ADR3425/ADR3450

Rev. 0 | Page 14 of 20

THEORY OF OPERATION

BANDGAP

VOLTAGE

REFERENCE

ENABLE

GND FORCE

REF FORCE

REF SENSE

VDD

GND SENSE

Figure 39. Block Diagram

The ADR342

5/ADR3450 use a patented voltage reference

architecture to achieve high accuracy, low temperature

coefficient (TC), and low noise in a CMOS process. Like all

bandgap references, the ADR3425/ADR3450 combine two

voltages of opposite TCs to create an output voltage that is

nearly independent of ambient temperature. However, unlike

traditional bandgap voltage references, the temperature-

independent voltage of the ADR3425/ADR3450 are 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.

The bandgap voltage is then buffered and amplified to 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 ADR3425/ADR3450 leverage Analog Devices patented

DigiTrim technology to achieve high initial accuracy and low

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

drift and thermal hysteresis.

LONG-TERM STABILITY

One of the key parameters of the ADR3425/ADR3450

references is long-term stability. Regardless of output voltage,

internal testing during development showed a typical drift of

approximately 30 ppm after 1,000 hours of continuous, non

loaded operation in a +50°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 30 ppm specification at any time,

especially during the first 200 hours of operation. For systems

that require highly stable output voltages 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. See the AN-713 Application Note for more

information regarding the effects of long-term drift and how it

can be minimized.

POWER DISSIPATION

The ADR3425/ADR3450 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

T

T

P

JA

A

J

D

θ

−

=

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 because doing so

can result in premature failure or permanent damage to the

device.