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DAC8760: Use the 4 ch DAC8760 in the AO module

Chen Alex1
Genius 3685 points
Part Number: DAC8760
Other Parts Discussed in Thread: DAC8775, DAC8775EVM

hi Sir

I need to design a AO module which need 2 ch output or 4 Ch output ver.

i see the ADI/AD5423, TI /DAC8760 meet my needs

AD5423 have the daisy chain, and DAC8760 remove the function

if i want to use four DAC8760 x4 in my board, how to control it?

please advise it,thanks

PS: I only need SPI, & one pin to control DAC8760

  • 0
    TI__Guru* 97465 points

    Alex,


    For the microcontroller, I would assume that there is a /CS, DIN, DOUT, and SCLK already to control a single SPI device. When controlling four devices, you can tie the DIN of all devices together and tie all the DOUT of all devices together. After that, LATCH pins would be controlled independently. The microcontroller would use other GPIO pins as the LATCH pin for the three other devices. However, the SCLK must be gated to the for each device.

    We show this in the datasheet on page 41 in this way:

    In the figure, SCLK is shut off for each device when the LATCH is high (similar to the /CS function in SPI). The figure shows connections for two devices, but this method of control expands to four with the addition of other GPIO pins that can act as extra /CS lines.


    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Intellectual 1415 points

    Hi Joseph,

    For your reply, customer may need add logic in their design and will add additional cost and space in customer design.

    Is there any device we can compete with AD5423?

    Thank you.

  • 0 in reply to Bo Xian Yeh
    TI__Guru* 97465 points

    Hi,

    I think the DAC8760 is the best device positioned to compete with the AD5423. While the gating of the SCLK requires an extra digital line, I would guess that the logic would be small. 

    An alternate device would be the DAC8775, which has four configurable outputs. This device does have an integrated buck-boost converter, which may make the design a bit larger. I would note that each of the channels need to be individually and sequentially programmed and configured.


    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Intellectual 1415 points

    Hi Joseph, 

    Thanks for your information. I would like to double confirm that DAC8775 can meet customer requirements without additional logic design, am I right?

    Just DAC8775 integrated buck-boost converter, so chip size and design space will be larger than DAC8760, correct?

  • 0 in reply to Bo Xian Yeh
    TI__Guru* 97465 points

    Hi,


    For the DAC8775, this is just a single device with four output channels (various VOUT and IOUT ranges). In this device, there is a single SPI channel and there isn't a need for any of the SPI gating that is needed in the DAC8760. Again, I would have your customer review the datasheet to make sure that it suits their needs.

    The device does have an integrated buck-boost converter. It isn't absolutely needed for operation, if they have other supplies available. The DAC8775EVM is a good tool to review the device. They can use it to set up the configuration and review the features. The layout is not very compact, but they can look at it to see what needs to be included for the operation of the device.


    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Intellectual 1415 points

    Hi Joseph,

    Noticed with thank. Yes, we had promoted DAC8775 to customer already.

    But single channel still is customer first choice because of design flexibility.

    DAC8760 need additional gating circuit. This is bottle neck for this case.

    Thank you.