TPS61090 - start-up into 1A load

Q: TPS61090 - start-up into 1A load - PowerMat - URGENT!!!!!!!!!!!!! by 741196

I encounter the problem below that prevent them to wake up to 1A load.

I try to put a load switch at the output and to allow it after the step up converter is already stable.

 However it doesn’t work,  and after turning ON the load switch and expose the TPS61090 to the 1A load, the voltage is collapsing, not to GND but to a lower voltage.

 I believe a current limit event is happening due to the sudden load.  

Vin is Li-Ion and output voltage can reach a 1A load to charge a cell phone. Load will turn on in a sudden way.

 

Thanks

Amit

 

Hello Amit

I have looked at this in the lab using the standard TPS61090 EVM and also see what the customer is reporting.

But this is normal start up behavior for the device, see data sheet page 16 Softstart section.  If there is no load on the device it will start normally.  But if there is a load present during start up the device may get stuck in one of the start up steps.  Output current is reduced during start up and to exit each step of the voltage must rise.  Problems occur when the load is large enough to prevent the output voltage rising.

 

Also see

http://focus.ti.com/lit/an/slva387/slva387.pdf

 


A: Re: TPS61090 - PowerMat - URGENT!!!!!!!!!!!!! by 10449

Amit, per your separate email, the customer added additional output capacitance to the output of the TPS61090 and this solved their problem.  Can we consider this closed?  We know that the TPS61090 IC behavior of not starting into full load current with an electronic load is expected.  This can change from electronic load to electronic load.  Adding capacitance may have shifted the operation of the electronic load so it now works with the IC.

Thanks,