ADR445B(RevE) Просмотр технического описания (PDF) - Analog Devices

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Компоненты Описание

производитель

ADR445B
(Rev.:RevE)

Ultralow Noise, LDO XFET Voltage References with Current Sink and Source

Analog Devices 

ADR440/ADR441/ADR443/ADR444/ADR445

Table 9. Digital Potentiometer Parts

No. of

No. of

VDD1

Part No. Channels Positions ITF R (kΩ)

(V)

AD5251 2.00

64.00

I2C 1, 10, 50, 100 5.5

AD5207 2.00

256.00 SPI 10, 50, 100 5.5

AD5242 2.00

256.00

I2C 10, 100, 1M 5.5

AD5262 2.00

256.00 SPI 20, 50, 200 15

AD5282 2.00

256.00

I2C 20, 50, 100 15

AD5252 2.00

256.00

I2C 1, 10, 50, 100 5.5

AD5232 2.00

256.00 SPI 10, 50, 100 5.5

AD5235 2.00

1024.00 SPI 25, 250

5.5

ADN2850 2.00

1024.00 SPI 25, 250

5.5

1 Can also use a negative supply.

Adding a negative supply to the operational amplifier allows

the user to produce a negative programmable reference

by connecting the reference output to the inverting terminal

of the operational amplifier. Choose feedback resistors to

minimize errors over temperature.

PROGRAMMABLE CURRENT SOURCE

It is possible to build a programmable current source using a

setup similar to the programmable voltage source, as shown in

Figure 38. The constant voltage on the gate of the transistor sets

the current through the load. Varying the voltage on the gate

changes the current. This circuit does not require a dual digital

potentiometer.

VCC

0.1µF

2

VIN

ADR440/

ADR441/

ADR443/

ADR444/

ADR445

VOUT 6

RSENSE

GND

4

0.1µF

AD5259

ILOAD

Figure 38. Programmable Current Source

HIGH VOLTAGE FLOATING CURRENT SOURCE

Use the circuit in Figure 39 to generate a floating current source

with minimal self heating. This particular configuration can

operate on high supply voltages, determined by the breakdown

voltage of the N-channel JFET.

+VS

SST111

VISHAY

2

VIN

ADR440/

ADR441/

ADR443/

ADR444/

ADR445

VOUT 6

GND

4

OP90

2N3904

–VS

Figure 39. Floating Current Source

PRECISION OUTPUT REGULATOR

(BOOSTED REFERENCE)

VIN

CIN

0.1µF

2

VIN

ADR440/

ADR441/

ADR443/

ADR444/

ADR445

VOUT 6

GND

4

COUT

0.1µF

15V

–V

2N7002

RL

200Ω

VO

CL

1µF

Figure 40. Boosted Output Reference

Higher current drive capability can be obtained without

sacrificing accuracy by using the circuit in Figure 40. The

operational amplifier regulates the MOSFET turn-on, forcing

VO to equal the VREF. Current is then drawn from VIN, allowing

increased current drive capability. The circuit allows a 50 mA

load; if higher current drive is required, use a larger MOSFET.

For fast transient response, add a buffer at VO to aid with

capacitive loading.

Rev. E | Page 16 of 20

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