UCC27423, UCC27424, UCC27425

SLUS545B − NOVEMBER 2002 − REVISED NOVEMBER 2004

6

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Terminal Functions

TERMINAL

FUNCTION

NO.

NAME

I/O

FUNCTION

1

ENBA

I

Enable input for the driver A with logic compatible threshold and hysteresis. The driver

output can be enabled and disabled with this pin. It is internally pulled up to VDD with

100-k

Ω resistor for active high operation. The output state when the device is disabled

will be low regardless of the input state.

2

INA

I

Input A. Input signal of the A driver which has logic compatible threshold and hysteresis.

If not used, this input should be tied to either VDD or GND. It should not be left floating.

3

GND

−

Common ground. This ground should be connected very closely to the source of the

power MOSFET which the driver is driving.

4

INB

I

Input B. Input signal of the A driver which has logic compatible threshold and hysteresis.

If not used, this input should be tied to either VDD or GND. It should not be left floating.

5

OUTB

O

Driver output B. The output stage is capable of providing 4-A drive current to the gate of

a power MOSFET.

6

VDD

I

Supply. Supply voltage and the power input connection for this device.

7

OUTA

O

Driver output A. The output stage is capable of providing 4-A drive current to the gate of

a power MOSFET.

8

ENBB

I

Enable input for the driver B with logic compatible threshold and hysteresis. The driver

output can be enabled and disabled with this pin. It is internally pulled up to VDD with

100-k

Ω resistor for active high operation. The output state when the device is disabled

will be low regardless of the input state.

APPLICATION INFORMATION

General Information

High frequency power supplies often require high-speed, high-current drivers such as the UCC27423/4/5 family.

A leading application is the need to provide a high power buffer stage between the PWM output of the control

IC and the gates of the primary power MOSFET or IGBT switching devices. In other cases, the driver IC is

utilized to drive the power device gates through a drive transformer. Synchronous rectification supplies also

have the need to simultaneously drive multiple devices which can present an extremely large load to the control

circuitry.

Driver ICs are utilized when it is not feasible to have the primary PWM regulator IC directly drive the switching

devices for one or more reasons. The PWM IC may not have the brute drive capability required for the intended

switching MOSFET, limiting the switching performance in the application. In other cases there may be a desire

to minimize the effect of high frequency switching noise by placing the high current driver physically close to

the load. Also, newer ICs that target the highest operating frequencies may not incorporate onboard gate drivers

at all. Their PWM outputs are only intended to drive the high impedance input to a driver such as the

UCC27423/4/5. Finally, the control IC may be under thermal stress due to power dissipation, and an external

driver can help by moving the heat from the controller to an external package.