AN4539 datasheet(23/33 Pages) STMICROELECTRONICS

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AN4539

Voltage mode buck converter with synchronous rectification and fault protection

Figure 10. Buck operation with FAULT

Buck with synchronous rectification demo overview

The duty cycle on TA1 is continuously varied in an interrupt service routine generated on

repetition event, to mimic a real converter management. The FAULT1 input is enabled on

PA12 (active low) to demonstrate PWM shut down (low level sensitive), for both TA1 and

TA2.

When the fault is triggered (PA12 input connected to GND, TA1 and TA2 signals are shut-

down. The system can be re-armed by pressing the user button.

LEDs are indicating the following:

•

Blue LED: blinks during normal operation;

•

Red LED: blinks when FAULT is triggered;

•

Orange LED: indicates the occurrence and duration of the PWM update ISR.

The ADC is configured to have conversions triggered in the middle of the converter ON

time, on PA1 (Vin) and PA3 (Vout) inputs. To run the demo, the Vout input of the BUCK-

BOOST converter must be connected to the 5V_O supply. The resulting voltage is available

on Vout pin.

Note:

To have the Discovery kit’s BOOST stage bypassed, the PA11 pin must be forced at 1 (to

have the T6 PMOS switched ON).

Demo code

The example code is provided in the HRTIM_BuckSyncRect example.

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