ds8500 Maxim Integrated Products, Inc., ds8500 Datasheet - Page 3

• Manufacturer Part Number: ds8500
• Description: Hart Modem
• Manufacturer: Maxim Integrated Products, Inc.

3, 9, 16,
17, 18
PIN
1, 2
10
11
12
13
14
15
19
20
—
4
5
6
7
8
FSK_OUT
FSK_IN
D_OUT
XTAL1
NAME
DGND
XTAL2
AGND
DVDD
AVDD
XCEN
OCD
D_IN
RTS
REF
EP
D_OUT
XTAL1
XTAL2
XCEN
_______________________________________________________________________________________
D_IN
OCD
RTS
Digital Supply Voltage
Digital Ground
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.
Carrier Detect, Digital Output. A logic-high indicates a valid carrier detection on FSK_IN.
OCD = 1 when FSK_IN amplitude is greater than 120mV
OCD = 0 when FSK_IN amplitude is less than 80mV
Request to Send, Digital Input. When set high, the device is put into the demodulator mode. A logic-low
puts the device into modulator mode.
Crystal Pin or Input for External Clock at 3.6864MHz
Crystal Pin or Output of the Crystal Amplifier
External Clock Enable, Digital Input. When set high, this pin allows the user to drive an external clock
signal through XTAL1. When in this mode, XTAL2 should be left unconnected. An external crystal must
be connected between XTAL1 and XTAL2 when set low.
Analog Supply Voltage
FSK Out, Analog Output. Output of the modulator. Provides a phase-continuous, FSK-modulated output
signal (1200Hz and 2200Hz output frequencies) to the 4–20mA current loop interface circuit.
Reference, Analog Output. The internal voltage reference is provided as output. This pin must be
connected to a 0.1μF capacitor.
FSK In, Analog Input. Input for the FSK-modulated HART receive signal from the 4–20mA current loop
interface circuit.
Analog Ground
Digital Data Out, Digital Output. Output from the demodulator.
Digital Data In, Digital Input. Input to the modulator.
Exposed Pad. Should be connected to ground (DGND, AGND).
DEMODULATOR
OSCILLATOR
MODULATOR
CRYSTAL
Rx
Tx
GENERATOR
CLOCK
RST
DS8500
DIGITAL
FILTER
DVDD
MONITOR
POWER
FUNCTION
DGND
P-P
AGND
.
P-P
SAMPLE/HOLD
1.23V
V
.
REF
ADC
DAC
AVDD
HART Modem
Pin Description
Block Diagram
REF
FSK_IN
FSK_OUT
3