Datasheet

ADA4691-2/ADA4691-4/ADA4692-2/ADA4692-4
Rev. C | Page 16 of 20
SHUTDOWN OPERATION
INPUT PIN CHARACTERISTICS
The ADA4691-2 has a classic CMOS logic inverter input for each
shutdown pin, as shown in Figure 56.
0
7950-149
V
DD
P-CHANNEL
N-CHANNEL
INPUT
OUTPUT
Figure 56. CMOS Inverter
With slowly changing inputs, the top transistor and bottom
transistor may be slightly on at the same time, increasing the
supply current. This can be avoided by driving the input with
a digital logic output having fast rise and fall times. Figure 57
through Figure 59 show the supply current for both sections
switching simultaneously with rise times of 1 μs, 10 μs, and 1 ms.
Clearly, the rise and fall times should be faster than 10 μs.
Using an RC time constant to enable/disable shutdown is not
recommended.
07950-150
TIME (400µs/DIV)
I
SY
= 196mV/1k = 196µA
SD A, SD B
DUT OUTPUT
Figure 57. Shutdown Pin Rise Time = 1 μs
07950-151
TIME (400µs/DIV)
I
SY
= 192mV/1k = 196µA
SD A, SD B
DUT OUTPUT
Figure 58. Shutdown Pin Rise Time = 10 μs
07950-152
TIME (400µs/DIV)
I
SY
= 724mV/1k = 724µA
SD A, SD B
DUT OUTPUT
Figure 59. Shutdown Pin Rise Time = 1 ms
INPUT THRESHOLD
The input threshold is approximately 1.2 V above the V− pin when
operating on ground and 5 V and 0.9 V when operating on 2.7 V
(see Figure 60 and Figure 61). The threshold is relatively stable
over temperature. For operation on split supplies, the logic swing
may have to be level shifted.
500
450
400
350
300
250
200
150
100
50
0
05.04.54.03.53.02.52.01.51.00.5
I
SY
(µA)
SD VOLTAGE (V)
ADA4691-2
T
A
= 25°C
V
SY
= 5V
07950-155
T
A
= +125°C
T
A
= +25°C
T
A
= –40°C
T
A
= +85°C
Figure 60. Supply Current vs. Temperature, V
SY
= 5 V
300
250
200
150
100
50
0
02.72.42.11.81.51.20.90.60.3
I
SY
(µA)
SD VOLTAGE (V)
ADA4691-2
V
SY
= 2.7V
07950-156
T
A
= +125°C
T
A
= –40°C
T
A
= +85°C
T
A
= +25°C
Figure 61. Supply Current vs. Temperature, V
SY
= 2.7 V