APW7165C datasheet(11/20 Pages) ANPEC

11 / 20 page

Rev. A.2 - Oct., 2012

APW7165C

www.anpec.com.tw

Under-Voltage Protection

Over-Voltage Protection (OVP)

Shutdown and Enable

Pulse Skipping Mode (PSM)

Adaptive Shoot-Through Protection

The under-voltage function monitors the voltage on FB

FB) by Under-Voltage (UV) comparator to protect the PWM

converter against short-circuit conditions. When the V

falls below the falling UVP threshold (50% V

REF), a fault

signal is internally generated and the device turns off

high-side and low-side MOSFETs. The converter is shut-

down and the output is latched to be floating.

The over-voltage protection monitors the FB voltage to

prevent the output from over-voltage condition. When the

output voltage rises above 120% of the nominal output

voltage, the APW7165C turns off the high-side MOSFET

and turns on the low-side MOSFET until the output volt-

age falls below the falling OVP threshold, regulating the

output voltage around the OVP threshold.

The APW7165C can be shut down or enabled by pulling

low the voltage on COMP. The COMP is a dual-function

pin. During normal operation, this pin represents the

output of the error amplifier. It is used to compensate the

regulation control loop in combination with the FB pin.

Pulling the COMP low (V

DISABLE = 0.6V typical) places the

controller into shutdown mode which UGATE and LGATE

are pulled to PHASE and GND respectively.

When the pull-down device is released, the COMP volt-

age will start to rise. When the COMP voltage rises above

the V

DISABLE threshold, the APW7165C will begin a new

initialization and soft-start process.

At light loads, the inductor current may reach zero or re-

verse on each pulse. The low-side MOSFET is turned off

by the current reversal comparator, IZCMP, to block the

negative inductor current. In this condition, the converter

enters discontinuous current mode operation.

At very light loads, the APW7165C will automatically skip

pulses in pulse skipping mode operation to reduce

switching losses as well as maintain output regulation

for efficient applications.

The gate drivers incorporate an adaptive shoot-through

protection to prevent high-side and low-side MOSFETs

from conducting simultaneously and shorting the input

supply. This is accomplished by ensuring the falling gate

has turned off one MOSFET before the other is allowed to

rise.

During turn-off of the low-side MOSFET, the LGATE volt-

age is monitored until it is below 1.5V threshold, at which

time the UGATE is released to rise after a constant delay.

During turn-off of the high-side OCSFET, the UGATE-to-

PHASE voltage is also monitored until it is below 1.5V

threshold, at which time the LGATE is released to rise

after a constant delay.

Function Description (Cont.)

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