TPS61088-Q1: Part not turning on

Markus Suorsa

Part Number: TPS61088-Q1

I've implemented the TPS61088-Q1 into a design with the following schematic:

The input is 3-4.2 V and I need to boost up to 8V at 2A. I got this design using the WEBENCH tool.

When I supply the input voltage at 4V, I see 3.5V at Vout, which is expected when the device is not enabled. However, when I supply 3.3V logic at the enable pin, the state does not change at all. Still 3.5V at Vout. I probed both Vcc and the SS pins before and after asserting the enable pin, and strangely both pins read at 0V. I expect the Vcc pin to have some kind of voltage output regardless of enable, but it appears that the internal LDO isn't being enabled to supply the IC. Am I missing something or is there an error in my application?

Thanks,

Markus

over 6 years ago

0 Helen chen over 6 years ago

TI__Mastermind 40080 points

Dear Sir,

Please check whether the Vcc pin, SS pin is well soldered. If the VCC pin is well soldered, there should be an ESD diode from the GND to the pin. If you can detect out the diode, then the solder is OK!

By the way, what is the total output capacitance in your application?

0 Markus Suorsa over 6 years ago in reply to Helen chen

Prodigy 70 points

Hi Helen,

Thanks for the reply. I checked for diode between VCC and GND and I indeed detected a 0.5V drop. I had the chip replaced too and made sure it was soldered properly.

As you can see in my schematic I have 2x 15uF capacitors and a 10 uF capacitor for a total of 40 uF. Immediately following the capacitors I have a 30mOhm shunt resistor for current sense.

Thanks,

Markus

0 Helen chen over 6 years ago in reply to Markus Suorsa

TI__Mastermind 40080 points

Dear Sir,

it seems the IC didn't startup at all, did you measure the Vin pin, EN pin/FB pin ESD diode?

0 Markus Suorsa over 6 years ago in reply to Helen chen

Prodigy 70 points

I found the problem. I had the pins wrong in the footprint - pin 1 starts at the short side of the IC instead of the long side. Thank you for the support.

Thanks,

Markus

0 Helen chen over 6 years ago in reply to Markus Suorsa

TI__Mastermind 40080 points

Thanks for the update. Good luck!

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TPS61088-Q1: Part not turning on