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

Voltage Reference

8

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Detailed Description

Temperature Stability

The MAX6220 is a highly stable, low-noise voltage ref-

erence that uses a low-power temperature-compensa-

tion scheme to achieve laboratory-standard temper-

ature stability. This produces a nearly flat temperature

curve, yet does not require the power associated with

heated references.

The output voltage can be trimmed 0.6% (min) by con-

necting a 10k

Ω potentiometer between OUT and GND,

and connecting its tap to the TRIM pin (Figure 1). The

external trimming does not affect temperature 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 MAX6220 is 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. The MAX865 generates approximately ±9V to

operate both the MAX6220 reference and the MAX480

inverting amplifier. The +5V is inverted by the MAX480.

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.

MAX6220

IN

8V TO 40V INPUT

REFERENCE OUT

OUT

TRIM

10k

Ω

NR

GND

MAX6220

IN

8V TO 40V INPUT

REFERENCE OUT

OUT

TRIM

NR

*OPTIONAL

1

µF

GND

2.2

µF*

Figure 1. Output Voltage Adjustment

Figure 2. Noise-Reduction Capacitor