AD5522JSVD AD [Analog Devices], AD5522JSVD Datasheet - Page 25

• Manufacturer Part Number: AD5522JSVD
• Description: Quad Parametric Measurement Unit With Integrated 16-Bit Level Setting DACs
• Manufacturer: AD [Analog Devices]

Preliminary Technical Data
Reference Selection Example
Nominal Output Range = 10V (-2V to +8V)
Offset Error = ±100mV
Gain Error = ±0.5%
REFGND = AGND = 0V
1)
2)
3)
If the solution yields an inconvenient reference level, the user
can adopt one of the following approaches:
In this case, the optimum reference to choose is a 2.5V
reference, then use the m and c registers and the OFFSET DAC
to achieve the required -2V to +8V range. The ISENSE
amplifier gain should be changed to a gain of 5. This ensures a
full scale current range of the specified values and also allows
optimization of power supplies and minimizes power
consumption within the device.
CALIBRATION
The user can perform a system calibration by overwriting the
default values in the m and c registers for any individual DAC
channels as follows:
Calibration Example
Nominal Offset Coefficient = 32768
Nominal Gain Coefficient = 10/10.25x 65535 = 63937
Calculate the nominal offset and gain coefficients for the new
output range (see previous example)
Calculate the new m and c values for each channel based on
the specified offset and gain errors
Gain Error = ±0.5%
=> Maximum Positive Gain Error = +0.5%
=> Output Range incl. Gain Error
= 10 + 0.005(10)=10.05V
Offset Error = ±100mV
=> Maximum Offset Error Span = 2(100mV)=0.2V
=> Output Range including Gain Error and Offset Error =
10.05V + 0.2V = 10.25V
V
Actual Output Range = 10.25V, that is -2.125V to +8.125V
(centered);
V
1.
2.
3.
REF
REF
Calculation
= (8.125V + 2.125V)/4.5 = 2.28V
Use a resistor divider to divide down a convenient,
higher reference level to the required level.
Select a convenient reference level above V
modify the Gain and Offset registers to digitally
downsize the reference. In this way the user can use
almost any convenient reference level.
Use a combination of these two approaches
REF
and
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12/12.26× 65535 = 64145
Example 1: Gain Error = +0.5%, Offset Error = +100mV
1) Gain Error (0.5%) Calibration: 63937 × 0.995 = 63617
=> Load Code “0b1111 1000 1000 0001” to m register
2) Offset Error (100mV) Calibration:
LSB Size = 10.25/65535 = 156 µV;
Offset Coefficient for 100mV Offset = 100/0.156 = 641 LSBs
SYSTEM LEVEL CALIBRATION
There are many ways to calibrate the device on power on. The
following gives an example of how to calibrate the FIN DAC of
the device without a DUT or DUT board connected.
Calibration Procedure for Force and Measure circuitry:
1)
2)
3)
4)
5)
Similarly, calibrate the comparators and clamp DACs and load
the appropriate gain and offset registers. Calibrating these
DACs will require some successive approximation to find where
the comparator trips or the clamps engage.
=> Load Code “0b0111 1101 0111 1111” to c register
Calibrate Force Voltage (2 point)
Write zero scale to the Force DAC (FIN), connect
SYS_FORCE to FOHx and SYS_SENSE to MEASVHx,
close the internal Force/Sense Switch (SW 7). Using the
System PMU, measure the error between voltage at FOHx,
MEASVHx and desired value.
Similarly, load Full scale to the Force DAC, and measure
the error between FOHx , MEASVH and the desired value.
Work out m and c values. Load these values to appropriate
m and c registers for Force DAC.
Calibrate Measure Voltage (2 point)
Connect SYS_FORCE to FOH, SYS_SENSE to MEASVHx
Close Internal Force/Sense switch (SW 7). Force voltage on
FOH via SYS_FORCE and measure voltage at MEASOUT.
The difference is the error between the actual forced
voltage and the voltage at MEASOUT.
Calibrate Force current (2 point)
In Force current mode, write zero and fullscale to the Force
DAC. Connect SYS_FORCE to external ammeter and to
FOH pin. Measure error on zero and fullscale current and
calculate m and c values.
Calibrate Measure Current (2 Point)
Write zero scale to the Force DAC in Force Current mode.
Connect SYS_FORCE to an external ammeter and to the
FOH pin. Measure the error between ammeter reading and
MEASOUT reading. Repeat with Full scale loaded to the
Force DAC.
Repeat for all four channels.
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