AD780CRZ-REEL7 查看數據表（PDF） - Analog Devices
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AD780CRZ-REEL7 Datasheet PDF : 12 Pages
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AD780
Data Sheet
5V
2
+VIN
VOUT 6
1F
AD780
GND
4
2.5V/3.0V
SELECT
8
AD7884
VREF + F
VREF + S
Figure 21. Precision 3 V Reference for the AD7884 16-Bit, High Speed ADC
The AD780 is also ideal for use with higher resolution
converters, such as the AD7710/AD7711/AD7712 (see Figure
22. While these parts are specified with a 2.5 V internal
reference, the AD780 in 3 V mode can be used to improve the
absolute accuracy, temperature stability, and dynamic range. It
is shown in Figure 22 with the two optional noise reduction
capacitors.
5V
1F
100nF
2
+VIN
VOUT 6
AD780
3
2.5V/3.0V
GND O/P SELECT
4
8
AD7710
REF IN+
100F
REF IN–
Figure 22. Precision 2.5 V or 3.0 V Reference for the
AD7710 High Resolution, Σ-Δ ADC
4.5 V REFERENCE FROM 5 V SUPPLY
Some 5 V high resolution ADCs can accommodate reference
voltages up to 4.5 V. The AD780 can be used to provide a
precision 4.5 V reference voltage from a 5 V supply using the
circuit shown in Figure 23. This circuit provides a regulated
4.5 V output from a supply voltage as low as 4.7 V. The high
quality tantalum 10 μF capacitor, in parallel with the ceramic
AD780 0.1 μF capacitor and the 3.9 Ω resistor, ensures a low
output impedance around 50 MHz.
VSUPPLY
2
6
AD780
4
0.1F 1k
3+ 7
OP90 6
2– 4
0.1F
2N2907
2.5k
10F
3.9
VOUT
0.1F
5k
0.01%
4k
0.01%
Figure 23. 4.5 V Reference from a Single 5 V Supply
NEGATIVE (–2.5 V) REFERENCE
The AD780 can produce a negative output voltage in shunt
mode by connecting the input and output to ground, and
connecting the AD780’s GND pin to a negative supply via a bias
resistor, as shown in Figure 25.
2
7
+VIN
NC
1 NC
VOUT 6
AD780
1F
TRIM 5
3 TEMP
O/P SELECT
2.5V – NC
GND 3.0V – GND
4
8
R
=
VOUT – (V–)
IL + IS MIN
V–
–2.5 VOUT
NOTES
1. IL = LOAD CURRENT
2. IS MIN = MINIMUM SHUNT CURRENT
3. NC = NO CONNECT
Figure 24. Negative (−2.5 V Shunt Mode Reference)
A precise –2.5 V reference capable of supplying up to 100 mA to
a load can be implemented with the AD780 in series mode,
using the bootstrap circuit shown in Figure 25.
+5V
+VIN
2
1k
+5V
OUT AD780
6
8
4
–
OP07
+
2N3906
CONNECT IF
–3V OUTPUT
DESIRED
–2.5V (IL 100mA)
–5V
–5V
Rev. F | Page 10 of 12
1000pF
Figure 25. −2.5 V High Load Current Reference
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