Common Mode Selection Jumpers - Texas Instruments ADS9110EVM-PDK User Manual

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J1 Setting
J2 Setting
(R Comp)
1
CLOSED CLOSED
CLOSED OPEN
CLOSED OPEN
2.2.3 R Setting vs Source Impedance
1
The external source impedance ( R
output common mode of the OPA625 amplifiers. To compensate for this, R
the particular external source impedance value used with the evaluation board to allow full-scale input
range without saturating the OPA625 amplifiers.
The board is shipped with R
Ω to 32 Ω for 0 V common mode configuration (J1:closed and J2:closed). For floating or AC-Coupled
signals, the input common mode is set by the OPA625 amplifiers themselves and R
kΩ for any given source impedance. The range of values of R
Equation 1.
7
2 6 . 10
u
9000

R 96

S
In the case of unipolar input signals, R
for any practical value of external source impedance (R
mode is determined using
8
1 9 . 10
u

R 1000

S
SBAU249 – October 2015
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Figure 2. Common Mode Selection Jumpers
Table 3. J1 and J2 Configuration per Input Common Mode
External Signal
Common Mode
0 V
2.25 V
Floating
) will add up to the 1 kΩ of the input resistor, thereby moving the
S
as 280 kΩ that allows an external source impedance ( R
1
7
2 7 . 10
u
R 9000

1
R 67

S
must be replaced since 280 kΩ is not large enough to compensate
1
Equation 2.
8
2 8 . 10
u
177500 R
1
R 1000

S
Copyright © 2015, Texas Instruments Incorporated
Differential Source Type
Bipolar: If R1 = 280 kΩ, R
Unipolar: Must change R1 to match R
AC-Coupled Bipolar: If R1 = 280 kΩ, no R
for 0-V common mode is determined using
1
). The range of values of R
S
270000

Analog Interface
range is 0 Ω to 32 Ω
S
S
restriction
S
can be modified according to
1
) range between 0
S
should remain at 280
1
for 2.25-V common
1
ADS9110EVM-PDK
(1)
(2)
7