• Can be used in designs presently using the SYM20C15
• 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
1.0 Features
•Low power: optimal for intrinsically safe applications
•CMOS compatible
•Internal oscillator requires 460.8 kHz 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
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
2.0 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.
AMI Semiconductor
www.amis.com
10
TEST5 525
TEST11
6
INRESET 24 ITXD
7
TEST7 23 INRTS
8
TEST8 22 VDD
9
TEST9 21 VSS
OTXA 20 IXTL
11
IAREF 19 OXTL
34
TEST4
12
ICDREF
TEST3
13
OCBIAS
14
TEST10
2
TEST2
16
IRXA
28
TEST12
17
ORXAF
27
OCD
18
IRXAC
26
ORXD
XXXXYZZ
A5191HRTP
1
15
VDDA TEST1
M
TEST5 1TEST11
24
TEST6 2ITXD
23
3
TEST7 22 INRTS
4
TEST8 21 VDD
5
TEST9 20 VSS
6
VSS 19 VSSA
OTXA 7IXTL
18
8
IAREF 17 OXTL
XXXXYZZ
A5191HRTL
32
TEST4
9
ICDREF
31
TEST3
10
OCBIAS
30
VDD
11
TEST10
27
TEST12
14
IRXA
26
OCD
15
ORXAF
25
ORXD
16
IRXAC
TEST1
28
VDDA
13
29
TEST2
12
VSSA
M
Figure 1: 28-Pin PLCC Pinout Diagram Figure 2: 32-Pin LQFP Pinout Diagram
1
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
Pin No. Signal Name Type Pin Description
Table 1: Pinout Summary 28-Pin PLCC, A5191HRTP (12197-504)
1 TEST1 Input Connect to Vss
2 TEST2 - No connect
3 TEST3 - No connect
4 TEST4 - No connect
5 TEST5 Input Connect to Vss
6 INRESET Input Reset all digital logic when low
7 TEST7 Input Connect to Vss
8 TEST8 Input Connect to Vss
9 TEST9 Input Connect to Vss
10 OTXA Output Output transmit analog. FSK modulated HART transmit signal
to 4-20 mA loop interface circuit.
11 IAREF Input Analog reference voltage
12 ICDREF Input Carrier detect reference voltage
13 OCBIAS Output Comparator bias current
14 TEST10 Input Connect to Vss
15 VDDA Power Analog supply voltage
16 IRXA Input FSK modulated HART receive signal from 4-20 mA loop interface circuit
17 ORXAF Output Analog receive filter output
18 IRXAC Input Analog receive comparator input
19 OXTL Output Crystal oscillator output
20 IXTL Input Crystal oscillator input
21 VSS Ground Ground
22 VDD Power Digital supply voltage
23 INRTS Input Request to send
24 ITXD Input Input transmit date. Transmitted HART data stream from UART.
25 TEST11 - No connect
26 ORXD Output Received demodulated HART data to UART
27 OCD Output Carrier detect output
28 TEST12 - No connect
2
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
Pin No. Signal Name Type Pin Description
Table 2: Pinout Summary 32-Pin LQFP, A5191HR TL (12197-503)
1 TEST5 Input Connect to Vss
2 INRESET Input Reset all digital logic when low. Connect to VDD for normal operation
3 TEST7 Input Connect to Vss
4 TEST8 Input Connect to Vss
5 TEST9 Input Connect to Vss
6 VSS Ground Digital ground
7 OTXA Output Output transmit analog. FSK modulated HART transmit signal to
4-20 mA loopinterface circuit.
8 IAREF Input Analog reference voltage
9 ICDREF Input Carrier detect reference voltage
10 OCBIAS Output Comparator bias current
11 TEST10 Input Connect to Vss
12 VSSA Ground Analog ground
13 VDDA Power Analog supply voltage
14 IRXA Input FSK modulated HAR T receive signal from 4-20 mA loop interface circuit
15 ORXAF Output Analog receive filter output
16 IRXAC Input Analog receive comparator input
17 OXTL Output Crystal oscillator output
18 IXTL Input Crystal oscillator input
19 VSSA Ground Analog ground
20 VSS Ground Digital ground
21 VDD Power Digital supply voltage
22 INRTS Input Request to send
23 ITXD Input Input transmit data. Transmitted HART data stream from UART.
24 TEST11 - No connect
25 ORXD Output Received demodulated HART data to UART
26 OCD Output Carrier detect output
27 TEST12 - No connect
28 TEST1 Input Connect to Vss
29 TEST2 - No connect
30 VDD Power Digital supply voltage
31 TEST3 - No connect
32 TEST4 - No connect
3
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
IAREF: Analog Reference Voltage
This analog input sets the dc operating point of the oper-
ational amplifiers and comparators and is usually selected
to split the dc potential between VDD and VSS. See IAREF
in DC Characteristics on page 8.
ICDREF: Carrier Detect Reference Voltage
This 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.
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 below.
Figure 3: Reset Timing
Note: This signal is also present on the LSI 20C15. It is
labeled as Test6. The 20C15 datasheet 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.
INRTS: Request To Send
This active-low input selects the operation of the modula-
tor. 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
3.0 Pin Descriptions
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 ceramic resonator when using
the internal oscillator or grounded when using an external
460.8 kHz clock signal.
OCBIAS: Comparator Bias Current
The current thr ough this output controls the operating param-
eters of the internal operational amplifiers and comparators.
For normal operation, OCBIAS current is set to 2.5 4A.
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.
ORXD: 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.
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 VDC 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): Factor y Test
These are factory test pins. For normal operation, tie
these signals as per Table 1 and Table 2.
VDD: Digital Power
This is the power for the digital modem circuitry.
VDDA: Analog Supply Voltage
This is the power for the analog modem circuitry.
VSS: Ground
This is the analog and digital ground.
VSSA: Analog Ground
VDD
10 nS
VDD
0
0
2.5 V
INRESET
4
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
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.
Figure 4: A5191HRT Block Diagram
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.
4.1 A5191HRTLOGIC
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 is 1200 bits/second.
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 mod-
ulator 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 sec-
ond. Figure 5 illustrates the demodulation process.
Figure 5: Demodulator Signal Timing
4.0 Functional Description
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 pr oduce r eceived 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.
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 (1200 Hz)
Figure 7: OTXA Waveform (2200 Hz)
INRTS
ORXD
OCD
IXTL
OXTL OCBIAS
ICDREF
IAREF
ORXAF
IRXAC
OTXA
IRXA
Modulator
and Transmit
W ave Shaping
Receive
Filter and
Demodulator
Oscillator
Carrier
Detect
Control
Logic
ITXD
IRXA
ORXD
1/1200 Sec
01111
T
M 200µs Ch 3 4mV 200mVCh3Ch3Ch3
5
A5191HRT AMIS HART™Modem
T
M 200µs Ch 3 4mV 200mVCh3Ch3Ch3
AMI Semiconductor
www.amis.com
4.3 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 (see Figure 4 on page 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.
4.4 ANALOG RECEIVER CIRCUITRY
Voltage References
The A5191HRT requires two voltage references, IAREF
and ICDREF.
IAREF sets the dc operating point of the internal opera-
tional 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.
Bias Current Resistor
The A5191HRT requires a bias current resistor to be
connected between OCBIAS and VSS. The bias current
controls the operating parameters of the internal opera-
tional amplifiers and comparators.
The value of the bias current r esistor is determined by the
reference voltage IAREF and the following formula:
The recommended bias current resistor is 500KΩ 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 3 MΩwhich has a tolerance of
±5 percent. External to the A5191HRT, the filter exhibits
a three-pole, high-pass filter at 624 Hz and a one-pole,
low-pass filter at 2500 Hz. Internally, the A5191HRT 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 ±30 percent.
The input impedance of the entire filter is greater than
150 MΩat frequencies below 50 kHz.
6
A5191HRT AMIS HART™Modem
+
–
+
–
+
–
Hart_In C3
470pf (14)
IRXA
R1*
499k
C1
C2 1 nf
1 nf
220pf
R6
422k R7
216k
44k
40pf
214k
R9
14.7k
300pf (16)IRXAC
(15)
ORXAF
15M
Recieve
Filter
Amplifier
R2
3M
R3
787k
R4*
215k
R5*
215k
V+
R8
Z1
1.235V
(8)IAREF
(9)ICDREF
R10*
200k
Receive
Comparator To Receive
Demodulator
To Carrier
Detect
Carrier
Detect
Comparator
Modem3
Figure 8: Receive Filter Schematic
AMI Semiconductor
www.amis.com
4.5 OSCILLATOR
The A5191HRT r equir es a 460.8 kHz clock signal on OXTL.
This can be provided by an external clock or external
components may be connected to the A5191HRT 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 (±I percent tolerance) parallel resonant
crystal and two tuning capacitors. The actual values of the
C1
C2
460.8 kHz IXTL
OXTL
OSCILLATOR
CELL Frequenc
y
Out
460.8 kHz OXTL
IXTL
OSCILLATOR
CELL Frequency
Out
capacitors may depend on the recommendations of the
manufacturer of the resonator. Typically, capacitors in the
range of 100 pF to 470 pF are used.
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 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.
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 r epr esentative for mor e
information: www.amis.com/sales.
5.0 Ordering Information
Package Type Part Name Part Number
32-pin LQFP A5191HR TL 12197-503
28-pin PLCC A5191HRTP 12197-504
6.0 Electrical Specifications
ABSOLUTE MAXIMUMS
Symbol
TAAmbient +85
150
250
6.0
VDD+0.3
°C
TSStorage Temperature -55
-40 °C
VDD Supply V oltage -0.3 V
VIN , VOUT DC Input, Output -0.3 V
TLLead Temperature (Soldering 10 °C
Parameter Min. Max. Units
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.
Figure 9: Crystal Oscillator Figure 10: Oscillator with External Clock
7
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
Symbol Parameter VDD Typical Max. UnitsMin.
DC CHARACTERISTICS
(VDD = 3.0 V to 5.5 V, VSS = 0V, TA = -40°C to +85°C)
V
IL Input Voltage, Low 3.0-5.5 0.3*VDD V
VIH Input Voltage 3.0-5.5 0.7*VDD V
VOL Output Voltage, Low (IOL = 0.67mA) 3.0-5.5 0.4 V
VOH Output V oltage, High (IOH= -0.67mA) 3.0-5.5 2.4 V
CIN Input Capacitance 2.9 pF
Analog Input 25
IRXA 3.5
Digital Input
IIL/IH Input Leakage Current ±500 nA
IOLL Output Leakage Current ±10 µA
IDD Power Supply Current 3.3 330 450 µA
(RBIAS = 500kΩ, IAREF =1.235 V) 5.0 400 600
IAREF Analog Reference 3.3 1.2 1.235 2.6 V
5.0 2.5
ICDREF1 Carrier Detect Reference 1.15 V
(IAREF - 0.08 V)
OCBIAS Comparator Bias Current 2.5 µA
(RBIAS = 500kΩ, IAREF =1.235 V)
1. 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.
8
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
Parameter
MODEM CHARACTERISTICS
(VDD = 3.0 V to 5.5 V, VSS = 0V, TA = -40°C to +85°C)
Demodulator Jitter
Conditions 12 % of 1 bit
1. Input frequencies at 1200 Hz ±10 Hz,
2200 Hz ±20 Hz
2. Clock frequency of 460.8 kHz ±0. 1 %
3. Input (HLXA) asymmetry, 0
Min. Typical Max. Units
Parameter
CERAMIC RESONATOR - EXTERNAL CLOCK SPECIFICATIONS
(VDD = 3.0 V to 5.5 V, VSS = 0V, TA = -40°C to +85°C)
Resonator
Tolerance 1.0 %
Frequency 460.8 kHz
External
Clock Frequency 456.2 460.8 465.4 kHz
Duty Cycle 40 50 60 %
Amplitude V
OH
- V
OL
V
Min. Typical Max. Units
Pin Name Description
AC CHARACTERISTICS
(VDD = 3.0 V to 5.5 V, VSS = 0V, TA = -40°C to +85°C)
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
Slew Rate 0.025 V/µs
Gain Bandwith (GBW) 150 kHz
V oltage Range 0.15 V DD – 0.15 V/µs
IRXAC Carrier Detect & Receive Filter Input
Leakage Current ±500 nA
OTXA Modulator Output
Frequency' - Mark (Logic 1) 1196.9 Hz
Frequency - Space (Logic 0) 2194.3 Hz
Amplitude (IAREF 1.235 V) 500 mVp-p
Slope 2.79 mV/µs
Loading (IAREF = 1.235 V) 30 kΩ
ORXD Receive Digital Output ns
Rise/Fall Time 20
OCD Carrier Detect Output ns
Rise/Fall Time 20
The modular output frequencies are proportional to the input clock frequency (460.8 kHz).
Min. Typical Max. Units
9
A5191HRT AMIS HART™Modem
AMI Semiconductor
www.amis.com
7.0 Mechanical Specifications
10
PIN 1
IDENTIFIER & ZONE
D3
E3 .048 / .042
2 PLCS
Symbol Max.Min. Nom.
A .165 .172 .180
A1 .099 .101 .110
D .485 .490 .495
D1 .450 .452 .455
D2 .390 .420 .430
D3 .300 REF
E .485 .490 .495
E1 .450 .452 .455
E2 .390 .420 .430
E3 .300 REF
e .050 BSC
Figure 11: 28 Lead PLCC
D
D1
E
E1
D2 / E2
.021 / .013 .020 min
R .045 / .025
e0.076
.032 / .026
A1
A
SEATING PLANE
A5191HRT AMIS HART™Modem
Top View Bottom View
Side View
AMI Semiconductor
www.amis.com 11
1.00 (REF)
SEE DETAIL A
c
A2
A1
A
DETAIL A
0.08 R min
0° min
0.20 min
0.08 / 0.20 R
0°– 7°
L
e8
9
b
16
32
25
24 17
E/2
D1
DD/2D/2
EE1
E/2
1
INDEX
Symbol Max.Min. Nom.
A - - 1.60
A1 0.05 0.10 0.15
A2 1.35 1.40 1.45
D 9.00 BSC
D/2 4.50 BSC
D1 7.00 BSC
E 9.00 BSC
E/2 4.50 BSC
E1 7.00 BSC
L 0.45 0.60 0.75
e 0.80 BSC
b 0.30 0.37 0.45
c 0.09 - 0.20
ccc - - 0.10
ddd - - 0.20
Figure 12: 32 Lead LQFP
A5191HRT AMIS HART™Modem
© 2001 AMI Semiconductor, Inc.
AMI Semiconductor makes no warranty for the use of its products, other than those expressly contained in the company’s standard warranty contained in AMI Semiconductor’s
Terms and Conditions. The company assumes no responsibility for any errors which may appear in this document, reserves the right to change devices or specifications detailed
herein at any time without notice, and does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of AMI
Semiconductor are granted by the company in connection with the sale of AMI Semiconductor products, expressly or by implication.
HART is a registered trademark of the HART Communication Foundation.
