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My application is for Smart Water meter. The TDC-IC I'm using is MAX35103 https://datasheets.maximintegrated.com/en/ds/MAX35103.pdf. My device is battery powered and operating at 2.5V .Which is regulated down using TPS62740https://www.ti.com/lit/ds/symlink/tps62740.pdf?ts=1625463213017&ref_url=https%253A%252F%252Fwww.google.com%252F from 3.6V(battery voltage). The application is current sensitive since being battery operated hence, using a DC-DC such as TPS62740. Current requirement of the board: 200uA-50mA(min-max)

my questions are as below:

  1. Will the power consumption of my board increase if I operate at 3.6 given directly from the battery(all the components on board are rated for 3.6 or above)?
  2. What could be the alternative for DC-DC which has low o/p ripple noise that won't interfere with the TDC?
  3. What techniques can be used to reduce the output ripples on the DC-DC and up to what extent?
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    \$\begingroup\$ Maxim Applications engineer here: save yourself some trouble and just run directly from the battery. Time-of-flight flow meters are hard enough without the added headache of troubleshooting an onboard source of DC-DC converter noise. First make sure you have a good flow body pipe design; make sure your firmware servos on the t1/t2 ratio and corrects for temperature drift. Once your prototype hardware and firmware works, then think about optimizing the design with a DC-DC if the MAX35103 power management isn't enough for your application. \$\endgroup\$
    – MarkU
    Jul 5, 2021 at 6:32
  • \$\begingroup\$ @MarkU Thankyou for your answer. BTW my device is at a far later stage than prototype and had made sure to follow the suggestions and design guidelines provided by Maxim. \$\endgroup\$ Jul 5, 2021 at 6:57
  • \$\begingroup\$ optimization is the only thing left in the application. I cannot use LDO because of their high quiescent current. Could you please suggest DC-DC optimization techniques to reduce output ripple for this application?? @MarkU \$\endgroup\$ Jul 5, 2021 at 6:59

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  1. The power consumption will increase with higher voltage if you do not have DC/DC conversion.

  2. LDOs directly from the battery, but efficiency is lower (shorter battery life).

  3. A good way to reduce ripple is to use a capacitor multiplier circuit.

LDOs in general aren't so good at smoothing ripple (see EEVBlog video on the link) although will have low/no ripple if the source (battery) has no ripple.

If you go directly from the battery without any DC regulation, you have to make sure your circuit is not influenced by voltage variations.

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  • \$\begingroup\$ A capacitor multiplier circuit wont be an option at this stage as it will mean changing PCB construction. \$\endgroup\$ Jul 5, 2021 at 9:12
  • \$\begingroup\$ Could you please elaborate on this "If you go directly from the battery without any DC regulation, you have to make sure your circuit is not influenced by voltage variations." \$\endgroup\$ Jul 5, 2021 at 9:13
  • \$\begingroup\$ If you have analog circuitry, if your voltage changes as the battery discharge, you need to consider the effects that might cause, it may, or may not impact but that really depends on the design. @PralayPanchwate \$\endgroup\$
    – Damien
    Jul 5, 2021 at 9:33

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