ADP1048 Analog Devices, ADP1048 Datasheet - Page 15

• Manufacturer Part Number: ADP1048
• Description: Digital Power Factor Correction Controller with accurate AC Power Metering
• Manufacturer: Analog Devices

Data Sheet
OVERVOLTAGE PROTECTION
The
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
register (Register 0x41). If the disable PWM option is selected,
a voltage hysteresis can be programmed for the accurate OVP
threshold using Register 0xFE50.
Table 6. Programmable Options for Fast Overvoltage Protection (Fast OVP)
Parameter
Debounce Time
Blanking Time
Propagation Delay
Threshold Rising
Threshold Falling
Actions for Fast OVP
ADP1047/ADP1048
have two OVP circuits: an ADC-based
Values or Options
120 ns, 240 ns, 480 ns, 640 ns
10 μs (fixed)
120 ns max (fixed)
1 V to 1.5 V
1 V to 1.5 V
Immediate shutdown and wait for PSON;
disable PWM until the flag is cleared;
shut down and soft start; ignore (do nothing)
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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.
Comments
Minimum duration of pulse to be considered;
programmable using Register 0xFE31, Bits[1:0]
Duration of time while the comparator is blanked
and the threshold changes from rising to falling
Does not include blanking or debounce
Programmable using Register 0xFE2F, Bits[6:0]
Programmable using Register 0xFE30, Bits[6:0]
Register 0xFE01, Bits[7:6]
ADP1047/ADP1048