Analog Devices ADuCM355 Hardware Reference Manual page 91

ADuCM355 Hardware Reference Manual
Table 106. Recommended Switch Settings in Low Power Potentiostat Loop
Measurement Name
Amperometric Mode
Amperometric Mode with
Diode Protection
Amperometric Mode with
Short Switch Enabled
Amperometric Mode for
Zero-Biased Sensor
Amperometric Mode for 2-
Lead Sensor
Chronoamperometry (Low
Power Pulse Test) Using
Low Power TIA
Chronoamperometry (Full
Power Pulse Test) Using
High Speed TIA on Sense
Electrode
Voltammetry (Full Power
Pulse Test) Using High
Speed TIA
Potentiostat Amplifier and
Low Power TIA in Unity-
Gain Mode (Test Mode)
Electrochemical Impedance Spectroscopy
In many electrochemical applications, there is significant value to carrying out a diagnostic measurement. A typical diagnostic technique
is carrying out an impedance measurement on the sensor. For some sensor types, the dc bias on the sensor must be maintained when
carrying out the impedance measurement. The
LPDACCONx, Bit 5 = 1. VZEROx is set to the input of the high speed TIA, and the high speed DAC is used to generate an ac signal. The
level of the ac signal is set via the VBIASx output of the low power DAC. The voltage on the SE0 and SE1 pins is maintained by VZEROx.
The high speed DAC dc buffers must also be enabled by setting AFECON, Bit 21.
LPDACCONx LPDACSWx
Bit 5 Setting Bits[5:0] Setting
0 0xXX (don't care)
0 0xXX (don't care)
0 0xXX (don't care)
0 0xXX (don't care)
0 0xXX (don't care)
1 0x32
1 0x31
1 0x31
0 0xXX (don't care)
ADuCM355
LPTIASWx
Bits[13:0] Setting
0x302C or 0b11
0000 0010 1100
0x302D or 0b11
0000 0010 1101
0x302E or 0b11
0000 0010 1110
0x306C or 0b11
0000 0110 1100
0x342C or 0b11
0100 0010 1100
0x0014 or 0b00
0000 0001 0100
0x0094 or 0b00
0000 1001 0100
0x0094 or 0b00
0000 1001 0100
0x04A4 or 0b00
0100 1010 0100
facilitates this measurement. To maintain the dc bias on the sensor, set
Rev. B | Page 91 of 312
Description
Normal dc current measurement. External
capacitors to VBIASx and VZEROx DACs are
connected.
Normal dc current measurement with low power
TIA back to back diode protection enabled.
External capacitors to VBIASx and VZEROx DACs
connected.
Normal dc current measurement with short switch
protection enabled. SW1 is closed to connect the
sense electrode input to the output of the low
power TIA. External capacitors to VBIASx and
VZEROx DACs connected. Useful if external
sensor must be charged after a power-up and
many currents flow in or out of the SEx pin.
Amperometric mode with SW6 configured to set
sensors reference electrode and sense electrode
to VBIASx level. Potentiostat amplifier inverting
and low power TIA noninverting inputs shorted.
Gives optimal noise performance for zero bias
voltage sensors.
Amperometric mode with SW10 closed to short
counter electrode to reference electrode
internally.
VBIASx output generates pulse to counter
electrode. Capacitors on low power DACs are
disconnected. Low power TIA measures sense
electrode current response.
VBIASx output generates pulse to counter
electrode. Capacitors on low power DACs are
disconnected. High speed TIA measures sense
electrode current response.
VBIASx output generates pulse to counter
electrode. Capacitors on low power DACs are
disconnected. High speed TIA measures sense
electrode or the DEx pin current response. High
speed TIA resistors and switches are configured
separately.
Potentiostat amplifier in unity gain mode,
output to CEx pin. Low power TIA in unity gain
mode, output to RCx_1 pin. Useful for checking
VBIASx or VZEROx DAC outputs.
UG-1262