Low Power Tia0/Tia1 Gain Resistor Calibration - Analog Devices EVAL-ADuCM355QSPZ Manual

UG-1308
LOW POWER TIA0/TIA1 GAIN RESISTOR
CALIBRATION
The ADuCM355 contains two independent, low power
TIA channels.
Each TIA has an independent, programmable gain resistor to
scale the input current from the SE0 pin and the SE1 pin to a
voltage that the ADC can measure.
Figure 36 shows the gain resistor for the low power TIA0. A
similar diagram is valid to use for the low power TIA1.
Similar to the example described in the High Speed TIA Gain
Resistor Calibration section, adjust the gain resistor to convert
the current from the SE0 input pin and the SE1 input pin to a
differential voltage across the R
These resistors have an initial accuracy range and vary with
temperature, as specified in the
When these resistors are uncalibrated, an error is present when
measuring an absolute input current.
To generate a precision calibration current, use the low power
DAC to create a differential voltage across an external precision
CE0
CAP_POT0
RE0
SE0
RC0_0
RC0_1
resistors.
TIA
ADuCM355 data sheet.
VBIAS0
RE0
SW12
SW15
PA
SW2
SW3
SW8
SW10
10kΩ 10kΩ
SW4
SW11
R
LOAD
LPTIACON0
SW7
[12:10]
PROGRAMMABLE
GAIN RESISTOR
SW1
R
TIA
LPTIACON0
[9:5]
SW5
Figure 36. LPTIA0 Gain Calibration Resistor
EVAL-ADuCM355QSPZ
R resistor that is connected to the
CAL
and RCAL1 pin. The precision calibration current is routed
through either the low power TIA0 gain resistor or the low
power TIA1 gain resistor.
Because the calibration current value is known and the ADC
can measure the voltage drop across each R
R resistor value can be determined.
TIA
Figure 37 and Figure 38 show the setup and switch settings
used to connect the low power DAC outputs to the external
R resistor so that the current flows into the LPTIAx gain
CAL
resistors, LPRTIAx.
Several example projects in the
function to calibrate the gain resistor. For further details on
how to use this function, visit
https://wiki.analog.com/resources/eval/user-guides/eval-
ad5940/calibration_routines/lptia_cal?doc=EVAL-
ADuCM355QSPZ-UG-1308.PDF.
VZERO0 VREF2V5
SW13
LPDAC0
TO
SW14
CHANNEL 1
SW6
ULPTIACON0
LPTIA
SW9
FORCE/SENSE
SW0
Rev. A | Page 20 of 24
Evaluation Board
ADuCM355
ADuCM355
AIN4/LPF0
ULPBUF
ULPREF
R
LPF
[15:13]
LPTIA0_P_LPF0
ADC
MUX
RCAL0 pin
resistor, the exact
TIA
SDK implement a