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ADDAC85 Просмотр технического описания (PDF) - Analog Devices

Номер в каталогеADDAC85 ADI
Analog Devices ADI
Компоненты ОписаниеComplete Low Cost 12-Bit D/A Converters
ADDAC85 Datasheet PDF : 16 Pages
First Prev 11 12 13 14 15 16
ADDAC80/ADDAC85/ADDAC87
DRIVING A RESISTOR LOAD BIPOLAR
The equivalent output circuit for a bipolar output voltage range
is shown in Figure 13, RL = RLI + RLS. VOUT is determined by:
VOUT
=
±1
mA

RL
RL
× 3.22 kΩ 
+ 3.22 kΩ
(2)
where RL max = 11.18 kand VOUT max = ± 2.5 V
To achieve specified drift, connect the internal scaling resistors
(RLI) as shown in Table IV for the COB or CTC codes and add
an external metal film resistor (RLS) in series to obtain a full scale
output range of ± 1 V. In this configuration, with RLS equal to
zero, the full scale range will be ± 0.874 V.
؎1mA 3.22k
RLI
1.2k
CURRENT CONTROLLED
BY DIGITAL INPUT
15
+
20 RLS
VOUT
21 COMMON
Figure 13. ADDAC80-CBI-I Connected for Bipolar
Output Voltage with Resistive Load
DRIVING AN EXTERNAL OP AMP
The current model ADDAC80 will drive the summing junction
of an op amp used as a current to voltage converter to produce
an output voltage. As seen in Figure 14,
VOUT = IOUT × RF
(3)
where IOUT is the ADDAC80 output current and RF is the feed-
back resistor. Using the internal feedback resistors of the current
model ADDAC80 provides output voltage ranges the same as
the voltage model ADDAC80. To obtain the desired output
voltage range when connecting an external op amp, refer to
Table V and Figure 14.
19
20V RANGE
5kCBI
18
5k
10V RANGE
15
A
I
0 TO 2mA
6.6k
21
AD509KH* VOUT
*FOR FAST SETTLING TIME
Figure 14. External Op Amp Using Internal
Feedback Resistors
OUTPUT LARGER THAN 20 V RANGE
For output voltage ranges larger than ± 10 V, a high voltage op
amp may be employed with an external feedback resistor. Use
IOUT values of ± l mA for bipolar voltage ranges and –2 mA for
unipolar voltage ranges (see Figure 15). Use protection diodes
when a high voltage op amp is used.
The feedback resistor, RF, should have a temperature coefficient
as low as possible. Using an external feedback resistor, overall
drift of the circuit increases due to the lack of temperature track-
ing between RF and the internal scaling resistor network. This will
typically add 50 ppm/°C + RF drift to total drift.
I
0 TO 2mA
V VREF
6.3V
+
17
6.3k
16
15
6.6k
21
24
RF
171K*
VOUT
*FOR OUTPUT VOLTAGE SWINGS UP TO 140V p-p
Figure 15. External Op Amp Using External
Feedback Resistors
Table IV. Current Model/Resistive Load Connections
Digital
Input Codes
CSB
COB or CTC
CCD
Output
Range
Internal
Resistance
RLI (k)
0 to –2 V 0.968
±1 V
1.2
0 to ± 2 V 3
1%
Metal Film
External
RLI Connections
Reference
Resistance Connect Connect Connect Connect
RLS
Pin 15 to Pin 18 to Pin 20 to Pin 16 to
210
20
19 and RLS 15
24
249
18
19
RLS
24
N/A
NC
21
NC
24
Bipolar Offset
Connect
Pin 17 to
Com (21)
15
NC
RLS
Between
Pin 18 and
Com (21)
Between
Pin 20 and
Com (21)
N/A
–12–
REV. B
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PRODUCT DESCRIPTION
The ADDAC80 Series is a family of low cost 12-bit digital-to-analog converters with both a high stability voltage reference and output amplifier combined on a single monolithic chip. The ADDAC80 Series is recommended for all low cost 12-bit D/A converter applications where reliability and cost are of paramount importance.
Advanced circuit design and precision processing techniques result in significant performance advantages over conventional DAC80 devices. Innovative circuit design reduces the total power consumption to 300 mW, which not only improves reliability, but also improves long term stability.

FEATURES
   Single Chip Construction
   On-Board Output Amplifier
   Low Power Dissipation: 300 mW
   Monotonicity Guaranteed over Temperature
   Guaranteed for Operation with 12 V Supplies
   Improved Replacement for Standard DAC80, DAC800
      Hl-5680
   High Stability, High Current Output
      Buried Zener Reference
   Laser Trimmed to High Accuracy
      1/2 LSB Max Nonlinearity
   Low Cost Plastic Packaging

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