Testing Support for ADL5308 EVAL Board needed

Hello,

33 mA quiescent current is the expected current for the distribution.

For using with ACE software operation can you confirm if the firmware loaded is green after connecting to linduino.

For using an photodiode, can you confirm if the steps under the Driving the Input using an Actual Photodiode were followed i.e R18, R24 and R25 resistors and C10 capacitor were removed and 0 ohm resistors were installed at R18 and R25.

With using the Keithley SMU source can you confirm if from the output of the SMU a Triax Cable with a Triax to BNC adaptor  + BNC to SMA adaptor was used as specified in the userguide? 

If problems for measuring VLOG still persist after confirming the setup requirements, please post the concerns here.

Thanks,
Dushyanth. 

Hi Dushyanth,

Thank you for your response. I've attached some pictures for more details.

I've followed the suggested steps in the user guide for photodiode usage i.e. R18,R24,R25 and C10 is removed. the picture above shows the photodiode is around -60 nA when covered and 6uA when exposed to natural light without a voltage applied. Instead of adding  a 0 Ohm jumper, I've soldered the anode of this photodiode direct to the INP port as shown below.

And the INP and IREF are closed by connecting and SMA connection to it and connecting its + and - connections to itself.

The cathode of the photodiode was connected to ground. however the VPOS would get cut in half.

I've also tried connecting IREF to ground and I would get 1.8 to 2 volts but  it wouldn't show the 2 uA to 60nA  to the VLOG relation that I saw in the ADL5308 datasheet. 

My concern is: how do i solve this issue? so that it matches the 60nA to 2 uA relationship shown in the V-LOG vs I-INP chart

Many thanks in advice your help. it is all appreciated.

Hello,

Sorry for the late response, I will look at the result by directly connecting the Photo diode as you have shown in the figure. In the mean time, were you able to directly measure the output with the SMU and using a traix connecter instead of using the photodiode? (Please refer to Quick Test procedure section) in the datasheet. In the meantime, I will comeback with results after making connections as shown above.

Thanks,
Dushyanth.

Hi Dushyanth,

Thank you for the follow up. Below is the most recent update on this:

" Two issues occurred. 

1. we received a second EVAL board and it initially somewhat worked but now, with an applied voltage of less than 0.01 V, causes it to draw 0.04A. Does this mean that the TIA is broken?
   
   
2. Another issue is that I was able to get it to measure an output voltage that depends on the input current for the second eval board, but the voltage stability was on the order of 0.1 - 0.5 V when a stability of 0.001 V is needed. SMA cables were used and plugged directly into a DMM. The SMA to BNC cable was a 12 inch cable, the PD current values did not have a large instability, and range from 5 - 10 nA ( no light) to 1000 nA (light). The voltage output would vary from ~2.75 V to ~1.5 V but would stay at 2.75 when light is projected onto the PD.  what could cause this issue?

Output of one of the Voltage measurements:

Hello, 

Glad that the second evaluation board works,

1. can you confirm if you were using the same Keithley Source meter for less than 0.01V input? But the board works by using the source meter at other input levels? It is highly unlikely that TIA is broken, there might be some leakage, can you try using the Keithly SMU-Triax to Triax-to-BNC to BNC-to-SMA for input?

LPD 3080 - OSI Laser Diode, Inc. | Photodiode (gophotonics.com)

We used the above OSI photodiode for characterization measurements. Below was the schmatic of photodiode

Pin 1 of the Photo diode i.e anode was connected to Pin 1 of P2 header on baord, Pin 2 of the Photo diode i.e Cathode was directly connected to the INP trace on the board and finally Pin 3 of the diode i.e GND of the photodiode was connected to the Pin 3 of the P2 header on board

Please let me know if this configuration or setup helps?

Thanks,
Dushyanth.

Hi Dushyanth,

Sorry for the unclear terminology, when I said input I mean 0.01 volt applied to the VPOS terminal of the EVAL Board to power the device.

1. Does this still imply that there should be a leakage in the EVAL Board? 

2. My PD does not have a ground. Would it be important to connect P2_Pin3 to ground?

Also, unfortunately, we don't have a Triax cable. Only SMA and BNC. I have to debug and repair the EVAL Board again to test this. 

3. In your configuration, I see that the GND and SUM pins are soldier. In my rough drawings, I chose to connect them all to GND. Is my setup wrong with respect to your configuration? In other words, what are your GND and SUM nodes connected to?

4. Sorry to ask, but with the photodiode that you use, how stable is the VLOG output when the PD is at 0.5 nA or at it's dark current value? Could I find this VLOG stability in the spec sheet? 

Sincere thanks and appreciation again for all your help.