ADR540(RevA) Просмотр технического описания (PDF) - Analog Devices

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ADR540
(Rev.:RevA)

High Precision Shunt Mode Voltage References

Analog Devices 

ADR520/ADR525/ADR530/ADR540/ADR550

Stacking ADR5xx for User-Definable Outputs

Multiple ADR5xx parts can be stacked together to allow the

user to obtain a desired higher voltage. Figure 22a shows three

ADR550s configured to give 15 V. The bias resistor, RBIAS, is

chosen using Equation 3, noting that the same bias current will

flow through all the shunt references in series. Figure 22b shows

three ADR550s stacked together to give –15 V. RBIAS is calculated

in the same manner as before. Parts of different voltages can

also be added together, i.e., an ADR525 and an ADR550 can be

added together to give an output of +7.5 V or –7.5 V, as desired.

Note, however, that the initial accuracy error is now the sum of

the errors of all the stacked parts, as are the tempco and output

voltage change versus input current.

+VDD

R

+15V

ADR550

ADR550

ADR550

GND

(a)

ADR550

GND

ADR550

ADR550

R

–15V

–VDD

(b)

Figure 22. 15 V Output with Stacked ADR550s

Adjustable Precision Voltage Source

The ADR5xx, combined with a precision low input bias op amp,

such as the AD8610, can be used to output a precise adjustable

voltage. Figure 23 illustrates the implementation of this

application using the ADR5xx. The output of the op amp, VOUT,

is determined by the gain of the circuit, which is completely

dependant on the resistors, R1 and R2.

VOUT = (1 + R2/R1)VREF

An additional capacitor, C1, in parallel with R2, can be added to

filter out high frequency noise. The value of C1 is dependent on

the value of R2.

VCC

RBIAS

VREF

ADR5xx

AD8610

R2

VOUT = VREF (1+R2/R1)

R1

GND

C1

(OPTIONAL)

Figure 23. Adjustable Voltage Source

Rev. A | Page 12 of 16

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