AD5755-1 View Datasheet(PDF) - Analog Devices
Part Name
Description
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AD5755-1 Datasheet PDF : 52 Pages
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Data Sheet
AD5755-1
INDUSTRIAL HART CAPABLE ANALOG OUTPUT
APPLICATION—SHARED VOUT_X AND IOUT_X PIN
Many industrial control applications have requirements for
accurately controlled current output signals, and the AD5755-1
is ideal for such applications. Figure 89 shows the AD5755-1 in
a circuit design for a HART-enabled output module, specifically
for use in an industrial control application in which both the
voltage output and current output are available—one at a time—on
one pin, thus reducing the number of screw connections required.
There is no conflict with tying the two output pins together
because only the voltage output or the current output can be
enabled at any one time.
The design provides for a HART-enabled current output, with
the HART capability provided by the AD5700/AD5700-1 HART
modem, the industry’s lowest power and smallest footprint HART-
compliant IC modem. For additional space-savings, the AD5700-1
offers a 0.5% precision internal oscillator. The HART_OUT
signal from the AD5700 is attenuated and ac-coupled into the
CHARTx pin of the AD5755-1. Such a configuration results in
the AD5700 HART modem output modulating the 4 mA to 20
mA analog current without affecting the dc level of the current.
This circuit adheres to the HART physical layer specifications as
defined by the HART Communication Foundation.
For transient overvoltage protection, a 24 V transient voltage
suppressor (TVS) is placed on the IOUT/VOUT connection. For
added protection, clamping diodes are connected from the
IOUT_x/VOUT_x pin to the AVDD and AVSS power supply pins. A
5 kΩ current limiting resistor is also placed in series with the
+VSENSE_x input. This is to limit the current to an acceptable level
during a transient event. The recommended external band-pass
filter for the AD5700 HART modem includes a 150 kΩ resistor,
which limits current to a sufficiently low level to adhere to
intrinsic safety requirements. In this case, the input has higher
transient voltage protection and should, therefore, not require
additional protection circuitry, even in the most demanding of
industrial environments.
10µF
0.1µF
2.7V TO 5.5V
10µF
0.1µF 10kΩ
MCU
UART
INTERFACE
+15V +5V
DVDD AVDD AVCC
SW (×4)
VBOOST (×4)
RESET
ALERT
FAULT
CLEAR
SYNC
SCLK
SDIN
SDO
LDAC
DGND
VOUT B, C, D
AD5755-1
IOUT B, C, D
CHART B, C, D
IOUT A
D2
RP
D1
D3
5kΩ
+VSENSE_A
VOUTA
AVSS
REFOUT REFIN CHART A
0.1µF
0.1µF
TXD
RXD
VCC
HART_OUT
22nF
C1
RTS
CD
AD5700/AD5700-1
AVSS GND
47nF
C2
GND
REF
ADC_IP
1.2MΩ
1.2MΩ
1µF
300pF
150kΩ
150pF
Figure 89. AD5755-1 in HART Configuration
4mA TO 20mA
CURRENT LOOP
RL
500Ω
Rev. E | Page 49 of 52
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