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MIC45212-2

26V, 14A DC-to-DC Power Module

Microchip Technology 

MIC45212-1/-2

EQUATION 4-3: PROGRAMMING

CURRENT LIMIT

(ICLIM + IL(PP)  0.5)  RDS(ON) + VCL_OFFSET

R15 =

ICL

Where:

ICLIM = Desired current limit

RDS(ON) = On resistance of low-side power

MOSFET, 6 m typically

VCL_OFFSET = Current-limit threshold (typical

absolute value is 14 mV per Table 1-1)

ICL = Current-limit source current (typical value is

70 µA per Table 1-1)

IL(PP) = Inductor current peak-to-peak; since the

inductor is integrated, use Equation 4-4 to calculate

the inductor ripple current

The peak-to-peak inductor current ripple is:

EQUATION 4-4:

PEAK-TO-PEAK

INDUCTOR CURRENT

RIPPLE

IL(PP) =

VOUT  (VIN(MAX) – VOUT)

VIN(MAX)  fSW  L

The MIC45212 has a 0.6 µH inductor integrated into

the module. In case of a hard short, the short limit is

folded down to allow an indefinite hard short on the out-

put without any destructive effect. It is mandatory to

make sure that the inductor current used to charge the

output capacitance during soft start is under the folded

short limit; otherwise, the supply will go into hiccup

mode and may not finish the soft start successfully.

The MOSFET RDS(ON) varies 30% to 40% with

temperature; therefore, it is recommended to add a

50% margin to ICLIM in Equation 4-3 to avoid false

current limiting due to increased MOSFET junction

temperature rise.

With R15 = 1.69 k and C15 = 15 pF, the typical output

current limit is 16.8A.

DS20005607A-page 18

 2017 Microchip Technology Inc.

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