Reference Manual ADuCM356
USE CASE CONFIGURATIONS
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â–º For LPTIA0, set LPTIASW0 = 0x302C to set the low-power
TIA0 switches for normal mode.
â–º See Figure 38 for details about how these settings affect the
low-power potentiostat loop.
â–º Configure the low-power TIA R
LOAD
as per the ADuCM356 speci-
fications via LPTIACON0, Bits[12:10]. For example, as follows:
pADI_AFE->LPTIACON0 =
0xE680; // Enable LPTIA, 1 MΩ
Low-Pass Filter resistor, 10 Ω RLOAD, 100 K
Gain resistor
After setting the sensor bias voltage, wait the settling period of
the sensor before beginning to measure its output current.
Configure ADC for DC Measurement Mode
The ADC mux has two measurement options for the low-power
TIA0. One is through the low-pass filter (ADCCON, Bits[5:0] =
0x21), and the other is the bypassed low-pass filter option (ADC-
CON, Bits[5:0] = 0x02). Select the low-pass filter as the positive
input channel of the ADC for lowest noise. Select the LPTIA0
inverting input (ADCCON, Bits[12:8] = 0x2) as the ADC negative
input channel.
Using the provided software libraries, the following function call
selects LPTIA0 as the ADC input:
AfeAdcChan(MUXSELP_LPTIA0_LPF,
MUXSELN_VZERO0); // Select
LPTIA0_LPF input versus VZERO0 to the ADC
To select LPTIA1 as the ADC input, use the following function call:
AfeAdcChan(MUXSELP_LPTIA1_LPF,
MUXSELN_VZERO1); // Select
LPTIA1_LPF input versus VZERO1 to the ADC
For optimal performance, do not perform any read or write access-
es to the analog die while the ADC is converting to minimize
noise from the die to die interface coupling onto the ADC circuits.
Optionally, halt the Arm Cortex-M3 core until the ADC conversions
are complete.
The ADCCON and ADCBUFCON registers must also be config-
ured. For example, as follows:
ADCCON = 0x010XXX; // PGA gain =1.5x
ADCBUFCON[3:0] = 0x4; // Enaâ–º
bles chopping of the ADC input – default value
Configure LPTIACON, Bits[15:13] to select the resistor value for
the low-pass filter on the TIA output. This setting configures the
programmable resistor, R
F
, which is between the low-power TIA
output and the ADC mux. The programmable resistor combines
with the external capacitor on the AIN4_LPF0 and AIN7_LPF1 pins
to form a low-pass filter on the low-power TIA outputs. The user
must trade off the required ADC measurement settling time with the
cutoff frequency on the low-power TIA output filter.
The ADuCM356 ADC provides optional digital postprocessing and
filtering that can improve measurement accuracy of the sensor
measurement. The ADCFILTERCON register provides programma-
ble options for averaging, oversampling, and 50 Hz and 60 Hz
mains rejection filtering. Trade the ADC update rate vs. required
ADC noise performance when configuring the ADCFILTERCON
register.
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