AMG-LI080

Timer/Dimmer with Gate Driver, Zero Detection & Protection

5. Block Descriptions

5.1. Zero Crossing

Detects the Zero Crossing of the AC sine wave. The INZ input is connected to the rectified

mains with a resistor divider. For noise suppression, the INZ input should also be connected to

GND with a capacitor. This capacitor will cause a time delay between the actual zero crossing

and the detection. Bigger capacitors will cause a longer time delay than smaller ones. This

time delay may or may not affect the function.

5.2. Time Reset

Determines the on time of the output, thus the duty cycle, or the time of the reverse phase cut.

The Time Reset is triggered by the zero crossing. The Time Reset is reset by an external R

and C, which determines the time to reset.

5.3. Gate Driver + Output Latch

Supplies the gate charge for the external MOSFETs. Continuous current capability is around

10mA. The output latch is set by the Zero Crossing and reset by the Time Reset.

5.4. Protection Logic

The IC has 3 sense inputs for over voltage, over current and over temperature protection.

OVP: Over Voltage Protection

OTP: Over Temperature Protection

OCP: Over Current Protection

These sense inputs have an internal pull up and are connected to a comparator. The

comparator thresholds are set according to their dedicated protection function, but

nevertheless, they can be used for something else. The sense inputs all need some additional

external circuitry to enable the protection. Please refer to the example application diagram or

the application note. If a specific protection function is not needed, the corresponding sense

input should be connected to GND. All 3 protection comparators individually set a latch when

the threshold is reached. When set, the latch will inhibit the Zero Crossing and thus the output

of the device and activate the LED driver. The protective latch is reset at power up. As such

the protection functions work like a recoverable fuse.

5.5. Soft Start

Soft Start is in essence adjustable current source. With an external C, the time to reach max.

current can be adjusted. In that way, a soft start function can be built. Please refer to the

example application diagram or the application note. In case, a 1-10V analog signal shall

control the dimmer, it can be connected to the CS pin.

AMG-LI080

Revision: B

8. Nov. 2012

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