Low-Noise, Precision, +2.5V/+4.096V/+5V
Voltage References
_____________________Pin Description
PIN
1, 7, 8
2
NAME
I.C.
IN
FUNCTION
Internally Connected.
Do not use.
Positive Power-Supply Input
Noise Reduction. Optional capacitor
connection for wideband noise
reduction. Leave open if not used
(Figure 2).
Ground
External Trim Input. Allows ±1%
output adjustment (Figure 1).
Leave open if not used.
Voltage Reference Output
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.
MAX6225/MAX6241/MAX6250
3
NR
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.
4
5
6
GND
TRIM
OUT
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.
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 10kΩ 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.
8V TO 36V INPUT
8V TO 36V INPUT
IN
OUT
REFERENCE OUT
*
TRIM
10k
1µF
NR
IN
OUT
REFERENCE OUT
NR
MAX6225
MAX6241
MAX6250
GND
MAX6225
MAX6241
MAX6250
GND
TRIM
*OPTIONAL
Figure 1. Output Voltage Adjustment
Figure 2. Noise-Reduction Capacitor
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9
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
