欢迎访问ic37.com |
会员登录 免费注册
发布采购

5962-87702042X 参数 Datasheet PDF下载

5962-87702042X图片预览
型号: 5962-87702042X
PDF下载: 下载PDF文件 查看货源
内容描述: [PARALLEL, WORD INPUT LOADING, 12-BIT DAC, CQCC20, CERAMIC, LCC-20]
分类和应用: 输入元件转换器
文件页数/大小: 8 页 / 315 K
品牌: ADI [ ADI ]
 浏览型号5962-87702042X的Datasheet PDF文件第1页浏览型号5962-87702042X的Datasheet PDF文件第2页浏览型号5962-87702042X的Datasheet PDF文件第3页浏览型号5962-87702042X的Datasheet PDF文件第5页浏览型号5962-87702042X的Datasheet PDF文件第6页浏览型号5962-87702042X的Datasheet PDF文件第7页浏览型号5962-87702042X的Datasheet PDF文件第8页  
AD7545A  
CIRCUIT INFORMATION—D/A CONVERTER SECTION  
Figure 1 shows a simplified circuit of the D/A converter section  
of the AD7545A, and Figure 2 gives an approximate equivalent  
circuit. Note that the ladder termination resistor is connected to  
AGND. R is typically 15 k.  
input buffers operate in their linear region and draw current  
from the power supply. To minimize power supply currents it is  
recommended that the digital input voltages be as close to the  
supply rails (VDD and DGND) as is practically possible.  
The AD7545A may be operated with any supply voltage in the  
range 5 VDD 15 volts. With VDD = +15 V the input logic  
levels are CMOS compatible only, i.e., 1.5 V and 13.5 V.  
The binary weighted currents are switched between the OUT1  
bus line and AGND by N-channel switches, thus maintaining a  
constant current in each ladder leg independent of the switch  
state.  
BASIC APPLICATIONS  
Figures 4 and 5 show simple unipolar and bipolar circuits using  
the AD7545A. Resistor R1 is used to trim for full scale. The L,  
C, U grades have a guaranteed maximum gain error of 1 LSB  
at +25°C, and in many applications it should be possible to  
dispense with gain trim resistors altogether. Capacitor C1 pro-  
vides phase compensation and helps prevent overshoot and  
ringing when using high speed op amps. Note that all the cir-  
cuits of Figures 4, 5 and 6 have constant input impedance at the  
VREF terminal.  
The circuit of Figure 4 can either be used as a fixed reference  
D/A converter so that it provides an analog output voltage in the  
range 0 to –VIN (note the inversion introduced by the op amp)  
or VIN can be an ac signal in which case the circuit behaves as  
an attenuator (2-Quadrant Multiplier). VIN can be any voltage  
in the range –20 VIN +20 volts (provided the op amp can  
Figure 1. Simplified D/A Circuit of AD7545A  
The capacitance at the OUT1 bus line, COUT1, is code-  
dependent and varies from 70 pF (all switches to AGND) to  
150 pF (all switches to OUT1).  
handle such voltages) since VREF is permitted to exceed VDD  
.
One of the current switches is shown in Figure 2. The input  
resistance at VREF (Figure 1) is always equal to R. Since RIN at  
the VREF pin is constant, the reference terminal can be driven by  
a reference voltage or a reference current, ac or dc, of positive or  
negative polarity. (If a current source is used, a low temperature  
coefficient external RFB is recommended to define scale factor.)  
Table II shows the code relationship for the circuit of Figure 4.  
Figure 4. Unipolar Binary Operation  
Table I. Recommended Trim Resistor Values vs. Grades  
Trim Resistor  
K/B/T  
L/C/U  
Figure 2. N-Channel Current Steering Switch  
R1  
R2  
200 Ω  
68 Ω  
100 Ω  
33 Ω  
CIRCUIT INFORMATION—DIGITAL SECTION  
Figure 3 shows the digital structure for one bit.  
Table II. Unipolar Binary Code Table for Circuit of Figure 4  
Binary Number in  
The digital signals CONTROL and CONTROL are generated  
from CS and WR.  
DAC Register  
Analog Output  
4095  
4096  
1 1 1 1  
1 1 1 1  
1 1 1 1  
–VIN  
VIN  
VIN  
2048  
4096  
1 0 0 0  
0 0 0 0  
0 0 0 0  
= 1/2 VIN  
Figure 3. Digital Input Structure  
1
4096  
The input buffers are simple CMOS inverters designed such  
that when the AD7545A is operated with VDD = 5 V, the buffers  
convert TTL input levels (2.4 V and 0.8 V) into CMOS logic  
levels. When VIN is in the region of 2.0 volts to 3.5 volts, the  
0 0 0 0  
0 0 0 0  
0 0 0 0  
0 0 0 0  
0 0 0 1  
0 0 0 0  
0 Volts  
–4–  
REV. C