TPS62740: When Vin<2.2V, TPS62740 does not work, but the resistance between the Vout and GND is 20-30 ohms.

Kevin Chen81

Part Number: TPS62740

TPS62740 Vin Voltage range is 2.2~5.5V

We encounter a problem that when Vin is less than 2.2V, Vout is almost connected to the ground.

Is the resistance between the Vout and the GND very small when the chip is not working?

Is there any explanation from the internal circuit of the chip?Like the Vout Discharge circuit, the internal feedback divider network, etc.

TPS62740 TPS62742 bd_TPS62740_41.gif

over 6 years ago

0 Alfonso Furio over 6 years ago

TI__Expert 3645 points

Hello,
Sorry for the delay due to the holidays period. We will get back to you as soon as possible in the first week of January.

0 Chris Glaser over 6 years ago

TI__Guru**** 150950 points

Hi Kevin,

How/where did you measure the 2.2Vin? Was this on the IC's pins? Can you share a waveform of Vin, Vout, and SW at 2.3Vin and 2.2Vin?

2.2Vin is quite low and near the UVLO level. Per the D/S, the output discharge resistor (30 Ohm typical) is activated in UVLO.

0 Kevin Chen81 over 6 years ago in reply to Chris Glaser

Intellectual 340 points

Hi Chris,

Thanks for your reply.

I am not very clear about how they mesure the voltage.

I have got the following information from the datasheet of TPS62740.

1)Vuvlo+ is from 2.075 to 2.15V.
2)Vuvlo- is from 1.925 to 2 V

The confusion of our users is when Vin =1.8V，the Vout is connect to GND.
The Vin is lower than 1.925, and the Vout is lockout. I explained that to them. And I showed the figure 6 of the datasheet too.
Our customers agree with this view very much.

I look forward to your reply.And I wander if there is any problem with my explanation.

Best Regards.

0 Chris Glaser over 6 years ago in reply to Kevin Chen81

TI__Guru**** 150950 points

Yes, figure 6 explains this.

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TPS62740: When Vin<2.2V, TPS62740 does not work, but the resistance between the Vout and GND is 20-30 ohms.