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Part Number: ADS1294R
I am Vignesh From AKAS Medical.
We are using ADS1294R in patient monitor products. We observed below issues.
10 Machines are working well in a production lot. After few days 2 Machines displayed the Respiration rate values since the Lead off registers bits showing as "Connected" when ECG cable not connected to the patient or not connected to the Machine.
When we remove/Connect the ECG cable from machine, the register values are given below when Comparator threshold 95% in Positive and 5% in Negative.
RA – 0
LA – 0
LL – 1
When we remove the ECG cable from machine, the register values are given below when Comparator threshold 70% in Positive and 30% in Negative.
RA – 1
LA – 1
Issue No 2;
ECG Cable is connected to the machine, We are observing the Lead off registers are getting flickering when the cable disturbed/Shacked in the below order.
RA – No Flickering Observed.
LA – Light Flickering Observed.
LL – Heavy Flickering observed.
What could be the causes for these problems?
Alex SmithApplications Engineer | Precision Delta-Sigma Converters
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In reply to Alexander Smith:
Are you using the current souce or pullup/pulldown resistor method?
We are using Current Source method for Lead off Detection.
What current magnitude are you using?
Initially 6 nA. Now Changed to 24 nA to faster Lead off detections.
What is your lead-off frequency?
LOFF - Register value is EF : Lead off Frequency is 11 : DC lead-off detection turned on
Were the machines being rigorously tested during the few days before the problem presented itself?
Yes, It was tested properly passed after 7 days testing.
Are the symptoms the same on both machines? Did the issues appear at the same time on both machines?
both the machines have same problem/Symptoms but time is different in both the machines.
What is the ECG cable connection to the board like? Can you take a picture?
Attached the picture of ECG Cable Connection to the board.
For the second case on Issue No1, is the reading correctly displayed with the ECG cable is connected?
Reading is displayed with graph properly when connected to the patient.
Is there any noise on the supplies?
There is no noise observed from Supplies
Additional Observation From Failed Machines is ADS1294R Reference voltages -2.5V and +2.5V pins are getting shorted.
In these machines ECG Graphs are not displayed when connected to the patients.
Why the Pins are getting shorted after working 1 or 2 months good.
How many channels(RA,LA,LL,Chest,RL) do we need to route to RLDSENSEP and RLDSENSEN and what is the practical usage of this RLD in Lead off Detections.
In reply to vignesh N:
1 Register settings Details
CONFIG1 0X 86
2) AVDD (Analog supply) is short with AVSS(Analog ground).
3). Please find the attached schematic diagram.
4.) disconnect all channels from RLD. Set all RLDSENS bits to 0.
We didn't observed any changes between connected and not connected to RLD. Power noise is reduced little bit When Channels are connected to RLD,
SCHEMATIC1 _ ECG _ELECTRODE_wtih Comments.zip
Initially, the machines are working well for 2 to 3 months after production, after that in 5 out of 50 machines we observed like that.
The Short observed in ADS1294R. The Board is working fine when we replaced with new ADS1284R IC. What could be the reason for this problem?
Did you verify the Register Configurations which i shared in the last post? Hope the configurations are fine. Kindly confirm the same to verify the Lead off Detection Bits flickering issue.
Thanks and Regards,
In reply to Tom Hendrick:
The PCB might be the problem for this case. we will confirm this based on the Hardware team verifications and testing which is going on.
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