TPS63070: TPS63070 FB Resistors

Ian Wang

Mastermind 30090 points

Part Number: TPS63070

Hi Sir,

Can I use 0201(1/20W) resistors in FB/EN pin? It looks small current only, just double check.

Thanks, Ian.

over 5 years ago

0 Milos over 5 years ago

TI__Expert 7925 points

Hi Ian,

Thanks for reaching out.

Yes you can.

Best regards,
Milos

0 Ian Wang over 5 years ago in reply to Milos

TI__Mastermind 30090 points

Hi Milos,

One more question, what current spec. of L? 1A is enough? Thanks.

Thanks, Ian.

0 Milos over 5 years ago in reply to Ian Wang

TI__Expert 7925 points

Hi Ian,

That depends on the operating conditions. Please refer to section 9.2.2.2 Inductor Selection of the datasheet to calculate the required current rating of the inductor.

Best regards,
Milos

0 Ian Wang over 5 years ago in reply to Milos

TI__Mastermind 30090 points

Hi Milos,

Yes, I saw the table.5 of 9,2.2.2. but my customer complain current is around 4.6A(15uH).

I it really need 4.6A inductor? Can it reduce ?

Thanks, Ian.

0 Milos over 5 years ago in reply to Ian Wang

TI__Expert 7925 points

Hi Ian,

Can you please post the customers Vin, Vout and Iout range, so I can double check it?

Whatever the equation says, that should be the rating of the inductor, not less. Otherwise the inductor will saturate and the converter will not operate properly.

Best regards,
Milos

0 Milos over 5 years ago in reply to Ian Wang

TI__Expert 7925 points

Hi Ian,

Also, a note. I was referring to equations 7 and 8 to estimate the ratings fro the inductor, not the table. The table just gives some recommended inductors, depending on the input/output voltage and output current the rating can be lower.

Best regards,
Milos

0 Ian Wang over 5 years ago in reply to Milos

TI__Mastermind 30090 points

Hi Milos,

VIN=6~20V，VOUT=5V， IOUT=2A.

Thanks, Ian.

0 Milos over 5 years ago in reply to Ian Wang

TI__Expert 7925 points

Hi Ian,

Could you please double check and confirm the requirements? Because:

The maximum input voltage for the TPS63070 is 16 V.
For the above conditions, it seems that a buck device would be a better choice than a buck-boost device.

Nevertheless, if I assume Vin,max = 16 V, the inductor has to have a saturation current of at least 3 A.

Best regards,
Milos

0 Ian Wang over 5 years ago in reply to Milos

TI__Mastermind 30090 points

Hi Milos,

correction: Vin(max) is 14.5V

Pls advise how to calculate 3A?

Thanks, Ian.

0 Milos over 5 years ago in reply to Ian Wang

TI__Expert 7925 points

Hi Ian,

Worst conditions: V_IN,MAX = 14.5 V, I_OUT,MAX = 2 A.

Duty cycle:
D = V_OUT / (V_IN,MAX * eff) = 0.38

Peak inductor current:
I_L,MAX = I_OUT,MAX + (V_IN,MAX - V_OUT) * D / (2 * f_S * L) = 2.5 A

Add 20% headroom, and the required inductor saturation current is 3 A.

For more information on calculations, refer to:
http://www.ti.com/lit/pdf/slva535

Best regards,
Milos

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TPS63070: TPS63070 FB Resistors