REF01/REF02/REF03

Rev. K | Page 15 of 20

TEMPERATURE MONITORING

In addition to the optional TRIM function, the REF0x series of

references provides the ability to monitor changes in temper-

ature by way of tracking the voltage present at the TEMP pin.

The output voltage of this pin is taken directly from the band

gap core and, as a result, varies linearly with temperature. The

approximately 1.96 mV/°C. Refer to Figure 32 for a graph of

output voltage vs. temperature.

As an example, given these ideal values, a voltage change of

39.2 mV at the TEMP pin corresponds to a 20°C change in

temperature.

The TEMP function is provided as a convenience, rather than a

precise feature, of the reference. In addition, because the voltage

at the TEMP pin is taken directly from the band gap core, any

current injected into or pulled from this pin has a significant

TEMP pin can cause the output to fall out of regulation. Should

the designer wish to take advantage of this feature, it is neces-

sary to buffer the output of the TEMP pin with a low bias

current op amp, such as the AD8601 or AD8641. Any of these

op amps, if used as shown in Figure 36, causes less than a

U2

15V

U1

TEMP TRIM

GND

V–

V+

AD8641

1.9mV/°C

REF01/

REF02/

REF03

Figure 36. Temperature Monitoring

LONG-TERM STABILITY

One of the key parameters of the REF0x series of references is

long-term stability. Regardless of output voltage, internal testing

during development showed a typical drift of approximately

50 ppm after 1,000 hours of continuous, nonloaded operation

in a +25°C environment.

It is important to understand that long-term stability is not

guaranteed by design, and that the output from the device may

shift beyond the typical 50 ppm specification at any time, especially

during the first 200 hours of operation. For systems that require

highly stable output over long periods of time, the designer should

consider burning-in the devices prior to use to minimize the

amount of output drift exhibited by the reference over time. Refer

to the AN-713 Application Note for more information regarding

the effects of long-term drift and how it can be minimized.

BURN-IN

Burn-in, wherein the part is powered and allowed to operate

normally for an extended period of time, can be useful for

minimizing the effects of long-term drift. A sample burn-in

circuit is shown below in Figure 37.

GND

+18V

–18V

+

10µF

+

10µF

10

Ω

OPTIONAL

REF01/

REF02/

REF03

Figure 37. Burn-In Circuit

The part may be burned in with or without a constant resistive

load. The load current should not exceed 10 mA.

POWER DISSIPATION

The REF0x series of voltage references are capable of sourcing

up to 10 mA of load current at room temperature across the

rated input voltage range. However, when used in applications

subject to high ambient temperatures, the input voltage and

load current should be carefully monitored to ensure that the

device does not exceeded its maximum power dissipation

rating. The maximum power dissipation of the device can be

calculated via the following equation:

[]

W

JA

A

j

D

θ

T

T

P

−

=

where:

Because of this relationship, acceptable load current in high-

temperature conditions may be less than the maximum

current-sourcing capability of the device. In no case should

the part be operated outside of its maximum power rating as

doing so may result in premature failure or permanent damage

to the device.