AD5421CREZ-RL7 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD5421CREZ-RL7

16-Bit, Serial Input, Loop-Powered, 4 mA to 20 mA DAC

Analog Devices 

Data Sheet

AD5421

Pin No.

TSSOP LFCSP

13, 14 4, 11, 12

15, 16,

17

18

19

20

21

13, 14, 15

17

18

19

20

22, 23

24

21, 22

23

25

23

26

26

27

27

28

28

N/A1

EPAD

9, 16, 25

EPAD

1 N/A means not applicable.

Mnemonic

COM

REG_SEL2,

REG_SEL1,

REG_SEL0

REFIN

REFOUT2

REFOUT1

CIN

REXT1, REXT2

LOOP−

VLOOP

DRIVE

REGIN

REGOUT

NC

Exposed Pad

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 (REGOUT) voltage (see the Voltage Regulator

section).

Reference Voltage Input. VREFIN = 2.5 V for specified performance.

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 CIN to

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. As shown in Figure 1, the COM and LOOP− pins can be used to sense

the loop current across the internal 52 Ω resistor. Note that the voltage measured at LOOP− will

be negative with respect to COM.

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). If REGOUT is driving a

microconverter supply (see Figure 50), this pin should be decoupled to COM with a >1 µF

capacitor.

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. H | Page 13 of 36

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