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參數(shù)資料
| 型號(hào)： | AD8303ARZ-REEL |
| 廠商： | Analog Devices Inc |
| 文件頁(yè)數(shù)： | 4/16頁(yè) |
| 文件大?。?/td> | 0K |
| 描述： | IC DAC 12BIT SERIAL 14SOIC |
| 產(chǎn)品培訓(xùn)模塊： | Data Converter Fundamentals DAC Architectures |
| 產(chǎn)品變化通告： | AD8303 Obsolescence 15/Apr/2011 |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 設(shè)置時(shí)間： | 14µs |
| 位數(shù)： | 12 |
| 數(shù)據(jù)接口： | 串行，SPI? |
| 轉(zhuǎn)換器數(shù)目： | 2 |
| 電壓電源： | 單電源 |
| 功率耗散（最大）： | 9.6mW |
| 工作溫度： | -40°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 14-SOIC（0.154"，3.90mm 寬） |
| 供應(yīng)商設(shè)備封裝： | 14-SOICN |
| 包裝： | 標(biāo)準(zhǔn)包裝 |
| 輸出數(shù)目和類型： | * |
| 采樣率（每秒）： | * |
| 其它名稱： | AD8303ARZ-REELDKR |
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AD8303
REV. 0
–12–
BIPOLAR OUTPUT OPERATION
Although the AD8303 has been designed for single-supply
operation, the output can also be configured for bipolar
operation. A typical circuit is shown in Figure 31. This circuit
uses the AD8303’s internal voltage reference to generate a
bipolar offset. Since VREF must source current in this
application, one half of an OP293 dual op amp is used as a
buffer. The other op amp then amplifies the DAC output
voltage to produce a bipolar output swing. The output voltage is
coded in offset binary and is given by:
VO = 0.5 mV × Digital Code ×
R4
R3
+ R4
× 1+
R2
R1
–1.0 V
×
R2
R1
where 0.5 mV represents the pretrimmed value for one LSB of
the AD8303, Digital Code is the digital code sent to the DAC,
and 1.0 V is the AD8303 reference voltage.
SDI
CLK
CS
LDA
LDB
RS
MSB
SHDN
AD8303
13
2
14
4
1
VOUTA
VOUTB
+3V
AGND DGND
VDD
OPTIONAL
FULL-SCALE
TRIM
3
+3V
–3V
1/2
OP293
VOUT = ±2.048V
OPTIONAL
ZERO TRIM
R4
19.08k
R1
10k
R2
20.48k
R3
10k
VREF
7
6
5
8
10
9
11
12
1/2
OP293
Figure 31. Bipolar Output Operation
For a
±2.048 V full scale using the circuit values shown, the
transfer function becomes:
VO = 1 mV × Digital Code – 2.048 V
Note that the full-scale span has increased from 2.048 V to
4.096 V (
±2.048 V). Therefore, although each AD8303 LSB
represents 0.5 mV, each output LSB of the bipolar circuit has
been scaled to 1 mV. The code table for this circuit is shown in
Table IV.
Table IV. Bipolar Code Table
Hexadecimal Number Decimal Number
Analog Output
in DAC Register
Voltage (V)
FFF
4095
2.047
801
2049
0.001
800
2048
0
7FF
2047
–0.001
000
0
–2.048
As with the false-ground generator circuit, resistor matching is
important to maintain accuracy. Resistor pairs R1-R2 and
R3-R4 should be selected to match within 0.01%. In addition,
these resistors must be of the same type (preferably metal film)
to insure temperature coefficient matching. Mismatching
between R1 and R2 causes offset and gain errors while an R3 to
R4 mismatch yields gain errors.
GENERATING A NEGATIVE SUPPLY VOLTAGE
Some applications may require a bipolar output configuration,
as shown in Figure 31, but only have a single power supply rail
available. This is very common in data acquisition systems using
microprocessor-based systems. In these systems, +12 V, +15 V,
and/or +5 V only are available. Single supply rails are, of course,
common in battery-powered systems. Shown in Figure 32 is a
method of generating a negative supply using a single IC and
technique to invert supply voltages as low as 1.5 V. A shutdown
feature on the ADM8660 complements the shutdown of the
AD8303. Note, however, that the ADM8660 requires about
500
s to turn on after exiting the shutdown state.
+3V
10F
ADM8660
V+
GND
SHUTDOWN
LV
OSC
FC
CAP+
CAP–
2
4
61
3
7
5
8
10F
1/6
74HC04
SHDN FROM AD8303
–3V
Figure 32. Generating a Negative Supply Voltage
MICROCOMPUTER INTERFACES
The AD8303 serial data input provides an easy interface to a
variety of single-chip microcomputers (
Cs). Many Cs have a
built-in serial data capability which can be used for communi-
cating with the DAC. In cases where no serial port is provided,
or it is being used for some other purpose (such as an RS-232
communications interface), the AD8303 can easily be addressed
in software.
Twelve data bits are required to load a value into the AD8303.
If more than 12 bits are transmitted before the Chip Select
input goes high, the extra (i.e., the most significant) bits are
ignored. This feature is valuable because most
Cs only transmit
data in 8-bit increments. Thus, the
C sends 16 bits to the DAC
instead of 12 bits. The AD8303 will only respond to the last 12
bits clocked into the SDI input, however, so the serial data
interface is not affected.
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