®

REF10

5

THEORY OF OPERATION

The following discussion refers to the diagram on the first

page.

In operation, approximately 6.3V is applied to the

noninverting input of op amp A

voltage is amplified by A

The gain is determined by R

and R

2

are actively laser-trimmed to produce an exact

10.00V output. The zener operating current is derived from

the regulated output voltage through R

This feedback

arrangement provides closely regulated zener current. R

actively laser-trimmed to set the zener current to a level

which results in low drift at the output of A

trimming of the output voltage by providing for a small

external adjustment of amplifier gain. Since the TCR of R

4

closely matches the TCR of the gain setting resistors, the

voltage trim has minimal effect on the drift of the reference.

DISCUSSION OF

PERFORMANCE

The REF10 is designed for applications requiring a precision

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 REF10 is specified with 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.

For the REF10, each J and K unit is tested at temperatures

of 0

°C, +25°C, +50°C, and +70°C. Each R and S unit is

tested at –55

°C, –25°C, 0°C, +25°C, +50°C, +75°C, +100°C

and +125

°C. The minimum and maximum test voltages

must meet this condition:

This assures the user that the variations of output voltage

that occur as the temperature changes within the specifica-

tion range, T

whose diagonal has a slope 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 exactly known either.

It is, however, bounded by V

Figure 1).

Figure 1 uses the REF10KM as an example. It has a drift

specification of 1ppm/

°C maximum and a specification

temperature range of 0

°C to +70°C. The “box” height (V

V

are a maximum of 700

µV away from the voltage at +25°C.

FIGURE 1. REF10KM Output Voltage Drift.

INSTALLATION AND

OPERATING INSTRUCTIONS

BASIC CIRCUIT CONNECTION

Figure 2 shows the proper connection of the REF10. To

achieve the specified performance, pay careful attention to

layout. A low resistance star configuration will reduce volt-

age errors, noise pickup, and noise coupled from the power

supply. Commons should be connected as indicated being

sure to minimize interconnection resistances.

REF10

2

6

4

1µF

Tantalum

+

R

L1

R

L2

R

L3

(2)

(2)

(1)

(1)

V

CC

FIGURE 2. REF10 Installation.

NOTES: (1) Lead resistances here of up to a few

Ω have negligible effect on

performance. (2) A resistance of 0.1

Ω in series with these leads will cause

a 1mV error when the load current is at its maximum of 10mA. This results

in a 0.01% error of 10V.

OPTIONAL OUTPUT VOLTAGE ADJUSTMENT

Optional output voltage adjustment circuits are shown in

Figures 3 and 4. Trimming the output voltage will change

the voltage drift by approximately 0.01ppm/

°C per mV of

trimmed voltage. In the circuit in Figure 3, any mismatch in

TCR between the two sections of the potentiometer will also

V

UPPER BOUND

+10.0007

V

1

V

NOMINAL

+10.0000

V

2

+9.9993

025

70

Temperature (°C)

700µV

Worst-case

∆V

OUT

for REF10KM

V

UPPER BOUND

(T

Typical Drift

Diagonal

1ppm/°C for REF10KM

(T

V

T

















X 10

Drift

Specification