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Going against v-reg datasheet recommendation for more robust design
sebmadgwick:
I am using the TPS63000 to generate 2.2V and 3.3V supply rails. The TPS63000 output voltage is set by feedback from a potential divider as shown in the attached schematic.
The datasheet (page 11) recommends the use of high resistor values, "...keep the value for this resistor in the range of 200 kΩ" and "...a 1-MΩ resistor should be chosen...". TI's WEBENCH Designer recommends the specific values shown in the attached schematic.
I am uncomfortable using such high resistances because of the risk of contaminants or even handling of the PCB resulting in destructively high voltages. My preference would be to use resistor values one or two orders of magnitude lower. The total device current consumption is 100-300 mA so the increased quiescent loss is not of concern.
Is there any reason I should stick to TI's recommendation here? The recommendation seem specific without justification.
iMo:
The divider is at the output, therefore no need to stick with such values.
wraper:
--- Quote from: sebmadgwick on December 16, 2019, 08:44:53 pm ---Is there any reason I should stick to TI's recommendation here? The recommendation seem specific without justification.
--- End quote ---
Justification is simple, quiescent current and intended operation from battery in portable devices. By using low resistance divider, it can easily consume more than IC itself.
iMo:
The DS says the current through the divider should be at least 100x higher than the current into the FB pin (10nA). As wraper wrote they want to show high efficiency and low quiescent current therefore they recommend the values at higher side.
sebmadgwick:
The quiescent current of the IC is ~5 mA without Power Save and it is rated for up to 1.5 A output. It therefore seems strange that recommendations would optimise to save a few uA without qualifying this. The datasheets sates, "...keep the value for this resistor in the range of 200 kΩ", unconditionally.
Anyway, it looks like I was reading too much into this. Thank you for your comments.
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