Low-Noise, Precision, +2.5V/+4.096V/+5V

Voltage References

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Detailed Description

Temperature Stability

The MAX6225/MAX6241/MAX6250 are highly stable,

low-noise voltage references that use a low-power tem-

perature-compensation scheme to achieve laboratory-

standard temperature stability. This produces a nearly

flat temperature curve, yet does not require the power

associated with heated references.

The output voltage can be trimmed a minimum of 0.6%

by connecting a 10k

Ω potentiometer between OUT and

GND, and connecting its tap to the TRIM pin, as shown

in Figure 1. The external trimming does not affect tem-

perature stability.

Noise Reduction

To augment wideband noise reduction, add a 1µF

capacitor to the NR pin (Figure 2). Larger values do not

improve noise appreciably (

see Typical Operating

Characteristics).

Noise in the power-supply input can affect output

noise, but can be reduced by adding an optional

bypass capacitor to the IN pin and GND.

Bypassing

The MAX6225/MAX6241/MAX6250 are stable with

capacitive load values from 0µF to 100µF, for all values

of load current. Adding an output bypass capacitor can

help reduce noise and output glitching caused by load

transients.

Applications Information

Negative Regulator

Figure 3 shows how both a +5V and -5V precision ref-

erence can be obtained from a single unregulated +5V

supply. A MAX681 generates approximately ±9V to

operate the MAX6250 reference and MAX432 inverting

amplifier. The +5V is inverted by the MAX432 chopper-

stabilized amplifier. Resistor R1 is optional, and may be

used to trim the ±5V references. R2 and R4 should be

matched, both in absolute resistance and temperature

coefficient. R3 is optional, and is adjusted to set the -5V

reference.

_____________________Pin Description

NAME

FUNCTION

1, 7, 8

I.C.

Internally Connected. Do not use.

2

IN

Positive Power-Supply Input

PIN

4

GND

Ground

3

NR

Noise Reduction. Optional capacitor

connection for wideband noise

reduction. Leave open if not used

(Figure 2).

6

OUT

Voltage Reference Output

5

TRIM

External Trim Input. Allows ±1%

output adjustment (Figure 1).

Leave open if not used.

MAX6225

MAX6241

MAX6250

IN

8V TO 36V INPUT

REFERENCE OUT

OUT

TRIM

10k

NR

GND

MAX6225

MAX6241

MAX6250

IN

8V TO 36V INPUT

REFERENCE OUT

OUT

TRIM

NR

*OPTIONAL

*

1

µF

GND

Figure 1. Output Voltage Adjustment

Figure 2. Noise-Reduction Capacitor