TPS56428: TPS56428 and TPS54325 : Applying slow ramp voltage to EN pin

Masanori Tachibana

Part Number: TPS56428
Other Parts Discussed in Thread: TPS54325

Hi support team,

I have a question about the EN terminal of TPS54325 and TPS56428.
Our customer is going to design using TPS54235 and TPS56428 now.

[Question]
1. How much is the hysteresis voltage of VEN (EN pin input voltage) of TPS56428?
I think it of TPS54325 would be 100 mV according to the following thread:
e2e.ti.com/.../2837454

2. Since these ICs have hysteresis in VEN, can I consider that there is no problem to apply slow ramp voltage to EN pin?
For example, as ramp rate of voltage,
about 6 ms from 0 V to VENH
about 1515 ms from 8 V to VENL
The customer wants to set up an RC low pass filter on front of EN pin.

3.How much is the input impedance of the EN pin of the TPS54325?
The above thread states that there is a 350 kΩ pull-down on EN pin. Is that correct?
By the way, the datasheet of TPS56428 states that the EN terminal has a 350 kΩ (TYP) pull-down resistor.

Best regards,
M. Tachibana

over 4 years ago

0 JohnTucker over 4 years ago

TI__Guru**** 191445 points

Tachibana-san,

I originally researched that post you referenced. Yes there is 100 mV typical hysteresis and the internal pull down is 350 ohm. Slow ramp on EN should work.

0 Masanori Tachibana over 4 years ago in reply to JohnTucker

Genius 5350 points

Hi John-san,

Thank you for your reply.
Let me confirm once again, just in case.

1. Both TPS54325 and TPS56428 have 100 mV of hysteresis in VEN.
2. Both TPS54325 and TPS56428 have a pull-down resistance on VEN, which is 350 kohm instead of 350 ohm.

Are all the above 1 and 2 correct?

Best regards,
M. Tachibana

0 Masanori Tachibana over 4 years ago in reply to Masanori Tachibana

Genius 5350 points

Hi John-san,

I will ask you a same question again because there is no reply from you.
I organised my understandings int the previous post.
Is that correct?

Best regards,
M. Tachibana

0 JohnTucker over 4 years ago in reply to Masanori Tachibana

TI__Guru**** 191445 points

Tachibana-san,

Both devices have 350 ohm pull down. I am reasonably certain about the hysteresis bring 100 mV. The devices in that product family had two different EN threshold voltages, one slightly below 1 V and one slightly above. I do not have any easy way to verify TPS56428. I worked with those devices several years ago. I just answer this post to support during CNY.

0 Zhao Ma over 4 years ago in reply to Masanori Tachibana

TI__Genius 15135 points

Yes, 1 and 2 are correct.

0 Masanori Tachibana over 4 years ago in reply to Zhao Ma

Genius 5350 points

Hello Zhao-san,

Thank you very much for helping me.
I understand well.

Sincerely,
M. Tachibana

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TPS56428: TPS56428 and TPS54325 : Applying slow ramp voltage to EN pin