P r o d u c t I n n o v a t i o n F r o m

VRE3025

VRE3025DS

5

EXTERNal CONNECTIONS

PIN DESCRIPTIONS

1, 3, 7

N. C.

Internally connected. Do not use

2

V

IN

Positive power supply input

4

GND

Ground

5

TRIM

External trim input. Leave open if not

used.

6

OUT

Voltage reference output

8

NR

Noise Reduction

4. BaSIC CIRCuIT CONNECTION

To achieve the specified performance, pay careful attention to the layout. A low resistance star configuration will

reduce voltage errors, noise pickup, and noise coupled from the power supply. Commons should be connected to

a single point to minimize interconnect resistances.

5. TEMPERaTuRE PERFORMaNCE

The VRE3025 is designed for applications where the initial error at room temperature and drift over temperature

are important to the user. For many instrument manufacturers, a voltage reference with a temperature coefficient

less than 1 ppm/°C makes it possible to not have to perform a system temperature calibration, a slow and costly

process.

Of the three TC specification methods (slope, butterfly, and box), the box method is used commonly used. A box

is formed by the min/max limits for the nominal output voltage over the operating temperature range. The equation

follows:

V

V

T.C. =

This method corresponds more accurately to the method of test and provides a closer estimate of actual error than

the other methods. The box method guarantees limits for the temperature error but does not specify the exact shape

and slope of the device under test.

A designer who needs a 14-bit accurate data acquisition system over the industrial temperature range (-40°C to

+85°C), will need a voltage reference with a temperature coefficient (TC) of 1.0 ppm/°C if the reference is allowed

to contribute an error equivalent to 1LSB. For 1/2LSB equivalent error from the reference you would need a volt-

age reference with a temperature coefficient of 0.5 ppm/°C. Figure 4 shows the required reference TC vs. delta T

change from 25°C for resolution ranging from 8 bits to 20 bits.

8

6

5

2

4

VRE3025

10kΩ

Optional Noise

Reduction

Capacitor

Optional Fine

Trim Adjustment