UG-261 Datasheet, PDF (4/8 Pages) Analog Devices – The EVAL-INAMP-62RZ is designed for evaluation

UG-261
Evaluation Board User Guide
QUICK START FOR THE EVAL-INAMP-62RZ BOARD
CIRCUIT OPTIONS
Single-Supply Operation
A jumper is provided to select between single or dual power
supplies. The evaluation board is shipped with W14 in the dual-
supply position. To convert to single supply, place W14 in the
position marked with a ground symbol.
Gain Adjustment
The gain of the AD621 is pin selectable where G = 1 (default) or
G = 100 (strap Pin 1 and Pin 8). In contrast, the gain of the AD620,
AD622, and AD623 devices is resistor dependent (the resistor is
connected between the RG pins). Without a resistor, the gain is
unity. Table 1 to Table 3 provide calculated gains for each device.
See the individual product data sheet for the gain equations.
Table 3. AD623 Gain Resistor Values
Desired Gain 1% Standard Value of RG (Ω)
2
100 k
5
24.9 k
10
11 k
20
5.23 k
33
3.09 k
40
2.55 k
50
2.05 k
65
1.58 k
100
1.02 k
200
499
500
200
1000
100
Calculated Gain
2
5.02
10.09
20.12
33.36
40.21
49.78
64.29
99.04
201.4
501
1001
Table 1. AD620 Gain Resistor Values
1% Standard Calculated 0.1% Standard
Value of RG(Ω) Gain
Value of RG (Ω)
49.9 k
1.990
49.3 k
12.4 k
4.984
12.4 k
5.49 k
9.998
5.49 k
2.61 k
19.93
2.61 k
1.00 k
50.40
1.01 k
499
100.0
499
249
199.4
249
100
495.0
98.8
49.9
991.0
49.3
Calculated
Gain
2.002
4.984
9.998
19.93
49.91
100.0
199.4
501.0
1003.0
Table 2. AD622 Gain Resistor Values
Desired Gain 1% Standard Value of RG (Ω)
2
51.1 k
5
12.7 k
10
5.62 k
20
2.67 k
33
1.58 k
40
1.3 k
50
1.02 k
65
787
100
511
200
255
500
102
1000
51.1
Calculated Gain
1.988
4.976
9.986
19.91
32.96
39.85
50.50
65.17
99.83
199.0
496.1
989.3
External Reference or Offset Adjustment
When shipped, the reference of the EVAL-INAMP-62RZ board
is connected to ground. Certain single-supply applications (for
example, an ADC connected to the output of the in-amp) require a
symmetrical output voltage centered on a nonzero value. The
reference can be equal to half the supply, or an application-specific
voltage can be provided by an ADC. The user can install a jumper
at W13 and connect an external reference to the EXT_REF pin.
To maintain proper operation of the in-amp, the reference
should be provided by a voltage source.
Similarly, a provision is made for an offset adjustment of ±1.12 V
by installing the parts listed in Table 6. Although the A2 and A3
ICs can be used with a single or dual power supply connection,
A1 requires a dual supply. To enable the offset feature, install a
shunt in Position W11. To adjust the offset of the in-amp,
ground both inputs and measure the output voltage. Adjust
Potentiometer R1 for 0 V.
LOAD RESISTOR
Although not required for normal operation, a load resistor can
be inserted at Position R8.
CMRR PERFORMANCE
The AD621 CMRR performance degrades at gains of 100 when
using this board due to the high performance of the AD621.
Rev. C | Page 4 of 8