TPS2421 Faulting at startup

Mark Nohr

Other Parts Discussed in Thread: TPS2421-2

I'm finding at loads above 1.5A the TPS2421 faults at startup. Below that value there is no fault generated. Which rock to look under?

Vin - 5V

CCT - 0.047uF

Iset - 3A - 66.5K resistor

If I increase the CCT capacitor to something large to stave off the fault the PG led is green for ~500ms then the fault is still triggered.

TPS2421_Design_Tool_Rev-.xls

over 9 years ago

0 Eric Wright over 9 years ago

TI__Mastermind 42795 points

Mark,

Moving this to the load switch forum. Your value choices seem fine from the tool you attached. Is the load attached start up resistive or is it an E-load?

0 Mark Nohr over 9 years ago in reply to Eric Wright

Intellectual 570 points

Have tried both resistors and a programmable load.

0 Mark Nohr over 9 years ago in reply to Mark Nohr

Intellectual 570 points

I should also mention if I start up under 1.5A I can then increase the load to 3A without faulting.

0 Venkata Nandam over 9 years ago in reply to Mark Nohr

TI__Intellectual 2800 points

Hi Mark,

I have modified the TPS2421-2 EVM to check the startup with load. It does not seems to have any issue even in starting with 2.3A load current.

Here is the scope shot for the following test conditions:

Vin=5V, Load = 1.6A (Resistive load), Cout=100uF, Rlim=68k, Ct=0.1uF.

Please provide scope shot of the issue, schematic and layout. Will be useful to debug. Make sure to use resistive load for start-up.

Regards,

Venkat

Power management

Power management forum

TPS2421 Faulting at startup