Other Parts Discussed in Thread: DAC8760, DAC7750
we use four DA-converters DAC8760IPWPR, whereby each two DAC8760 are connected as daisy chain configuration and are galvanically isolated from an microcontroller. Furthermore, other devices such as shift registers and AD-converters are operated on the same SPI bus.
The firmware process flow is the following:
- Power on
- SPI communication with other devices
- Initialization of the DAC
- SPI communication with other devices
- Main loop
- Change voltage or current output if requested
- SPI communication with other devices
- Handle DAC Data (Write Data and detect Errors)
- SPI communication with other devices
During several function tests our implementation worked for hours and days without problems, but due to some random samples we suddenly got some strange behavior on the analog outputs. Where the second DAC8760 in a daisy chain is usually more affected.
Problems:
- The analog output voltage does not correctly follow the digital set value.
- The analog output is falling to zero although the digital set value is not zero.
- The alarm pin is going active but we could not discover any errors on the DAC.
- After sending a register read command, the read back value is the command itself instead the register value.
- Sometimes it was impossible to setup the DAC8760 by software but only by power on.
We registered that the problems seem to be triggered by the communication with the other devices on the SPI bus. So we eliminated hardware and surrounding software issues by implementing a special test software running on a DAC8760 evaluation board. We have done many tests with this software, to find out what is going wrong.
In the attachment you can find an more detailed description of our problem also with some logic analyzer screenshots of the SPI bus. What is the proposed word-around for our problem?
There are already some discussions on this forum, which are going in the same direction. Unfortunately no solution or work-arounds are given for these problems. Are there some news for this purpose?
DAC8760 intermittent false Alarm Output.:
https://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/409925#pi318173=2
This discussion is moved to e-Mail conversation. What are the results and solution for this problem?
DAC7750 - Is it possible for the device to take action on its input shift register contents without seeing a rising edge on LATCH if a particular pattern is present on DIN and SCLK.:
https://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/471368
