Datasheet

AD8253 Data Sheet
Rev. B | Page 18 of 24
POWER SUPPLY REGULATION AND BYPASSING
The AD8253 has high PSRR. However, for optimal performance,
a stable dc voltage should be used to power the instrumentation
amplifier. Noise on the supply pins can adversely affect per-
formance. As in all linear circuits, bypass capacitors must be
used to decouple the amplifier.
Place a 0.1 µF capacitor close to each supply pin. A 10 µF tantalum
capacitor can be used farther away from the part (see Figure 55)
and, in most cases, it can be shared by other precision integrated
circuits.
AD8253
+
V
S
+IN
–IN
LOAD
REF
0.1µF
10µF
0.1µF
10µF
–V
S
DGND
V
OUT
DGND
A0
A1
WR
06983-054
Figure 55. Supply Decoupling, REF, and Output Referred to Ground
INPUT BIAS CURRENT RETURN PATH
The AD8253 input bias current must have a return path to its
local analog ground. When the source, such as a thermocouple,
cannot provide a return current path, one should be created
(see Figure 56).
THERMOCOUPLE
+V
S
REF
–V
S
AD8253
CAPACITIVELY COUPLED
+V
S
REF
C
C
–V
S
AD8253
TRANSFORMER
+V
S
REF
–V
S
AD8253
INCORRECT
CAPACITIVELY COUPLED
+V
S
REF
C
R
R
C
–V
S
AD8253
1
f
HIGH-PASS
=
2RC
THERMOCOUPLE
+V
S
REF
–V
S
10M
AD8253
TRANSFORMER
+V
S
REF
–V
S
AD8253
CORRECT
06983-055
Figure 56. Creating an I
BIAS
Path
INPUT PROTECTION
All terminals of the AD8253 are protected against ESD. An external
resistor should be used in series with each of the inputs to limit
current for voltages greater than 0.5 V beyond either supply rail.
In such a case, the AD8253 safely handles a continuous 6 mA
current at room temperature. For applications where the AD8253
encounters extreme overload voltages, external series resistors
and low leakage diode clamps such as BAV199Ls, FJH1100s, or
SP720s should be used.