AD7849AR-REEL Analog Devices Inc, AD7849AR-REEL Datasheet - Page 15

• Manufacturer Part Number: AD7849AR-REEL
• Description: IC DAC 16BIT SRL INP 20-SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD7849AR-REEL

• Rohs Status: RoHS non-compliant
• Settling Time: 7µs
• Number Of Bits: 16
• Data Interface: Serial
• Number Of Converters: 1
• Voltage Supply Source: Analog and Digital, Dual ±
• Power Dissipation (max): 100mW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)

Other Output Voltage Ranges
In some cases, users may require output voltage ranges other than
those already mentioned. One example is systems that need the
output voltage to be a whole number of millivolts (that is,1 mV or
2 mV). If the circuit shown in Figure 22 is used, then the LSB size is
125 μV. This makes it possible to program whole millivolt values at
the output. Table 9 shows the code table for the circuit shown in
Figure 22.
Table 9. Code Table for Figure 22
Binary Number in DAC Latch
MSB
1111 1111 1111 1111
1000 0000 0000 0000
0000 0000 0000 1000
0000 0000 0000 0100
0000 0000 0000 0010
0000 0000 0000 0001
Table 9 assumes a 16-bit resolution; 1 LSB = 8.192 V/2
Generating a ±5 V Output Range from a Single +5 V
Reference
Figure 23 shows how to generate a ±5 V output range when
using a single +5 V reference. V
is connected to V
pins. With all 0s loaded to the DAC, the noninverting terminal
of the output stage amplifier is at 0 V, and V
V
the output stage amplifier is 5 V and, therefore, V
1nF
*ADDITIONAL PINS OMITTED FOR CLARITY.
*
AD584
C1
ADDITIONAL PINS OMITTED FOR CLARITY.
SIGNAL
REF+
GND
4
8
. With all 1s loaded to the DAC, the noninverting terminal of
Figure 23. Generating a ±5 V Output Range from a Single +5 V
SIGNAL GND
8
1
AD586
2
4
R1 8.192V
6
5
Figure 22. 0 V to 8.192 V Output Range
REF+
R2
. The 5 V reference input is applied to these
R1
10kΩ
LSB
R
V
V
Analog Output (V
8.192 V (65,535/65,536) = 8.1919 V
8.192 V (32,768/65,536) = 4.096 V
8.192 V (8/65,536) = 0.001 V
8.192 V (4/65,536) = 0.0005 V
8.192 V (2/65,536) = 0.00025 V
8.192 V (1/65,536) = 0.000125 V
REF−
V
V
OFS
REF+
REF–
+15V
REF+
REF–
+15V
V
V
AD7849*
AD7849*
DD
DD
is connected to 0 V, and R
–15V
V
SS
+5V
DGND
AGND
V
+5V
V
DGND
AGND
V
R
CC
V
OUT
CC
OFS
OUT
OUT
is the inverse of
OUT
OUT
V
(–5V TO +5V)
16
OUT
V
(0V TO 8.192V)
OUT
)
is also 5 V.
= 125 μV.
Rev. C | Page 15 of 20
OFS
MICROPROCESSOR INTERFACING
Microprocessor interfacing to the AD7849 is via a serial bus
that uses standard protocol compatible with DSP processors
and microcontrollers. The communications channel requires a
3-wire interface consisting of a clock signal, a data signal, and a
synchronization signal. The AD7849 requires a 16-bit data-word
with data valid on the falling edge of SCLK. For all the interfaces,
the DAC update can be done automatically when all data is
clocked in, or it can be done under control of LDAC .
Figure 24 through Figure 27 show the AD7849 configured for
interfacing to a number of popular DSP processors and
microcontrollers.
AD7849-to-DSP56000 Interface
A serial interface between the
shown in Figure 24. The DSP56000 is configured for normal
mode asynchronous operation with a gated clock. It is also
setup for a 16-bit word with SCK and SC2 as outputs and the
FSL control bit set to 0. SCK is internally generated on the
DSP56000 and applied to the AD7849 SCLK input. Data from
the DSP56000 is valid on the falling edge of SCK. The SC2 output
provides the framing pulse for valid data. This line must be
inverted before being applied to the SYNC input of the
In this interface, an LDAC pulse generated from an external timer
is used to update the outputs of the DAC. This update can also
be produced using a bit programmable control line from the
DSP56000.
*ADDITIONAL PINS OMITTED FOR CLARITY.
DSP56000
Figure 24. AD7849-to-DSP56000 Interface
SCK
STD
SC2
TIMER
AD7849
and the DSP56000 is
SCLK
SYNC
LDAC
SDIN
AD7849*
AD7849
AD7849
.