Rainbow Electronics MAX4492 - Manual (Page 5)

MAX4490/MAX4491/MAX4492
Low-Cost, High-Slew-Rate,
Rail-to-Rail I/O Op Amps in SC70
_______________________________________________________________________________________ 5
NAME FUNCTION
MAX4490
1 IN+ Noninverting Input
PIN
2 V SS Negative Supply Input. Connect to ground for single-supply operation.
3 IN- Inverting Input
— INA- Inverting Input to Amplifier A
— INA+ Noninverting Input to Amplifier A
5 V DD Positive Supply Input
4 OUT Amplifier Output
— INC+, IND+ Noninverting Inputs to Amplifiers C and D
— OUTB Amplifier B Output
— INB- Inverting Input to Amplifier B
— INB+ Noninverting Input to Amplifier B
— OUTA Amplifier A Output
Pin Description
MAX4492
—
11
—
2
3
4
—
10, 12
7
6
5
1
MAX4491
—
4
—
2
3
8
—
—
7
6
5
1
— — 9, 13 INC-, IND- Inverting Inputs to Amplifiers C and D
— — 8, 14 OUTC, OUTD Amplifiers C and D Outputs
Detailed Description
Rail-to-Rail Input Stage
The MAX4490/MAX4491/MAX4492 CMOS operational
amplifiers have parallel-connected N- and P-channel
differential input stages that combine to accept a com-
mon-mode range extending to both supply rails. The N-
channel stage is active for common-mode input
voltages typically greater than (V
SS + 1.2V), and the P-
channel stage is active for common-mode input volt-
ages typically less than (V
DD - 1.2V).
Rail-to-Rail Output Stage
The MAX4490/MAX4491/MAX4492 CMOS operational
amplifiers feature class-AB push-pull output stages that
can drive a 100k
Ω load to within 1.5mV of either supply
rail. Short-circuit output current is typically ±50mA.
Figures 1a and 1b show the typical temperature depen-
dence of output source and sink currents, respectively,
for three fixed values of (V
DD - V OH ) and (V OL - V
SS
).
For example, at V DD = 5.0V, the load currents that main-
tain (V DD - V OH ) = 100mV and (V OL - V SS ) = 100mV at
T A = +25°C are 2.2mA and 3.3mA, respectively, when
the load is connected to V DD /2. Consistent resistive-
drive capability is (2.5 - 0.1) / 2.2 = 1.1k Ω. For the same
application, resistive-drive capability is 2.2k Ω when the
load is connected to V DD or V SS .
Applications Information
Power-Supply Considerations
The MAX4490/MAX4491/MAX4492 operate from a sin-
gle 2.7V to 5.5V supply or from dual ±1.35V to ±2.75V
supplies with typically 800µA supply current per ampli-
fier. A high power-supply rejection ratio of 100dB
allows for extended operation from a decaying battery
voltage, thereby simplifying designs for portable appli-
cations. For single-supply operation, bypass the power
supply with a 0.1µF ceramic capacitor placed close to
the V
DD pin. For dual-supply operation, bypass each
supply to ground.
Input Capacitance
One consequence of the parallel-connected differential
input stages for rail-to-rail operation is a relatively large
input capacitance C
IN (typically 5pF). This introduces a