AS3696

austriamicrosystems

www.austriamicrosystems.com

Rev 1.10 / 1011-04-04

8 - 16

The Oscillator frequency can be calculated:

.

.

.

[Hz]

4.4

Power supply

The device has a build in electronic Zener-diode at pin VDD for building a shunt regulator. To obtain a

5.2V regulated supply, a series resistor Rvdd has to be connected in series to the internal zener diode.

An external capacitor Cvdd is used to filter the supply on the pin VDD.

The external resistor Rvdd has to be calculated according to the following formula:

.

Vsupply...Minimum Supply voltage

Power dissipation of Rvdd;

,

To ensure proper operation the minimum supply voltage should be choosen as Vsupply.

If a stable supply voltage between 4V and 5V is available in the system this supply can also be used for

VDD. In that case there is no need for the series resistor Rvdd.

4.5

Safety features

4.5.1

Temperature shutdown

If the die temperature reaches 140°C all outputs are turned off. If the die temperature goes below 130°C

the outputs are turned on again.

4.5.2

xPD input

In addition to the build in power on reset circuit there is an external power down input “xPD” available.

This gives the possibility to keep the outputs turned off until all blocks of the LED-driver circuits are fully

working ( DCDC, MCU ... )

VDD

Rvdd

Cvdd

Vsupply

GND

Shunt

2.2uF

Regulator

5.2V