AN2946 datasheet(28/38 Pages) STMICROELECTRONICS

28 / 38 page

Firmware design

AN2946

28/38

Doc ID 15473 Rev 2

In system monitoring management, LED_Fault IRQ is the only interrupt to trigger the MCU

EXTI peripheral which is implemented by the hardware and firmware. In some abnormal

situations, the primary current of LED driving might rise radically, and then the pulse-shaped

LED_Fault signal is generated by a comparator. Several rising edges of this interrupt in EXTI

tell the controller to stop driving the LED and wait for system recovery. The flowchart is

shown in Figure 37.

Figure 37.

LED_fault IRQ flowchart

A complete monitoring system should include a self-recovery function. Every second, which

is defined by 'Timth1', the controller tries to recover system errors by clearing 'ErrorFlag'.

This enables all the error functions paused at the last system monitoring routine to run

again. The system self-recovery flowchart is shown in Figure 38.

Figure 38.

System self-recovery flowchart

To prevent battery power backflow through the charger, KCHG should be turned off when

charging current is very low. In normal conditions, KCHG is turned on to reduce power loss in

its body diode. The flowchart of anti-backflow for the battery charger is shown in Figure 39.

AN2946 데이터시트(PDF) 28 Page - STMicroelectronics