Texas Instruments TPS40090EVM-002 manual Overcurrent Limit Protection, Out

SLUU195 − June 2004

With the chosen inductor described in Inductance Value, (section 4.2, of this document) the following values are used.

•R=19.6 kΩ

•C=10 nF

•RNTC=100 kΩ

•R1=124 kΩ

•R2=22.6 kΩ

VDCR

L

L

DCR

VIN

DCR

R

C

VIN

R

C

VC

VOUT

R1

R2

RNTC

RTHE

UDG−03136

Figure 6. DCR Current Sensing Circuit with Copper Temperature Compensation

4.7Overcurrent Limit Protection

The overcurrent function monitors the voltage level separately on each current sense input and compares it to the voltage on ILIM pin set by the divider from the controller’s reference.

If the threshold of VILIM/2.7 is exceeded, the PWM cycle on the respected phase is terminated. Voltage level on the ILIM pin is determined by (11).

VILIM + 2.7 IPH(max)	RCS; IPH(max)	+ IOUT )	￿VIN * VOUT￿		VOUT	(11)
			2 LOUT	fSW	VIN

where

•IPH(max) is the maximum allowable value of the phase current

•RCS is the value of the current sense resistor

12TPS40090 Multi-Phase Buck Converter and TPS2834 Drivers Steps-Down from 12-V to 1.5-V at 100 A