UCC2897A: reference design VIN question

Hardy Xue

Part Number: UCC2897A
Other Parts Discussed in Thread: PMP5123, PMP3162

Hi Team,

The VIN pin (pin1) of UCC2897A only support minimum 18V in datasheet. I found a reference design PMP5123 that can support VIN form 8V to 36V. I saw there is additional circuit in PMP5123 as below picture. Due to my customer's spec that VIN need to support 7V-36V, I would like to know this working principle of circuit. Could you please explain the working principle?

https://www.ti.com/tool/PMP5123

Customer's spec:

Total power supply: 200W

Vin range: 7V~36V

Vout_nominal: 12V

Remain operational time when input power loss: 5mS

Isolation voltage: >500VDC

Best regards,

Hardy

over 3 years ago

0 Steven Mappus1 over 3 years ago

TI__Mastermind 33115 points

Hardy,

The PMP5123 design is working down to VIN=8V. I'm not sure if it will go down to 7V but if necessary, you should be able to adjust the gain of the op amp to achieve lower input voltage operation.

Attached is the test report and full schematic for the PMP5123 erf design:

Regards,

Steve

PMP5123_REVB_TEST.pdf

PMP5123_REVB_SCHEMATIC.pdf

0 Hardy Xue over 3 years ago in reply to Steven Mappus1

TI__Expert 3640 points

Hi Steven,

Thanks for your feedback.

Due to we are not familiar this circuit.

1. Could you please explain the working principle and how to adjust the gain?

2. Could we combine two reference design with PMP5123 and PMP3162? ex: add circuit of VIN in PMP5123 to PMP3162?

Best regards,

Hardy

0 Steven Mappus1 over 3 years ago in reply to Hardy Xue

TI__Mastermind 33115 points

1. Could you please explain the working principle and how to adjust the gain?

I would recommend to test the circuit as it is shown and determine if it can operate down to VIN=7V. You can adjust the gain just like any op amp with negative feedback. You increase/decrease R24.

2. Could we combine two reference design with PMP5123 and PMP3162? ex: add circuit of VIN in PMP5123 to PMP3162?

Yes

Regards,

Steve

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UCC2897A: reference design VIN question