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Original question:

ADS8556EVM: "BUSY" is always high

ADS8556EVM: "BUSY" is always high (2)

Marco Schindler1
Prodigy 150 points

Part Number: ADS8556EVM

Like in the related question, the "BUSY/INT" signal of the ADS8556 (16 bit) stays high, when I a set "CONVST_A" to high. However it never goes back to low.  Since my controller waits for it go back to low, it is stuck.

The related question does not really provide a solution, besides tying the analog inputs to ground.

I have an ADS8558EVM (12 bit) here, too, and I see the same behavior, so I assume it has to do with the test setup or configuration, since a few years ago I worked with the 12 bit version of the chip and was able to use it.

Settings (hardware + serial):

SW1.1:   0

SW1.2:   0 (4x)

SW1.3:   0 (hardware mode)

SW1.4:   1 (serial)

SW1.5:   0 (refbuf enabled)

SW1.6:   0 (no daisy chain)

SW1.7:   1 (serial A enabled)

SW1.8:   1 (serial B enabled)

SW1.9:   1 (serial C enabled)

SW1.10:  1 (internal reference enabled)

JP1/2/5/6/7/8:  1-2

JP3:  7-8 (FS/CS - J1.7)

JP4:  2-3 (3.3V)

JP9:  1-2, 4-5 and 7-8 (CONVST - J4.17)

JP10/11:  2-3  (+/-12V)

JP12:  none

Voltages measured:

TP1:  -12V

TP2:  +12V

TP3:   5V

TP8:  0V

TP16:  3.3V

  • 0
    TI__Mastermind 45435 points

    Hi Marco,

    What's the controller board you are using to interface ADS8556EVM? the EVM itself does not have a controller on the board.

    Please check and make sure /STBY is always high. Also, all unused data bus DBx in hardware mode and serial interface should be connected to the ground vis U7 and J5, please check. 

    Please check if the AVdd, BVdd and Vref on REFIO are correct. Also, make sure all digital input pins have correct input signal, for example, RANGE, RESET.

    When you say "CONVST_A", is this  the"DC_TOUT" signal or just "HOLD_A#" signal you are controlling on the EVM board?

    Can you make a low-high-low on CONVST_x signal instead of a continuous high after completely power up the device? then check BUSY signal, a timing plot with CONVST_x and BUSY signals will be helpful.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 150 points

    Thanks Dale,

    it was indeed the STBY pin, that needs to be high.

    FYI, the controller board I'm using is the Intel (Altera) DK-DEV-5CGTD9N.

    Marco