MICROCYBER HT1200M User Manual HART Modem ASIC
Contents
1. Analog Supply Voltage This is the power for the analog modem circuitry VSS Ground This is the analog and digital ground MICROCYBER VSSA Analog Ground Analog Ground Function Description The HT1200M is a functional equivalent of the SYM20CI5 HART Modem It contains a transmit data modulator and signal shaper carrier detect circuitry analog receiver and demodulator circuitry and an oscillator as shown in Figure 4 The internal HART modulates the transmit signal and demodulates the receive signal The transmit signal shaper enables the HT1200M to transmit a HART compliant signal The carrier is detected by comparing the receiver filter output with the difference between two external voltage references The analog receive circuitry band pass filters the received signal for input to the modem and the carrier detect circuitry The oscillator provides the modem with a stable time base using either a simple external resonator or an external clock source ITXD Modulator and Transmit Wave Shaping Control Logic INRTS pix ORXD OTXA IRXAC ORXAF IAREF ICREF OCBIA OCD Carrier Detect Receive Filter And IXTL Demodulator OXTL Figure 4 HT1200M Block Diagram HT1200M LOGIC The modem consists of a modulator and demodulator The modem uses shift frequencies of nominally 1200 Hz for a 1 and 2200 Hz for a 0 The bit rate 151200 bits second Modulator The modulator accepts digital data in NRZ form at the2. Input Leakage Current Output Leakage Current Power Supply Current RBIAS 500kQ IAREF 1 235V IAREF Analog Reference ICDREF Carrier Detect Reference IAREF 08V OCBIAS Comparator Bias Current RBIAS 500kQ IAREF 1 235V INRESET INRTS 2 7 3 3V V V V Input Voltage 2 7 5 5V V V V C IL IL IH IH OL OH IN Ipp MICROCYBER AC CHARACTERISTICS VDD 2 7V to 5 5V VSS OV TA 40C to 85C Typical Units Name IRXA Receive Analog Input Leakage Current 150 nA Frequency Mark Logic 1 1190 1200 1210 Hz Frequency Space Logic 0 2180 2200 2220 Hz ORXAF Output of the High pass Filter Pin Description Slew Rate 0 025 V us Gain Bandwidth GBW 150 kHz Voltage Range 0 15 VDD 0 15 V us IRXAC Carrier Detect amp Receive Filter Input Leakage Current OTXA Modulator Output Frequency Mark Logic1 Hz Frequency Space Logic0 Hz Amplitude IAREF1 235V mV p p Slop mV us Loading IAREF 1 235V 30 KQ ORXD Receive Digital Output ns Rise Fall Time 20 OCD Carrier Detect Output ns Rise Fall Time 20 MODEM CHARACTERISTIC VDD 2 7V to 5 5V VSS OV TA 40 C to 85 C Parameter in Typical Demodulater Jitter Conditions 12 of 1 bit I Input frequencies at 1200Hz 10Hz 2200Hz 20Hz 2 Clock frequency of 460 8kHz 0 1 3 Input HLXA asymmetry 0 MICROCYBER CERAMIC RESONATOR EXTERNAL CLOCK
3. P R China 110016 WWW sia cn MICROCYBER Revision History Version Release Date Detail of Changes 1 1 07 12 22 First release MICROCYBER List of Contents General M us 5 dcin pe 5 Typical Application nsn 6 6 PinJjOeSCHDLUOD a see 8 Function Descfiption cce u ede 10 Package Information eene enne enne nennen 15 Chia RI M 17 List of Tables Table 1 HT1200M Pin Descriptions nennen entren enne 7 List of Figures Figure 1 HT1200M Hart Modem Typical Application 6 Figure2 a 28Pin PLCC Pinout Package b 32Pin LQFP Pinout Package 6 Fipure3 MM roni bi 8 Figure 4 HT1200M Block nennen nennen 10 Figure5 Demodulator Signal Timing nennen enne 11 Figure6 Waveform
4. SPECIFICATIONS VDD 2 7V to 5 5V VSS OV TA 40 C to 85 C 0 Resonator Tolerance Frequency 460 8 External Clock Frequency 456 2 460 8 Duty Cycle 4 50 Amplitude Von Vor MICROCYBER
5. The carrier detect block drives the carrier detect output pin OCD high if INRTS is high and four consecutive pulses out of the comparator have arrived OCD stays high as long as INRTS is high and the next comparator pulse is received in less than 2 5 ms Once OCD goes inactive it takes four consecutive pulses out of the comparator to assert OCD again Four consecutive pulses amount to 3 33 ms when the received signal is 1200 Hz and to 1 82 ms when the received signal is 2200 Hz ANALOG RECEIVER CIRCUITRY Voltage References The HT1200M requires two voltage references IAREF and ICDREF IAREF sets the do operating point of the internal operational amplifiers and comparators A 1 235 Vpc reference Analog Devices AD589 is suitable as IAREF The level at which OCD carrier detect becomes active is determined by the do voltage difference ICDREF IAREF Selecting a voltage difference of 0 08 Vpc will set the carrier detect to a nominal 100 mVp p Bias Current Resistor The HT1200M requires a bias current resistor to be connected between OCBIAS and Vss The bias current controls the operating parameters of the internal operational amplifiers and comparators The value of the bias current resistor is determined by the reference voltage IAREF and the following formula IAREF Reus 2 5uA MICROCYBER The recommended bias current resistor is 500 ohm when IAREF is equal to 1 235 Vpc In Figure 8 all external capacitor values have a tolerance
6. of 15 percent and the resistors have a tolerance of 1 percent except the 3 ohm which has a tolerance of 15 percent External to the HT1200M the filter exhibits a three pole high pass filter at 624 Hz and a one pole low pass filter at 2500 Hz Internally the HT1200M has a high pass pole at 35 Hz and a low pass pole at 90 kHz The low pass pole can vary as much as 130 percent The input impedance of the entire filter is greater than 150 ohm at frequencies below 50 kHz R6 R7 732k 216k 220pf C3 C2 Hartin 470pf 1 nf Co V 1 235V Figure 8 Receive Schematic OSCILLATOR The HT1200M requires a 460 8 kHz clock signal on OXTL This can be provided by an external clock or external components may be connected to the HT1200M internal oscillator Internal Oscillator Option The oscillator cell will function with either a 460 8 kHz crystal or ceramic resonator A parallel resonant ceramic resonator can be connected between OXTL and IXTL Figure 9 illustrates the crystal option for clock generation using a 460 8 kHz 1 percent tolerance parallel resonant crystal and two tuning capacitors The actual values of the capacitors may depend on the recommendations of the manufacturer of the resonator Typically capacitors in the range of 100 pF to 470pF are used MICROCYBER Page 13 of 19 External Clock Option It may be desirable to use an external 460 8 kHz clock as shown in Figure 10 rather than the internal oscillator because of th
7. 1200 sese 11 Figure7 Waveform 2200 Hz a 12 Figure 8 RECEIVE Sche matt ene zu assia eden cuia ds 13 Figure 9 a Crystal Oscillator b Oscillator eeeeeenne 14 Figure 10 LOLTP32 15 Figure ER JUS 0 7 ERR 16 MICROCYBER General Description The HT1200M is a single chip CMOS modem for use in Highway Addressable Remote Transducer HART field instruments and masters The modem and a few external passive components provide all of the functions needed to satisfy HART physical layer requirements including modulation demodulation receive filtering carrier detect and transmit signal shaping The HT1200M is pin compatible with the SYM20C15 See the Pin Description and Functional Description sections for details on pin compatibility with the SYM20C15 The HT1200M uses Phase Continuous Frequency Shift Keying FSK at 1200 bits per second To conserve power the receive circuits are disabled during transmit operations and vice versa This provides the half duplex operation used in HART communications Features Can be used in designs presently using the SYM20C15 or equivalent type chip Single chip half duplex 1200 bits per second FSK modem Bell 202 shift frequencies of 1200 Hz and 2200 Hz 3 3V 5 0V power supply Transmit signal wave shaping Receive band pass filter Low power optimal for intrinsically safe
8. Detect Reference Voltage This analog input controls at which level the carrier detect OCD becomes active This is determined by the do voltage difference between ICDREF and IAREF Selecting ICDREF IAREF equal to 0 08 Vpc will set the carrier detect to a nominal 100 mVp p INRESET Reset Digital Logic When at logic low VSS this input holds all the digital logic in Reset During normal operation INRESET should be at VDD INRESET should be held low for a minimum of 10 ns after VDD 2 5 V as shown in Figure 3 VDD INRESET Figure 3 Reset Timing INRTS Request To Send This active low input selects the operation of the modulator OTXA is enabled when this signal is low This signal must be held high during power up IRXA Analog Receive Input This input accepts the 1200 2200 Hz signals from the external filter IRXAC Analog Receive Comparator Input This is the positive input of the carrier detect comparator and the receiver filter comparator ITXD Digital Transmit Input CMOS This input to the modulator accepts digital data in NRZ form When ITXD is low the modulator output frequency is 2200 Hz When ITXD is high the modulator output frequency is 1200 Hz IXTL Oscillator Input This input to the internal oscillator must be connected to a parallel mode 460 8 kHz MICROCYBER ceramic resonator when using the internal oscillator or grounded when using an external 460 8 kHz clock signal OCBIAS Comparator Bias Current T
9. ITXD input and generates the FSK modulated signal at the OTXA output INRTS must be a logic low for the modulator to be active Demodulator The demodulator accepts an FSK signal at the IRXA input and reproduces the original modulating signal at the ORXD output The nominal bit rate is 1200 bits per second Figure 5 illustrates the demodulation process MICROCYBER lt 1 1200 Sec Figure 5 Demodulator Signal Timing The output of the demodulator is qualified with the carrier detect signal OCD therefore only IRXA signals large enough to be detected 100 mVp p typically by the carrier detect circuit produce received serial data at ORXD Maximum demodulator jitter is 12 percent of one bit given input frequencies within HART specifications a clock frequency of 460 8 kHz 1 0 percent and zero input IRXA asymmetry TRANSMIT SIGNAL SHAPER The transmit signal shaper generates a HART compliant FSK modulated signal at OTXA Figure 6 and Figure 7 show the transmit signal forms of the HT1200M For IAREF 1 235 Vpc OTXA will have a voltage swing from approximately 0 25 to 0 75 200mV v M200us Ch37 4mV Figure 6 OTXA Waveform 1200 Hz MICROCYBER 200mV v M200us Ch3 4mV Figure 7 OTXA Waveform 2200 Hz CARRIER DETECT CIRCUITRY The Carrier Detect Comparator shown in Figure 8 below generates logic low output if the IRXAC voltage is below ICDREF The comparator output is fed into a carrier detect block
10. MICROCYBER HT1200M User Manual HART Modem ASIC According to HCF SPEC 54 Version 1 1 Date 07 12 Copyright and Disclaimer Copyright 2007 SIA All rights reserved The information in this document is proprietary and confidential to SIA and for its customers internal use In any event no part of this document may be reproduced or redistributed in any form without the express written consent of SIA None of the information contained in this document constitutes an express or implied warranty by SIA as to the sufficiency fitness or suitability for a particular purpose of any such information or the fitness or suitability for a particular purpose merchantability performance compatibility with other parts or systems or any portion thereof referred to in this document SIA expressly disclaims all representations and warranties of any kind regarding the contents or use of the information including but not limited to express and implied warranties of accuracy completeness merchantability fitness for a particular use or non infringement In no event will SIA be liable for any direct indirect special incidental or consequential damages including but not limited to lost profits lost business or lost data resulting from any use of or reliance upon the information whether or not SIA has been advised of the possibility of such damage Shenyang Institute of Automation SIA No 114 Nanta Street Dongling District Shenyang
11. applications CMOS compatible Internal oscillator requires 460 8kHz crystal or ceramic resonator Meets HART physical layer requirements Industrial temperature range of 40 C to 85 C Available in a 28 pin PLCC and 32 pin LQFP packages MICROCYBER VI 1 HT1200M User Manual Typical Application 4 8 2NF VDD VDD po gt OTXA OCD 330K ORXD ORXD y nD ad INRTS y INRESET SIA TEST3 HT1200M TEST2 TESTI2 VDD TFSTII VDD u vpp 2 10UF 0 0 UF lt Lus ep lw 220 2 220 A R 2 Jem Figure 1 HT1200M Hart Modem Typical Application Pin Assignment e a B tno w a w a a Q a F 5 F F gt FEF FF OD TESTS TESTII TESTS TESTI INRESET ITXD INRESET ITXD TEST INRTS TEST INRTS TEST VDD TESTS VDD TEST vss TEST9 VSS OTXA IXTL VSS VSSA OTXA IXTL IAREF OXTL IAREF OXTL ICDREF VDDA IRXA a Figure 2 ORXAF a 28Pin PLCC Pinout Package lt lt z z 2 5 R42 x X X x gt gt b b 32Pin LQFP Pinout Package MICROCYBER Page 6 of 19 Table 1 HT1200M Pin Descriptions Signal Type LQFP Description TESTI input 1 28 to Vss TEST2 A 2 29 No connect TEST3 3 31 No connect TEST4 4 32 No connect TESTS input 5 1 Connect to Vss INRESET
12. e high cost and low availability of ceramic resonators In addition the HT 1200M consumes less current when an external clock is used Minimum current consumption occurs with the clock connected to OXTL and IXTL connected to VSS OXTL 460 8 kHz OXTL OSCILLATOR CELL OSCILLATOR CELL Frequen Frequency Our T Out IXTL a b Figure 9 a Crystal Oscillator b Oscillator MICROCYBER 1 1 1200 User Manual Package Information bom Mua I Sd 5mm scale A 1 0 20 1 45 0 4 0 18 7 1 7 1 9 15 9 15 0 75 0 9 0 9 7 Lm rs fei s o os 2 Jos n Jos jos ve Figure 10 LQFP32 Page 15 of 19 MICROCYBER 1 1 HT1200M User Manual OSt 0 9Sv 0 S8v 0 S6V0 1 1 1 1 1 1 1 1 7 0 456 0 450 0 495 0 485 690 080 060 0 0ZL 0 10 0 120 0 OZO O 0 430 0 390 Figure 11 PLCC28 MICROCYBER Page 16 of 19 Characteristics ABSOLUTE MAXIMUMS Parameter 1 Ambient Storage Temperature Supply Voltage DC Input Output VDD 0 3 Lead Temperature soldering DC CHARACTERISTICS VDD 2 7V to 5 5V VSS OV 40C to 85C Symbol Parameter VDD Input Voltage Low 2 7 5 5V INRESET INRTS 2 7 3 3V Output Voltage Low IOL 1 8 2 7 3 3V Output Voltage High IOH 1 8mA 2 7 3 3V Input Capacitance Analog Input IRXA Digital Input
13. he current through this output controls the operating parameters of the internal operational amplifiers and comparators For normal operation OCBIAS current is set to 2 5 uA OCD Carrier Detect Output This output goes high when a valid input is recognized on IRXA If the received signal is greater than the threshold specified on ICDREF for four cycles of the IRXA signal the valid input is recognized ORXAF Analog Receive Filter Output This signal is the square wave output of the receiver high pass filter ORCD Digital Receive Output CMOS This signal outputs the digital receive data When the received signal IRXA is 1200 Hz ORXD outputs logic high When the received signal IRXA is 2200 Hz ORXD outputs logic low ORXD is qualified internally with OCD and is logic high when OCD is low OTXA Analog Transmit Output This output provides the trapezoidal signal controlled by ITXD When ITXD is low the output frequency is 2200 Hz When ITXD is high the output frequency is 1200 Hz This output is active when INRTS is low and 0 5 VDD when INRTS is high OXTL Oscillator Output This output from the internal oscillator must be connected to an external 460 8 kHz clock signal or to a parallel mode 460 8 kHz ceramic resonator when using the internal oscillator TEST 12 1 Test Pin These are test pins For normal operation tie these signals as per Tablel VDD Digital Power This is the power for the digital modem circuitry VDDA
14. input 6 2 Reset all digital logic when low TEST7 input 7 3 Connect to Vss 8 input 8 4 Connect to Vss TEST9 input 9 5 Connect to Vss OTXA output 10 7 Modulated output transmit and transmit signal to 4 20mA loop FSK modulated HART interface circuit IAREF input 11 8 Analog reference voltage ICDREF input 12 9 Carrier detect reference voltage OCBIAS output 13 10 Comparator bias current TESTIO input 14 11 Connect to Vss VDDA power 15 13 Analog supply voltage IRXA input 16 14 FSK modulated HART receive signal from 4 20mA loop interface circuit ORXAF output I7 15 Analog receiver filter input IRXAC input 18 16 Analog receive comparator input OXTL output 19 I7 Crystal oscillator output IXTL Input 20 18 Crystal oscillator input VSS ground 21 6 20 Ground VDD power 22 21 30 Digital supply voltage INRTS input 23 22 Request to send ITXD input 24 23 Input transmit data Transmitted HART data stream from UART TESTII um 25 24 No connect ORXD output 26 25 Received demodulated HART data to UART OCD output 27 26 Carrier detect output TEST12 28 27 No connect VSSA ground 12 19 Analog ground MICROCYBER Pin Description IAREF Analog Reference Voltage This analog input sets the do operating point of the operational amplifiers and comparators and is usually selected to split the do potential between VDD and Vss IAREF in DC Characteristics refer to Electrical Characteristics ICDREF Carrier
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