MPQ4430 Problem

DC-DC Power Converters
1

I made a 2A 5V switching regulator using MPQ4430. It is pretty much same as typical application in datasheet (fig 12)

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However the circuit does not work. Vout is 0.8V, which seems to be the same voltage as internal Vref. Some measurements:
Vin: 24V
EN: 24V
BIAS: 0.815
SW: 0.815V
BST: 5.01V
VCC: 4.85V
SS: 4.76V
FB: 0.812V
FREQ: 3mV
There seems to be no switching going on in SW output. What could be the problem here? Double checked all the footprint pinouts and resistor values, all seems OK.

2

Hello,

If it is not switching and there is input supplied, VCC is up, and EN on, I suggest checking if there are any shorts on high and low side fet. Additionally you can monitor the input, switch node, inductor current, and output voltage on the scope to check the behavior in time as opposed to a single measurement from DMM.

Best Regards,
Yu