Datasheet
Data Sheet AD8436
Rev. B | Page 15 of 24
16kΩ
16kΩ
16kΩ
16kΩ
OGND
OBUFOUT
OBUFIN+
OBUFIN–
–
+
CORE
C
8
14
13
129
OUT
10033-036
2C
Figure 36. Output Buffer Amplifier Configured as a Two-Pole, Sallen-Key
Low-Pass Filter
Configure the output buffer (see Figure 37) to invert dc output.
OUT
16kΩ
16kΩ
OGND
OBUFOUT
OBUFIN+
OBUFIN–
CORE
32.4kΩ
8
14
12
139
–
+
10033-037
Figure 37. Inverting Output Configuration
Current Output Option
If a current output is required, connect the current output,
OUT, to the destination load. To maximize precision, provide a
means for external calibration to replace the internal trimmed
resistor, which is bypassed. This configuration is useful for conve-
nient summing of the AD8436 result with another voltage, or
for polarity inversion.
–
+
8kΩ
15kΩ
16kΩ
19
CAVG
18
CCF
9
OUT
2
RMS
8
OGND
DIRECTION OF
DC OUTPUT
CURRENT
2kΩ
(OPTIONAL)
INVERTED DC
VOLTAGE
OUTPUT
32.4kΩ
DO NOT CONNECT FOR
CURRENT OUTPUT
CORE
10033-138
Figure 38. Connections for Current Output Showing Voltage Inversion
Single Supply
Connections for single supply operation are shown in Figure 39
and are similar to those for dual power supply when the device is
ac-coupled. The analog inputs are all biased to half the supply
voltage, but the output remains referred to ground because the
output of the AD8436 is a current source. An additional bypass
connection is required at IGND to suppress ambient noise.
IGND
4.7µF
RMS
10µF
0.47µF
VEE
CAV VCC
OGND
2
11
10
19
8
9
17
10MΩ
4
5
3
IBUFOUT
IBUFIN+
IBUFIN–
OUT
AD8436
4.7µF
10033-039
Figure 39. Connections for Single Supply Operation
Recommended Application
Figure 40 shows a circuit for a typical application for frequencies
as low as power line, and above. The recommended averaging,
crest factor and LPF capacitor values are 10 μF, 0.1 μF and
3.3 μF. Refer to the Using the Output Buffer section if additional
low-pass filtering is required.
AC IN
VCC
VEE
DC
OUT
10MΩ
VEE
CAVG VCC
OBUFOUT
IGND
OBUFIN+
OBUFIN–
OBUFV+
OUTDNC
IBUFIN–
IBUFOUT
IBUFIN+
SUM IBUFV+
1
4
3
2
5
876 9
12
11
10
16
15
14
13
10µF
0.47µF
OGNDIBUFGN
CCF
10µF
+
19 18 1720
DNC
RMS
3.3µF
0.1µF
AD8436
10033-040
Figure 40. Typical Application Circuit
Converting to Average Rectified Value
To configure the AD8436 for rectified average instead of rms
conversion, simply reduce the value of CAVG to 470 pF (see
Figure 41). To enable both modes of operation, insert a switch
between capacitor CAVG and Pin CAVG.