UCC27323, UCC27324, UCC27325

UCC37323, UCC37324, UCC37325

SLUS492B – JUNE 2001 – REVISED SEPTEMBER 2002

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APPLICATION INFORMATION

input stage

The inputs of UCC37323/4/5 family of drivers are designed to withstand 500-mA reverse current without either

damage to the IC for logic upset. The input stage of each driver should be driven by a signal with a short rise

or fall time. This condition is satisfied in typical power supply applications, where the input signals are provided

by a PWM controller or logic gates with fast transition times (<200 ns). The input stages to the drivers function

as a digital gate, and they are not intended for applications where a slow changing input voltage is used to

generate a switching output when the logic threshold of the input section is reached. While this may not be

harmful to the driver, the output of the driver may switch repeatedly at a high frequency.

Users should not attempt to shape the input signals to the driver in an attempt to slow down (or delay) the signal

at the output. If limiting the rise or fall times to the power device is desired, limit the rise or fall times to the power

device, then an external resistance can be added between the output of the driver and the load device, which

is generally a power MOSFET gate. The external resistor may also help remove power dissipation from the IC

package, as discussed in the section on Thermal Considerations.

output stage

Inverting outputs of the UCC37323 and OUTA of the UCC37325 are intended to drive external P-channel

MOSFETs. Noninverting outputs of the UCC37324 and OUTB of the UCC37325 are intended to drive external

N-channel MOSFETs.

Each output stage is capable of supplying

±4-A peak current pulses and swings to both VDD and GND. The

pullup/ pulldown circuits of the driver are constructed of bipolar and MOSFET transistors in parallel. The peak

output current rating is the combined current from the bipolar and MOSFET transistors. The output resistance

of the bipolar transistor. Each output stage also provides a very low impedance to overshoot and undershoot

due to the body diode of the external MOSFET. This means that in many cases, external-schottky-clamp diodes

are not required.

The UCC37323 family delivers 4-A of gate drive where it is most needed during the MOSFET switching

transition – at the Miller plateau region – providing improved efficiency gains. A unique BiPolar and MOSFET

hybrid output stage in parallel also allows efficient current sourcing at low supply voltages.