Power-Up Settling Time
The MAX4289 typically requires 300µs to power-up
after V
CC
is stable. During this startup time, the output
is indeterminate. The application circuit should allow for
this initial delay.
Driving Capacitive Loads
The MAX4289 is unity-gain stable for loads up to
200pF. Applications that require greater capacitive-
drive capability should use an isolation resistor
between the output and the capacitive load (Figure 4).
Note that this solution results in a loss of gain accuracy
because R
ISO
forms a voltage-divider with the load
resistor.
Using the MAX4289 as a Comparator
Although optimized for use as an operational amplifier,
the MAX4289 can also be used as a rail-to-rail I/O com-
parator (Figure 5). External hysteresis can be used to
minimize the risk of output oscillation. The positive feed-
back circuit, shown in Figure 5, causes the input thresh-
old to change when the output voltage changes state.
Power Supplies and Layout
The MAX4289 operates from a single 1V to 5.5V power
supply. Bypass the power with a 0.1µF capacitor to
ground.
Good layout techniques optimize performance by
decreasing the amount of stray capacitance at the op
amp’s inputs and outputs. To decrease stray capaci-
tance, minimize trace lengths by placing external com-
ponents close to the op amp’s pins.
MAX4289
1.0V Micropower, SOT23, Operational Amplifier
_______________________________________________________________________________________ 7
vs. SUPPLY VOLTAGE
