ADP1048ARQZ-R7 datasheet(15/84 Pages) AD

15 / 84 page

Data Sheet

ADP1047/ADP1048

Rev. 0 | Page 15 of 84

OVERVOLTAGE PROTECTION

The ADP1047/ADP1048 have two OVP circuits: an ADC-based

comparator and a fast comparator.

Accurate Overvoltage Protection (VFB Pin)

Overvoltage protection (OVP) is implemented using the infor-

mation available on the output of the VFB ADC. The information

from the VFB ADC is averaged over one half the ac line frequency;

therefore, the response of this OVP is relatively slow.

The threshold for the accurate OVP is fully programmable

using the VOUT_OV_FAULT_LIMIT register (Register 0x40).

The programmed value is the dc average voltage.

When the accurate OVP threshold is crossed, the accurate OVP

flag is set. The response to this flag can be programmed for one

of several actions using the VOUT_OV_FAULT_RESPONSE

a voltage hysteresis can be programmed for the accurate OVP

threshold using Register 0xFE50.

Fast Overvoltage Protection (OVP Pin)

A fast OVP mode is implemented using a programmable

comparator on the OVP pin. Fast OVP is used for overvoltage

protection of the bulk capacitors and to provide open-loop

protection. The sense point on the power rail requires an

external resistor divider to match the divider applied to VFB.

This separate divider introduces a level of redundancy in

sensing the output voltage to improve system reliability.

If the voltage divider on the VFB pin is damaged or drifts in

value, the OVP pin can still detect an overvoltage condition

and take the appropriate programmed action.

The fast OVP signal is fed into a comparator with a program-

mable threshold to set the trip point for overvoltage. The

threshold is set using a DAC.

Table 6. Programmable Options for Fast Overvoltage Protection (Fast OVP)

Parameter

Values or Options

Comments

Debounce Time

120 ns, 240 ns, 480 ns, 640 ns

Minimum duration of pulse to be considered;

programmable using Register 0xFE31, Bits[1:0]

Blanking Time

10 μs (fixed)

Duration of time while the comparator is blanked

and the threshold changes from rising to falling

Propagation Delay

120 ns max (fixed)

Does not include blanking or debounce

Threshold Rising

1 V to 1.5 V

Programmable using Register 0xFE2F, Bits[6:0]

Threshold Falling

1 V to 1.5 V

Programmable using Register 0xFE30, Bits[6:0]

Actions for Fast OVP

Immediate shutdown and wait for PSON;

disable PWM until the flag is cleared;

shut down and soft start; ignore (do nothing)

ADP1048ARQZ-R7 数据表(PDF) 15 Page - Analog Devices

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