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TPS74801: DRCT

JIONG QIU
Prodigy 60 points
Part Number: TPS74801
Other Parts Discussed in Thread: TPS7A88

Tool/software:

Hello, the project is urgent and we hope to get your reply as soon as possible  !!!

1.The voltage of Vbias in the design of TPS74801 is 3.3V. We want to use it to convert from 2.1V to 1.8V, and the current is about 0.5A. Is this design reasonable? Since the voltage of Vbias in the specification must be VOUT+1.6V, if the load current is less than 1.5A, can the voltage drop of Vbais be reduced?

2，There is also a question about the TPS7A8801; This is a two-channel LDO, whether there will be crosstalk between the two Ldos inside the chip, or through the peripheral devices and GND crosstalk, and the two are respectively to supply analog power.

  • 0
    TI__Genius 14450 points

    Hi Jiong Qiu,

    1. From Figure 5-13 and 5-14 in the TPS748 datasheet, if load current is 500mA or less, typical Vbias dropout voltage will be around 1.2V for both legacy and new chips. With the new chip, max Vbias dropout is 1.43V, which would allow 1.8V output with a 3.3V bias supply.

    For legacy devices, a 3.3V bias supply might not be sufficient, as the 1.2V typical can be expected to vary over process and temperature conditions.

    You can order the TPS74801DRCRM3 part number to ensure you receive the new chip, if desired. 

    2. The TPS7A8801's 2 regulators are completely independent, with typical channel to channel isolation of 60dB or more up to 200kHz (see TPS7A88 datasheet figure 7). Careful layout will be required to minimize other crosstalk sources, like ground crosstalk or the impacts of load transients on the TPS7A8801's Vin. 

    Best Regards,

    Alex Davis