Datasheet ADR440, ADR441, ADR443, ADR444, ADR445 (Analog Devices) - 16

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ADR440/ADR441/ADR443/ADR444/ADR445 Data Sheet APPLICATIONS INFORMATION OUTPUT ADJUSTMENT +VDD
The ADR440/ADR441/ADR443/ADR444/ADR445 family
2
features a TRIM pin that allows the user to adjust the output
VIN
voltage of the device over a limited range. The TRIM pin allows
ADR440/
errors from the reference and overall system errors to be
ADR441/ ADR443/
trimmed out by connecting a potentiometer between the output
ADR444/ 0.1µF
and the ground, with the wiper connected to the TRIM pin.
ADR445
Figure 37 shows the optimal trim configuration. R1 allows fine
V 6 OUT +5V R1 0.1µF
adjustment of the output and is not always required. R
GND 10kΩ R2 10kΩ
P must be
4
sufficiently large so that the maximum output current from the
+10V
ADR440/ADR441/ADR443/ADR444/ADR445 is not exceeded.
–5V R3 0.1µF 5kΩ
036
–10V
05428-
2 V
Figure 38. ADR440/ADR441/ADR443/ADR444/ADR445 Bipolar Outputs
IN V V OUT 6 O = ±0.5% PROGRAMMABLE VOLTAGE SOURCE 0.1µF ADR440/ ADR441/
Extra components are needed to obtain different voltages than
ADR443/ ADR444/
those offered by the ADR440/ADR441/ADR443/ADR444/
ADR445 R
ADR445. Two potentiometers set the desired voltage and the
TRIM P 5 10kΩ GND R1
buffering amplifier, as shown in Figure 39. The potentiometer
100kΩ R2 4 1kΩ
connected between VOUT and GND, with its wiper connected to 035 the noninverting input of the operational amplifier, takes care of 05428- coarse trim. The second potentiometer, with its wiper connected Figure 37. ADR440/ADR441/ADR443/ADR444/ADR445 Trim Function to the trim terminal of the ADR440/ADR441/ADR443/ADR444/ Using the trim function has a negligible effect on the temperature ADR445, is used for fine adjustment. Resolution depends on the performance of the ADR440/ADR441/ADR443/ADR444/ end to end resistance value and the resolution of the selected ADR445. However, al resistors need to be low temperature potentiometer. coefficient resistors, or errors may occur.
+VDD BIPOLAR OUTPUTS 2
It is possible to obtain both positive and negative reference
VIN
voltages by connecting the output of the ADR440/ADR441/
ADR440/
ADR443/ADR444/ADR445 to the inverting terminal of an
ADR441/ ADR443/
operational amplifier. Care must be taken when choosing
ADJ VREF ADR444/
Resistors R1 and R2 (see Figure 38). These resistors must be
ADR445
matched as closely as possible to ensure minimal differences
6 VOUT
between the negative and positive outputs. In addition, care
GND R1 R2 10kΩ 10kΩ 4
must be taken to ensure performance over temperature. Use low 038 temperature coefficient resistors if the circuit is used over tempera- 05428- ture; otherwise, differences exist between the two outputs. Figure 39. Programmable Voltage Source For a completely programmable solution, replace the two potentiometers in Figure 39 with one Analog Devices dual digital potentiometer, offered with either a serial peripheral interface (SPI) or an I2C interface. These interfaces set the position of the wiper on both potentiometers and allow the output voltage to be set. Table 10 lists compatible Analog Devices digital potentiometers. Rev. G | Page 16 of 19 Document Outline Features Applications Pin Configurations General Description Revision History Specifications ADR440 Electrical Characteristics ADR441 Electrical Characteristics ADR443 Electrical Characteristics ADR444 Electrical Characteristics ADR445 Electrical Characteristics Absolute Maximum Ratings Thermal Resistance ESD Caution Pin Configurations and Function Descriptions Typical Performance Characteristics Theory of Operation Power Dissipation Considerations Basic Voltage Reference Connections Noise Performance Turn On Time Applications Information Output Adjustment Bipolar Outputs Programmable Voltage Source Programmable Current Source High Voltage Floating Current Source Precision Output Regulator (Boosted Reference) Outline Dimensions Ordering Guide