A5191HRT Datasheet, PDF (3/13 Pages) AMI SEMICONDUCTOR – AMIS HART™ Modem

A5191HRT
Table 2: Pin Out Summary 32-Pin LQFP, A5191HRTl/Lg (12197-503/507)
Pin No. Signal Name Type
Pin Description
1
TEST5
Input
Connect to VSS
2
INRESET
Input
Reset all 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 4-20mA loop interface 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
FS modulated HART receive signal from 4-20mA loop interface circuit
15
ORXAF
Output
Analog receive filter input
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, transmit 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
3.0 Pin Descriptions
Table 3: Pin Descriptions
Symbol
Pin Name
Analog reference voltage
IAREF
ICDREF
Carrier detect reference voltage
INRESET Reset digital logic
INRTS
IRXA
IRXAC
ITXD
Request to send
Analog receive input
Analog receive comparator input
Digital transmit input (CMOS)
IXTL
Oscillator input
OCBIAS
Comparator bias current
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 Table 5.
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 Table 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.
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