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A5191HRT AMIS HARTTM Modem
1.0 Features
* * * * * * * * * * * * Can be used in designs presently using the SYM20C15 Single-chip, half-duplex 1200 bits per second FSK modem Bell 202 shift frequencies of 1200Hz and 2200Hz 3.3V - 5.0V power supply Transmit-signal wave shaping Receive band-pass filter Low power: optimal for intrinsically safe applications CMOS compatible Internal oscillator requires 460.8kHz crystal or ceramic resonator Meets HART physical layer requirements Industrial temperature range of -40C to +85C Available in 28-pin PLCC and 32-pin LQFP packages
Data Sheet
2.0 Description
The A5191HRT 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 A5191HRT is pin-compatible with the SYM20C15. See the Pin Description and Functional Description sections for details on pin compatibility with the SYM20C15. The A5191HRT 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.
Figure 1: 28-Pin PLCC Pinout Diagrams (green & non-green)
Figure 2: 32-Pin LQFP Pinout Diagrams (green & non-green)
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A5191HRT AMIS HARTTM Modem
Table 1: Pinout Summary 28-Pin PLCC, A5191HRTP/Pg (12197-504/508) Pin No. Signal Name Type 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 TEST1 TEST2 TEST3 TEST4 TEST5 INRESET TEST7 TEST8 TEST9 OTXA IAREF ICDREF OCBIAS TEST10 VDDA IRXA ORXAF IRXAC OXTL IXTL VSS VDD INRTS ITXD TEST11 ORXD OCD TEST12 Input Input Input Input Input Input Output Input Input Pin Description Connect to VSS No connect No connect No connect Connect to VSS Reset all digital logic when low Connect to VSS Connect to VSS Connect to VSS 8 Output transmit analog, FSK modulated HART transmit signal to 4-20mA loop interface circuit Analog reference voltage Carrier detect reference voltage 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 IAREF ICDREF OCBIAS TEST10 VSSA VDDA IRXA ORXAF IRXAC OXTL IXTL VSSA VSS VDD INRTS ITXD TEST11 ORXD OCD TEST12 TEST1 TEST2 VDD TEST3 TEST4 Input Input 3 4 5 6 7 TEST7 TEST8 TEST9 VSS OTXA Input Input Input
Data Sheet
Table 2: Pinout Summary 32-Pin LQFP, A5191HRTL/Lg (12197-503/507) Pin No. Signal Name 1 2 TEST5 INRESET Type Input Input Pin Description Connect to VSS Reset all digital logic when low, connect to VDD for normal operation Connect to VSS Connect to VSS Connect to VSS Output transmit analog, FSK modulated HART transmit signal to 4-20mA loop interface circuit Analog reference voltage Carrier detect reference voltage
Ground Digital ground Output
Output Comparator bias current Input Connect to VSS Ground Analog ground Power Analog supply voltage Input FSK modulated HART receive signal from 4-20mA loop interface circuit Analog receive comparator input Crystal oscillator input
Output Comparator bias current Connect to VSS Input Power Input Analog supply voltage FSK modulated HART receive signal from 4-20mA loop interface circuit Analog receive comparator input Crystal oscillator input Digital supply voltage Request to sent Input transmit date, transmitted HART data stream from UART No connect
Output Analog receive filter output Input Input Output Crystal oscillator output Ground Analog ground Ground Digital ground Power Digital supply voltage Input Input Request to send Input transmit data, transmitted HART data stream from UART No connect
Output Analog receive filter output Input Input Power Input Input Output Crystal oscillator output Ground Ground
Output Received demodulated HART data to UART Output Carrier detect output No connect
Output Received demodulated HART data to UART Output Carrier detect output Input No connect Connect to VSS No connect No connect No connect
Power Digital supply voltage
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A5191HRT AMIS HARTTM Modem
3.0 Pin Descriptions
Table 3: Pin Descriptions Symbol IAREF Pin Name Analog Reference Voltage
Data Sheet
Description Analog input sets the dc operating point of the operational amplifiers and comparators and is usually selected to split the dc potential between VDD and VSS. See IAREF in DC Characteristics, Table 6 Analog input controls at which level the carrier detect (OCD) becomes active. This is determined by the dc voltage difference between ICDREF and IAREF. Selecting ICDREF - IAREF equal to 0.08 VDC will set the carrier detect to a nominal 100 mVp-p 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 10nS after VDD = 2.5V as shown in Figure 3 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 Input accepts the 1200/2200Hz signals from the external filter Positive input of the carrier detect comparator and the receiver filter comparator Input to the modulator accepts digital data in NRZ form. When ITXD is low, the modulator output frequency is 2200Hz. When ITXD is high, the modulator output frequency is 1200Hz. Input to the internal oscillator must be connected to a parallel mode 460.8kHz ceramic resonator when using the internal oscillator or grounded when using an external 460.8kHz clock signal The current through this output controls the operating parameters of the internal operational amplifiers and comparators. For normal operation, OCBIAS current is set to 2.54A. 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. Signal is the square wave output of the receiver high-pass filter Signal outputs the digital receive data. When the received signal (IRXA) is 1200Hz, ORXD outputs logic high. When the received signal (IRXA) is 2200Hz, ORXD outputs logic low. ORXD is qualified internally with OCD. Output provides the trapezoidal signal controlled by ITXD. When ITXD is low, the output frequency is 2200Hz. When ITXD is high, the output frequency is 1200Hz. This output is active when INRTS is low and 0.5 VDC when INRTS is high. Output from the internal oscillator must be connected to an external 460.8kHz clock signal or to a parallel mode 460.8kHz ceramic resonator when using the internal oscillator Factory test pins; for normal operation, tie these signals as per Table 1 and Table 2 Power for the digital modem circuitry Power for the analog modem circuitry Analog and digital ground
ICDREF
Carrier Detect Reference Voltage
INRESET INRTS IRXA IRXAC ITXD IXTL OCBIAS OCD ORXAF ORXD OTXA OXTL
Reset Digital Logic Request to Send Analog Receive Input Analog Receive Comparator Input Digital Transmit Input (CMOS) Oscillator Input Comparator Bias Current Carrier Detect Output Analog Receive Filter Output Digital Receive Output (CMOS) Analog Transmit Output Oscillator Output
TEST(12:1) Factory Test VDD VDDA VSS VSSA Digital Power Analog Supply Voltage Ground Analog Ground
Figure 3: Reset Timing
Note: This signal is also present on the LSI 20C15. It is labeled as Test6. The 20C15 data sheet mentions the reset function of this pin but does not emphasize its use to reset the chip. Reliable operation of the modem requires a hardware reset as shown in Figure 3. This is true for the AMIS 12197-503 and 12197-504 as well as the LSI 20C15.
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A5191HRT AMIS HARTTM Modem
4.0 Functional Description
Data Sheet
The A5191HRT is a functional equivalent of the SYM20C15 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 modem modulates the transmit-signal and demodulates the receive signal. The transmit-signal shaper enables the A5191HRT 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.
Figure 4: A5191HRT Block Diagram
4.1 A5191HRT Logic The modem consists of a modulator and demodulator. The modem uses shift frequencies of nominally 1200Hz (for a 1) and 220Hz (for a 0). The bit rate is 1200 bits/second.
4.1.1 Modulator
The modulator accepts digital data in NRZ form at the ITXD input and generates the FSK modulated signal at the OTXA output. INRTS must be a logic low for the modulator to be active.
4.1.2 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.
Figure 5: Demodulator Signal Timing
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A5191HRT AMIS HARTTM Modem
Data Sheet
The output of the demodulator is qualified with the carrier detect signal (OCD), therefore, only IRXA signals large enough to be detected (100mVp-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 460.8kHz (1.0 percent) and zero input (IRXA) asymmetry.
4.2 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 A5191HRT. For IAREF = 1.235 VDC, OTXA will have a voltage swing from approximately 0.25 to 0.75 VDC.
Figure 6: OTXA Waveform (1200Hz)
Figure 7: OTXA Waveform (2200Hz)
4.3 Carrier Detect Circuitry The carrier detect comparator shown in Figure 8 generates logic low output if the IRXAC voltage is below ICDREF. The comparator output is fed into a carrier detect block (see Figure 4). 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 2.5ms. Once OCD goes inactive, it takes four consecutive pulses out of the comparator to assert OCD again. Four consecutive pulses amount to 3.33ms when the received signal is 1200Hz and to 1.82ms when the received signal is 2200HZ. 4.4 Analog Receiver Circuitry
4.4.1 Voltage References
The A5191HRT requires two voltage references, IAREF and ICDREF. IAREF sets the dc operating point of the internal operational amplifiers and comparators. A 1.235 VDC reference (Analog Devices AD589) is suitable as IAREF. The level at which OCD (carrier detect) becomes active is determined by the dc voltage difference (ICDREF - IAREF). Selecting a voltage difference of 0.08 VDC will set the carrier detect to a nominal 100 mVp-p.
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A5191HRT AMIS HARTTM Modem
4.4.2 Bias Current Resistor
Data Sheet
The A5191HRT 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:
The recommended bias current resistor is 500KW when IAREF is equal to 1.235 VDC. In Figure 8 all external capacitor values have a tolerance of 5 percent and the resistors have a tolerance of 1 percent, except the 3MW which has a tolerance of 5 percent. External to the A5191HRT, the filter exhibits a three-pole, high-pass filter at 624Hz and a one-pole, low-pass filter at 2500Hz. Internally, the A5191HRT has a high-pass pole at 35Hz and a low-pass pole at 90kHz. The low-pass pole can vary as much as 30 percent. The input impedance of the entire filter is greater than 150MW at frequencies below 50kHz.
Figure 8: Receive Filter Schematic
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A5191HRT AMIS HARTTM Modem
4.5 Oscillator
Data Sheet
The A5191HRT requires a 460.8kHz clock signal on OXTL. This can be provided by an external clock or external components may be connected to the A5191HRT internal oscillator.
4.5.1 Internal Oscillator Option
The oscillator cell will function with either a 460.8kHz 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 460.8kHz (I 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 100pF to 470pF are used.
4.5.2 External Clock Option
It may be desirable to use an external 460.8kHz clock as shown in Figure 10 rather than the internal oscillator because of the high cost and low availability of ceramic resonators. In addition, the A5191HRT consumes less current when an external clock is used. Minimum current consumption occurs with the clock connected to OXTL and IXTL connected to VSS.
Figure 9: Crystal Oscillator
Figure 10: Oscillator with External Clock
5.0 Ordering Information
The A5191HRT is available in a 28-pin plastic leaded chip carrier (PLCC) and 32-pin low-profile quad flat pack (LQFP). Use the following part number when ordering. Contact your local sales representative for more information: www.amis.com/sales.
Table 4: Ordering Codes Package 32-pin LQFP 28-pin PLCC 32-pin LQFP 28-pin PLCC Package Type Standard (non-Pb-free) Standard (non-Pb-free) Green/RoHS compliant Green/RoHS compliant Part Name A5191HRTL A5191HRTP A5191HRTLg A5191HRTPg Ordering Code* 12197-503-XTP 12197-504-XTP 12197-507-XTP 12197-508-XTP
*The part number extension -XTP refers to the device being shipped as tape and reel. The suffix -XTD refers to shipment in tubes or tray.
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A5191HRT AMIS HARTTM Modem
6.0 Electrical Specifications
Table 5: Absolute Maximums Symbol TA TS VDD VIN, VOUT TL
Cautions: 1. CMOS devices are damaged by high-energy electrostatic discharge. Devices must be stored in conductive foam or with all pins shunted. Precautions should be taken to avoid application of voltages higher than the maximum rating. Stresses above absolute maximum ratings may result in damage to the device. 2. Remove power before insertion or removal of this device.
Data Sheet
Parameter Ambient Storage temperature Supply voltage DC input,output Re-flow solder profile
Min. -40 -55 -0.3 -0.3
Max. +85 150 6.0 VDD+0.3 per IPC/JEDEC J-STD-020C
Units C C V V C
Table 6: DC Characteristics
VDD = 3.0V to 5.5V, VSS = 0V, TA = -40C to +85C
Symbol VIL VIH VOL VOH Parameter Input voltage, low Input voltage Output voltage, low (IOL = 0.67mA) Output voltage, high (IOH = -0.67mA) Input capacitance Analog input IRXA Digital input Input leakage current Output leakage current Power supply current (RBIAS = 500kW, IAREF = 1.235V) Analog reference Carrier detect reference (IAREF - 0.08V) Comparator bias current (RBIAS = 500kW, IAREF = 1.235V) 3.3 5.0 3.3 5.0 1.2 330 400 1.235 2.5 1.15 2.5 VDD 3.0 - 5.5 3.0 - 5.5 3.0 - 5.5 3.0 - 5.5 2.4 2.9 25 3.5 +500 +10 450 600 2.6 0.7*VDD 0.4 Min. Typ. Max. 0.3*VDD Units V V V V
CIN
pF
IIL/IH IOLL IDD IAREF ICDREF* OCBIAS
nA mA mA V V mA
*The HART specification requires carrier detect (OCD) to be active between 80 and 120 mVp-p. Setting ICDREF at IAREF - 0.08 VDC will set the carrier detect to a nominal 100 mVp-p.
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A5191HRT AMIS HARTTM Modem
Table 7: AC Characteristics
Data Sheet
VDD = 3.0V to 5.5V, VSS = 0V, TA = -40C to +85C
Pin Name IRXA Description Receive analog input Leakage current Frequency - mark (logic 1) Frequency - space (logic 0) Output of the high-pass filter Slew rate Gain bandwidth (GBW) Voltage range Carrier detect and receive filter input Leakage current Modulator output Frequency - mark (logic 1) Frequency - space (logic 0) Amplitude (IAREF 1.235V) Slope Loading (IAREF = 1.235V) Receive digital output Rise/fall time Carrier detect output Rise/fall time Min. Typ. Max. +150 1210 2220 Units nA Hz Hz
1190 2180
1200 2200
ORXAF
150 0.15
0.025
V/ms kHz VDD - 0.15 V/ms +500 nA Hz Hz mVp-p mV/ms kW ns ns
IRXAC
OTXA
30 20 20
1196.9 2194.3 500 2.79
ORXD OCD
The modular output frequencies are proportional to the input clock frequency (460.8kHz).
Table 8: Modem Characteristics
VDD = 3.0V to 5.5V, VSS = 0V, TA = -40C to +85C
Parameter Demodulator Jitter Conditions 1. Input frequencies at 1200Hz + 10Hz, 2200Hz + 20Hz 2. Clock frequency of 460.8kHz + 0.1% 3. Input (HLXA) asymmetry, 0 Min. Typ. Max. 12 Units % of 1 bit
Table 9: Ceramic Resonator - External Clock Specifications
VDD = 3.0V to 5.5V, VSS = 0V, TA = -40C to +85C
Parameter Resonator Tolerance Frequency External Clock frequency Duty cycle Amplitude Min. Typ. Max. Units % kHz kHz % V
460.8 460.8 50 VOH - VOL
1.0
456.2 40
465.4 60
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A5191HRT AMIS HARTTM Modem
7.0 Mechanical Specifications
Data Sheet
Symbol A A1 D D1 D2 D3 E E1 E2 E3 e
Min. .165 .099 .485 .450 .390 .485 .450 .390
Nom. .172 .101 .490 .452 .420 .300 REF .490 .452 .420 .300 REF .050 BSC
Max. .180 .110 .495 .455 .430 .495 .455 .430
Figure 11: 28 Lead PLCC
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A5191HRT AMIS HARTTM Modem
Data Sheet
Symbol A A1 A2 D D/2 D1 E E/2 E1 L e b c ccc ddd
Min. 0.05 1.35
Nom. 0.10 1.40 9.00 BSC 4.50 BSC 7.00 BSC 9.00 BSC 4.50 BSC 7.00 BSC
Max. 1.60 0.15 1.45
0.45 0.30 0.09 -
0.60 0.80 BSC 0.37 -
0.75 0.45 0.20 0.10 0.20
Figure 12: 32 Lead LQFP
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Devices sold by AMIS are covered by the warranty and patent indemnification provisions appearing in its Terms of Sale only. AMIS makes no warranty, express, statutory, implied or by description, regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. AMIS makes no warranty of merchantability or fitness for any purposes. AMIS reserves the right to discontinue production and change specifications and prices at any time and without notice. AMI Semiconductor's products are intended for use in commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment, are specifically not recommended without additional processing by AMIS for such applications. Copyright (c)2005 AMI Semiconductor, Inc.

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