AS3696

austriamicrosystems

www.austriamicrosystems.com

Rev 1.10 / 1011-04-04

7 - 16

accumulated and if the time exceeds 100ms a fault is indicated and the output is turned off. If the high-

time of the waveform is shorter than 100ms it will take more periods to trigger this fault. After 500ms the

channel is turned on again. A short will be detected if:

((V_Dx -VsetX) /5 + VsetX) > Vshort

For proper detection the PWM high time has to be longer than 500us.

4.2

PWM controller

The PWM controller can operate in normal mode or 3D mode. Depending on the mode different output

currents can be set.

“3D-

Mode”

“SEL”

Mode

Comment

Vref_INT

0

0

Normal

PWM external

External PWM is used as PWM_INT

Vset1

0

1

Normal

PWM internal

PWM-frequency is generated by internal oscillator

PWM-duty cycle is set by voltage on pin “Vduty”

Vduty can either be an external voltage ( PWM=0 )

or can be derived from the PWM signal by filtering

with an ext capacitor

Vset1

1

X

3D mode

3D_PWM12 is used for driving Channels 1 and 2

3D_PWM34 is used for driving Channels 3 and 4

Vset2

4.3

Oscillator

The build in oscillator can be used to generate internal PWM frequencies. The external Capacitor is

charged with the current 1.24V/Rosc and discharged with the current 1.24V*10/Rosc.

3.1 ,

.

,

.

Oscillator

PWM

100k

Vduty

Rosc

Cosc

Sel

PWM_INT Ch1/Ch2

3D_PWM12

3D_PWM34

Vset2

Vset1

PWM_INT Ch3/Ch4

Vref_INT

3D_Mode

Cosc

Cosc

Rosc

Rosc

1.24V

Iosc = 1.24V/Rosc

10*Iosc

1*Iosc

UrefH

UrefL

UrefH

UrefL

3.2V

0.1V

T1

T2

Ud