Reference Manual ADuCM356
HIGH-SPEED TIA CIRCUITS
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The high-speed TIA is intended for measuring wide bandwidth input
signals up to 200 kHz. The output of the high-speed TIA transfers to
the main ADC mux, where the high-speed TIA can be selected as
the ADC input channel. The high-speed TIA is especially designed
for impedance measurements in conjunction with the high-speed
DAC and excitation amplifier. To connect the high-speed TIA to the
external sensor pins, the user must configure the transmit switches
as described in the Tx Switches section.
KEY FEATURES
To turn on the high-speed TIA, set AFECON, Bit 11 = 1. Clear to
0 to power down the high-speed TIA. The high-speed TIA is off by
default.
The high-speed TIA has programmable flexibility built into its in-
put signal selection, R
TIA
selection, R
LOAD
selection, and common-
mode voltage source. The input signal options are as follows:
â–º SE0 input pin from sense electrode of Channel 0 sensor.
â–º SE1 input pin from sense electrode of Channel 1 sensor.
â–º AIN0, AIN1, AIN2, and AIN3/BUF_VREF1V8 input pins.
â–º
DE0 input pin. This is the Diagnostic Electrode 0 pin (DE0). This
pin has its own R
LOAD03
and R
TIA2_03
options configurable via the
DE0RESCON register.
â–º DE1 input pin. This is the Diagnostic Electrode 1 pin (DE1). This
pin has its own R
LOAD05
and R
TIA2_05
options configurable via the
DE1RESCON register.
The R
TIA2_x
options are in the 50 Ω to 160 kΩ.1 kΩ range for the
DE0 and DE1 inputs. For all other pins, the gain range is 200 Ω to
160 kΩ.
The R
LOADx
option for the SE0 and SE1 channels is a fixed 100 Ω
resistor. However, for the DE0 and DE1 input pins, the R
LOADx
is
programmable. The R
LOADx
values are 0 Ω, 10 Ω, 30 Ω, 50 Ω, and
100 Ω.
Table 120. Configuration of R
LOAD
and R
TIA
of High-Speed TIA When Using DE0 and DE1 Electrodes
DE0RESCON, Bits[7:0] (DE0) and DE1RESCON, Bits[7:0] (DE1) Setting R
LOAD03
and R
LOAD05
Value (Ω) R
TIA2_03
and R
TIA2_05
Value
0xFF Disconnected Disconnected
0x00 0 50 Ω
0x18 0 100 Ω
0x38 0 200 Ω
0x58 0 1.1 kΩ
0x60 0 5.1 kΩ
0x68 0 10.1 kΩ
0x70 0 20.1 kΩ
0x78 0 40.1 kΩ
0x80 0 80.1 kΩ
0x88 0 160.1 kΩ
0x9 10 50 Ω
0x21 10 100 Ω
0x39 10 190 Ω
0x59 10 1.09 Ω
0x61 10 5.09 kΩ
0x69 10 10.09 kΩ
0x71 10 20.09 kΩ
0x79 10 40.09 kΩ
0x81 10 80.09 kΩ
0x89 10 160.09 kΩ
0x12 30 50 Ω
0x2A 30 100 Ω
0x4A 30 210 Ω
0x5A 30 1.07 kΩ
0x62 30 5.07 kΩ
0x6A 30 10.07 kΩ
0x72 30 20.07 kΩ
0x7A 30 40.07 kΩ
0x82 30 80.07 kΩ
0x8A 30 160.07 kΩ
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