LMR23625-Q1: Low Dropout Operation

tateo yamashiro

Guru 10890 points

Part Number: LMR23625-Q1

Hi,

We got a question from the customer about LMR23625-Q1.
Could you help us?

[Question]
They are considering using this IC under the following condition.

Vin=3.9V min
Vout=3.3V
Iout=1A

In this condition, the IC will enter the low dropout operation. Therefore they want to make sure whether the IC can regulate 3.3V output at 3.9V input voltage conditoin. Could you provide below datas?

- How much is the maximum value of Rds_on_HS and Toff_min?
- How much is the variation of the minimum switching frequency at low dropout condition?

They don't need guarantee. They will use it as reference.

Best Regards,
tateo

over 7 years ago

0 Arief Hernadi over 7 years ago

TI__Mastermind 23845 points

Hi,

The max Rdson is approximately 320 mohm
The max off time is approximately 150 ns
For the variation are you asking for the variation at the same Iout or at different Iout?

Thanks
-Arief

0 tateo yamashiro over 7 years ago in reply to Arief Hernadi

Guru 10890 points

Hi, Thank you for your quick reply.
They want to know the variation at 1A and 1.5A. Does the switching frequency increase as Iout increases at low dropout operation?

Best Regards,
tateo

0 Arief Hernadi over 7 years ago in reply to tateo yamashiro

TI__Mastermind 23845 points

Yes, given the same VIN, the frequency will be slightly different due to efficiency. The higher the current, the switching frequency will be slightly higher because it has to switch more to keep the same output voltage. But this value is also dependent on what inductor because of the (DCR) series resistor on the inductor.

0 tateo yamashiro over 7 years ago in reply to Arief Hernadi

Guru 10890 points

Hi, Thank you for your support.

They measured the low dropout operation by EVM. As the result, the minimum fold-back frequency was 175kHz at 1A load. The IC could regulate 3.3V even it the input voltage reduces to 3.63V. So they want to make sure the variation of 175kHz. How much the variation should they consider? Is there possibility to vary to such as 400kHz?

Best Regards,
tateo

0 tateo yamashiro over 7 years ago in reply to tateo yamashiro

Guru 10890 points

Hi, Is there any update on that? We would appreciate it if you could give us your feedback.

Best Regards,

tateo

0 Arief Hernadi over 7 years ago in reply to tateo yamashiro

TI__Mastermind 23845 points

Hi Tateo,

Yes, there will be some variation but we do not have the characterization for the data.

Thanks
-Arief

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LMR23625-Q1: Low Dropout Operation