Electronics > Projects, Designs, and Technical Stuff

PSA: do not use the TPS61099 boost reg in your designs

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jeremy:

--- Quote from: MasterTech on January 22, 2019, 10:56:13 pm ---But the reference design, unless I read wrongly, only starts up once. It is a very low Iq design designed to be on forever. The problem lies at the startup in these converters, always, not in steady state.

If you can’t change the requirement that your system be turned on by connecting a battery repeatedly, then you have 2 choices, come up with a way of controlling the EN pin in an effective manner, or choose a boost converter with a programmable soft-start, that allows very looooong startup time.

--- End quote ---

Yes, the reference design is sort of only intended to startup until the battery is depleted, but the contact bounce of connecting the battery initially could cause the issue. Also, “forever” is relative, a typical cellular modem in this configuration will draw 100mA for many seconds (I’ve measured it). Forever could be years, yes, but not literally forever.

Bud:
I am suggesting we start from where you sourced the parts. If out of eBay or Aliexpress, the conversation should end right there.

tszaboo:
These converters sometimes go through a silicon revision. If there is a TPS61099A arriving, that is basically TI improving on it's silicon to avoid this. It wouldnt be the first time, and wont be the last.

T3sl4co1l:

--- Quote from: Siwastaja on January 22, 2019, 06:19:58 am ---they are overcomplicated and have excess state space, and therefore tend to hit unwanted states - and a typical "wrong state" tends to mean: blow up everything.

--- End quote ---

This, this and ALL OF THIS!!!

It's a bloody switcher, what does it need all that logic for?  Do they start with an MCU and strip out unused bits?  Just look:
https://zeptobars.com/en/read/Ti-TPS62321-3-MHz-Step-Down-Chip-Scale-CSP

They're great when they work, but it's all too easy to trip over this bullshit. It's not a new thing, I've got a question on E2E (that shall remain unanswered, it seems) regarding the apparently old TPS40210, which seems to have an analog discrepancy.  Also relating to startup conditions, oddly enough.

I wish they'd put the transistor count on the datasheet, just so I can avoid these stinkers.  But who knows.  Transistor count doesn't really mean anything, it's the shitty design that makes it shitty. :(

Tim

jeremy:

--- Quote from: Bud on January 22, 2019, 11:16:29 pm ---I am suggesting we start from where you sourced the parts. If out of eBay or Aliexpress, the conversation should end right there.

--- End quote ---

Digi-Key  :-+

But good point nonetheless.

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