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Original question:

TL7702B: Power consumption of TL77xxB vs. TL77xxA

TL7702B: Vit- internal circuit

Shunsuke Nagata
Genius 12580 points
Part Number: TL7702B
Other Parts Discussed in Thread: TL7705B, TL7733B, , TPS3808, TPS3890

Hi,

Could you please give me advice about TL7702B, TL7705B and TL7733B? 

My customer would like to adjust voltage divider rate which consists R1 and R2 by adding series resister at SENSE pin. Then, he would like to know below information .

1. Is the Vx made from Vcc? or made from Reference Voltage 1 (REF)? 
 Vx voltage is higher than REF. I guess Vx made from Vcc. Is it correct?

2. Could you please give me R1 and R2 information for TL7702B, TL7705B and TL7733B?
I found application note (http://www.tij.co.jp/jp/lit/an/slvae04/slvae04.pdf)

There are TL7702 and TL7705 information. But are these data same as TL7702B and TL7705B?

And could you please let me know  R1 and R2 data of TL7733B?

3. Do you have reference schematic which adjust divider rate of R1 and R2 by adding resister at SENSE pin?

Regards,
Nagata.

  • 0
    TI__Genius 12630 points

    Nagata,

    I was able to locate old version datasheet for TL7702B and TL7705B.

    1. From block diagram, Vx comes from the reference voltage and reference voltage comes from Vcc. But the Vx voltage is not directly equal to reference voltage which is why there is the adjustable resistor symbol in between the reference and Vx. This indicates the Vx changes depending on the device variant.

    2. From previous revision of datasheet before TI switched to new format for datasheets, I found the schematic attached.

    3. We typically don't recommend adding series resistor to change voltage threshold because the additional resistor provides more inaccuracy because of the tolerance of the external resistors and also the internal resistors have tolerance. A resistor divider is usually a more accurate approach but I think a series resistor can also work since the internal resistor value estimates are known.

    If you can tell me more about the application, I can recommend a newer and better device with the correct threshold.

  • 0 in reply to Michael_DeSando
    TI__Genius 12580 points

    Hi, Michael

    Thank you very much for your support. Could you please let me check about your #1 comment?

    Is the resister which is for Vx connected between Vcc and GND?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Genius 12580 points

    Hi, Michael,

    Could you please let me know the your recommend device which user can adjust threshold voltage via SENSE?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Genius 12630 points

    Nagata,

    The Vx value is shown above in Note A for each device variant. For TL7702B, Vx = Vref. For TL7705B and TL7733B, Vx ~1.43V.

    Our top devices with separate adjustable SENSE pin, please try TPS3890 (smaller SON package, adjustable to monitor any voltage of 1.15V or higher) or TPS3808 (SOT23 package, adjustable to monitor any voltage of 0.4V or higher).