AD1582 Analog Devices, AD1582 Datasheet - Page 11

• Manufacturer Part Number: AD1582
• Description: 2.5V Micropower, Precisions Series Mode Voltage References
• Manufacturer: Analog Devices

AC PERFORMANCE
To successfully apply the AD1582/AD1583/AD1584/AD1585
family of references, it is important to understand the effects of
dynamic output impedance and power supply rejection. In
Figure 8a, a voltage divider is formed by the AD1582’s output
impedance and the external source impedance. Figure 8b shows
the effect of varying the load capacitor on the reference output.
Power supply rejection ratio (PSRR) should be determined when
characterizing the ac performance of a series voltage reference.
Figure 9a shows a test circuit used to measure PSRR, and
Figure 9b demonstrates the AD1582’s ability to attenuate line
voltage ripple.
2X V
100
0.1
10
1E+01
2V
1
OUT
200mV
10V
10k
10k
10k
10k
1E+02
X1
X1
1E+03
FREQUENCY – Hz
100 A
0.22 F
1585
10k
1582
1E+04
V
LOAD
1 F CAP
5V
1 F
2k
100mV
DC
DUT
1E+05
DUT
5V
V
OUT
0.22 F
1E+06
5 F
NOISE PERFORMANCE AND REDUCTION
The noise generated by the AD1582 is typically less then
70 µV p-p over the 0.1 Hz to 10 Hz frequency band. Figure 10
shows the 0.1 Hz to 10 Hz noise of a typical AD1582. The noise
measurement is made with a high gain bandpass filter. Noise in
a 10 Hz to 10 kHz region is approximately 50 µV rms. Figure 11
shows the broadband noise of a typical AD1582. If further noise
reduction is desired, a 1-pole low-pass filter may be added
between the output pin and ground. A time constant of 0.2 ms
will have a –3 dB point at roughly 800 Hz, and will reduce the
high frequency noise to about 16 µV rms. It should be noted,
however, that while additional filtering on the output may improve
the noise performance of the AD1582/AD1583/AD1584/AD1585
family, the added output impedance could degrade the ac per-
formance of the references.
AD1582/AD1583/AD1584/AD1585
100
1.E+00
90
80
70
60
50
40
30
20
10
0
100
100
0%
0%
90
10
1.E+01
90
10
10 V
100 V
1.E+02
FREQUENCY – Hz
1.E+03
1585
1582
1.E+04
1s
10ms
1.E+05
1.E+06