Si9124

Vishay Siliconix

New Product

Document Number: 72099

S-03638—Rev. B, 20-Mar-03

www.vishay.com

11

Hiccup Operation

Current limiting is achieved by monitoring the differential

voltage between CS1 and CS2 pins which are connected

across a primary sense resistor. Once the differential voltage

exceeds the 150-mV trigger point, Hiccup operation is started.

The soft-start voltage on the SS pin is pulled to ground and

a duty cycle limited soft start is initiated. The upper and lower

switching points of the current limit have 50 mV of hysteresis.

The Si9124 provides a means of sensing the voltage on

feed-forward control voltage to the PWM controller. This is

achieved by choosing an appropriate resistive tap between

enabled, but switching is stopped.

function by adjusting the amplitude of the PWM ramp to the

PWM comparator.

Shutdown Mode

SHUTDOWN mode. This powers down all unnecessary

functions of the controller, ensures that the primary switches

are off and results in a low level current demand of 150

mA from

TYPICAL CHARACTERISTICS

7.5

8.0

8.5

9.0

9.5

10.0

- 50

- 25

0

25

50

75

100

125

150

7.90

7.95

8.00

8.05

8.10

8.15

8.20

- 50

- 25

0

25

50

75

100

125

150

Temperature (

_C)

Temperature (

_C)

15

17

19

21

23

25

- 50

- 25

0

25

50

75

100

125

Temperature (

_C)

80

90

100

110

120

130

140

- 50

- 25

0

25

50

75

100

125

Temperature (

_C)