SD card interface

[jremote]

I am a new user and will help in this forum as much as possible.

My project:

I have a SD(secure digital) card that I R/W with Pic16f877A. The SD card operates on 3.3 v but I need the Pic to run at 5v. I need an IC that I can interface to the SD card for 3.3V data. (resistors are not acceptable).

Anyone ?

 

[Nigel Goodwin]

I am a new user and will help in this forum as much as possible.

My project:

I have a SD(secure digital) card that I R/W with Pic16f877A. The SD card operates on 3.3 v but I need the Pic to run at 5v. I need an IC that I can interface to the SD card for 3.3V data. (resistors are not acceptable).

Why aren't resistors acceptable?.

 

[jremote]

Res

They will work but I like to keep my design as accurate as possible. there is a small margin of error with load resistors. I would rather get the digital 3.3 volts. I think maxum makes a chip but I fail to find one. The SD card I am useing has specs that allow 5v operation but some on the market require Max 3.3v I dont have control on the end user's choice of cards.

Thanks for your replay.

Jerry

 

[jremote]

res

I have decided to proceed with Res. I calc a 100 omh / 150 ohm to get me within 3v tolerance. The DO should still trigger the Pic at 3.3 v ? Does anyone have a good schematic ?

 

[Nigel Goodwin]

Re: res

I have decided to proceed with Res. I calc a 100 omh / 150 ohm to get me within 3v tolerance. The DO should still trigger the Pic at 3.3 v ? Does anyone have a good schematic ?

From the 3.3V to the PIC requires nothing, a PIC will quite happily accept 3.3V logic levels to it's inputs. From the PIC to the 3.3V simply requires a potential divider, consisting of two resistors in the ratio 50/33, there's not really any schematic required?.

 

[jremote]

card

I am stumped I cannot get the code to work.

I set up the SPI , Initialize card with 80 clock ticks and followed the advice of the pros. I think I will try AT45DB041 chip.

 

[melissagirl]

I know this is an old post, but for anybody who happens to have the same question: You need to use a voltage translator such as MAX3002 or ADG3308. You should be able to get that from mouser or digikey.

Melissa

 

[Papabravo]

I use the following part in both directions. When powered from 3.3 Volts the inputs are 5V tolerant. When powered from +5V the thresholds are TTL.

https://www.electro-tech-online.com/custompdfs/2007/11/MC74VHC1GT125-DPDF.pdf

 

[mongerson]

or you could use the VHCT125AG if you wanted 4 buffers instead of 1

- Michael