Datasheet

AD8293G80/AD8293G160
Rev. 0 | Page 12 of 16
he addition of another single pole of 700 Hz on the output
hs
C3 (nF)
T
(from the secondary filter in Figure 18) is required for bandwidt
greater than 10 Hz. These two filters, together, produce an overall
bandwidth of 500 Hz. The internal resistors, R2 and R3, have an
absolute tolerance of 20%. Tabl e 8 lists the standard capacitors
needed to create a filter with an overall bandwidth of 500 Hz.
Table 8. Standard Capacitors Used to Form a Filter with an
Overall Bandwidth of 500 Hz
Model C2 (pF)
AD8293G80 1300 39
AD8293G160 680 39
For applications with low bandwi ths (<10 Hz), only the primary
H
use two synchronized clocks
ncies can be observed at
d
filter is required. In such an event, the high frequency noise
from the auto-zero amplifier (output amplifier) is not filtered
before the following stage.
CLOCK FEEDTHROUG
The AD8293G80/AD8293G160
to perform the autocorrection. The input voltage-to-current
amplifiers are corrected at 60 kHz.
Trace amounts of these clock freque
the OUT pin. The amount of visible correction feedthrough
is dependent on the values of the filters set by R2/C2. Use
ADC OUT to create a filter using R3/C3 to further reduce
correction feedthrough as described in the Output Filtering
section.
POWER SUPPLY BYPASSING
The AD8293G80/AD8293G160 use internally generated clock
signals to perform autocorrection. As a result, proper bypassing
is necessary to achieve optimum performance. Inadequate or
improper bypassing of the supply lines can lead to excessive
noise and offset voltage.
A 0.1 µF surface-mount capacitor should be connected between
the supply lines. This capacitor is necessary to minimize ripple
from the correction clocks inside the IC. For dual-supply operation,
a 0.1 µF (ceramic) surface-mount capacitor should be connected
from each supply pin to GND.
For single-supply operation, a 0.1 µF surface-mount capacitor
should be connected from the supply line to GND.
All bypass capacitors should be positioned as close to the DUT
supply pins as possible, especially the bypass capacitor between
the supplies. Placement of the bypass capacitor on the back of
the board directly under the DUT is preferred.
INPUT OVERVOLTAGE PROTECTION
All terminals of the AD8293G80/AD8293G160 are protected
against ESD. In the case of a dc overload voltage beyond either
supply, a large current would flow directly through the ESD
protection diodes. If such a condition can occur, an external resistor
should be used in series with the inputs to limit current for voltages
beyond the supply rails. The AD8293G80/AD8293G160 can safely
handle 5 mA of continuous current, resulting in an external
resistor selection of
R
EXT
= (V
IN
− V
S
)/5 mA
1
8
7 5 6
4
ADC OUT
FILT+V
S
I
1.8V
–IN
+IN
R1
4kΩ
R2
160kΩ
R
SHUNT
R3
5kΩ
+3.3V
10µF
0.1µF
C3
39nF
OUT
C2
1.3nF
07451-023
AD8293G80 REFGND
32
IN-AMP
ADC
REF
LOAD
DC-DC
+5
V
0.1µF
Figure 21. Measuring Current Through a Shunt Resistor (Filter Is Set to 500 Hz)