Hi

I am using MAX11060 as a adc for my DC Monitoring system. However FAULT and OVRFLW pin are always go low as the chip startup. That mean voltage between AIN+ and AIN- are exceed the fault threshold. But Even if all AIN+- pins are leave floating. FAULT and OVRFLW still go low and DRDYOUT never goes low too.

Anyway I can communicate with this chip through SPI and I can read or write any register. That mean the chip still working.
I'm setting XTALEN bit to 1 and leave everything to default.

I'm trying to measure voltage between AIN+ and AIN-. When the chip is not powered. I can measure the voltage as same as the the voltage source (around 0.124 V) but when chip is powered the voltage between AIN+ and AIN- were dropped to 0.034V and I think because of fault protection circuit in the chip. (this happen whatever I set FAULTDIS in configuration register to 1 or 0)

I read all of the data sheet and in page 15 said that:
"When the analog input voltage changes between the ADC full scale and the fault threshold faster than the latency of the converter, OVRFLW goes low with the FAULT output. OVRFLW remains invalid until a valid clock frequency is available at XIN."

So I think that it must be something wrong with my Crystal or Capacitor Coupling so I change it from 20pF to 18pF and 10pF and I still have no luck.

Here is my schematic

ADC Datasheet - https://datasheets.maximintegrated.com/en/ds/MAX11040K-MAX11060.pdf

 

Hi Watanyou, I cant see anything wrong with your schematic. The crystal oscillator part is usually not too fussy with regards to teh capactiors you use on it +/- 5pF or so. Have you connected all the AIN pins? It might be that you simply cant leave these unconnected / floating.

 

Hi Watanyou, I cant see anything wrong with your schematic. The crystal oscillator part is usually not too fussy with regards to teh capactiors you use on it +/- 5pF or so. Have you connected all the AIN pins? It might be that you simply cant leave these unconnected / floating.

Thanks for your answer.
Actually every AIN+ and AIN- are connected by a voltage divider as show

 

Hmmm.. ok.. you could just try connecting the AIN- to GND and see if it makes any difference.

 

Hmmm.. ok.. you could just try connecting the AIN- to GND and see if it makes any difference.

Thanks.
result is the same

 

hi WD,
Using a DVM what is the voltage between pins 1 and 2 and also to 0v Common.?
E

 

hi WD,
Using a DVM what is the voltage between pins 1 and 2 and also to 0v Common.?
E

Hi ericgibbs,

When AIN- disconnected from GND and no voltage source between all of AIN+ and AIN-.
Voltage between AIN+ and AIN- is 0.000V and voltage between AIN- and GND is around 0.095-0.170V and voltage between AIN- and GND is around 0.095-0.500V

 

As I check there are no output at CLKOUT (XTALEN is set to 1 ) and I think crystal did not starting.

 

Morning WD,
Have you set XTALEN=1.?
E
EDIT:
To confirm that the XTALEN =1, Read the CONFIG reg to confirm that it is actually written as 1.

 

Hi,

After a very long debuging I found a mistake that I accidentally reset a config before waiting a DRDYOUT.
It was a tiny mistake that took me a couple of day to debug. And I accidentally found a mistake after I use an oscilloscope to probe CLKOUT and CS pin.

After solving that issue I found another problem that even I wait a DRDYOUT goes to low and read an adc value the adc value still not valid. They swing from -3000 to 2500 even no input connected. When I apply a 12.2V passing through voltage divider and voltage between AIN+ and AIN- should be 0.122V and ADC value should be 1817 (1817 * (4.4/65535) = 0.1219 V.) but the result was randomly from 25000 to -30000.