TPS3702: Rpu value and question about IUV(min)

Zhihong Huang

Part Number: TPS3702
Other Parts Discussed in Thread: TPS3700

Hi Team

As you can see in the picture, I used 10K as the value of Rpu in my design. But in the datasheet of TPS3702, the range of IUV is 0.3mA to 10mA. so I want to ask;

1. If I used 10K as the value of Rpu in my design, the IUV is 0.33 which is closed to the IUV(min), is there any risk when IUV closed to the IUV(min)? please kindly explain it specifically.

2. Why you put the IUV IOV current limit in the datasheet, it seems that this spec won't cause any issue when use the TPS3702, could you help me understand that?

Thanks

Best reagrds

Wesley huang

Wesley-huang@ti.com

over 4 years ago

0 Abhinav.Sharma over 4 years ago

TI__Genius 9375 points

Hi Wesley,

For your question, this should not be a problem. If you look at our absolute maximum ratings, we actually specify ±40 mA as the range for IUV and IOV. Although we recommend 0.3 to 10 mA, getting close should not be a big issue. We put the current limits on the datasheet because operating at the edges could cause issues maintaining a stable output voltage. I don't think low output current should be an issue, however.

Thanks,
Abhinav.

0 Zhihong Huang over 4 years ago in reply to Abhinav.Sharma

TI__Intellectual 1550 points

Hi Abhinav

Thanks for your answer. I still have two questions.

1. Could you explain more specifically about why operating at the edges could cause issues maintaining a stable output voltage from the perspective of low IUV

2. Could you specifically explain the consequence when output voltage is unstable?

3. Could you please recommend a Rpu based on the design I have put in the former reply?

Thanks

Best reagrds

Wesley huang

Wesley-huang@ti.com

0 Abhinav.Sharma over 4 years ago in reply to Zhihong Huang

TI__Genius 9375 points

Hi Wesley,

I can reach out to the design team for a little more clarity on the issues with using certain pull-up resistances. That being said, you should use a 10k resistor for Rpu, as is also used in the EVM.

Thanks,
Abhinav.

0 Zhihong Huang over 4 years ago in reply to Abhinav.Sharma

TI__Intellectual 1550 points

Hi Abhinav

Thanks for your answer and Rpu recommendation .I hope that I could get the answer as soon as possible.

Thanks

Best regards

Wesley huang

Wesley-huang@ti.com

0 Abhinav.Sharma over 4 years ago in reply to Zhihong Huang

TI__Genius 9375 points

Hi Wesley,

To answer this question, please take a look at the TPS3700 datasheet section 8.2.2.2:

This will allow you to appropriately pick a pull-up for the similar device TPS3702.

Thanks,
Abhinav.

0 Zhihong Huang over 4 years ago in reply to Abhinav.Sharma

TI__Intellectual 1550 points

Hi Abhinav

Thanks for your answer. I still have a questions.

1. the 8.2.2.2 just mentioned about the pull-up voltage does not exceed the sink-current capability of the device, but it still can't explain why the Rpu can't not be selected the too large value.

Thanks

Best reagrds

Wesley huang

Wesley-huang@ti.com

0 Abhinav.Sharma over 4 years ago in reply to Zhihong Huang

TI__Genius 9375 points

Hi Wesley,

The resistor cannot be too large to affect the recognition of logic low levels on the output. A in-depth and careful analysis of this is provided in Choosing an Appropriate Pull-up/Pull-down Resistor for Open Drain Outputs. This app note will help analyze the range that is appropriate.

Thanks,
Abhinav.

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TPS3702: Rpu value and question about IUV(min)