TPSM82810: Low Drop Out Resistance

Kazuki Itoh

Genius 10820 points

Part Number: TPSM82810
Other Parts Discussed in Thread: TPSM82480

Hello team,

My customer is looking for low drop out resistance module for the requirement below:

VIN 3.3V or 5V (nominal)

VOUT 3.3V

IOUT 1A

I proposed my customer TPSM8282x and TPSM8281x. My customer told me that the max. dropout resistance needs to be < 30mOhm to secure the margin.

My customer is considering to build 3.3VIN and 5VIN model seperately, but if TI has module solution with lower dropout resistance, it would be helpful to unify the models.

Does TI have such a solution?

Regards,

Itoh

over 5 years ago

0 Chris Glaser over 5 years ago

TI__Guru**** 150930 points

Hi Itoh-san,

The TPSM82480 gets very close to 30 mOhm. Because of its dual-phase architecture, we divide the Rdson by 2 to get an equivalent resistance. See equation 3 in the D/S.

0 Kazuki Itoh over 5 years ago in reply to Chris Glaser

TI__Genius 10820 points

Hi Chris,

The high-side Rds-on is close to 50mOhm at VIN = 3.3V and 85degC.

Therefore,

R_dropout = 50mOhm/2 + 13.5mOhm = 38.5 mOhm.

Is my calculation correct?

Regards,

Itoh

0 Chris Glaser over 5 years ago in reply to Kazuki Itoh

TI__Guru**** 150930 points

Hi Itoh-san,

Yes, that is basically correct. From figure 4, it looks more like 48 mOhm at 3.3Vin and 85 C.

One clarification on the inductor DCR in equation 3: the 27 mOhm is the maximum DCR at 125 C. Typically at 25 C, it is 20 mOhm. This DCR needs to be divided by half to account for the 2 phases.

So for 85 C and 3.3Vin, the dropout resistance estimate would be: 48/2 + ~24/2 = ~36 mOhm.

0 Kazuki Itoh over 5 years ago in reply to Chris Glaser

TI__Genius 10820 points

Hi Chris,

I was missing the temperature dependence of DCR. Thank you for your help!

Regards,

Itoh

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TPSM82810: Low Drop Out Resistance