LM5064: Add different voltage to VCC and VAUXH

K. Sasaki14

Part Number: LM5064

Can we add different voltage to VCC and VAUXH with LM5064. Also it is not GND level.

Our customer is thinking the following using method.

Input rail: -48V
VCC: -35V
VAUXH: -41.2V (when input rail is -48V)

Please refer to the attached file for more information.
Is there no problem with such usage? Do you think that this circuit is more resistant to lightning surge?

LM5064 circuit.pdf

Best Regards,
Kohei Sasaki

over 6 years ago

0 Brian Daugherty over 6 years ago

TI__Expert 5940 points

Kohei,

With that you will have 13v bias on Vin at Vin = -48v (assume you have a 13v zener on Vcc). Vauxh will be 6.8v. This should function ok, but keep in mind impact on Vin telemetry scaling with the resistor divider on VauxH. Recommend you try on a LM5064 EVM, should be easy to see.

Brian

0 K. Sasaki14 over 6 years ago in reply to Brian Daugherty

Guru 10200 points

Brian-san,

Thank you for your answer.
Do you think that this resistor divider circuit is more resistant to lightning surge?

Best Regards,
Kohei Sasaki

0 Brian Daugherty over 6 years ago in reply to K. Sasaki14

TI__Expert 5940 points

It will be better, especially if a zener is added to VauxH. But you still need to protect the FETs. A well sized front end TVS protects all.

Brian

0 K. Sasaki14 over 6 years ago in reply to Brian Daugherty

Guru 10200 points

Brian-san,

In this circuit, where should we put the output shottky diode (datasheet Fig.17 D1)?

5545.LM5064 circuit.pdf

Is it between GND and OUT? or VCC and VEE?
If it is placed between VCC and OUT, the zener of VCC is damaged because current flows from out to zener when FET is OFF.

Is there any concern if shottky is placed between VCC and VEE?

Best Regards,
Kohei Sasaki

0 Brian Daugherty over 6 years ago in reply to K. Sasaki14

TI__Expert 5940 points

Kohei,

See your other E2E, responded to just now. Follow DS System Consideration section and refer to fig 15.

Brian

0 K. Sasaki14 over 6 years ago in reply to Brian Daugherty

Guru 10200 points

Brian-san,

I would like to know the shottky position with attached circuit. It has the protection circuit of OUT, SENSE, SENSE_K and VEE_K as a DS Fig.17.
Do you think we should put between OUT pin and GND?
Our customer is thinking to put between VCC and VEE.

Best Regards,
Kohei Sasaki

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LM5064: Add different voltage to VCC and VAUXH