1/16
October 2002
s
ESD PROTECTION:
15KV HUMAN BODY MODEL
8KV IEC 1000-4-2 CONTACT DISCHARGE
s
OPERATE FROM A SINGLE 3.3V SUPPLY -
NO CHARGE PUMP REQUIRED
s
INTEROPERABLE WITH 5V LOGIC
s
1
A LOW CURRENT SHUTDOWN MODE
MAX
s
GUARANTEED 12 Mbps DATA RATE
s
-7 TO 12 COMMON MODE INPUT VOLTAGE
RANGE
s
HALF DUPLEX VERSIONS AVAILABLE
s
INDUSTRY STANDARD 75176 PINOUT
s
CURRENT LIMITING AND THERMAL
SHUTDOWN FOR DRIVER OVERLOAD
PROTECTION
s
GUARANTEED HIGH RECEIVER OUTPUT
STATE FOR FLOATING INPUTS WITH NO
SIGNAL PRESENT
s
ALLOW UP TO 64 TRANSCEIVERS ON THE
BUS
DESCRIPTION
The ST3485E is 15kV ESD protected, 3.3V low
power
transceiver
for
RS-485
and
RS-422
communications. The device contains one driver
and one receiver in half duplex configuration. The
ST3485E transmit and receive at guaranteed data
rate at least to 12Mbps.
All transmitter outputs and receiver inputs are
protected to 15kV using Human Body Model.
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 ST3485E input has a true fail-safe feature
that guarantees a logic high output if both inputs
are open circuit, shorted together or in presence of
the termination with no signal on the bus.
ORDERING CODES
Type
Temperature
Range
Package
Comments
ST3485ECN
0 to 70 C
DIP-8
50parts per tube / 40tube per box
ST3485EBN
-40 to 85 C
DIP-8
50parts per tube / 40tube per box
ST3485ECD
0 to 70 C
SO-8 (Tube)
100parts per tube / 20tube per box
ST3485EBD
-40 to 85 C
SO-8 (Tube)
100parts per tube / 20tube per box
ST3485ECDR
0 to 70 C
SO-8 (Tape & Reel)
2500 parts per reel
ST3485EBDR
-40 to 85 C
SO-8 (Tape & Reel)
2500 parts per reel
ST3485E
3.3V POWERED, 15KV ESD PROTECTED, TRASMIT AT
UP TO 12MBPS TRUE RS-485/RS-422 TRANSCEIVER
DIP
SOP
ST3485E
2/16
PIN CONFIGURATION
PIN DESCRIPTION
TRUTH TABLE (DRIVER)
X= Don't Care; Z=High Impedance
TRUTH TABLE (RECEIVER)
X= Don't Care; Z=High Impedance
PlN 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
2
RE
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.
3
DE
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.
4
DI
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
5
GND
Ground
6
A
Non-inverting Receiver Input and Non-inverting Driver Output
7
B
Inverting Receiver Input and Inverting Driver Output
8
V
CC
Supply Voltage: V
CC
= 3V to 3.6V
INPUTS
OUTPUTS
MODE
RE
DE
DI
B
A
X
H
H
L
H
Normal
X
H
L
H
L
Normal
L
L
X
Z
Z
Normal
H
L
X
Z
Z
Shutdown
INPUTS
OUTPUT
MODE
RE DE
A-B
RO
L
L
-0.015V
H
Normal
L
L
-0.2V
L
Normal
L
L
Inputs Open
H
Normal
L
L
Inputs Shorted
H
Normal
H
L
X
Z
Shutdown
ST3485E
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ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
ESD PERFORMANCE: TRANSMITTER OUTPUTS, RECEIVER INPUTS
ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 3.6V, T
A
= -40 to 85C, unless otherwise specified. Typical values are referred to T
A
= 25C)
LOGIC INPUT ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 3.6V, T
A
= -40 to 85C, unless otherwise specified. Typical values are referred to T
A
= 25C)
Symbol
Parameter
Value
Unit
V
CC
Supply Voltage
7
V
V
I
Control Input Voltage (RE, DE)
-0.3 to 7
V
V
DI
Driver Input Voltage (DI)
-0.3 to 7
V
V
DO
Driver Output Voltage (A, B)
-7.5 to 12.5
V
V
RI
Receiver Input Voltage (A, B)
-7.5 to 12.5
V
V
RO
Receiver Output Voltage (RO)
-0.3 to (V
CC
+ 0.3)
V
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 Disharge
8
KV
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
I
SUPPLY
V
CC
Power Supply Current
No Load, DI=0V or V
CC
DE=V
CC
,
RE=0V or V
CC
1.3
2.2
mA
DE=0V,
RE=0V
1.2
1.9
mA
I
SHDN
Shutdown Supply Current
DE=0V, RE=V
CC
, DI=0V or V
CC
0.002
1
A
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
IL
Input Logic Threshold Low
DE, DI, RE
1.3
0.8
V
V
IH
Input Logic Threshold High
DE, DI, RE
2
V
I
IN1
Logic Input Current
DE, DI, RE
2.0
A
I
IN2
Input Current (A, B)
DE=0V, V
CC
= 0 or 3.6V
V
IN
=12V
1
mA
V
IN
=-7V
-0.8
mA
ST3485E
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TRANSMITTER ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 3.6V, T
A
= -40 to 85C, unless otherwise specified. Typical values are referred to T
a
= 25C)
RECEIVER ELECTRICAL CHARACTERISTICS
V
CC
= 3V to 3.6V, T
A
= -40 to 85C, unless otherwise specified. Typical values are referred to T
a
= 25C)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
OD
Differential Drive Output
R
L
= 100
(RS-422) (Figure 1)
2
V
R
L
= 54
(RS-485) (Figure 1)
1.5
V
R
L
= 60
(RS-485) (Figure 2)
1.5
V
V
OD
Change in magnitude of
Driver Differential Output
Voltage for Complementary
Output States (Note1)
R
L
= 54
or 100
(Figure 1)
0.2
V
V
OC
Driver Common Mode
Output Voltage
R
L
= 54
or 100
(Figure 1)
3
V
V
OC
Change in magnitude of
Driver Common Mode
Output Voltage (Note1)
R
L
= 54
or 100
(Figure 1)
0.2
V
I
OSD
Driver Short Circuit Output
Current
250
mA
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
TH
Receiver Differential
Threshold Voltage
V
CM
= -7V to 12V, DE = 0
-0.2
-0.015
V
V
TH
Receiver Input Hysteresis
V
CM
= 0V
30
V
V
OH
Receiver Output High
Voltage
I
OUT
= -4mA, V
ID
= 200mV, (Figures 8,9)
2
V
V
OL
Receiver Output Low
Voltage
I
OUT
= 4mA, V
ID
= -200mV, (Figure 3)
0.4
V
I
OZR
3-State (High Impedance)
Output Current at Receiver
V
CC
= 3.6V
V
O
= 0V to V
CC
1
A
R
RIN
Receiver Input Resistance
V
CM
= -7V to 12V
24
K
I
OSR
Receiver Short-Circuit
Current
V
RO
= 0V to V
CC
7
60
mA
ST3485E
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DRIVER SWITCHING CHARACTERISTICS
V
CC
= 3V to 3.6V, T
A
= -40 to 85C, unless otherwise specified. Typical values are referred to T
a
= 25C)
RECEIVER SWITCHING CHARACTERISTICS
V
CC
= 3V to 3.6V, T
A
= -40 to 85C, unless otherwise specified. Typical values are referred to T
a
= 25C)
Note 1:
V
OD
and
V
OC
are the changes in V
OD
and V
OC
, respectively, when the DI input changes state.
Note 2: measured on |t
PLH
(A)-t
PHL
(A)| and |t
PLH
(B)-t
PHL
(B)|
Note 3: The transceivers are put into shutdown by bring RE high and DE low. If the input are in state for less than 80ns, the part are guaren-
teed not to enter shutdown. If the inputs are in this state for at least 300ns, the parts are guarenteed to have entered shutdown.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
D
R
Maximum Data Rate
12
15
Mbps
t
DD
Differential Output Delay
R
L
= 60
C
L
= 15pF, (Figures 4,5)
18
30
ns
t
TD
Differential Output
Transition Time
R
L
= 60
C
L
= 15pF, (Figures 4,5)
12
20
ns
t
PLH
t
PHL
Propagation Delay
R
L
= 27
C
L
= 15pF, (Figures 8,9)
18
30
ns
t
PDS
|t
PLH -
t
PHL
| Propagation
Delay Skew (Note2)
R
L
= 27
C
L
= 15pF, (Figures 8,9)
2
5
ns
t
PZL
Output Enable Time
R
L
= 110
(Figures 10,11)
19
35
ns
t
PZH
Output Enable Time
R
L
= 110
(Figures 6,7)
30
50
ns
t
PHZ
Output Disable Time
R
L
= 110
(Figures 6,7)
19
35
ns
t
PLZ
Output Disable Time
R
L
= 110
(Figures 10,11)
30
50
ns
t
SKEW
Differential Output Delay
Skew
1
3
ns
t
ZH(SHDN)
Driver Enable from
Shutdown to Output High
30
50
ns
t
ZL(SHDN)
Driver Enable from
Shutdown to Output Low
19
35
ns
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
t
PLH
t
PHL
Propagation Delay
V
ID
=0V to 3V C
L1
= 15pF, (Figures 12,13)
30
50
ns
t
RPDS
|t
PLH -
t
PHL
| Propagation
Delay Skew
V
ID
=0V to 3V C
L1
= 15pF, (Figures 12,13)
1
3
ns
t
PZL
Output Enable Time
C
RL
= 15pF
(Figures 14-18)
10
20
ns
t
PZH
Output Enable Time
C
RL
= 15pF
(Figures 14-18)
10
20
ns
t
PHZ
Output Disable Time
C
RL
= 15pF
(Figures 14-18)
10
20
ns
t
PLZ
Output Disable Time
C
RL
= 15pF
(Figures 14-18)
10
20
ns
t
ZH(SHDN)
Receiver Enable from
Shutdown to Output High
C
RL
= 15pF
(Figures 14-18)
10
20
ns
t
ZL(SHDN)
Receiver Enable from
Shutdown to Output Low
C
RL
= 15pF
(Figures 14-18)
20
40
ns
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