Datasheet

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AVAILABLE

EVALUATION KIT AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.

Functional Diagrams continued at end of data sheet.

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General Description

The DS8500 is a single-chip modem with Highway

Addressable Remote Transducer (HART) capabilities

and satisfies the HART physical layer requirements.

The device integrates the modulation and demodulation

of the 1200Hz/2200Hz FSK signal, has very low power

consumption, and needs only a few external compo-

nents due to the integrated digital signal processing.

The input signal is sampled by an analog-to-digital con-

verter (ADC), followed by a digital filter/demodulator.

This architecture ensures reliable signal detection in

noisy environments. The output digital-to-analog con-

verter (DAC) generates a sine wave and provides a

clean signal with phase-continuous switching between

1200Hz and 2200Hz. Low power is achieved by dis-

abling the receive circuits during transmit and vice

versa. The DS8500 is ideal for low-power process con-

trol transmitters.

Applications

4–20mA Loop-Powered Transmitters for

Temperature, Pressure, Flow, and Level

Measurement

HART Multiplexers

HART Modem Interface Connectivity

Features

♦ Single-Chip, Half-Duplex, 1200bps FSK

Modulation and Demodulation

♦ Digital Signal Processing Provides Reliable Input

Signal Detection in Noisy Conditions

♦ Sinusoidal Output Signal with Lowest Harmonic

Distortion

♦ Few External Components Enable a Space-Saving

Solution

♦ Standard Component 3.6864MHz Crystal

♦ Complies to HART Physical Layer Requirements

♦ 2.7V to 3.6V Operating Voltage

♦ 285µA (max) Current Consumption

♦ Space-Saving, 5mm x 5mm x 0.8mm, 20-Pin TQFN

Package

HART Modem

THIN QFN

(5mm

5mm)

TOP VIEW

DVDD

RST

OCD

DVDD

FSK_IN

FSK_OUT

AVDD

AGND

DGND

15 14 12 11

D_OUT

D_IN

DGND

XTAL2

XTAL1

RTS

DGND REF

DGND

16 10 XCEN

DGND

DS8500

*EP

*EXPOSED PAD.

Pin Configuration

Ordering Information

PART TEMP RANGE PIN-PACKAGE

DS8500-JND+ -40° C to +85°C 20 TQFN-EP*

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

Rev 1; 2/09

DS8500

Summary of content (7 pages)

PAGE 1
EVALUATION KIT AVAILABLE LE AVAILAB DS8500 HART Modem General Description The DS8500 is a single-chip modem with Highway Addressable Remote Transducer (HART) capabilities and satisfies the HART physical layer requirements. The device integrates the modulation and demodulation of the 1200Hz/2200Hz FSK signal, has very low power consumption, and needs only a few external components due to the integrated digital signal processing.
PAGE 2
DS8500 HART Modem ABSOLUTE MAXIMUM RATINGS Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-65°C to +150°C Soldering Temperature...........................Refer to the IPC/JEDEC J-STD-020 Specification. Voltage Range on All Pins (including AVDD, DVDD) Relative to Ground .................................-0.5V to +3.6V Voltage Range on Any Pin Relative to Ground Except AVDD, DVDD .............-0.5V to (VDVDD + 0.
PAGE 3
DS8500 HART Modem Pin Description PIN NAME 1, 2 DVDD Digital Supply Voltage FUNCTION 3, 9, 16, 17, 18 DGND Digital Ground 4 RST Active-Low Reset, Digital Input/Output. This pin includes an internal pullup resistor and is driven low as an output when an internal reset condition occurs. 5 OCD Carrier Detect, Digital Output. A logic-high indicates a valid carrier detection on FSK_IN. OCD = 1 when FSK_IN amplitude is greater than 120mVP-P. OCD = 0 when FSK_IN amplitude is less than 80mVP-P.
PAGE 4
DS8500 HART Modem Introduction to HART HART is a backward-compatible enhancement to existing 4–20mA instrumentation networks that allows twoway, half-duplex, digital communication with a microcontroller-based field device. The digital signal is encoded on top of the existing instrumentation signal. Communication is accomplished through a series of commands and responses dependent on the specific protocol and network topology.
PAGE 5
DS8500 HART Modem 1200bps/833μs D_IN STOP START 8-BIT DATA PARITY FSK_OUT Figure 2. Actual DS8500 Modulator Waveform FSK_IN START 8-BIT DATA STOP PARITY D_OUT 1200bps/833μs ONE UART CHARACTER (START, 8 DATA BITS, PARITY, STOP) Figure 3.
PAGE 6
DS8500 HART Modem POWER SUPPLY 2.7V TO 3.6V 3.6864MHz RST DVDD DGND AGND AVDD XTAL1 3.6864MHz CRYSTAL CRYSTAL OSCILLATOR CLOCK GENERATOR VREF 1.23V POWER MONITOR REF XTAL2 C1 XCEN R1 OCD Rx DEMODULATOR D_OUT DIGITAL FILTER SAMPLE/HOLD ADC C2 FSK_IN R3 HART IN C3 R2 DS8500 C4 RTS Tx MODULATOR D_IN DAC HART AND 4–20mA OUT FSK_OUT MICROCONTROLLER 4–20mA DAC OUTPUT Figure 4.
PAGE 7
DS8500 HART Modem Revision History REVISION NUMBER REVISION DATE 0 10/08 1 2/09 DESCRIPTION PAGES CHANGED Initial release. — In the Electrical Characteristics table, changed the Frequency of FSK_OUT parameter units from kHz to Hz. 2 Added the EP description to the Pin Description table. 3 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.