1/12March 2002
■LOW QUIESCENT CURRENT: 300µA
■DESIGNED FOR RS-485 INTERFACE
APPLICATIONS
■-7V TO 12V COMMON MODE INPUT
VOLTAGE RANGE
■DRIVER MAINTAINS HIGH IMPEDANCE IN
3-STATE OR WITH THE POWER OFF
■70mV TYPICAL INPUT HYSTERESIS
■30ns PROPAGATION DELAYS, 5ns SKEW
■OPERATE FROM A SINGLE 5V SUPPLY
■CURRENT LIMITING AND THERMAL
SHUTDOWN FOR DRIVER OVERLOAD
PROTECTION
■ALLOWS UP TO 64 TRANSCEIVERS ON
THE BUS
DESCRIPTION
The ST485 is al low power transceiver for RS-485
and RS-422 communication. Each part contains
one driver and one receiver.
This transceiver draw 300µA (typ.) of supply
current when unloaded or fully loaded with
disabled drivers.
It operates from a single 5V supply.
Driver is short-circuit current limited and is
protected against excessive power dissipation by
thermal shutdown circuitry that placed the driver
outputs into a high-impedance state. .
The ST485 is designed for bi-directional data
communications on multipoint bus transmission
line (half-duplex applciations).
ORDERING CODES
Type Temperature
Range Package Comments
ST485CN 0 to 70 °C DIP-8 50parts per tube / 40tube per box
ST485BN -40 to 85 °C DIP-8 50parts per tube / 40tube per box
ST485AN -55 to 125 °C DIP-8 50parts per tube / 40tube per box
ST485CD 0 to 70 °C SO-8 (Tube) 100parts per tube / 20tube per box
ST485BN -40 to 85 °C DIP-8 50parts per tube / 40tube per box
ST485AD -55 to 125 °C SO-8 (Tube) 100parts per tube / 20tube per box
ST485CDR 0 to 70 °C SO-8 (Tape & Reel) 2500 parts per reel
ST485BDR -40 to 85 °C SO-8 (Tape & Reel) 2500 parts per reel
ST485ADR -55 to 125 °C SO-8 (Tape & Reel) 2500 parts per reel
ST485
LOW POWER
RS-485/RS-422 TRANSCEIVER
DIP SOP
ST485
2/12
PIN CONFIGURATION
PIN DESCRIPTION
TRUTH TABLE (DRIVER)
X= Don’t Care; Z=High Impedance
TRUTH TABLE (RECEIVER)
X= Don’t Care; Z=High Impedance
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.
PlN N°SYMBOL NAME AND FUNCTION
1 RO Receiver Output
2 RE Receiver 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
8VCC Supply Voltage
INPUTS OUTPUTS
RE DE DI B A
XHHLH
XHLHL
XLXZZ
INPUTS OUTPUT
RE DE A-B RO
LL≥ +0.2V H
LL≤ -0.2V L
L L INPUTS OPEN H
HL X Z
Symbol Parameter Value Unit
VCC Supply Voltage 12 V
VIControl Input Voltage (RE, DE) -0.5 to (VCC + 0.5) V
VDI Driver Input Voltage (DI) -0.5 to (VCC + 0.5) V
VDO Driver Output Voltage (A, B) ± 14 V
VRI Receiver Input Voltage (A, B) ± 14 V
VRO Receiver Output Voltage (RO) -0.5 to (VCC + 0.5) V
ST485
3/12
DC ELECTRICAL CHARACTERISTICS
(VCC =5V± 5%, TA=TMIN to TMAX , unlessotherwise specified. Typicalvalues arereferredto TA=25°C)
(See Note 1)
Note 1: All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device ground
unless specified.
Note 2: Supply current specification is valid for loaded transmitters when VDE =0V
Note 3: Applies to peak current. See typical Operating Characteristics.
Symbol Parameter Test Conditions Min. Typ. Max. Unit
VOD1 Differential Driver Output
(No Load) 5V
V
OD2 Differential Driver Output
(With Load) RL=27
Ω
(RS-485) (See Fig. 1)
RL=50
Ω
(RS-422) (See Fig. 1) 1.4 5
5V
V
∆VOD Change in Magnitude of
Driver Differential Output
Voltage for Complementary
Output States
RL=27
Ω
or 50
Ω
(See Fig. 1) 0.2 V
VOC Driver Common-Mode
Output Voltage RL=27
Ω
or 50
Ω
(See Fig. 1) 3 V
∆VOC Change in Magnitude of
Driver Common-Mode
Output Voltage for
Complementary Output
States
RL=27
Ω
or 50
Ω
(See Fig. 1) 0.2 V
VIH Input High Voltage RE, DE, DI 2.0 V
VIL Input Low Voltage RE, DE, DI 0.8 V
IIN1 Input Current RE, DE, DI ± 2µA
IIN2 Input Current (A, B) VCM = 0V or 5.25V VDE =0V
V
IN = 12V
VIN = -7V 1
-0.8 mA
mA
VTH Receiver Differential
Threshold Voltage VCM = -7 to 12V -0.2 0.2 V
∆VTH Receiver Input Hysteresis VCM =0V 70 mV
V
OH Receiver Output High
Voltage IO= -4mA VID = 200mV 3.4 V
VOL Receiver Output Low
Voltage IO=4mA V
ID = -200mV 0.5 V
IOZR 3-State (High Impedance)
Output Current at Receiver VO= 0.4 to 2.4V ± 1µA
RIN Receiver Input Resistance VCM = -7 to 12V 24 KΩ
ICC No Load Supply Current
(Note 2) VRE =0VorV
CC
VDE =V
CC
VDE =0V 400
300 900
500 µA
µA
IOSD1 Driver Short-Circuit Current,
VO=High VO= -7 to 12V (Note 3) 35 250 mA
IOSD2 Driver Short-Circuit Current,
VO=Low VO= -7 to 12V (Note 3) 35 250 mA
IOSR Receiver Short-Circuit
Current VO=0VtoV
CC 795mA
ST485
4/12
DRIVER SWITCHING CHARACTERISTICS
(VCC =5V± 5%, TA=TMIN to TMAX ,unless otherwise specified.Typical valuesare referredto TA=25°C)
(See Note 1)
Note 1: All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device ground
unless specified.
RECEIVER SWITCHING CHARACTERISTICS
(VCC =5V± 5%, TA=TMIN to TMAX , unlessotherwise specified. Typicalvalues arereferred to TA=25°C)
(See Note 1)
Note 1: All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device ground
unless specified.
Symbol Parameter Test Conditions Min. Typ. Max. Unit
tPLH
tPHL
Propagation Delay Input to
Output RDIFF =54ΩC
L1 =C
L2 = 100pF
(See Fig. 3 and 5)
10 30 70 ns
tSK Output Skew to Output RDIFF =54ΩC
L1 =C
L2 = 100pF
(See Fig. 3 and 5)
510ns
t
TLH
tTHL
Rise or Fall Time RDIFF =54ΩC
L1 =C
L2 = 100pF
(See Fig. 3 and 5)
31545ns
t
PZH Output Enable Time CL= 100pF S2 = Closed
(See Fig. 4 and 6) 70 90 ns
tPZL Output Enable Time CL= 100pF S1 = Closed
(See Fig. 4 and 6) 70 90 ns
tPLZ Output Disable Time CL= 15pF S1 = Closed
(See Fig. 4 and 6) 70 90 ns
tPHZ Output Disable Time CL= 15pF S2 = Closed
(See Fig. 4 and 6) 70 90 ns
Symbol Parameter Test Conditions Min. Typ. Max. Unit
tPLH
tPHL
Propagation Delay Input to
Output RDIFF =54ΩC
L1 =C
L2 = 100pF
(See Fig. 3 and 7) 20 130 230 ns
tSKD Differential Receiver Skew RDIFF =54ΩC
L1 =C
L2 = 100pF
(See Fig. 3 and 7) 13 ns
tPZH Output Enable Time CRL = 15pF S1 = Closed
(See Fig. 2 and 8) 20 55 ns
tPZL Output Enable Time CRL = 15pF S2 = Closed
(See Fig. 2 and 8) 20 55 ns
tPLZ Output Disable Time CRL = 15pF S1 = Closed
(See Fig. 2 and 8) 20 55 ns
tPHZ Output Disable Time CRL = 15pF S2 = Closed
(See Fig. 2 and 8) 20 55 ns
fMAX Maximum Data Rate 2.5 Mbps
ST485
5/12
TEST CIRCUITS AND TYPICAL CHARACTERISTICS
Figure 1 : Driver DC Test Load
Figure 2 : Receiver Timing Test Load
Figure 3 : Drive/Receiver Timing Test Circuit
Figure 4 : Driver Timing Test Load
ST485
6/12
Figure 5 : Driver Propagation Delay
Figure 6 : Driver Enable and Disable Time
ST485
7/12
Figure 7 : Receiver Propagation Delay
Figure 8 : Receiver Enable and Disable Time
ST485
8/12
Figure 9 : Receiver Output Current vs Output
Low Voltage
Figure 10 : Receiver Output Current vs Output
High Voltage
Figure 11 : Driver Output Current vs Output Low
Voltage
Figure 12 : Driver Output Current vs Output High
Voltage
Figure 13 : Supply Current vs Temperature
Figure 14 : Receiver High Level Output Voltage
vs Temperature
ST485
9/12
Figure 15 : Receiver Low Level Output Voltage
vs Temperature Figure 16 : Differential Driver Output Voltage vs
Temperature
ST485
10/12
DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 3.3 0.130
a1 0.7 0.028
B 1.39 1.65 0.055 0.065
B1 0.91 1.04 0.036 0.041
b 0.5 0.020
b1 0.38 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
I 4.8 0.189
L 3.3 0.130
Z 0.44 1.6 0.017 0.063
Plastic DIP-8 MECHANICAL DATA
P001F
ST485
11/12
DIM. mm. inch
MIN. TYP MAX. MIN. TYP. MAX.
A 1.75 0.068
a1 0.1 0.25 0.003 0.009
a2 1.65 0.064
a3 0.65 0.85 0.025 0.033
b 0.35 0.48 0.013 0.018
b1 0.19 0.25 0.007 0.010
C 0.25 0.5 0.010 0.019
c1 45°(typ.)
D 4.8 5.0 0.189 0.196
E 5.8 6.2 0.228 0.244
e 1.27 0.050
e3 3.81 0.150
F 3.8 4.0 0.149 0.157
L 0.4 1.27 0.015 0.050
M 0.6 0.023
S8°(max.)
SO-8 MECHANICAL DATA
0016023
ST485
12/12
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