ОБЩЕЕ ОПИСАНИЕ

The ADR440/ADR441/ADR443/ADR444/ADR4451 series is a family of XFET® voltage references featuring ultralow noise, high accuracy, and low temperature drift performance. Using Analog Devices, Inc., temperature drift curvature correction and extra implanted junction FET (XFET) technology, voltage change vs. temperature nonlinearity in the ADR440/ADR441/ ADR443/ADR444/ADR445 is greatly minimized.

The XFET references offer better noise performance than buried Zener references, and XFET references operate off low supply voltage headroom (500 mV). This combination of features makes the ADR440/ADR441/ADR443/ADR444/ ADR445 family ideally suited for precision signal conversion applications in high end data acquisition systems, optical networks, and medical applications.

The ADR440/ADR441/ADR443/ADR444/ADR445 family has the capability to source up to 10 mA of output current and sink up to −5 mA. It also comes with a trim terminal to adjust the output voltage over a 0.5% range without compromising performance.

The ADR440/ADR441/ADR443/ADR444/ADR445 family is available in 8-lead MSOP and narrow SOIC packages and offered in two electrical grades. All versions are specified over the extended industrial temperature range of −40°C to +125°C.

 

ОСОБЕННОСТИ

Ultralow noise (0.1 Hz to 10 Hz)

ADR440: 1 µV p-p

Superb temperature coefficient

A grade: 10 ppm/°C

B grade: 3 ppm/°C

Low dropout operation (supply voltage headroom): 500 mV

Input range: (VOUT + 500 mV) to 18 V

High output source and sink current +10 mA and −5 mA, respectively

Wide temperature range: −40°C to +125°C

 

ПРИЛОЖЕНИЯ

Precision data acquisition systems

High resolution data converters

Приборы с питанием от аккумулятора

Portable medical instruments

Industrial process control systems

Precision instruments

Optical control circuits

 

ТЕОРИЯ ЭКСПЛУАТАЦИИ

The ADR440/ADR441/ADR443/ADR444/ADR445 series of references uses a new reference generation technique known as XFET. This technique yields a reference with low dropout, optimal thermal hysteresis, and exceptionally low noise. The core of the XFET reference consists of two junction field effect transistors (JFETs), one of which has an extra channel implant to raise its pinch-off voltage. By running the two JFETs at the same drain current, the difference in pinch off voltage can be amplified and used to form a highly stable voltage reference.

The intrinsic reference voltage is around 0.5 V with a negative temperature coefficient of about −120 ppm/°C. This slope is essentially constant to the dielectric constant of silicon, and it can be closely compensated for by adding a correction term generated in the same fashion as the proportional to absolute temperature (PTAT) term used to compensate band gap references. The advantage of an XFET reference is its correction term, which is approximately 20 times lower and requires less correction than that of a band gap reference. Because most of the noise of a band gap reference comes from the temperature compensation circuitry, the XFET results in much lower noise.

The ADR440/ADR441/ADR443/ADR444/ADR445 devices are created by on-chip adjustment of R2 and R3 to achieve the different voltage options at the reference output.

 

POWER DISSIPATION CONSIDERATIONS

The ADR440/ADR441/ADR443/ADR444/ADR445 family of references is guaranteed to deliver load currents to 10 mA with an input voltage that ranges from 3 V to 18 V. When these devices are used in applications at higher currents.

 

BASIC VOLTAGE REFERENCE CONNECTIONS

The ADR440/ADR441/ADR443/ADR444/ADR445 family requires a 0.1 µF capacitor on the input and the output for stability. Although not required for operation, a 10 µF capacitor at the input can help with line voltage transient performance.

 

NOISE PERFORMANCE

The noise generated by the ADR440/ADR441/ADR443/ ADR444/ADR445 family of references is typically less than or equal to 2.25 µV p-p over the 0.1 Hz to 10.0 Hz band for the ADR440, ADR441, and ADR443. The noise measurement is made with a band-pass filter composed of a twopole high-pass filter with a corner frequency at 0.1 Hz and a twopole low-pass filter with a corner frequency at 10.0 Hz.