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TPS628301: Precautions when using TPS628301 as a negative power supply

Conor
Guru 12175 points
Part Number: TPS628301
Other Parts Discussed in Thread: LM2776

Tool/software:

Hi,

First, please see the following URL.
https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/1427348/tps63700-replacement-for-lm2662m/5471835#5471835

We are considering a negative power supply solution using TPS628301 as a replacement for LM2662M. The conditions are as follows:
 - Vin : +2.5V
 - Vout : -2.5V
 - Iout : 0.2A

Please let me know if there are any precautions to take when using TPS628301 as a negative power supply under the above conditions. Also, since the reason for replacing LM2662M is "supplyability," I would like to consider using a new product (manufactured on 300mm wafers) as much as possible.

Thanks,

Conor

  • 0
    TI__Mastermind 22720 points

    Hello Conor,

    thanks for reaching out in E2E.

    I think the most comparable replacement for the LM2662M would be the LM2776. It is also an inverting charge pump with similar parameters but at higher switching frequency and in a smaller package. As of now there are no plans for EOL of the LM2776 and it is manufactured on 300mm wafers.

    If you want to evaluate the alternative of an inverting buck-boost converter configuration then there are some precautions, compared to the "normal" buck converter:

    • Reduced input voltage range, as the IC is getting supplied with the total voltage of VIN + |VOUT|
    • Reduced output current rating due to higher inductor peak current
    • Additional components are required:
      • Bypass capacitor from Vin to Vout
      • Schottky-diode at the output
    • The bypass cap might impact the line transient response performance. The output cap might be increased to reduce that effect.
    • A leaky Schottky-diode would reduce the overall light load efficiency.

    In general any buck converter should be able to operate in an inverting buck-boost configuration. I have not yet evaluated the TPS628301 for that purpose. But by chance I tried the TPS62840 as inverted buck-boost recently without any issues. Both devices should be able to fulfill your required voltage- and current-parameters.

    Let me know if you have any questions.

    Best regards,

    Andreas.