Data Sheet

ADR3525/ADR3530/ADR3533/ADR3540/ADR3550

Rev. 0 | Page 17 of 20

THEORY OF OPERATION

BAND GAP

VOLTAGE

REFERENCE

ENABLE

GND FORCE

GND SENSE

Figure 36. Block Diagram

The ADR3525W/ADR3530W/ADR3533W/ADR3540W/

ADR3550W use a patented voltage reference architecture to

achieve high accuracy, low temperature coefficient (TC), and

low noise in a CMOS process. Like all band gap references, the

references combine two voltages of opposite TCs to create an

output voltage that is nearly independent of ambient tempera-

ture. However, unlike traditional band gap voltage references, the

temperature-independent voltage of the references is arranged to

voltage of silicon). A corresponding positive TC voltage is then

The key benefit of this technique is that the trimming of the

initial accuracy and TC can be performed without interfering

with one another, thereby increasing overall accuracy across

temperature. Curvature correction techniques further reduce

the temperature variation.

produce stable output voltages of 2.5 V and 5.0 V. The output

buffer can source up to 10 mA and sink up to −3 mA of load

current.

The ADR35xx references leverage Analog Devices patented

DigiTrim technology to achieve high initial accuracy and low

TC, and precision layout techniques lead to very low long-term

drift and thermal hysteresis.

LONG-TERM OUTPUT VOLTAGE DRIFT

One of the key parameters of the ADR35xx references is long-

term output voltage drift. Independent of the output voltage

model and in a 50°C environment, these devices exhibit a

typical drift of approximately 30 ppm after 1000 hours of

continuous, unloaded operation.

It is important to understand that long-term output voltage drift

is not tested or guaranteed by design and that the output from

the device may shift beyond the typical 30 ppm specification.

Because most of the drift occurs in the first 200 hours of device

operation, burning in the system board with the reference

mounted can reduce subsequent output voltage drift over time.

See the AN-713 Application Note, The Effect of Long-Term Drift

on Voltage References, at www.analog.com for more information

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

minimized.

POWER DISSIPATION

The ADR35xx 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 cur-

rent should be carefully monitored to ensure that the device

does not exceed its maximum power dissipation rating. The

maximum power dissipation of the device can be calculated via

the following equation:

]

[W

T

T

P

JA

A

J

D







where:

Because of this relationship, the 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 because doing so

can result in premature failure or permanent damage to the device.