TPS56C230: Recommended inductance for 0.9Vout

Kazuto Tatsumi

Part Number: TPS56C230
Hi,

The recommended component value is mentioned as Figure 3 on the datasheet, but the customer wants to know the recommended value for 0.9Vout not listed on the table.

According to the webench, the recommended inductance for the system requirement below is 0.68uH. Which is better to use 0.47uH or 0.68uH?

System requirements:
Vin = 12.1V (+/-5%)
Vout = 0.9V
Iout = 12A (Max)
Load: Vcore for processor

Inductor: SPM6530T-R47M170 or SPM6530T-R68M140

https://product.tdk.com/info/en/catalog/datasheets/inductor_commercial_power_spm6530_en.pdf

Best Regards,
Kazuto

over 5 years ago

0 Yuchang Zhang over 5 years ago

TI__Mastermind 18510 points

Kazuto, recommend to use 0.68uH as default.

Yuchang

0 Kazuto Tatsumi over 5 years ago in reply to Yuchang Zhang

TI__Intellectual 2820 points

Hi Yuchang,

Thanks! However if they choose 0.68uH (SPM6530T-R68M140), the Isat looks close to the peak IL according to the WEBENCH below. Do you think is it no problem?

https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=747FF2864601CA31

Regards,
Kazuto

0 Yuchang Zhang over 5 years ago in reply to Kazuto Tatsumi

TI__Mastermind 18510 points

Hi Kazuto,

You can check the curve of inductor value & current, for SPM6530T-R68M140, when current is close to 16A, inductor value will drop to around 0.5uH, and for R47-0.47uH, it is about 0.39uH@16A, so SPM6530T-R68M140 looks better.

Yuchang

0 Kazuto Tatsumi over 5 years ago in reply to Yuchang Zhang

TI__Intellectual 2820 points

Hi Yuchang,

Thanks for checking the inductor.

I have an additional question. Does the inductor peak current affect to the OCP? Is the overcurrent detected at the bottom of inductor current?

According to the datasheet, the output overcurrent limit is implemented using a cycle-by-cycle valley detect control circuit during OFF state. If the OCP is detected just after turn-off, too high peak current lead to trigger OCP reluctantly. If the OCP is detected at the bottom of inductor current, too much ripple may cause a saturation beyond the OCP, I think.

Best Regards,
Kazuto

0 Yuchang Zhang over 5 years ago in reply to Kazuto Tatsumi

TI__Mastermind 18510 points

Kazuto,

IC sense valley of current ripple to trigger OCP, in my opinion, the peak value should not impact the OCP, even it has, it should be a little. and also you can see the inductor VS current curve is for DC current not peak current.

Yuchang

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TPS56C230: Recommended inductance for 0.9Vout