TPS61322: inductor selection

Toshiro Imi

Part Number: TPS61322
Other Parts Discussed in Thread: TPS61098, TPS61099

Hello,

Our customer is looking for a way to get higher efficiency by using TPS613222A, so I am running WEBENCH to know the most effective inductor to take. Because the inductor is the one of the parameter to fix the switching frequency, larger the inductor lower the switching frequency. Then finally the customer is going to achieve higher efficiency by taking lower switching frequency.

However WEBECH do not recommend higher than 2.2uH inductor whereas the datasheet specify TPS613222A is able to take up to 13uH inductor.

Could you please let me know if TPS613222A bans larger than 2.2uH inductor. Our customer test condition is Vin=3.3V, Vout=5V, Iout=30mA.

Best regards,

over 4 years ago

0 Minqiu Xie over 4 years ago

TI__Mastermind 21565 points

Hi Imi:

It's ok to select larger inductance which still within the recommend table. But the larger inductance may need larger Cout to keep the loop stable.

What's the efficiency target of customer? For such light load, TPS61098 and TPS61099 can do well.

0 Toshiro Imi over 4 years ago in reply to Minqiu Xie

TI__Expert 7190 points

Thank you for your feedback.

Do I understand WEBECH design works incorrectly? WEBENCH bans to choose >4.7uH inductor.

I have also checked the efficiency differences by WEBENCH and found out 2 to 3% improvement.

Even if it might be came from DRC differences but lower the switching frequency also contributes the efficiency improvement.

I also understood either TPS61099 or TPS61098 is the best but this customer 1st priority is the price.

best regards,

+1 Minqiu Xie over 4 years ago in reply to Toshiro Imi

TI__Mastermind 21565 points

Hi Imi:

If the inductance is too large, it will bring bad loop because of the right-half-phase zero. But I think the risk is not large if the L within 10uH. It's better to do load transient test to ensure that.

0 Toshiro Imi over 4 years ago

TI__Expert 7190 points

thank you for your help. I understood.

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TPS61322: inductor selection