MAX4043 Maxim, MAX4043 Datasheet - Page 11

• Manufacturer Part Number: MAX4043
• Description: The MAX4040–MAX4044 family of micropower op amps operates from a single +2
• Manufacturer: Maxim

For example, a MAX4040 running from a single +2.4V
supply, operating at T
within 100mV of V
load resistor to V
The same application can drive a 4.6k
when terminated in V
The MAX4040–MAX4044 are unity-gain stable for loads
up to 200pF (see Load Resistor vs. Capacitive Load
graph in Typical Operating Characteristics).
Applications that require greater capacitive drive capa-
bility should use an isolation resistor between the output
and the capacitive load (Figures 6a–6c). Note that this
alternative results in a loss of gain accuracy because
R
The MAX4040–MAX4044 family operates from either a
single +2.4V to +5.5V supply or dual ±1.2V to ±2.75V
supplies. For single-supply operation, bypass the
power supply with a 100nF capacitor to V
case GND). For dual-supply operation, both the V
and V
separate 100nF capacitors.
Good PC board layout techniques optimize perfor-
mance by decreasing the amount of stray capacitance
at the op amp’s inputs and output. To decrease stray
capacitance, minimize trace lengths by placing exter-
nal components as close as possible to the op amp.
Surface-mount components are an excellent choice.
Although optimized for use as operational amplifiers,
the MAX4040–MAX4044 can also be used as rail-to-rail
I/O comparators. Typical propagation delay depends
on the input overdrive voltage, as shown in Figure 7.
External hysteresis can be used to minimize the risk of
output oscillation. The positive feedback circuit, shown
in Figure 8, causes the input threshold to change when
the output voltage changes state. The two thresholds
create a hysteresis band that can be calculated by the
following equations:
ISO
V
V
V
HYST
LO
HI
forms a voltage divider with the load resistor.
EE
= V
= [(R2 / R1 x V
Power-Supply Bypassing and Layout
supplies should be bypassed to ground with
R
= V
(1 + R1 / R2 + R2 / R
IN
L
HI
x R2 / (R1 + (R1 x R2 / R
=
- V
EE
2.4V - 0.1V
Using the MAX4040–MAX4044
CC
______________________________________________________________________________________
LO
:
240 A
CC
and is capable of driving a 9.6k
A
Driving Capacitive Loads
= +25°C, can source 240µA to
/ 2 (+1.2V in this case).
IN
Micropower, Rail-to-Rail I/O Op Amps
) + (R2 / R
Single/Dual/Quad, Low-Cost, SOT23,
HYST
9.6k to V
as Comparators
)
HYST
HYST
) + R2)
load resistor
EE
) x V
EE
(in this
CC
CC
] /
Figure 6a. Using a Resistor to Isolate a Capacitive Load from
the Op Amp
Figure 6b. Pulse Response without Isolating Resistor
Figure 6c. Pulse Response with Isolating Resistor
50mV/div
50mV/div
50mV/div
50mV/div
R
R
ISO
ISO
= 1k , R
= NONE, R
MAX4040–
MAX4044
L
L
= 100k , C
= 100k , C
100 s/div
100 s/div
L
L
= 700pF
R
= 700pF
ISO
R
MAX4040/42/44 fig06b
MAX4040/42/44 fig06c
L
A
V
=
R
L
R
+ R
L
ISO
C
L
IN
IN
OUT
OUT
1
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