Features
■ Low quiescent current: 300 µA
■ Designed for RS-485 interface application
■ - 7 V to 12 V common mode input voltage range
■ Driver maintains high impedance in 3-state or
with the power OFF
■ 70 mV typical input hysteresis
■ 30 ns propagation delay, 5 ns skew
■ Operates from a single 5 V supply
■ Current limiting and thermal shutdown for
driver overload protection
■ ESD protection:
– ± 15 kV (HBM)
– ± 8 kV (IEC-1000-4-2 contact discharge)
■ Allows up to 256 transceivers on the bus
ST485EB
ST485EC - ST485EX
±15 kV ESD protected, low power
RS-485/RS-422 transceiver
SO-8
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 ST485E is designed for bi-directional data
communications on multipoint bus transmission
lines (half-duplex applications).
Description
The ST485E is a low power transceiver for RS485 and RS-422 communication. Each driver
output and receiver input is protected against
± 15 kV electrostatic discharge (HBM) (ESD)
shocks, without latch-up. These parts contain one
driver and one receiver in half duplex
configuration.
This transceiver draws 300 µA (typ.) of supply
current when unloaded or fully loaded with
disabled drivers.
It operates from a single 5 V supply.
Table 1. Device summary
Order codes
ST485EBD - 40 to 85 °C SO-8 (tube) 100 parts per tube / 20 tube per box
ST485ECDR 0 to 70 °C SO-8 (tape and reel) 2500 parts per reel
ST485EBDR - 40 to 85 °C SO-8 (tape and reel) 2500 parts per reel
ST485EXDR - 55 to 125 °C SO-8 (tape and reel) 2500 parts per reel
Temperature
range
Package Packaging
February 2009 Rev 14 1/18
www.st.com
18
Contents ST485EB - ST485EC - ST485EX
Contents
1 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Test circuit and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2/18
ST485EB - ST485EC - ST485EX Pin configuration
1 Pin configuration
Figure 1. Pin connections (top view)
Table 2. Pin description
Pin n° Symbol Name and function
1 RO Receiver output
2REReceiver output enable
3 DE Driver output enable
4 DI Driver input
5 GND Ground
6 A Non-inverting receiver input and non-inverting driver output
7 B Inverting receiver input and inverting driver output
8V
CC
Supply voltage
3/18
Truth tables ST485EB - ST485EC - ST485EX
2 Truth tables
Table 3. Truth table (driver)
Inputs Outputs
RE DE DI B A
XHHLH
XHLHL
XLXZZ
Note: X = Don’t care; Z = High impedance
Table 4. Truth table (receiver)
Inputs Outputs
RE DE A-B RO
LL
LL
L L Inputs open H
HLX Z
Note: X = Don’t care; Z = High impedance
≥ +0.2V H
≤ -0.2V L
4/18
ST485EB - ST485EC - ST485EX Maximum ratings
3 Maximum ratings
Table 5. Absolute maximum ratings
Symbol Parameter Value Unit
V
V
V
V
V
V
CC
DI
DO
RI
RO
Supply voltage 7 V
Control input voltage (RE, DE) -0.5 to (VCC + 0.5) V
I
Driver input voltage (DI) -0.5 to (VCC + 0.5) V
Driver output voltage (A, B) ± 14 V
Receiver input voltage (A, B) ± 14 V
Receiver output voltage (RO) -0.5 to (VCC + 0.5) V
Note: Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these is not implied.
5/18
Electrical characteristics ST485EB - ST485EC - ST485EX
4 Electrical characteristics
Table 6. ESD performance: transmitter outputs, receiver inputs
Symbol Parameter Test conditions Min. Typ. Max. Unit
ESD ESD protection voltage Human body model ±15 kV
ESD ESD protection voltage IEC-1000-4-2 ±8kV
VCC = 5 V ± 5 %, TA = T
to T
= 25 °C
A
Table 7. DC electrical characteristics
MIN
to T
, unless otherwise specified. Typical values are referred
MAX
Symbol Parameter Test conditions
V
V
OD1
OD2
Differential driver output (no
load)
Differential driver output
(with load)
RL = 27 Ω (RS-485) (Figure 2)
RL = 50 Ω (RS-422) (Figure 2.)
Change in magnitude of
ΔV
driver differential output
OD
voltage for complementary
= 27 Ω or 50 Ω (Figure 2)0.2V
R
L
output states
V
Driver common-mode output
OC
voltage
R
= 27 Ω or 50 Ω (Figure 2)3V
L
Change in magnitude of
ΔV
driver common-mode output
OC
voltage for complementary
= 27 Ω or 50 Ω (Figure 2)0.2V
R
L
output states
V
ΔV
V
I
V
V
I
IN1
I
IN2
V
OZR
Input high voltage RE, DE, DI 2.0 V
IH
Input low voltage RE, DE, DI 0.8 V
IL
Input current RE, DE, DI ± 2µA
V
= 0 V or 5.25 V, VDE = 0 V
Input current (A, B)
Receiver differential
TH
threshold voltage
Receiver input hysteresis VCM = 0 V 70 mV
TH
Receiver output high voltage IO = -4 mA, VID = 200 mV 3.5 V
OH
Receiver output low voltage IO = 4 mA, VID = -200 mV 0.4 V
OL
3-State (high impedance)
output current at receiver
CM
= 12 V
V
IN
= -7 V
V
IN
= -7 to 12 V -0.2 0.2 V
V
CM
V
= 0.4 to 2.4 V ± 1µA
O
(1)
Min. Typ. Max. Unit
5V
1.5
5
5
V
V
1
-0.8mAmA
R
I
CC
Receiver input resistance VCM = -7 to 12 V 96 kΩ
IN
VRE = 0V or V
No load supply current
(2)
VDE = V
CC
VDE = 0 V
6/18
CC
400
300
900
500
µA
µA
ST485EB - ST485EC - ST485EX Electrical characteristics
Table 7. DC electrical characteristics (continued)
Symbol Parameter Test conditions
(1)
Min. Typ. Max. Unit
I
OSD1
I
OSD2
I
OSR
1. All currents into device pins are positive; all out of device pins are negative; all voltages are referenced to device ground
unless specified.
2. Supply current specification is valid for loaded transmitters when V
3. Applies to peak current. See typical Operating Characteristics.
Driver short-circuit current,
VO=High
Driver short-circuit current,
VO=Low
Receiver short-circuit current VO = 0 V to V
VCC = 5 V ± 5 %, TA = T
to T
= 25 °C
A
Table 8. Driver switching characteristics
V
= -7 to 12 V
O
= -7 to 12 V
V
O
to T
MIN
MAX
Symbol Parameter Test conditions
t
PLH
tPHL
t
SK
t
TLH
t
THL
t
PZH
t
PZL
t
PLZ
Propagation delay input to
output
Output skew to output
Rise or fall time
Output enable time
Output enable time
Output disable time
R
= 54 Ω, CL1 = CL2 = 100 pF
DIFF
(See Figure 4 and Figure 6)
= 54 Ω, CL1 = CL2 = 100 pF
R
DIFF
(See Figure 4 and Figure 6)
= 54 Ω, CL1 = CL2 = 100 pF
R
DIFF
(See Figure 4 and Figure 6)
C
= 100 pF, S2 = Closed
L
(See Figure 5 and Figure 7)
= 100 pF, S1 = Closed
C
L
(See Figure 5 and Figure 7)
= 15 pF, S1 = Closed
C
L
(See Figure 5 and Figure 7)
CC
(3)
(3)
DE
= 0 V
35 250 mA
35 250 mA
795mA
, unless otherwise specified. Typical values are referred
(1)
Min. Typ. Max. Unit
25 45 ns
25ns
15 40 ns
35 50 ns
25 40 ns
25 40 ns
C
= 15 pF, S2 = Closed
t
PHZ
1. All currents into device pins are positive; all out of device pins are negative; all voltages are referenced to device ground
unless specified.
Output disable time
L
(See Figure 5 and Figure 7)
35 50 ns
7/18
Electrical characteristics ST485EB - ST485EC - ST485EX
VCC = 5 V ± 5%, TA = T
to T
= 25 °C
A
Table 9. Receiver switching characteristics
Symbol Parameter Test conditions
t
PLH
t
PHL
t
SKD
t
PZH
t
PZL
t
PLZ
t
PHZ
f
MAX
1. All currents into device pins are positive; all out of device pins are negative; all voltages are referenced to device ground
unless specified
Propagation delay input to
output
Differential receiver skew
Output enable time
Output enable time
Output disable time
Output disable time
Maximum data rate 5 Mbps
MIN
to T
R
DIFF
, unless otherwise specified. Typical values are referred
MAX
= 54 Ω, CL1 = CL2 = 100 pF
(See Figure 4 and Figure 8)
R
= 54 Ω, CL1 = CL2 = 100 pF
DIFF
(See Figure 4 and Figure 8)
= 15 pF, S1 = Closed
C
RL
(See Figure 2 and Figure 9)
= 15 pF, S2 = Closed
C
RL
(See Figure 2 and Figure 9)
C
= 15 pF, S1 = Closed
RL
(See Figure 2 and Figure 9)
= 15 pF, S2 = Closed
C
RL
(See Figure 2 and Figure 9)
(1)
Min. Typ. Max. Unit
110 130 ns
510ns
11 35 ns
13 35 ns
13 35 ns
11 35 ns
8/18
ST485EB - ST485EC - ST485EX Test circuit and typical characteristics
5 Test circuit and typical characteristics
Figure 2. Driver DC test load Figure 3. Receiver timing test load
Figure 4. Drive/receiver timing test circuit Figure 5. Driver timing test load
9/18
Test circuit and typical characteristics ST485EB - ST485EC - ST485EX
Figure 6. Driver propagation delay
Figure 7. Driver enable and disable time
10/18
ST485EB - ST485EC - ST485EX Test circuit and typical characteristics
Figure 8. Receiver propagation delay
Figure 9. Receiver enable and disable time
11/18
Test circuit and typical characteristics ST485EB - ST485EC - ST485EX
Figure 10. Receiver output current vs. output
low voltage
Figure 12. Driver output current vs. output low
voltage
Figure 11. Receiver output current vs. output
high voltage
Figure 13. Driver output current vs. output
high voltage
Figure 14. Supply current vs. temperature Figure 15. Receiver high level output voltage
12/18
vs. temperature
ST485EB - ST485EC - ST485EX Test circuit and typical characteristics
Figure 16. Receiver low level output voltage
vs. temperature
Figure 17. Differential driver output voltage vs.
temperature
13/18
Package mechanical data ST485EB - ST485EC - ST485EX
6 Package mechanical data
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
specifications, grade definitions and product status are available at: www.st.com. ECOPACK
is an ST trademark.
®
packages, depending on their level of environmental compliance. ECOPACK®
14/18
ST485EB - ST485EC - ST485EX Package mechanical data
SO-8 mechanical data
Dim.
A1.35 1.75 0.053 0.069
A1 0.10 0.25 0.04 0.010
A2 1.10 1.65 0.043 0.065
B0.33 0.51 0.013 0.020
C0.19 0.25 0.007 0.010
D4.80 5.00 0.189 0.197
E 3.80 4.00 0.150 0.157
e 1.27 0.050
H5.80 6.20 0.228 0.244
h 0.25 0.50 0.010 0.020
L 0.40 1.27 0.016 0.050
k 8° (max.)
ddd 0.1 0.04
Min. Typ. Max. Min. Typ. Max.
mm. inch.
0016023/C
15/18
Package mechanical data ST485EB - ST485EC - ST485EX
Tape & reel SO-8 mechanical data
mm. inch.
Dim.
Min. Typ. Max. Min. Typ. Max.
A 330 12.992
C 12.8 13.2 0.504 0.519
D 20.2 0.795
N60 2.362
T 22.4 0.882
Ao 8.1 8.5 0.319 0.335
Bo 5.5 5.9 0.216 0.232
Ko 2.1 2.3 0.082 0.090
Po 3.9 4.1 0.153 0.161
P7.98.1 0.311 0.319
16/18
ST485EB - ST485EC - ST485EX Revision history
7 Revision history
Table 10. Document revision history
Date Revision Changes
21-Mar-2006 9 Order codes has been updated and new template.
05-Jun-2006 10 Change value row 10 on the features and RIN in Ta bl e 7 .
29-Jan-2007 11 Typo mistake on page 1.
29-Aug-2007 12 Change value RIN min. on Ta bl e 7 .
07-Feb-2008 13 Modified: Table 1 on page 1.
16-Feb-2009 14 Modified: Note: on page 5.
17/18
ST485EB - ST485EC - ST485EX
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