AD421BR Analog Devices Inc, AD421BR Datasheet - Page 9

• Manufacturer Part Number: AD421BR
• Description: Digital/Analog Converter IC Interface Type:Serial
• Manufacturer: Analog Devices Inc

Specifications of AD421BR

• Number Of Bits: 16
• Package/case: 16-SOIC-WIDE
• Leaded Process Compatible: No
• Features: Loop-Powered 4-20 MA DAC
• Linearity Error (inl): 0.01LSB
• Mounting Type: Surface Mount
• Rohs Status: RoHS non-compliant
• Settling Time: 8µs
• Data Interface: Serial
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 1.95mW
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Number Of Channels: 1
• Resolution: 16b
• Interface Type: Serial (3-Wire)
• Single Supply Voltage (typ): 3.3/5V
• Dual Supply Voltage (typ): Not RequiredV
• Architecture: Delta-Sigma
• Power Supply Requirement: Single
• Output Type: Current
• Single Supply Voltage (min): 2.95V
• Single Supply Voltage (max): 5.05V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 16
• Package Type: SOIC W
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

The HC11 generates the requisite eight clock pulses with data
valid on the rising edges. After the MSBY is transmitted, the
least significant byte (LSBY) is loaded from memory and
transmitted in a similar fashion. To complete the transfer, the
LATCH pin is driven high when loading the complete 16-bit
word into the AD421.
AD421 TO MICROWIRE INTERFACE
The flexible serial interface of the AD421 is also compatible
with the National Semiconductor MICROWIRE interface. The
MICROWIRE interface is used in microcontrollers such as the
COP400 and COP800 series of processors. A generic interface
to use the MICROWIRE interface is shown in Figure 9. The
G1, SK, and SO pins of the MICROWIRE interface respec-
tively connect to the LATCH, CLOCK, and DATA IN pins of
the AD421.
Opto-Isolated Interface
The AD421 has a versatile serial 3-wire serial interface making
it ideal for minimizing the number of control lines required for
isolation of the digital system from the control loop. In intrinsi-
cally safe applications or due to noise, safety requirements, or
distance, it may be necessary to isolate the AD421 from the
controller. This can easily be achieved by using opto-isolators.
Figure 10 shows an opto-isolated interface to the AD421 where
CLOCK, DATAIN and LATCH are driven from opto-couplers.
Be aware of signal inversion across the opto-couplers. If opto-
couplers with relatively slow rise and fall times are used, Schmitt
triggers may be required on the digital inputs to prevent errone-
ous data being presented to the DAC.
REV. C
MICROWIRE
Figure 9. AD421 to MICROWIRE Interface
* ADDITIONAL PINS OMITTED FOR CLARITY
SK
SO
G1
COM TO EXTERNAL
CLOCK
LATCH
DATA
COM
4.7 F
CIRCUITRY
REF IN
COM
REF OUT2
DATA IN
CLOCK
LATCH
Figure 11. Basic Connection Diagram
AD421*
REF OUT1
AD421
C1
0.01 F
V
CC
C2
0.01 F
CIRCUITRY
TO EXTERNAL
COM
2.2 F
–9–
C3
0.0033 F
APPLICATIONS SECTION
Basic Operating Configuration
Figure 11 shows the basic connection diagram for the AD421
operating at 5 V. This circuit shows the minimum of external
components to operate the AD421. In the diagram, the AD421’s
regulator loop in conjunction with the DN25D pass transistor
provides the V
devices in the transmitter. The V
pled with a 2.2 µF capacitor to ensure regulator stability and to
absorb power glitches on the V
devices in the system. If the AD421 is operated with V
the transfer function shifts negative. To correct for this a 16 kΩ
resistor connected between COM and LOOPRTN will approxi-
mately compensate for the V
5 V to 3 V by adjusting the gain of the AD421.
LV
DATA IN
CLOCK
LATCH
V
CC
DN25D
Figure 10. Opto-Isolated Interface
DRIVE
COMP 0.01 F
BOOST
LOOP RTN
* ADDITIONAL PINS OMITTED FOR CLARITY
CC
voltage for the AD421 itself and for other
1k
1000pF
CC
V
V
V
CC
CC
CC
10k
10k
10k
supply sensitivity in moving from
CC
CC
line of the AD421 and other
pin should be well decou-
V
LOOP
CLOCK
LATCH
DATA IN
AD421*
COM
V
V
CC
CC
AD421
2.2 F
CC
= 3 V,
0.1 F