LTC4213 datasheet(12/22 Pages) AD

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LTC4213

Rev. A

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ILIMIT(MAX) =

VCB(MAX)

RDS(ON)(MIN)

(5)

Most MOSFET data sheets have an RDS(ON) specification

with typical and maximum values but no minimum value.

Assuming a normal distribution with typical as mean, the

minimum value can be estimated as:

RDS(ON)(MIN) = 2•RDS(ON)(NOM) −RDS(ON)(MAX)

(6)

The LTC4213 gives higher gate drive than the manufac-

turer specified gate drive for RDS(ON) This gives a slightly

lower RDS(ON) than specified. Operating temperature also

modulates the RDS(ON) value.

Example Current Limit Calculation

An Si4410DY is used for current detection in a 5V

supply system with the LTC4213 VCB at 25mV (ISEL

pin grounded).

The RDS(ON) distribution for the Si4410DY is:

Typical RDS(ON) = 0.015Ω = 100%

Maximum RDS(ON) = 0.02Ω = 133.3%

Estimated MIN RDS(ON) = 2 • 15 – 20 = 0.010Ω = 66.7%

The RDS(ON) variation due to gate drive is:

RDS(ON) @ 4.5VGS = 0.015Ω = 100% (spec. TYP)

RDS(ON) @ 4.8VGS = 0.014Ω = 93% (MIN ∆VGSMAX)

RDS(ON) @ 7VGS = 0.0123Ω = 82% (NOM ∆VGSMAX)

RDS(ON) @ 8VGS = 0.012Ω = 80% (MAX ∆VGSMAX)

APPLICATIONS INFORMATION

Figure 2. Short Circuit Fault Timing Diagram

CB TRIPS

∆VSENSE

VGATE

VCB

>VCB

VREADY

CIRCUIT BREAKER TRIPS

GATE AND READY PINS PULL LOW

SHORT CIRCUIT

tFAULT

4213 F02

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