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TRS3253E: Deviation from Recommended charge pump cap values for TRS3253E

Akshat Garg
Intellectual 1040 points
Part Number: TRS3253E

Hi,

As per table in datasheet (Vcc vs cap values), Can customer use C2, C3 and C4 as 0.47uF and C1 as 0.1uF. Will this affect the operation? Operating voltage (VCC) is 5V.

Thanks,

Akshat

 

  • 0
    TI__Guru 62920 points

    Hi Akshat,

    These values are fine to use and align with the datasheet recommendations.

    To get a better understanding of the charge pump operation in these devices and how different capacitor values impact operation, you may want to reference this blog:

    https://e2e.ti.com/blogs_/b/analogwire/archive/2018/06/28/how-the-rs-232-transceiver-s-regulated-charge-pump-circuitry-works

    If you have any further questions please let us know.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Prodigy 20 points

    Hi Max,

    In the datasheet, given Vcc values are 3.3V, 5V and '3V to 5.5V'. For '3V to 5.5V' the given cap values are C1 = 0.1uF, C2, C3 and C4 = 0.47uF.

    In our design Vcc is 5V and used cap values are 0.047uF and 0.33uF for C1 and C2,C3 & C4 respectively. But due to cap unavailability in X7R value, we need to change cap value but need to maintain 5V Vcc. So can I use the cap values 'C1 = 0.1uF, C2, C3 and C4 = 0.47uF' for which Vcc range is '3V to 5.5V'?

    Can you give more info on Vcc range '3V to 5.5V'? Datasheet had not mentioned much about this option.

    Regards,

    Gurudev H P

    Review
    Anole-D ESD report
  • 0 in reply to Gurudev Prasad1
    TI__Mastermind 25705 points

    Gurudev,

    You're right. The config 'C1 = 0.1uF, C2, C3 and C4 = 0.47uF' can cover both 3.3V and 5V supplies. If your supply is 5V only, you have option to choose either 'C1 = 0.047uF, C2, C3 and C4 = 0.33uF' or 'C1 = 0.1uF, C2, C3 and C4 = 0.47uF'. If some cap values are not available, you could try to make C1/C3 ratio close to 0.0047/0.33 or 0.1/0.47, while keeping C2=C4. I hope this makes sense to you.

    Regards,

    Hao