problems with AD7564

Question

Hello- 
 We have been having an issuewith the quad DAC device AD7564. Every so often the device powers up in a bad state where it does not put out the programed currents.This happens perhaps 1% of the time.When it does happen, the problem continues until power is cycled again. It seems to be exacerbated by chattering power supply during power up. Timing and signal levels from the DSP are fine. Has any one else ever seen this problem? is there some kind of work around, perhaps a requirement on how the power supply comes up? 
 Thanks and Best Regards, 
 -Tim Starr on behalf of LM@PE

ADIApproved · Accepted Answer

Hi Leo, 
 Yes it does appear to be a timing issue and the part appears to lock-up in your case. 
 So it is important that none of the digital inputs are in an uncertain state upon power-up. 
 If the part recognises a clock on power-up before FSIN is activated for a write, it is possible 
 that the part enters an error mode. 
 So SCLK is the most important signal to be monitoring in this case. 0.8V should not be 
 recognised as a logic high anyhow. Can you hardwire this pin to 0V upon power-up. Also 
 this is the important digital input to monitor if you are taking some plots. 
 Yes you are correct in your understanding of /CLR pin. It is fine to tie this to Vdd. 
 But again it would be recommended to tie this pin to GND when powering up the device and 
 then assert to Vdd after Vdd has been used to power up the part. 
 Regards, 
 Michael Collins 
 PDA Applications