TDA4863

Functional Description

Data Sheet

11

V1.0, 2003-05

To prevent false tripping the zero current detector is designed as a Schmitt-Trigger with

a hysteresis of 0.5 V. An internal 5 V clamp protects the input from overvoltage

breakdown, a 0.6 V clamp prevents substrate injection. An external resistor has to be

used in series with the auxiliary winding to limit the current through the clamps.

2.8

Restart Timer

The restart timer function eliminates the need of an oscillator. The timer starts or restarts

the TDA4863 when the driver output has been off for more than 150 µs after the inductor

current reaches zero.

2.9

Undervoltage Lockout

An undervoltage lockout circuitry switches the IC on when V

threshold V

During start up the supply current is less then 100 µA.

An internal voltage clamp has been added to protect the IC from V

condition. When using this clamp special care must be taken on power dissipation.

Start up current is provided by an external start up resistor which is connected from the

AC line to the input supply voltage V

V

the application board. Otherwise the IC can be destroyed due to the high capacitor

voltage.

Bootstrap power supply is created with the previous mentioned auxiliary winding and a

diode (see “Application Circuit” on Page 21).

2.10

Gate Drive

The TDA4863 totem pole output stage is MOSFET compatible. An internal protection

ciruitry is activated when V

is turned off. The totem pole output has been optimized to minimize cross conduction

current during high speed operation.