AN2640 datasheet(16/36 Pages) STMICROELECTRONICS

16 / 36 page

ST7LIT19BF1 - 8-bit MCU

AN2640

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Figure 18.

Lamp detection circuit

The circuit shown in Figure 18 connected at this digital input is used to detect the lamp

presence. If the lamp is present, the cathode is in parallel to R30 and C17 and the

voltage across C17 is low. The low voltage is used by the micro to sense the lamp

presence. If the lamp is not present or the cathode is broken, the voltage across C17 is

high (5 V) and the MCU stops the ballast.

●

Pin 12: PA6 (not used). This pin is connected at micro VCC voltage by means of a 10 kΩ

resistor because this pin is also used as ICCCLK and during normal operation it must

be pulled up, internally or externally (external pull-up of 10 k

Ω is mandatory in noisy

environments).

●

Pin 13: PWM3 - PFC gate driver. This pin is connected to the L6382 driver in order to

control the PFC PMOS.

●

Pin 14: PA4 (not used). This pin is connected to micro VCC voltage by means of a 10 kΩ

resistor because an unused pin must be kept at a fixed voltage. It can be left

unconnected if it is configured as output (0 or 1) by the software.

●

Pin 15: PWM1 - High side input. This pin is connected to the L6382 driver and the

signal is used to drive the High side PMOS.

●

Pin 16: PWM0 - Low side input. This pin is connected to the L6382 driver and the signal

is used to drive the High side PMOS

●

Pin 17: PA1 - CSO. This pin is connected to the CSO pin of the L6382 and can be used

to lock the ballast when the CSI pin is high.

●

Pin 18: LTIC - Zero-current detect

Figure 19.

Zero-current detection circuit

AN2640 Datasheet(PDF) 16 Page - STMicroelectronics