UCD90320: Vout margin +/- 3% resistor calculation

Kam

Prodigy 40 points

Part Number: UCD90320

Hi ,

Can you sanity check the correct resistor value network for +/-3 % for following example :

Controller (LDO) device :

TPS7A5401

Vout = 0.90V

Vin = 1.20V

R1 = 12.4K

R2 = 100K

VFB pin is driven by UCD90320 Margin/GPIO (pin E12) through R3 = R4 = 178K , C1=1000pF. Are R3, R4 values correct to achieve 0.90V +/- 3% ?

Need a sanity check on calculation result, Please advise.

Thanks

Kam.

over 2 years ago

0 yihe over 2 years ago

TI__Guru 66380 points

Please provide your calculated spreadsheet.

Regards

Yihe

0 Kam over 2 years ago in reply to yihe

Prodigy 40 points

Hi Yihe,

I have provided the calculated values in original email :

R3 = R4 = 178K , C1=1000pF.

Do you need more info. ?

Thx.

Kamran

0 yihe over 2 years ago in reply to Kam

TI__Guru 66380 points

What is the vref?

Regards

Yihe

0 Kam over 2 years ago in reply to yihe

Prodigy 40 points

Hi Yehi,

The Vref is 0.60V.

Thx.

Kamran

0 yihe over 2 years ago in reply to Kam

TI__Guru 66380 points

That's why i asked your file at the first place

With Vref=0.6V, your Vout is 0.674 instead of 0.9V

Regards

Yihe

0 Kam over 2 years ago in reply to yihe

Prodigy 40 points

Hi Yihe,

My apologies, the Vref is 0.80V. Vout = [(12K/100) + 1] * (0.80V)

Thx.

Kamran

+1 yihe over 2 years ago in reply to Kam

TI__Guru 66380 points

Yes, For the C1. you may need adjust based on the ripple measurement.

Regards

Yihe

0 Kam over 2 years ago in reply to yihe

Prodigy 40 points

Thanks for your quick response..

Power management

Power management forum

UCD90320: Vout margin +/- 3% resistor calculation