TPS40057: Adjustment of sink and source phase compensation

Kaji@PAN

Part Number: TPS40057

Hi,

I am considering TPS40057 for VCOM of LCD circuit.
I will attach the circuit diagram and calculation result I created.
The constants of the circuit diagram are provisionally input. The final constant value is still under consideration.

I would like to ask about the phase compensation constant.
In my specification IOUT is both sink and source.
I entered "1" and "-1" in the IOUT_max field of the Excel sheet, but the phase margin is "1" worse.
Should I choose the phase compensation constant when setting "1"?

(specification)
VIN : 12V ± 1.2V
VOUT : 3.6V
IOUT : ±1A(typ), +1mA (min)
Ambient temperature: +85°C to -40°C

Best regards,

TPS40KType III Loop Stability kVenable_sluc263c-071312_test1_20171204.xls

TIBuck1chNEW20171204.xlsx

over 7 years ago

0 YangZhang over 7 years ago

TI__Genius 11085 points

I've notified the responsible engineer and he will get back to you soon.

-Yang

0 Ambreesh Tripathi over 7 years ago in reply to YangZhang

TI__Expert 6860 points

Kaji ,

What do you mean by -1 as the load . How are you sinking 1A load ? Is the loop active during the sink of 1A load .

Also are you using any electrolytic cap .If yes can you change the quantity to one in the calculation sheet .

----Ambreesh

0 Kaji@PAN over 7 years ago in reply to Ambreesh Tripathi

Mastermind 7775 points

Thank you for your reply.
I'd like to check the phase margin at sinking and the phase margin at source.
So, I set the sink "-1" and the source set "1" to calculate.
Is this correct?

A circuit diagram is attached to the attached Excel sheet, but the output capacitor is a ceramic capacitor. Four 10uF are arranged in parallel.
The ESR of the ceramic capacitor is 3 mΩ at 1 MHz, but 70 mΩ at 550 kHz.
Therefore I set 70 mΩ when calculating.

Best Regards,

0 Ambreesh Tripathi over 7 years ago in reply to Kaji@PAN

TI__Expert 6860 points

Kaji,

Can you please elaborate more on Source /Sinking of the load ? What is the application ?
Are you thinking about the CCM operation in light load application ?
I would recommend to use 1A source for the loop calculation .

---Ambreesh

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TPS40057: Adjustment of sink and source phase compensation