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LP87524B-Q1: Multi phase question

Zirui Su
Expert 5340 points
Part Number: LP87524B-Q1

Hi team

I would like to ask that 

1. Comparing the specifications of LP87524B and LP87524T, it is found that LP87524B does not support multiphase function. Are there any other differences between the two chips? Please help clarify, thank you.

2. In addition, if LP87524B does not have multiphase, what is the default phase of the 4 channels respectively?

0x02 register of LP87524TQ1

0x02 register of LP87524BQ1

Here is the LP87524T datasheet:

lp87524T.pdf

  • 0
    TI__Genius 11020 points

    Hello Zirui,

    LP87524B and LP87524T are both 4 output devices and don't use outputs connected together or work in multiphase mode. LP8752x datasheet is generic for all phase configurations, but LP87524x specifically is a 4 output device (the 4 in the part number denotes the phase configuration). LP87524B/T are the same device, but they are programmed with different default settings in the OTP memory. You can find the specifics in the TRMs: 

    https://www.ti.com/lit/ug/snvu606a/snvu606a.pdf

    https://www.ti.com/lit/ug/snvu663a/snvu663a.pdf

    LP87524B-Q1 has been configured to power AWR chip (radar) which has tight requirements on the noise performance and therefore the switching frequency is set to 4MHz. In LP87524T switching frequency is 2MHz. That is why there is a separate datasheet for the LP87524B/J/P since those are mainly for radar power and operate at higher SW frequency compared to the "normal" LP8752x.

    Thanks.

    Regards,

    Tomi Koskela

  • 0 in reply to Tomi Koskela
    TI__Expert 5340 points

    Hi Tomi

    Thanks for your quick reply. For question 1 I still want to know the detail. Do you mean the LP87524B and LP87524T both could work in multiphase mode? I do not see the configuration of LP87524B multiphase mode specification. Since in LP87524T there is a detailed instruction in 0x02 reg that could support multiphase, I want to know the configuration of LP387524B multiphase mode, thank you again.

  • 0 in reply to Zirui Su
    TI__Genius 11020 points

    Hello Zirui,

    Phase configuration is fixed by factory programming, so it is not possible to change it by register write. So all LP87524x devices are fixed to 4 output mode. The datasheet might be misleading in this sense, since it shows R/W access to the multiphase bits. Technically it is correct, you can read and write this register, but it won't effect the operation of the device. 

    Thanks.

    Regards,

    Tomi Koskela

  • 0 in reply to Tomi Koskela
    TI__Expert 5340 points

    Hi Tomi,

    Sure, so could I understand that the LP87524B is also fixed with 4 phases in 4-phase configuration? What is the relationship between you said '4 output mode' and '4 phases in 4-phase configuration', and what the phase configuration factor has programmed into it?  

  • 0 in reply to Zirui Su
    TI__Genius 11020 points

    Hi Zirui,

    Yes all LP87524x devices are configured to four single phase outputs. The FPWM_MP bits effect the operation only if the device is programmed to let's say 3+1 phase configuration (LP87522x). See LP87524 datasheet section 5, device comparison table. 

    Thanks.

    Regards,

    Tomi Koskela