Shutdown mode, Load-driving capability – Rainbow Electronics MAX4040_MAX4044 User Manual
Page 10
MAX4040–MAX4044
Single/Dual/Quad, Low-Cost, SOT23,
Micropower, Rail-to-Rail I/O Op Amps
10
______________________________________________________________________________________
Shutdown Mode
The MAX4041 (single) and MAX4043 (dual) feature a
low-power shutdown mode. When the shutdown pin
(SHDN) is pulled low, the supply current drops to 1µA
per amplifier, the amplifier is disabled, and the outputs
enter a high-impedance state. Pulling SHDN high or
leaving it floating enables the amplifier. Take care to
ensure that parasitic leakage current at the SHDN pin
does not inadvertently place the part into shutdown
mode when SHDN is left floating. Figure 4 shows the
output voltage response to a shutdown pulse. The logic
threshold for SHDN is always referred to V
CC
/ 2 (not to
GND). When using dual supplies, pull SHDN to V
EE
to
enter shutdown mode.
Load-Driving Capability
The MAX4040–MAX4044 are fully guaranteed over tem-
perature and supply voltage to drive a maximum resis-
tive load of 25k
Ω
to V
CC
/ 2, although heavier loads can
be driven in many applications. The rail-to-rail output
stage of the amplifier can be modeled as a current
source when driving the load toward V
CC
, and as a cur-
rent sink when driving the load toward V
EE
. The magni-
tude of this current source/sink varies with supply
voltage, ambient temperature, and lot-to-lot variations
of the units.
Figures 5a and 5b show the typical current source and
sink capability of the MAX4040–MAX4044 family as a
function of supply voltage and ambient temperature.
The contours on the graph depict the output current
value, based on driving the output voltage to within
50mV, 100mV, and 200mV of either power-supply rail.
1200
0
-60
-40
-20
100
200
400
1000
MAX4040-44 fig05a
TEMPERATURE (°C)
OUTPUT SOURCE CURRENT (
µ
A)
0
40
20
600
800
80
60
V
CC
= 5.5V, V
OH
= 200mV
V
CC
= 5.5V, V
OH
= 100mV
V
CC
= 2.4V, V
OH
= 50mV
V
CC
= 5.5V, V
OH
= 50mV
V
CC
= 2.4V,
V
OH
= 200mV
V
CC
= 2.4V,
V
OH
= 100mV
Figure 5a. Output Source Current vs. Temperature
3000
0
-60
-40
-20
100
500
1000
2500
MAX4040-44 fig05b
TEMPERATURE (°C)
OUTPUT SINK CURRENT (
µ
A)
0
40
20
1500
2000
80
60
V
CC
= 5.5V, V
OL
= 200mV
V
CC
= 2.4V, V
OL
= 200mV
V
CC
= 5.5V,
V
OL
= 100mV
V
CC
= 2.4V, V
OL
= 50mV
V
CC
= 5.5V, V
OL
= 50mV
V
CC
= 2.4V, V
OL
= 100mV
Figure 5b. Output Sink Current vs. Temperature
1V/div
OUT
IN
1V/div
MAX4040-44 fig03
200
µ
s/div
R
L
= 100k
Ω
TIED TO V
EE
V
IN
= 4.0V
f
IN
= 1kHz
Figure 3. Rail-to-Rail Input/Output Voltage Range
MAX4040-44 fig04
200
µ
s/div
5V/div
1V/div
SHDN
OUT
V
IN
= 2V
R
L
= 100k
Ω
TIED TO V
EE
Figure 4. Shutdown Enable/Disable Output Voltage