3.3 V powered, 15 kV ESD protected,
up to 12 Mbps RS-485/RS-422 transceiver
Features
■ ESD protection
– ±15 kV human body model
– ±8 kV IEC 1000-4-2 contact discharge
■ Operate from a single 3.3 V supply - no charge
pump required
■ Interoperable with 5 V logic
■ 1 µA low current shutdown mode max
■ Guaranteed 12 Mbps data rate
■ -7 to 12 V common mode input voltage range
■ Half duplex versions available
■ Industry standard 75176 pinout
■ Current limiting and thermal shutdown for
driver overload protection
■ Guaranteed high receiver output state for
floating inputs with no signal present
■ Allow up to 64 transceivers on the bus
ST3485EB
ST3485EC
DIP-8
Driver is short-circuit current limited and is
protected against excessive power dissipation by
thermal shutdown circuitry that places the driver
outputs into a high-impedance state.
SO-8
Description
The ST3485E is ±15 kV ESD protected, 3.3 V low
power transceiver for RS-485 and RS-422
communications. The device contains one driver
and one receiver in half duplex configuration. The
ST3485E transmits and receives at a guaranteed
data rate of at least 12 Mbps.
All transmitter outputs and receiver inputs are
protected to ±15 kV using Human Body Model.
Table 1. Device summary
Order code Temperature range Package Packaging
ST3485ECN 0 to 70 °C DIP-8 50 parts per tube / 40 tube per box
ST3485ECDR 0 to 70 °C SO-8 (tape and reel) 2500 parts per reel
ST3485EBDR -40 to 85 °C SO-8 (tape and reel) 2500 parts per reel
November 2007 Rev 5 1/22
www.st.com
22
Contents ST3485EB - ST3485EC
Contents
1 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Test circuits and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 9
6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/22
ST3485EB - ST3485EC Pin configuration
1 Pin configuration
Figure 1. Pin connections
Table 2. Pin description
Pin n° Symbol Name and function
1 RO Receiver output. If A>B by 200mV, RO will be high; if A<B by 200mV, RO will be low
2RE
3DE
4DI
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
Receiver output enable. RO is enabled when RE is low; RO is high impedance when RE
is high. If RE is high and DE is low, the device will enter a low power shutdown mode.
Driver output enable. The driver outputs are enabled by bringing DE high. They are high
impedance when DE is low. If RE is high DE is low, the device will enter a low-power
shutdown mode. If the driver outputs are enabled, the part functions as line driver, while
they are high impedance, it functions as line receivers if RE is low.
Driver input. A low on DI forces output A low and output B high. Similarly, a high on DI
forces output A high and output B low
Supply voltage: VCC= 3V to 3.6V
3/22
Truth tables ST3485EB - ST3485EC
2 Truth tables
Table 3. Truth table (driver)
Inputs Outputs
Mode
RE DE DI B A
XHHLH Normal
XHLHL Normal
LLXZZ Normal
H L X Z Z Shutdown
Note: X= Don’t care; Z=High impedance
Table 4. Truth table (receiver)
Inputs Output
Mode
RE DE A-B RO
LL ≥ 0.2V H Normal
LL ≤ -0.2V L Normal
L L Inputs Open H Normal
H L X Z Shutdown
Note: X= Don’t care; Z=High impedance
4/22
ST3485EB - ST3485EC Maximum ratings
3 Maximum ratings
Table 5. Absolute maximum ratings
Symbol Parameter Value Unit
V
CC
V
I
V
DI
V
DO
V
RI
V
RO
Supply voltage 7 V
Control input voltage (RE, DE) -0.3 to 7 V
Driver input voltage (DI) -0.3 to 7 V
Driver output voltage (A, B) ± 14 V
Receiver input voltage (A, B) ± 14 V
Receiver output voltage (RO) -0.3 to (VCC + 0.3) V
Note: Absolute maximum ratings are those values beyond which damage to the device may occur.
Functional operation under these condition is not implied.
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 Contact discharge ± 8kV
5/22
Electrical characteristics ST3485EB - ST3485EC
4 Electrical characteristics
Table 7. Electrical characteristics
= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred
V
CC
to T
= 25 °C)
A
Symbol Parameter Test conditions Min. Typ. Max. Unit
I
SUPPLYVCC
I
SHDN
Shutdown supply current DE=0V, RE=VCC, DI=0V or VCC 0.002 1 µA
Power supply current No Load, DI=0V or V
DE=VCC,
RE=0V or V
CC
DE=0V,
RE
CC
=0V
1.3 2.2 mA
1.2 1.9 mA
Table 8. Logic input electrical characteristics
V
= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred
CC
to T
= 25 °C)
A
Symbol Parameter Test conditions Min. Typ. Max. Unit
Input logic threshold low DE, DI, RE 1.3 0.8 V
IL
Input logic threshold high DE, DI, RE 2 V
IH
Logic input current DE, DI, RE ± 2.0 µA
V
=12V 1 mA
Input current (A, B) DE=0V, VCC= 0 or 3.6V
IN
V
=-7V -0.8 mA
IN
V
I
I
V
IN1
IN2
Table 9. Transmitter electrical characteristics
V
= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred
CC
to T
= 25°C)
A
Symbol Parameter Test conditions Min. Typ. Max. Unit
R
= 100Ω (RS-422) (Figure 1)2 V
L
V
Differential drive output
OD
= 54Ω (RS-485) (Figure 1)1.5 V
R
L
R
= 60Ω (RS-485) (Figure 2)1.5 V
L
Change in magnitude of driver
ΔV
differential output voltage for
OD
complementary output states
= 54Ω or 100Ω (Figure 1)0.2V
R
L
(Note: 1)
V
Driver common mode output
OC
voltage
= 54Ω or 100Ω (Figure 1)3V
R
L
Change in magnitude of driver
ΔV
common mode output voltage
OC
= 54Ω or 100Ω (Figure 1)0.2V
R
L
(Note: 1)
I
OSD
Driver short circuit output
current
6/22
± 250 mA
ST3485EB - ST3485EC Electrical characteristics
Table 10. Receiver electrical characteristics
V
= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred
CC
to T
= 25°C)
A
Symbol Parameter Test conditions Min. Typ. Max. Unit
V
ΔV
V
V
I
R
I
TH
TH
OH
OL
OZR
RIN
OSR
Receiver differential
threshold voltage
Receiver input hysteresis VCM = 0V 70 V
Receiver output high
voltage
Receiver output low
voltage
3-State (high impedance)
output current at receiver
Receiver input resistance VCM = -7V to 12V 24 kΩ
Receiver short-circuit
current
V
= -7V to 12V, DE = 0 -0.2 0.2 V
CM
I
= -4mA, VID = 200mV
OUT
(Figure 8 and Figure 9)
= 4mA, VID = -200mV, (Figure 3)0.4V
I
OUT
= 3.6V, VO = 0V to V
V
CC
V
RO
= 0V to V
CC
CC
2V
± 1µA
760mA
Table 11. Driver switching characteristics
V
= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred
CC
to T
= 25 °C)
A
Symbol Parameter Test conditions Min. Typ. Max. Unit
D
t
DD
t
TD
Maximum data rate 12 15 Mbps
R
= 60Ω, CL = 15pF, (Figure 4 and
R
Differential output delay
Differential output
transition time
L
Figure 5)
RL= 60Ω, CL = 15pF, (Figure 4 and
Figure 5)
18 30 ns
12 20 ns
t
PLH
t
PHL
t
PDS
t
PZL
t
PZH
t
PHZ
t
PLZ
t
SKEW
t
ZH(SHDN)
t
ZL(SHDN)
R
= 27Ω, CL = 15pF, (Figure 8 and
Propagation delay
|t
PLH - tPHL
| Propagation
delay skew (Note 2)
L
Figure 9)
RL= 27Ω, CL = 15pF, (Figure 8 and
Figure 9)
18 30 ns
25ns
Output enable time RL= 110Ω, (Figure 10 and Figure 11)1935ns
Output enable time RL= 110Ω, (Figure 6 and Figure 7)3050ns
Output disable time RL= 110Ω, (Figure 6 and Figure 7)1935ns
Output disable time RL= 110Ω, (Figure 10 and Figure 11)3050ns
Differential output delay
skew
Driver enable from
shutdown to output high
Driver enable from
shutdown to output low
13ns
30 50 ns
19 35 ns
7/22
Electrical characteristics ST3485EB - ST3485EC
Table 12. Receiver switching characteristics
V
= 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred
CC
to T
= 25 °C)
A
Symbol Parameter Test conditions Min. Typ. Max. Unit
t
PLH
t
PHL
t
RPDS
t
PZL
t
PZH
t
PHZ
t
PLZ
t
ZH(SHDN)
t
ZL(SHDN)
Note: 1
2 Measured on |t
3 The transceivers are put into shutdown by bring RE high and DE low. If the input are in state
Propagation delay
|t
PLH - tPHL
| Propagation
delay skew
ID
(Figure 12 and Figure 13)
VID =0V to 3V, CL1 = 15pF
(Figure 12 and Figure 13)
30 50 ns
13ns
=0V to 3V, CL1 = 15pF
V
Output enable time CRL = 15pF, (Figure 14 and Figure 18)1020ns
Output enable time CRL = 15pF, (Figure 14 and Figure 18)1020ns
Output disable time CRL = 15pF, (Figure 14 and Figure 18)1020ns
Output disable time CRL = 15pF, (Figure 14 and Figure 18)1020ns
Receiver enable from
shutdown to output high
Receiver enable from
shutdown to output low
Δ
VOD and ΔVOC are the changes in VOD and VOC, respectively, when the DI input changes
= 15pF, (Figure 14 and Figure 18)1020ns
C
RL
= 15pF, (Figure 14 and Figure 18)2040µs
C
RL
state.
PLH
(A)-t
(A)| and |t
PHL
PLH
(B)-t
PHL
(B)|
for less than 80 ns, the part are guaranteed not to enter shutdown. If the inputs are in this
state for at least 300 ns, the parts are guaranteed to have entered shutdown.
8/22
ST3485EB - ST3485EC Test circuits and typical characteristics
5 Test circuits and typical characteristics
Figure 2. Driver and VOC test load
Figure 3. Driver VOD with varying common mode voltage test load
Figure 4. Receiver VOH and VOL test circuit
9/22
Test circuits and typical characteristics ST3485EB - ST3485EC
Figure 5. Drive differential output delay transition time test circuit
Figure 6. Drive differential output delay transition time waveform
Figure 7. Drive enable and disable times test circuit
10/22
ST3485EB - ST3485EC Test circuits and typical characteristics
Figure 8. Drive enable and disable times waveforms
Figure 9. Drive propagation time test circuit
Figure 10. Drive propagation time waveform
11/22
Test circuits and typical characteristics ST3485EB - ST3485EC
Figure 11. Drive enable and disable times test circuit
Figure 12. Drive enable and disable times waveforms
Figure 13. Receiver propagation delay time test circuit
12/22
ST3485EB - ST3485EC Test circuits and typical characteristics
Figure 14. Receiver propagation delay time waveforms
Figure 15. Receiver enable and disable times test circuit
Figure 16. Receiver enable and disable times waveform
13/22
Test circuits and typical characteristics ST3485EB - ST3485EC
Figure 17. Receiver enable and disable times waveform
Figure 18. Receiver enable and disable times waveform
Figure 19. Receiver enable and disable times waveform
14/22
ST3485EB - ST3485EC Test circuits and typical characteristics
Figure 20. Receiver output current vs output
Figure 22. Low level driver output capability Figure 23. High level driver output capability
low voltage
Figure 21. Receiver output current vs output
high voltage
Figure 24. Receiver input characteristics Figure 25. Driver short circuit current
15/22
Test circuits and typical characteristics ST3485EB - ST3485EC
Figure 26. Driver short circuit current
16/22
ST3485EB - ST3485EC Package mechanical data
6 Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a lead-free second level interconnect. The category of
second level interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com
17/22
Package mechanical data ST3485EB - ST3485EC
Plastic DIP-8 mechanical data
Dim.
Min. Typ. Max. Min. Typ. Max.
A 3.3 0.130
a1 0.7 0.028
B1.39 1.65 0.055 0.065
B1 0.91 1.04 0.036 0.041
b 0.5 0.020
b10.38 0.5 0.015 0.020
D 9.8 0.386
E 8.8 0.346
e 2.54 0.100
e3 7.62 0.300
e4 7.62 0.300
F 7.1 0.280
I4.8 0.189
L 3.3 0.130
Z 0.44 1.6 0.017 0.063
mm. inch.
18/22
P001F
ST3485EB - ST3485EC 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
19/22
Package mechanical data ST3485EB - ST3485EC
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
20/22
ST3485EB - ST3485EC Revision history
7 Revision history
Table 13. Document revision history
Date Revision Changes
20-Jun-2005 2 Mistake on table 12
30-Aug-2005 3
07-Apr-2006 4 Order codes updated.
12-Nov-2007 5 Added Ta b le 1 .
Remove (TRUE) on title, description has been updated in cover page.
The V
and ΔVTH values are changed in table 10.
TH
t
ZL(SHDN)
ms ==> µs.
21/22
ST3485EB - ST3485EC
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