AD8222-EVAL View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD8222-EVAL Datasheet PDF : 24 Pages
| |||
The AD8222 should be decoupled with 0.1 μF bypass capacitors,
one for each supply. The positive supply decoupling capacitor
should be placed near Pin 16, and the negative supply
decoupling capacitor should be placed near Pin 8. Each supply
should also be decoupled with a 10 μF tantalum capacitor. The
tantalum capacitor can be placed further away from the
AD8222 and can generally be shared by other precision integrated
circuits. Figure 46 shows an example layout.
0.1µF
16 15 14 13
AD8222
1
12
2
RG
3
11
RG
10
4
9
5 6 78
0.1µF
Figure 46. Example Layout
SOLDER WASH
The solder process can leave flux and other contaminants on
the board. When these contaminants are between the AD8222
leads and thermal pad, they can create leakage paths that are
larger than the AD8222’s bias currents. A thorough washing
process removes these contaminants and restores the AD8222’s
excellent bias current performance.
INPUT BIAS CURRENT RETURN PATH
The input bias current of the AD8222 must have a return path
to common. When the source, such as a thermocouple, cannot
provide a return current path, one should be created, as shown
in Figure 47.
INCORRECT
+VS
AD8222
CORRECT
+VS
AD8222
REF
–VS
TRANSFORMER
+VS
AD8222
REF
–VS
TRANSFORMER
+VS
AD8222
REF
–VS
THERMOCOUPLE
AD8222
REF
10MΩ
–VS
THERMOCOUPLE
+VS
C
+VS
C
AD8222
fHIGH-PASS
=
1
2πRC
R
AD8222
C
REF
C
REF
R
–VS
–VS
CAPACITIVELY COUPLED
CAPACITIVELY COUPLED
Figure 47. Creating an IBIAS Path
INPUT PROTECTION
All terminals of the AD8222 are protected against ESD (1 kV—
human body model). In addition, the input structure allows for
dc overload conditions of about 2½ V beyond the supplies.
Input Voltages Beyond the Rails
For larger input voltages, an external resistor should be used in
series with each input to limit current during overload conditions.
The AD8222 can safely handle a continuous 6 mA current. The
limiting resistor can be computed from
R LIMIT
≥ VIN − VSUPPLY
6 mA
− 400 Ω
For applications where the AD8222 encounters extreme overload
voltages, such as cardiac defibrillators, external series resistors
and low leakage diode clamps, such as the BAV199L, the FJH1100s,
or the SP720, should be used.
Rev. 0 | Page 17 of 24
Share Link: 