Data Sheet

AD5700/AD5700-1

Rev. A | Page 17 of 20

APPLICATIONS INFORMATION

SUPPLY DECOUPLING

10 μF in parallel with 0.1 μF capacitors to ground. For many

applications, 1 μF in parallel with 0.1 μF ceramic capacitors to

ground should be sufficient. The REG_CAP voltage of 1.8 V is

used to supply the AD5700/AD5700-1 internal circuitry and is

LDO. Decouple this REG_CAP supply with a 1 μF ceramic

capacitor to ground. It is also required to decouple the REF pin

with a 1 μF ceramic capacitor to ground. Place decoupling

capacitors as close to the relevant pins as possible.

For loop-powered applications, it is recommended to connect a

any noise, which may, depending on the system configuration, be

introduced onto the loop as a result of current draw variations

from the AD5700/AD5700-1. For typical applications, 470 Ω of

resistance has proven most effective. However, depending on the

application conditions, alternative values may also be acceptable

(see R1 in Figure 27).

TYPICAL CONNECTION DIAGRAMS

Figure 26 shows a typical connection diagram for the AD5700/

AD5700-1 using the external and internal options. See the

Connecting to HART_IN or ADC_IP section for more details.

The AD5700/AD5700-1 are designed to interface easily with

Analog Devices, Inc., innovative portfolio of industrial

converters like the AD5421 loop-powered current-output DAC,

the AD5410/AD5420 and AD5412/AD5422 family of line-

powered current-output DACs, and the AD5755-1, a quad DAC

with innovative dynamic power control technology. The

combination of Analog Devices industrial converters and the

AD5700/AD5700-1 greatly simplifies system design, enhancing

reliability while reducing overall PCB size.

Figure 27 shows how the AD5700/AD5700-1 HART modem

can be interfaced with the AD5421 (4 mA to 20 mA loop-powered

DAC) and a microcontroller to construct a loop powered transmit-

ter circuit. The HART signal from HART_OUT is introduced to

The HART enabled smart transmitter reference demo circuit

(the block diagram shown in Figure 28) was developed by

Analog Devices and uses the AD5421, a 16-bit, loop-powered,

4 mA to 20 mA DAC, and the AD5700 modem. This circuit has

been compliance tested, verified, and registered as an approved

HART solution by the HART Communication Foundation.

Contact your sales representative for further information about

this demo circuit.

In conclusion, the AD5700/AD5700-1 enable quick and easy

deployment of a robust HART-compliant system.

Figure 26. AD5700/AD5700-1 Typical Connection Diagram for External and Internal Filter Options

10µF

0.1µF

0.1µF

1µF

10µF

150pF

1µF

2V TO 5.5V

1.71V TO 5.5V

AGND

AD5700/AD5700-1

150kΩ

1.2MΩ

1.2MΩ

300pF

REF

HART_OUT

DGND

CONFIGURATION

PINS

HART_IN

ADC_IP

CD

RXD

TXD

RTS

10µF

0.1µF

1µF

2V TO 5.5V

AGND

AD5700/AD5700-1

REF

HART_OUT

DGND

CONFIGURATION

PINS

HART_IN

ADC_IP

CD

RXD

TXD

RTS

680pF

2.2nF

1µF

+

0.1µF

10µF

1.71V TO 5.5V

+