SD Card powered by the VS1005 IOVDD

Discussion about writing software for VS1005 and the VSOS Operating System. Also posts about VS1005-related hardware design and device drivers should be posted here.
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gilvanl
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SD Card powered by the VS1005 IOVDD

Post by gilvanl »

Dear Vlsi staff.

I have one question about power sourced by chip VS1005 in the digital output.
I intend to use the 3.3 V IOVDD (any pin available in VS1005 Breakout Board) to
power one SD Card in read-only mode (only reading - never writing).

- Is that possible ?

Chip in use: VS1005
Board: VS1005 Breakout Board with custom board for periferals, output to spdif in the TX147 fiber optic transmitter.
Microcontroller: none - stand alone vs1005 in the board.
Software: VSOS 3.60

( I have seen that the schematics of other Vlsi Products like the VS1005 Hi-Res Player
show the SD Card powered by a voltage regulator. )

Thanks in advance, best regards , sorry again for elementary questions.
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Hannu
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Location: Finland
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Re: SD Card powered by the VS1005 IOVDD

Post by Hannu »

Hi,

The answer is it depends. If you have nice SD-card and you are comfortable with degraded reliability.

Not all SD-cards are nice. Some like to suck huge spikes of current. Measuring current spikes is hard. So it is easier to to use external regulator.

Remember to put the pull-ups show in the schematics. Otherwise you'll may find the rather rare situation where SD-card ends up to SPI mode. To recover that you need to reinsert the card.
Have a look at:
https://www.vlsi.fi/fileadmin/evaluatio ... matics.pdf
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pasi
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Re: SD Card powered by the VS1005 IOVDD

Post by pasi »

For your own tests / use, sure, you can try to power the SD from IOVDD. If you're only reading from the card, and the card goes to idle state at all, then reading will also work (most of the time).

Increasing the values of the IOVDD capacitors too much may have an opposite effect instead of helping. A high(er) AVDD might help provide more current from the IOVDD regulator.

But like Hannu said, the peak current consumption is the reason for using a separate regulator for the SD / uSD.
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gilvanl
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Re: SD Card powered by the VS1005 IOVDD

Post by gilvanl »

Thanks a lot !

I am doing tests with this option,
but i will go with the regulator in my new designs since is not so expensive ($$$).

Thanks again , best regards.
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