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MAX44251/MAX44252

20V, Ultra-Precision, Low-Noise Op Amps

Error Budget Example

When using the ICs as an ADC buffer in strain gauge

application, the temperature drift should be taken into

consideration to determine maximum input signal. A

typical strain gauge has sensitivity specification of just

2mV/V at rated out load. This means that when the strain

gauge load cell is powered with 10V, the full-scale output

voltage is 20mV. In this application, both offset voltage

and drift are critical parameters that directly affect the

accuracy of measurement. Even though offset voltage

could be calibrated out, its drift over temperature is still

a problem.

The ICs, with a typical offset drift of 5nV/°C, guarantee

that the drift over a 10°C range is only 50nV. Setting this

equal to 0.5 LSB in a 18-bit system yields a full-scale

range of 13mV. With a single 10V supply, an acceptable

closed-loop gain of 770V/V provides sufficient gain while

maintaining headroom.

Precision Low-Side Current Sensing

The ICs’ autozero feature produces ultra-low offset

voltage and drift, making them ideal for precision cur-

rent-sensing applications. Figure 2 shows the ICs in

a low-side current-sense configuration. This circuit pro-

Figure 2. Low-Side Current Sensing

Ordering Information

+Denotes a lead(Pb)-free/RoHS-compliant package.

*Future product—contact factory for availability.

Chip Information

PROCESS: BiCMOS

Functional Diagrams

PART

TEMP RANGE

PIN-

PACKAGE

TOP

MARK

MAX44251AKA+

-40NC to +125NC

8 SOT23

AERC

MAX44251AUA+

-40NC to +125NC

8 FMAX

—

MAX44252ASD+*

-40NC to +125NC

14 SOIC

—

OUT

MAX44251

MAX44252

5

6

7

10

9

8

INB-

INB+

1

2

8

7

OUTB

INA-

INA+

OUTA

TOP VIEW

3

4

6

5

MAX44251

+

IND+

INB+

1

2

14

13

OUTD

IND-

INA-

INA+

INB-

OUTB

OUTA

3

4

12

11

INC+

INC-

OUTC

MAX44252

+