TPS563257: Power management forum

Malsekar Karthik Krishna

Part Number: TPS563257

Hi,

For the circuit similar to the one mentioned in the datasheet of TPS563257, I have connected 100k( to +Vcc) and 32k (to -Vcc) resistors instead (10nF is not connected) for the voltage divider to the enable pin.
The supply voltage is steady 5V DC, the voltage divider is supposed to deliver 1.49V to the enable pin (which is delivering 1.170V mostly due to the change in resistor values I reckon), inductor value was suggested to be 680nH which has been used in the circuit,
but it only delivers 0.78V instead of the required 0.85V.,

What could be the possibility of the 0.7V drop?
Please consider Figure 8-1 from datasheet of TPS563257DRLR

s/resized-image/__size/320x240/__key/communityserver-discussions-components-files/196/4452.tps.png

11 months ago

0 Zixu Wang 11 months ago

TI__Expert 8100 points

Hi Malsekar,

My colleague will give you reply soon!

BRs

Zixu

0 Lucia Gao 11 months ago

TI__Mastermind 18540 points

Hi Malsekar,

Please allow me to check you with about below questions to better understand your problems:

(1) Do you mean that your target output voltage is 0.85V, but you only get 0.78V Vout?

(2) You also mentioned about 0.7V drop. Could you please kindly let us know what does it refer to?

Thanks!

BRs

Lucia

0 Malsekar Karthik Krishna 11 months ago in reply to Lucia Gao

Prodigy 100 points

Hi Lucia,

My target voltage is 0.85V and I am receiving only 0.78V

I was referring 0.7V drop from the target voltage itself (0.85V - 0.78V)

0 Lucia Gao 11 months ago in reply to Malsekar Karthik Krishna

TI__Mastermind 18540 points

Hi Malsekar,

1. Could you please send me the schematic and share the feedback resistor values?

2. What is the load current? How did you test the output voltage? Did you use DMM and tested between the output capacitor?

Thanks!

BRs

Lucia

0 Malsekar Karthik Krishna 11 months ago in reply to Lucia Gao

Prodigy 100 points

Hi Lucia,

Feedback resistor values are mentioned in below attachment (highlighted), please check below

(For 5V from SMPS) : The load current I'm receiving is 0.52mA and voltage as 0.78V as tested in between the output capacitor using DMM

0 Lucia Gao 11 months ago in reply to Malsekar Karthik Krishna

TI__Mastermind 18540 points

Hi Malsekar,

Let me check and get back to you. Thanks!

BRs

Lucia

0 Lucia Gao 11 months ago in reply to Malsekar Karthik Krishna

TI__Mastermind 18540 points

Hi Malsekar,

Thanks for your feedback. I may need your help to share the waveform of VIN, SW, VOUT. Would you please also test the value of the resistor (R4 and R5 in the schematic) with your DMM? Would you please test the voltage value of FB pin to GND using DMM when it's working under steady state?

Thanks!

BRs

Lucia