PI33XX Datasheet, PDF (33/42 Pages) Vicor Corporation – 8V to 36Vin Cool-Power ZVS B uck Regulator Family

in the Applications Description section for more
details.
Remote Sensing
An internal 100Ω resistor is connected between REM
pin and VOUT pin to provide regulation when the
REM is left open. With REM open, the converter will
regulate 100mV above its set point. Connect REM to
the desired reference node to be regulated.
Output Current Limit Protection
PI33XX has two methods implemented to protect
from output short or over current condition.
Slow Current Limit protection: prevents the output
load from sourcing current higher than the
regulator’s maximum rated current. If the output
current exceeds the Current Limit (I_{OUT_CL}) for 1024us,
a slow current limit fault is initiated and the regulator
is shutdown which eliminates output current flow.
After Fault Restart Delay (t_{FR_DLY}), a soft-start cycle is
initiated. This restart cycle will be repeated
indefinitely until the excessive load is removed.
Fast Current Limit protection: PI33XX monitors the
regulator inductor current pulse-by-pulse to prevent
the output from supplying very high current due to a
sudden low impedance short. If the regulator senses
a high inductor current pulse, it will initiate a fault
and stop switching until Fault Restart Delay ends and
then initiate a soft-start cycle.
Both the Fast and Slow current limit faults are stored
in a Fault Register and can be read and cleared
(PI33XX-20 and PI33XX-21 versions only) via I²C data
bus.
Input Under-Voltage Lockout
If VIN falls below the input Under Voltage Lockout
(UVLO) threshold, but remains high enough to power
the internal bias supply, the PI33XX will complete the
current cycle and stop switching. If VIN recovers
within 128 switching cycles, the PI33XX will resume
normal operation. If this time limit is exceeded, the
system will enter a low power state and initiate a
fault. The system will restart once the input voltage is
reestablished and after the Fault Restart Delay. A
UVLO fault is stored in a Fault Register and can be
PI33XX-X0
read and cleared (PI33XX-20 and PI33XX-21 versions
only) via I²C data bus.
Input Over Voltage Lockout
If VIN exceeds the input Over Voltage Lockout (OVLO)
threshold (V_OVLO), while the controller is running, the
PI33XX will complete the current cycle and stop
switching. If VIN recovers within 128 switching
cycles, the PI33XX will resume normal operation.
Otherwise, the system will enter a low power state
and sets an OVLO fault. The system will resume
operation when the input voltage falls below 98% of
the OVLO threshold and after the Fault Restart Delay.
The OVLO fault is stored in a Fault Register and can
be read and cleared (PI33XX-20 and PI33XX-21
versions only) via I²C data bus.
Output Over Voltage Protection
The PI33XX family is equipped with output Over
Voltage Protection (OVP) to prevent damage to input
voltage sensitive devices. If the output voltage
exceeds 20% of its set regulated value, the regulator
will complete the current cycle, stop switching and
issue an OVP fault. The system will resume operation
once the output voltage falls below the OVP
threshold and after Fault Restart Delay. The OVP
fault is stored in a Fault Register and can be read and
cleared (PI33XX-20 and PI33XX-21 versions only) via
I²C data bus.
Over Temperature Protection
The internal package temperature is monitored to
prevent internal components from reaching their
thermal maximum. If the Over Temperature
Protection Threshold (OTP) is exceeded (T_OTP), the
regulator will complete the current switching cycle,
enter a low power mode, set a fault flag, and will
soft-start when the internal temperature falls below
Over-Temperature Restart Hysteresis (T_{OTP_HYS}). The
OTP fault is stored in a Fault Register and can be read
and cleared (PI33XX-20 and PI33XX-21 versions only)
via I²C data bus.
Pulse Skip Mode (PSM)
PI33XX features a PSM to achieve high efficiency at
light loads. The regulators are setup to skip pulses if
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Rev 1.4
11/2012
Cool-Power^®
Page 33 of 42