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IWR1642: Low cost discrete solution to replace LP87542B-Q1

Part Number: IWR1642
Other Parts Discussed in Thread: LP87524B-Q1, , TPS652510, TPS61097A-33, TPS7A91, TPS7A88, TPS386000

Hi Team,

My customer is evaluating IWR1642 and feedback the related PMIC LP87524B-Q1 is too expensive and don't have Non-auto version.

So they're asking whether can use a discreta solution to replace LP87524B-Q1, so could you kindly help to check the possibility and suggestion?

Some related items like: whether IWR1642 need specific sequence / delay / Reset fucntion and so on come from LP87524B-Q1?

And whether it need dynamic adjust Vo @ operating?

Thanks & BRs,

Cheney

  • Hello Cheney,
    No dynamic adjustment of the voltages are required, the only requirement is that the voltages must be stable before the nRST of the IWR device is released. The requirement for the supplies are mentioned in the datasheet , section 5.5. If you can meet those requirements using discrete it should be fine.

    regards,
    Vivek
  • Hello,

    We have 4 power rails, and 3 LDOs.    1.2v core and DSP, 1.8v for 1.3v LDO and digital 1.8v, 2.2v for 1.8v LDO, and 3.3v for QSPI flash, and GPIO.

    The Power Management guide, slvt145q.pdf , can be used to select power supply components.

    a) the 1.2v core rail - a current of 1 to 1.5A, this can be driven as a digital power supply with bypass capacitance, VDDIN, VIN_SRAM, VNWA

    b) the 1.8v rail - is used to drive the RF 1.3v (2) 1A LDO (1.8 to 1.3v), the current needed depends on the number of Tx and Rx RF ports used.  the RF power is sized based on the Table 5-4.  VIOIN_18 is also driven without an LDO.  The (2) 1Amp LDOs  (1.3v RF loads are VIN_13RF1, VIN_13RF2)

    c) the 2.2v rail - is used to drive the 1.8v LDO.   VIN_18CLK, VIOIN_18DIFF, VIN_18BB, VIN_18VCO, this is listed as .85A

    d) the 3.3v rail VIOIN (can be 33 or 1.8, we currently use 3.3v QSPI flash) (50ma) can be driven from another DCDC converter or a BOOST converter from another rail.

    the Power Management Guide, slvt145q.pdf , lists both the multiple output DC DC Converter, and LDOs for the power supply, several power supplies are possible

    only the EVM power supply has been designed and tested with the Radar Sensor, an example is:

    a triple output DC to DC Buck Converter, 3A - 1.8v, 2A - 1.2v, 2A - 2.2v - TPS652510

    a single output DC to DC Boost Converter, 2.2v input, 3.3v output (< 100ma) - TPS61097A-33

    1A Single LDO Low Noise High PSRR, 2.2vin, 1.8v output - TPS7A91

    Dual 1A LDO Low Noise High PSRR, 1.8vin, 1,3vout - TPS7A88

    Voltage Supervisor - a power good indicator is needed for the host processor, to wait 3ms and then release the nRST signal for the Radar Sensor.

       TPS652510 - has PGOOD open drain output

       TPS61097A-33, 3v3 output would have to be sensed with Supervisor

        TPS7A91 - has PGOOD open drain output

        TPS7A88 - has dual PGOOD open drain outputs   

        TPS386000 - combines 3 PGOOD, and 1 3.3v comparator to generate overall PGOOD signal

    You can simulate the power supply design with Webench on the TI website.

    Regards,

    Joe Quintal