Tool/software:
This TPS56637 is being supplied with 15V and is designed to regulate it to 5V. The board it is powering draws 250 mA on idle (MCU, Amplifiers, Gates, etc.) and the converter works normally. The schematic for the converter is shown below:
The inductor is a XAL7070-332MEB 3.3 uH, 15.1 A, 9.42 mOhm inductor and the output capacitor is 47uF 16V low ESR X5R capacitor. The output voltage at board idle is kept at around 5V, ripple is very low.
Below is a screenshot of the layout used (2 oz copper, 6L board):
I am trying to switch on a relay with a 5V 106mA coil. The schematic for the relay driver is as follows:
When the SSR activates, this waveform is captured at the output of the converter:
The output remains off for around 25ms. The datasheets states under section 7.3.5: When the output voltage falls below 65% of the target voltage, the UVP comparator detects it and shuts down the device after a deglitch wait time of 0.25ms and then re-start after the hiccup time of 25ms. This suggests that the device is limiting the output current somehow, making the voltage drop and then switching off the output completely.
I tried to add extra capacitance near the relay coil (1000uF) and the problem persisted, so it doesn't appear to be an inrush current issue, even though DC relay coils do not draw inrush currents.
I would like to know if the design can be improved to fit my use case or if there is a chance I have a faulty IC.
