- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄376559 > DAC729 DAC729 - DISCONTINUED PRODUCT. No longer recommended for new design. PDF資料下載
參數(shù)資料
| 型號： | DAC729 |
| 英文描述： | DAC729 - DISCONTINUED PRODUCT. No longer recommended for new design. |
| 中文描述： | DAC729 -已停產(chǎn)產(chǎn)品。不再推薦用于新設計。 |
| 文件頁數(shù)： | 8/12頁 |
| 文件大?。?/td> | 251K |
| 代理商： | DAC729 |
DAC729
8
much more critical as the accuracy of the system increases.
The DAC729 has been designed to minimize these applica-
tions problems to a large degree. The basics of “Kelvin
sensing” and “holy point” grounding will be the most impor-
tant considerations in optimizing the absolute accuracy of
the system. Figure 9 shows the proper connection of the
DAC with the holy-point ground and the Kelvin-sensed-
output connection at the load.
The DAC729 has three separate supply common (ground)
pins. Reference common (pin 33) carries the return current
from the internal reference and the output I/V converter
common. The current in pin 33 is stable and independent of
code or load. Digital common (pin 20) carries the variable
currents of the biasing circuits. Analog common (pin 30) is
the termination of the R-2R ladder and also carries the
“waste current” from the off side of the current switches.
These three ground pins must be star connected to system
ground for the DAC to bias properly and accurately. Good
ground connections are essential, because an IR drop of just
39
μ
V completely swamps out a 10V FSR 18-bit LSB.
When the application is such that the DAC must control
loads of greater than
±
5mA with rated accuracy, it is recom-
mended that an external op amp or op amp buffer combina-
tion be used to dissipate the variable power external to the
DAC729. This minimizes the temperature variations on the
precision D/A converter. Figure 10 illustrates a method of
connecting the external amplifier for
±
10V operation, while
using an external reference.
When driving loads to greater than
±
10V, care must be taken
that the internal resistors are never exposed to greater than
±
10V, and that the summing junction is clamped to insure
that the voltage never exceeds
±
5V. Clamping the summing
junction with diodes (parallel opposing connection) to ground
will give the best transient response and settling times.
TRUE 18-BIT PERFORMANCE
(Differential Linearity Adjustment)
To take full advantage of the DAC729’s accuracy, the four
MSBs have adjustment capabilities. A simplified schematic
(Figure 11) shows the internal structure of the DAC current
source and the adjustment input terminal. The suggested
network for adjusting the linearity is shown in Figure 12.
This circuit has nearly twice the range that is required for the
DAC729JH. The range is intentionally narrow so as to
minimize the effect of temperature drift or stability problems
in the potentiometers. The potentiometers are biased in an
identical fashion to the internal DAC current sources to
minimize power supply sensitivity and drift over tempera-
ture. Low leakage capacitors such as Mylar or Teflon film
are essential.
The linearity adjustment requires a digital voltmeter with 7
digits of resolution on the 10V range (1
μ
V resolution) and
excellent linearity. For the DAC, 1LSB of the 0V to 10V
scale (10 FSR) is 38
μ
V. To be 1/2LSB linear, the measure-
ment must resolve 19
μ
V. The meter must be properly
calibrated and linear to 1ppm of range.
FIGURE 5. Relationship of Offset and Gain Adjustments for
a Unipolar D/A Converter.
FIGURE 6. Relationship of Offset and Gain Adjustments for
a Bipolar D/A Converter.
REFERENCE ADJUSTMENT
The internal reference may be fine adjusted using pin 35 as
shown in Figure 7. Adjusting the reference has a similar
effect on the DAC as gain adjust, except the transfer charac-
teristic rotates around bipolar zero for a bipolar connection
as shown in Figure 8.
LAYOUT/APPLICATIONS SUGGESTIONS
Obviously, the management of IR drops, power supply
noise, thermal stability, and environmental noise becomes
FIGURE 4. Equivalent Resistances.
180k
180k
3.9M
10k
1LSB
Full Scale
Range
A
Digital Input
Gain Adjustment
Rotates the Line
Range of
Gain Adj.
Input =
00000
H
Offset Adj.
Translates
the Line
Input =
3FFFF
H
+ Full
Scale
MSB on,
All Others Off
Range of
Gain Adj.
1LSB
Bipolar V
Offset
A
Digital Input
Input =
00000
H
Offset Adj.
Translates
the Line
Input =
3FFFF
H
+ Full Scale
Full Scale
Range
Gain Adjustment
Rotates the Line
Range of
Offset Adj.
–Full Scale
相關PDF資料 |
PDF描述 |
|---|---|
| DAC7528 | CMOS Dual 8-Bit Buffered Multiplying Digital-To-Analog Converter(CMOS雙路8位緩沖乘法型D/A轉(zhuǎn)換器) |
| DAC7541AJP-BI | Low Cost 12-Bit CMOS Four-Quadrant Multiplying DIGITAL-TO-ANALOG CONVERTER |
| DAC7541AJPG4 | Low Cost 12-Bit CMOS Four-Quadrant Multiplying DIGITAL-TO-ANALOG CONVERTER |
| DAC7541AJUG4 | Low Cost 12-Bit CMOS Four-Quadrant Multiplying DIGITAL-TO-ANALOG CONVERTER |
| DAC7541AKP-BI | Low Cost 12-Bit CMOS Four-Quadrant Multiplying DIGITAL-TO-ANALOG CONVERTER |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| DAC729JH | 制造商:BB 制造商全稱:BB 功能描述:Ultra-High Resolution 18-BIT DIGITAL-TO-ANALOG CONVERTER |
| DAC729KH | 制造商:BB 制造商全稱:BB 功能描述:Ultra-High Resolution 18-BIT DIGITAL-TO-ANALOG CONVERTER |
| DAC729KH-BI | 制造商:BB 制造商全稱:BB 功能描述:Ultra-High Resolution 18-BIT DIGITAL-TO-ANALOG CONVERTER |
| DAC72BH | 制造商:BB 制造商全稱:BB 功能描述:Monlithic 16-bit digital-to-analog converters |
| DAC72BH-CSB-I | 制造商:BB 制造商全稱:BB 功能描述:Monlithic 16-bit digital-to-analog converters |
發(fā)布緊急采購，3分鐘左右您將得到回復。