Datasheet

Data Sheet ADA4638-1
Rev. 0 | Page 19 of 24
ADA4638-1
A1 I
TOTAL
+
A3 I
SY
+
R
IN1
+V
SY
V
OUT
–V
SY
I
INPUT
+
R
IN2
I
INPUT–
A4 I
SY
–
A2 I
TOTAL
–
10072-062
Figure 62. Comparator B
Figure 63 and Figure 64 show the total supply current of the
system, I
TOTAL
, and the actual currents, I
SY
, that flow into and
out of the supply pins of the ADA4638-1. With R
IN1
= R
IN2
=
100 kΩ and supply voltage of 30 V, the total supply current of
the system is 800 µA to 900 A.
With smaller input series resistors, total supply current of the
system increases much more. Figure 65 and Figure 66 show the
supply currents with R
IN1
= R
IN2
= 0 Ω. The total current of the
system increases to 10 mA.
I
TOTAL
= I
SY
+ I
INPUT
Note that, at 30 V of supply voltage, 8 mA to 9 mA of current
flows through the input pins. This is undesirable. The ADA4638-1
is not recommended to be used as a comparator. If absolutely
necessary, place resistors in series with the inputs of the ampli-
fier to limit input current to less than 10 mA.
For more details on op amps as comparators, refer to the
AN-849 Application Note, Using Op Amps as Comparators.
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25 30
CURRENT (mA)
V
SY
(V)
I
SY
+
I
TOTAL
–
I
TOTAL
+
I
SY
–
10072-063
Figure 63. Supply Current vs. Supply Voltage
(Comparator A, R
IN1
= R
IN2
= 100 kΩ)
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
1.0
0 5 10 15 20 25 30
CURRENT (mA)
V
SY
(V)
I
SY
+
I
TOTAL
–
I
TOTAL
+
I
SY
–
10072-064
Figure 64. Supply Current vs. Supply Voltage
(Comparator B, R
IN1
= R
IN2
= 100 kΩ)
–12
–10
–8
–6
–4
–2
0
2
4
6
8
10
12
0 5 10 15 20 25 30
CURRENT (mA)
V
SY
(V)
I
SY
+
I
TOTAL
–
I
TOTAL
+
I
SY
–
10072-065
Figure 65. Supply Current vs. Supply Voltage
(Comparator A, R
IN1
= R
IN2
= 0 kΩ)
–12
–10
–8
–6
–4
–2
0
2
4
6
8
10
12
0 5 10 15 20 25 30
CURRENT (mA)
V
SY
(V)
I
SY
+
I
TOTAL
–
I
TOTAL
+
I
SY
–
10072-066
Figure 66. Supply Current vs. Supply Voltage
(Comparator B, R
IN1
= R
IN2
= 0 kΩ)