It seems everything is designed correctly. But the TPS output gives 0V. (Pin EN floating)
What could I have done wrong?
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
You are trying to get 0.8 V out of 24 V input. This is 30:1 ratio, which theoretically requires 1/30 duty cycle for PWM at the fixed switching frequency.
Now, you selected 162 k set resistor, which will set the switching frequency to about 600 kHz, which is about 1700 ns period. At 1/30 duty cycle the up-time of switch should be about 55 ns. The datasheet, however, says that minimum controllable on-time is 135 ns, and this is at 12V input. This time will be even longer at 24 V, since the edge rate is limited too.
Therefore, your design needs 55 ns on-time, while the IC can do only 135+. This design can't output 0.8 V if Vin=24V. Try 3.3 or 5V.
And again, the narrow duty cycles require extreme care in designing high-current switching loops to minimize transients, which needs traces as short (and wide) as possible. Your layout deviates from the recommended one significantly.
Also, are you sure that the SW signal is not shorted to ground around C24 boost capacitor?