Rainbow Electronics MAX9944 - Manual (Page 7)

Detailed Description
The MAX9943/MAX9944 are single/dual operational
amplifiers designed for industrial applications. They
operate from 6V to 38V supply range while maintaining
excellent performance. These devices utilize a three-
stage architecture optimized for low offset voltage and
low input noise with only 550µA supply current. The
devices are unity gain stable with a 1nF capacitive
load. These well-matched devices guarantee the high
open-loop gain, CMRR, PSRR, and low voltage offset.
The MAX9943/MAX9944 provide a wide input/output
voltage range. The input terminals of the MAX9943/
MAX9944 are protected from excessive differential volt-
age with back-to-back diodes. The input signal current
is also limited by an internal series resistor. With a 40V
differential voltage, the input current is limited to 20mA.
The output can swing to the negative rail while deliver-
ing 20mA of current, which is ideal for loop-powered
system applications. The specifications and operation
of the MAX9943/MAX9944 family is guaranteed over the
-40°C to +125°C temperature range.
Application Information
Bias Current vs. Input Common Mode
The MAX9943/MAX9944 use an internal bias current
cancellation circuit to achieve very low bias current
over a wide input common-mode range. For such a cir-
cuit to function properly, the input common mode must
be at least 300mV away from the negative supply V
EE .
The input common mode can reach the negative sup-
ply V
EE . However, in the region between V EE and V EE +
0.3V, there is an increase in bias current for both
inputs.
Capacitive Load Stability
Driving large capacitive loads can cause instability in
many op amps. The MAX9943/MAX9944 are stable with
capacitive loads up to 1nF. The Capacitive Load vs.
Resistive Load graph in the
Typical Operating
Characteristics gives the stable operation region for
capacitive versus resistive loads. Stability with higher
capacitive loads can be improved by adding an isola-
tion resistor in series with the op-amp output, as shown
in Figure 1. This resistor improves the circuit’s phase
MAX9943/MAX9944
High-Voltage, Precision, Low-Power Op Amps
_______________________________________________________________________________________ 7
Pin Description
MAX9943
6 TDFN-EP
MAX9943
8 µMAX
MAX9944
8 SO/TDFN-EP
NAME FUNCTION
1 6 — OUT Output
— — 1 OUTA Output A
— — 7 OUTB Output B
2 4 4 V EE Negative Power Supply. Bypass with a 0.1µF capacitor to ground.
3 3 — IN+ Positive Input
— — 3 INA+ Positive Input A
— — 5 INB+ Positive Input B
4 2 — IN- Negative Input
— — 2 INA- Negative Input A
— — 6 INB- Negative Input B
5 1, 5, 8 — N.C. No Connection
6 7 8 V
CC
Positive Power Supply. Bypass with a 0.1µF capacitor to ground.
— — — EP
Exposed Pad (TDFN Only). Connect to a large ground plane to
maximize thermal performance. Not intended as an electrical
connection point.