ADS1292R: Current sinks into the differential input pins

Hi Katsuya-san,

Thanks for the post. 

The device's IN2N and IN2P channel input should always be high impedance (min ≥ 1 GΩ or 500MΩ with leadoff current source). Please verify the channel input MUX setup is in the correct conditions for your hardware design? If all the setup is proper, then the channel input may be damaged due to EOS. Please check to see if you see this on other hardware or only for this particular hardware?

Thanks

-TC

Thanks for the reply.

If I set it as follows, IN2P and IN2N  should be high impedance?

MUX2[3:0]:0000(default)

The ECG is generally acquired without any problems, so it is not considered to be damaged.

The same problem is also seen on other hardware.

By the way, Figure 35 says the IN2P and IN2N can be set by MUX "1", is this correct?

Best regards,

Katsuya

 Hi Katsuya-san,

The IN2P and IN2N inputs should be high-impedance when the MUX2[3:0] is set to 0b0000 (Normal electrode input). Sorry, there is a typo in the datasheet for MUXn[3:0] label for channel 2; it should be MUX2[3:0] instead of MUX1[3:0]. Each channel input selection has its MUXn[3:0] setting in the CHnSET register.

Thanks

-TC

Hi TCT,

I'm sorry to reply late, and thanks for your reply.

By the way, what happens when a voltage higher than the supply voltage is input to the differential input pins?
Is there a protection diode inside the IC?

Best regards,

Katsuya

Hi Katsuya-san,

Yes, there is ESD protection diode internal to the device for analog input protection. Please refer to Section 9.3.1.2 for the analog input structure (Figure 24) that shows the protection diode and the EMI filter. 

Thanks

-TC