AD5421 Analog Devices, AD5421 Datasheet - Page 12

• Manufacturer Part Number: AD5421
• Description: 16-Bit, Serial Input, Loop-Powered, 4mA to 20mA DAC
• Manufacturer: Analog Devices

Specifications of AD5421

• Resolution (bits): 16bit
• Dac Settling Time: 50µs
• Max Pos Supply (v): +52V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: SPI

AD5421
TSSOP
13, 14
15, 16,
17
18
19
20
21
22, 23
24
25
26
27
28
N/A
EPAD
1
N/A means not applicable.
1
Pin No.
LFCSP
4, 11, 12
13, 14, 15
17
18
19
20
21, 22
23
23
26
27
28
9, 16, 25
EPAD
Mnemonic
COM
REG_SEL2,
REG_SEL1,
REG_SEL0
REFIN
REFOUT2
REFOUT1
C
R
LOOP−
V
DRIVE
REG
REG
NC
Exposed Pad
EXT1
LOOP
IN
IN
OUT
, R
EXT2
Description
Ground Reference Pin for the AD5421. It is recommended that a 4.7 V Zener diode be placed
between the LOOP− and COM pins. See the Applications Information section for more
information.
These three pins together select the regulator output (REG
section).
Reference Voltage Input. V
Internal Reference Voltage Output (1.22 V). It is recommended to connect a 100 nF capacitor
from this pin to COM.
Internal Reference Voltage Output (2.5 V). It is recommended to connect a 100 nF capacitor from
this pin to COM.
External Capacitor Connection and HART FSK Input. An external capacitor connected from C
COM implements an output slew rate control function (see the Loop Current Slew Rate Control
section). HART FSK signaling can also be coupled through a capacitor to this pin (see the HART
Communications section).
Connection for External Current Setting Resistor. A precision 24 kΩ resistor can be connected
between these pins for improved performance.
Loop Current Return Pin.
Voltage Input Pin. Voltage input range is 0 V to 2.5 V. The voltage applied to this pin is digitized to
eight bits, which are available in the fault register. This pin can be used for general-purpose
voltage monitoring, but it is intended for monitoring of the loop supply voltage. Connecting the
loop voltage to this pin via a 20:1 resistor divider allows the AD5421 to monitor and feedback the
loop voltage. The AD5421 also generates an alert if the loop voltage is close to the minimum
operating value (see the Loop Voltage Fault section).
Gate Connection for External Depletion Mode MOSFET. For more information, see the
Connection to Loop Power Supply section.
Voltage Regulator Input. The loop voltage can be connected directly to this pin. Or, to reduce on-
chip power dissipation, an external pass transistor can be connected at this pin to stand off the
loop voltage. For more information, see the Connection to Loop Power Supply section.
Voltage Regulator Output. Pin selectable values are from 1.8 V to 12 V via the REG_SEL0,
REG_SEL1, and REG_SEL2 pins (see the Voltage Regulator section).
No Connect. Do not connect to this pin.
The exposed paddle should be connected to the same potential as the COM pin and to a copper
plane for optimum thermal performance.
Rev. C | Page 12 of 36
REFIN
= 2.5 V for specified performance.
OUT
) voltage (see the Voltage Regulator
Data Sheet
IN
to