ST490AB
Low power high speed
RS-485/RS-422 transceiver
Features
■
Low supply current: 5 mA max
■
-7 V to 12 V common mode input voltage range
■
70 mV typical input hysteresis
■
Designed for 25 Mbps operation
■
Operate from a single 5 V supply
■
±4 kV ESD protection
■
Current limiting and thermal shutdown for
driver overload protection
DIP-8
SO-8
Description
The ST490A is a low power transceiver for RS485 and RS-422 communications. The device
contains one driver and one receiver in full duplex
configuration. The ST490A draws 5 mA (typ.) of
supply current when unloaded or fully loaded with
disabled drivers. It operates from a single 5 V
supply.
Driver is short-circuit current limited and is
protected against excessive power dissipation by
thermal shutdown circuitry that place the driver
outputs into a high-impedance state. The receiver
input has a fail-safe feature that guarantees a
logic high output if both inputs are open circuit.
Table 1.
Device summary
Order code
Temperature range
Package
Packaging
ST490ABN
-40 to 85 °C
DIP-8
50 parts per tube / 40 tube per box
ST490ABDR
-40 to 85 °C
SO-8 (tape and reel)
2500 parts per reel
February 2008
Rev 5
1/17
www.st.com
17
Contents
ST490AB
Contents
1
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2
Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5
Test circuit and typical characteristics
6
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2/17
......................... 8
ST490AB
Pin configuration
1
Pin configuration
Figure 1.
Pin connections
Table 2.
Pin description
Pin n°
Symbol
Name and function
1
VCC
Supply voltage
2
RO
Receiver output
3
DI
Driver input
4
GND
5
Y
Non-inverting driver output
6
Z
Inverting driver output
7
B
Inverting receiver input
8
A
Non-inverting receiver input
Ground
3/17
Truth tables
ST490AB
2
Truth tables
Table 3.
Truth table (driver)
Inputs
DI
Y
Z
L
L
H
H
H
L
Note:
X = Don’t care; Z = High impedance
Table 4.
Truth table (receiver)
Note:
4/17
Outputs
Differential inputs
Outputs
A-B
RO
≥ -0.2V
H
between -0.2V to 0.2V
?
≤-0.2V
L
OPEN
H
X = Don’t care; Z = High impedance
ST490AB
Maximum ratings
3
Maximum ratings
Table 5.
Absolute maximum ratings
Symbol
Parameter
VCC
Supply voltage
VDI
Driver input voltage
Value
Unit
7
V
-0.5 to 7
V
VY, VZ
Driver output voltage
-7.5 to 12.5
V
VA, VB
Receiver input voltage
-7.5 to 12.5
V
-0.3 to (VCC + 0.3)
V
3.5
kV
VRO
Receiver output voltage
ESD
Human body model
Note:
Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these condition is not implied.
5/17
Electrical characteristics
ST490AB
4
Electrical characteristics
Table 6.
Electrical characteristics
(VCC = 4.5 V to 5.5 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are
referred to TA = 25 °C)
Symbol
ISUPPLY
Parameter
Min.
No load supply current
Typ.
Max.
Unit
2
5
mA
CIN
Input capacitance
1.8
pF
CYZ
Driver output capacitance
1.2
pF
Output capacitance
2.3
pF
COUT
Table 7.
Transmitter electrical characteristics
(VCC = 4.5 V to 5.5 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are
referred to TA = 25 °C)
Symbol
Parameter
VOD1
Differential drive output (no load)
VOD2
Differential drive output (with
load)
RL= 54Ω (RS-422) (Figure 1)
1.5
2.6
VOD3
Differential drive output (with
load)
RL= 100Ω (RS-422) (Figure 1)
2
3
ΔVOD
Change in magnitude of driver
differential output voltage for
complementary output states
RL= 54Ω or 100Ω (Figure 1)
VOC
Driver common mode output
voltage
RL= 54Ω (Figure 1)
ΔVOC
Change in magnitude of driver
common mode output voltage
RL= 54Ω (Figure 1)
IOFF
Power off output current
VCC = 0V, VO=-7V to 12V
IOSD
Driver short circuit output current VO=-7V to 12V
6/17
VIL
Input logic threshold low
VIH
Input logic threshold high
Test conditions
Min.
Typ.
0
1
0
± 35
2
Max.
Unit
VCC
V
5
V
V
0.2
V
3
V
0.2
V
± 100
µA
± 250
mA
0.8
V
V
ST490AB
Table 8.
Symbol
Electrical characteristics
Receiver electrical characteristics
(VCC = 4.5 V to 5.5 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are
referred to TA = 25 °C)
Parameter
Test conditions
Min.
IIN1
Logic input current
IIN2
Input current (A, B)
VTH
Receiver differential threshold
voltage
VCM = -7V to 12V
ΔVTH
Receiver input hysteresis
VCM = 0V
VOH
Receiver output high voltage
IOUT = -8mA, VID = 200mV
VOL
Receiver output low voltage
IOUT = 8mA, VID = -200mV
RRIN
Receiver input resistance
VCM = -7V to 12V
12
IOSR
Receiver short-circuit current
VO = 0V to VCC
7
Table 9.
Symbol
Other input=0V
VCC= 0 or 5.25V
Typ.
Max.
Unit
± 2.0
μA
VIN=12V
0.5
1
mA
VIN=-7V
-0.35
-0.8
mA
0.2
V
-0.2
3.5
70
mV
4.7
V
0.2
0.4
24
V
kΩ
95
mA
Driver switching characteristics
(VCC = 4.5 V to 5.5 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are
referred to TA = 25 °C)
Parameter
Test conditions
Min.
Typ.
25
50
Max.
Unit
DR
Maximum data rate
Jitter
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