PD70101 datasheet(8/24 Pages) MICROCHIP

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1.1.6

Power Good

During Soft Start mode, the PD70100/PD70200 IC monitors VPNOUT to VPNIN differential voltage. When this voltage

is less than 0.7 V (max.), the IC enters normal operation mode and the isolation switch current limit is increased to

1.8 A (typical). At this same 0.7 V (max.) threshold the Power Good signal is asserted by means of an open drain

MOSFET between PGOOD and VPNOUT.

PGOOD pin is active low; a low impedance state between PGOOD and VPNOUT indicates the Soft Start mode has

finished and the isolation switch has transitioned into normal operating mode.

PGOOD MOSFET can handle current of 5 mA and can be pulled up to VPP.

1.1.7

Auxiliary Voltage Output

PD70100/PD70200 IC provides a 10.5 V (typical) regulated output to be used as a start-up supply for DC/DC

controllers whose VCC is provided via a bootstrap winding. This regulated supply is available at VAUX pin, and is

referenced to VPNOUT pin. VAUX supply is designed for low-duty operation, and should not be designed as a primary

housekeeping supply. The current capability is continuous 2 mA, with 10 mA peak (≤10 ms). VAUX output is current-

limited at 10 mA (min.).

For stability, the VAUX regulator requires a minimum of 4.7 μF ceramic capacitor connected directly between VAUX

and VPNOUT pins.

1.1.8

Thermal Protection

Both PD70100 and PD70200 IC include temperature sensors which individually monitor both the isolation MOSFET

and the Classification Current Source for over temperature conditions. In case of an over temperature condition, the

sensor will activate protection circuitry which will disconnect its respective monitored function.

1.1.9

Bulk Capacitor Discharge

The bulk capacitor discharge circuitry eliminates the need to place a diode in series with the VPP line to prevent an

application’s bulk capacitance from discharging through the detection resistor and the isolation switch MOSFET’s

body diode. Discharge current through the detection resistor can cause failure of the detection signature in cases

where a PD is connected and the bulk capacitance is not fully discharged.

During normal operation, PD70100/PD70200 IC continuously monitors voltage at VPP to VPNIN. Should VPP to VPNIN

voltage fall below isolation switch turn-off threshold (31 V to 34 V), isolation switch MOSFET is immediately placed in

a high-impedance state. At this point the internal logic monitors the voltage at VPP to VPNOUT. If VPP to VPNOUT

voltage is between 1.5 V to 32 V, a 23 mA (min.) constant current source is connected across the VPP and VPNOUT

pins. This constant current source provides bulk capacitor discharge.

A 220 μF bulk capacitance can be discharged from 32 V to 1.5 V in a maximal period of 292 ms.

PD70100/PD70200

Functional Descriptions

Datasheet

DS00003639A-page 8

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