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TPS7A87: VREF/ PG/ VOUT equation

Kurumi Hasegawa
Expert 6601 points
Part Number: TPS7A87

Hi team,

 

I’ve got three questions on TPS7A87. Could you kindly take a look below?

 

Q1: The datasheet show VREF typical value (0.8V) only. Is there any data on MIN/MAX?

 

Q2: To make PG=High (pull-up), VFBx should be larger than VIT(PGx) + VHYS(PGx) according to the datasheet.

Expressed as a percentage of VOUTx(target), VIT(PGx) is 88.9% typ and VHYS(PGx) is 1% typ.

So in total VFBx should be larger than 89.9% of VOUTx(target), is my understanding correct?

 

Q3: There is VOUTx equation expressed with VREF on the bottom-left of Figure 41.

On the other hand, equation 1 of section 8.1.1.1 expressed VOUTx with VFBx.

Which one is correct?

If both equations are correct, then VREF=VFBx=0.8V typ ?

 

Best regards,

Kurumi

  • +1
    TI__Genius 12040 points

    Hello Kurumi-San,

                                 Regarding Question 1, the variation in the reference voltage is covered in the VOUT accuracy spec (±1%). I would recommend that this variation be accounted for when designing your system. At this time we do not have data of sufficient sample size to provide Min/Max values.

                                 Regarding Question 2, yes your understanding is correct, the PG threshold when VOUT is transitioning from Low to High is 89.8% of VOUT (typically).

                                 Regarding Question 3, yes both equations are correct, VREF = VFBX = 0.8V when device is in regulation. Thanks!

    Regards,

    Srikanth

      

  • 0 in reply to Srikanth Lolla Venkata
    TI__Expert 6601 points

    HI Srikanth-san,

    Thank you so much for the reply! Understood.

    Best regards,

    Kurumi