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PI2002-EVAL1 User Guide Rev 1.0 Page 6 of 11

3.0 Over Current Timer: OCT

The OCT off-time is set with the OCT capacitor, where

the specific value can be determined from Figure 5.

Every time an overcurrent condition occurs the PI2002

pulls the Gate pin low, discharges the OCT capacitor

and then starts to charge it again over the

programmed off-time. Only when the OCT capacitor

voltage reaches the OCT threshold (1.75 V) will the

Gate pin then start to charge the MOSFET gates.

4.0 Short Circuit Detect: SCD

SCD pin can be connected to the load directly or

programmed to a higher voltage with a resistor

divider. SCD function allows the user to define the

(Hard Short) voltage level expected if a non-ideal

short circuit occurs at the load. This feature enables

distinguishing between a faulted load versus

powering capacitive and low resistive loads without

entering the OCT mode. This pin can be grounded to

provide a fast gate charge or pulled to Vc for lower

gate current to drive highly capacitive loads with

resulting slow gate charge under the fault condition.

5.0 Auxiliary Power Supply (Vaux):

5.1 The PI2002 Controller has a separate input (VC) that

provides power to the control circuitry and the gate

driver. An internal voltage regulator (VC)

clamps the VC voltage to 15.5 V typically.

5.2 Connect independent power source to Vaux inputs of

PI2002-EVAL1 Evaluation Board to supply power to

the VC input. The Vaux voltage should be 5V higher

than Vin (redundant power source output voltage) to

fully enhance the MOSFET. If the MOSFET is replaced

with a different MOSFET, make sure that the Vaux

voltage is equal to Vin + 0.5 V + the required voltage

to enhance the MOSFET.

5.3 10

Ω bias resistors (Rbias, reference designators R11

and R22) are installed on the PI2002-EVAL1 between

each Vaux input and VC pin of one of the PI2002

controller.

5.4 If Vaux is higher than the Clamp voltage, 15.5 V

typical, the Rbias value has to be changed using the

following equations:

5.4.1 Select the value of Rbias using the

following equations:

Rbias =

5.4.2 Calculate Rbias maximum power dissipation:

Where:

voltage, 16.0 V

voltage, 14.0 V

use 4.2 mA

Figure 5 – OCT off time vs. OCT capacitor value