AD1582B AD [Analog Devices], AD1582B Datasheet - Page 11

• Manufacturer Part Number: AD1582B
• Description: 2.5 V to 5.0 V Micropower, Precision Series Mode Voltage References
• Manufacturer: AD [Analog Devices]

AC PERFORMANCE
To 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
by 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.
REV. D
2
100
Figure 8b. Output Impedance vs. Frequency
0.1
100
10
90
80
70
60
50
40
30
20
10
V
1
Figure 9b. Ripple Rejection vs. Frequency
Figure 8a. Output Impedance Test Circuit
2V
0
OUT
200mV
10
Figure 9a. Ripple Rejection Test Circuit
1
10V
10k
10k
10k
10k
10
100
100
1
1
FREQUENCY (Hz)
FREQUENCY (Hz)
1k
AD1585
0.22 F
100 A
1k
AD1585
10k
AD1582
10k
V
5V
LOAD
1 F CAP
AD1582
1 F
10k
2k
100mV
DUT
DC
100k
DUT
100k
V
5V
OUT
0.22 F
1M
5 F
1M
–11–
NOISE PERFORMANCE AND REDUCTION
The noise generated by the AD1582 is typically less than
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 band-pass 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 the ground. A time constant of 0.2 ms
has a –3 dB point at roughly 800 Hz, and reduces 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
performance of the references.
AD1582/AD1583/AD1584/AD1585
Figure 11. 10 Hz to 10 kHz Wideband Noise
Figure 10. 0.1 Hz to 10 Hz Voltage Noise
100
100
0%
0%
90
10
90
10
10 V
100 V
1s
10ms