REF102

5

SBVS022A

www.ti.com

TYPICAL REF102 REFERENCE NOISE

6

4

2

0

−2

−4

−6

Low Frequency Noise (1s/div)

(See Noise Test Circuit)

–

+

OPA227

DUT

Noise Test Circuit.

100

µF

15.8k

Ω

20

Ω

2k

Ω

8k

Ω

2

µF

Oscilloscope

Gain = 100V/V

f

= 0.1Hz and 10Hz

−3dB

THEORY OF OPERATION

Refer to the diagram on the first page of this data sheet. The

10V output is derived from a compensated buried zener

10V output. The zener bias current is established from the

of the output voltage by providing for small external adjust-

ment of the amplifier gain. Because the temperature coeffi-

The output voltage noise of the REF102 is dominated by the

noise of the zener diode. A capacitor can be connected

between the Noise Reduction pin and ground to form a low-

zener.

DISCUSSION

OF PERFORMANCE

The REF102 is designed for applications requiring a preci-

sion voltage reference where both the initial value at room

temperature and the drift over temperature are of importance

to the user. Two basic methods of specifying voltage refer-

ence drift versus temperature are in common usage in the

industry—the “butterfly method” and the “box method.” The

REF102 is specified by the more commonly-used “box

method.” The “box” is formed by the high and low specifica-

tion temperatures and a diagonal, the slope of which is equal

to the maximum specified drift.

Since the shape of the actual drift curve is not known, the

vertical position of the box is not known, either. It is, however,

Figure 1 uses the REF102CU as an example. It has a drift

specification of 2.5ppm/

°C maximum and a specification

temperature range of –25

°C to +85°C. The “box” height,

REF102CU V

UPPER BOUND

+10.00275

V1

V

NOMINAL

+10.0000

2.75mV

Worst-case

∆V

REF102CU

V2

+9.99725

REF102CU V

LOWER BOUND

−25

0

+25

+50

+85

Temperature (

°C)

FIGURE 1. REF102CU Output Voltage Drift.