AD1580ART-R2 查看數據表（PDF） - Analog Devices

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AD1580ART-R2

1.2 V Micropower, Precision Shunt Voltage Reference

Analog Devices 

TRANSIENT RESPONSE

Many A/D and D/A converters present transient current loads

to the reference. Poor reference response can degrade the

converter’s performance.

Figure 22 displays both the coarse and fine settling characteristics

of the device to load transients of ±50 μA.

20mV/DIV

1mV/DIV

IR = 100µA + 50µA STEP

(a)

(b)

IR = 100µA – 50µA STEP

20mV/DIV

1mV/DIV

1µs/DIV

Figure 22. Transient Settling

Figure 22a shows the settling characteristics of the device for an

increased reverse current of 50 μA. Figure 22b shows the

response when the reverse current is decreased by 50 μA.

The transients settle to 1 mV in about 3 μs.

Attempts to drive a large capacitive load (in excess of 1000 pF) may

result in ringing, as shown in the step response (see Figure 23).

This is due to the additional poles formed by the load

capacitance and the output impedance of the reference.

A recommended method of driving capacitive loads of this

magnitude is shown in Figure 20. A resistor isolates the cap-

acitive load from the output stage, while the capacitor provides

a single-pole low-pass filter and lowers the output noise.

2.0V

1.8V

VIN

CL = 0.01µF

10mV/DIV

50µs/DIV

Figure 23. Transient Response with Capacitive Load

AD1580

PRECISION MICROPOWER LOW DROPOUT

REFERENCE

The circuit in Figure 24 provides an ideal solution for making a

stable voltage reference with low standby power consumption,

low input/output dropout capability, and minimum noise

output. The amplifier both buffers and optionally scales up the

AD1580 output voltage, VR. Output voltages as high as 2.1 V

can supply 1 mA of load current. A one-pole filter connected

between the AD1580 and the OP193 input can be used to

achieve low output noise. The nominal quiescent power

consumption is 200 μW.

3V

34.8kΩ

205Ω

4.7µF

OP193

VOUT = +1.225V

OR

VOUT = +1.225 (1 + R2/R3)

AD1580

R3 R2

Figure 24. Micropower Buffered Reference

USING THE AD1580 WITH 3 V DATA CONVERTERS

The AD1580 low output drift (50 ppm/°C) and compact

subminiature SOT-23 package make it ideally suited for today’s

high performance converters in space critical applications.

One family of ADCs for which the AD1580 is well suited is the

AD7714-3 and AD7715-3. The AD7714/AD7715 are charge-

balancing (∑-Δ) A/D converters with on-chip digital filtering

intended for the measurement of wide dynamic range, low

frequency signals such as those representing chemical, physical, or

biological processes. Figure 25 shows the AD1580 connected to the

AD7714/AD7715 for 3 V operation.

3V

34.8kΩ

REFIN(+)

AD1580

REFIN(–)

AD7714/AD7715–3

RSW

5kΩ (TYP)

HIGH

IMPEDANCE

CREF

>1GΩ

(3pF TO 8pF)

SWITCHING

FREQUENCY DEPENDS

ON fCLKIN

Figure 25. Reference Circuit for the AD7714/AD7715-3

Rev. C | Page 9 of 12

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