be reduced until VSD is reached.

VSD

(1)

(2)

lLIM

IREG

VREG

VREG-NOM

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