参数资料
| 型号： | AD7845JPZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC DAC 12BIT MULT LC2MOS 28-PLCC |
| 产品培训模块： | Data Converter Fundamentals DAC Architectures |
| 标准包装： | 39 |
| 设置时间： | 5µs |
| 位数： | 12 |
| 数据接口： | 并联 |
| 转换器数目： | 1 |
| 电压电源： | 双 ± |
| 功率耗散（最大）： | 150mW |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-LCC（J 形引线） |
| 供应商设备封装： | 28-PLCC（11.51x11.51） |
| 包装： | 管件 |
| 输出数目和类型： | 1 电压，单极；1 电压，双极 |
| 采样率（每秒）： | 200k |
AD7845
REV. B
–6–
PIN FUNCTION DESCRIPTION (DIP)
Pin
Mnemonic
Description
1VOUT
Voltage Output Terminal
2-11
DB11–DB2
Data Bit 11 (MSB) to Data Bit 2
12
DGND
Digital Ground. The metal lid on the ceramic package is connected to this pin
13-14
DB1–DB0
Data Bit 1 to Data Bit 0 (LSB)
15
WR
Write Input. Active low
16
CS
Chip Select Input. Active low
17
VREF
Reference Input Voltage which can be an ac or dc signal
18
AGND
Analog Ground. This is the reference point for external analog circuitry
19
VSS
Negative power supply for the output amplifier (nominal –12 V to +15 V)
20
VDD
Positive power supply (nominal +12 V to +15 V)
21
RA
Application resistor. RA = 4 RFB
22
RB
Application resistor. RB = 2 RFB
23
RC
Application resistor. RC = 2 RFB
24
RFB
Feedback resistor in the DAC. For normal operation this is connected to VOUT
CIRCUIT INFORMATION
Digital Section
Figure 11 is a simplified circuit diagram of the AD7845 input
control logic. When
CS and WR are both low, the DAC latch is
loaded with the data on the data inputs. All the digital inputs
are TTL, HCMOS and +5 V CMOS compatible, facilitating
easy microprocessor interfacing. All digital inputs incorporate
standard protection circuitry.
Figure 11. AD7845 Input Control Logic
D/A Section
Figure 12 shows a simplified circuit diagram for the AD7845
D/A section and output amplifier.
A segmented scheme is used whereby the 2 MSBs of the 12-bit
data word are decoded to drive the three switches A-C. The
remaining 10 bits drive the switches (S0–S9) in a standard R-2R
ladder configuration.
R
RR
2R
BA
S9
2R
C
VREF
S8
S0
SHOWN FOR ALL 1s ON DAC
2R
IOUT
AGND
Figure 12. Simplified Circuit Diagram for the AD7845 D/A
Section
Each of the switches A–C steers 1/4 of the total reference cur-
rent with the remaining 1/4 passing through the R-2R section.
An output amplifier and feedback resistor perform the current-
to-voltage conversion giving
VOUT = – D
× V
REF
where D is the fractional representation of the digital word. (D
can be set from 0 to 4095/4096.)
The amplifier can maintain
±10 V across a 2 k load. It is inter-
nally compensated and settles to 0.01% FSR (1/2 LSB) in less
than 5
s. The input offset voltage is laser trimmed at wafer
level. The amplifier slew rate is typically 11 V/
s, and the unity
gain small signal bandwidth is 600 kHz. There are three extra
on-chip resistors (RA, RB, RC) connected to the amplifier invert-
ing terminal. These are useful in a number of applications in-
cluding offset adjustment and gain ranging.
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| AD7845JPZ-REEL | 功能描述:IC DAC 12BIT MULT LC2MOS 28-PLCC RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数模转换器 系列:- 标准包装:47 系列:- 设置时间:2µs 位数:14 数据接口:并联 转换器数目:1 电压电源:单电源 功率耗散（最大）:55µW 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:28-SSOP（0.209"，5.30mm 宽） 供应商设备封装:28-SSOP 包装:管件 输出数目和类型:1 电流，单极；1 电流，双极 采样率（每秒）:* |
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| AD7845JRZ | 制造商:Analog Devices 功能描述:IC 12-BIT DAC |
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