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BL3085B
High ESD-Protected, Fail-Safe, Slew-Rate-Limited
RS-485 Transceivers
General Description
The BL3085B is a half-duplex RS-485 transceiver with ±18kV IEC 61000-4-2 contact discharge
protection. The BL3085B contains one driver and one receiver. The device features fail-safe circuitry,
which guarantees a logic-high receiver output when the receiver inputs are open or shorted. This means
that the receiver output will be logic high even if all transmitters on a terminated bus are disabled. The
BL3085B features reduced slew-rate driver that minimizes EMI and reduces reflections caused by
improperly terminated cables, allowing error-free data transmission up to 250kbps. The BL3085B has a
1/8 unit load receiver input impedance that allows up to 256 transceivers on the bus.
Configuration
Functional Block of BL3085B
Applications
RS-485 Communications
Level Translators
Transceivers for EMI-Sensitive Applications
Industrial Control Local Area Networks
Energy Meter Networks
Lighting Systems
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V1.2
BL3085B
Pin Function Description
Pin
Number
Name
1
RO
Receiver Output.
2
/RE
Receiver Output Enable. /RE is low to enable the Receiver; /RE is high
to disable the Receiver.
3
DE
Driver Output Enable: DE is high to enable the Driver; DE is low to
disable the Driver.
4
DI
Driver Input
5
GND
6
A
Non-inverting Receiver Input and Non-inverting Driver Output.
7
B
Inverting Receiver Input and Inverting Driver Output.
8
VCC
Function
Ground.
Power Supply.
Function Table
Receiving
Transmitting
Inputs
Inputs
Outputs
/RE
DE
DI
B
A
X
1
1
0
1
X
1
0
1
0
0
0
X
High-Z
High-Z
1
0
X
Page2
Shutdown
Outputs
/RE
DE
A-B
RO
0
X
≥-0.05V
1
0
X
≤-0.2V
0
0
X
Open/shorted
1
1
1
X
High-Z
1
0
X
Shutdown
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V1.2
BL3085B
Absolute Maximum Ratings
Parameter
Symbol
Rating
Units
VCC
+7
V
/RE, DE
-0.3 to VCC+0.3
V
DI
-0.3 to VCC+0.3
V
Transmitter Output Voltage
A, B
-8 to +13
V
Receiver Input Voltage
A, B
-8 to +13
V
Receiver Output Voltage
RO
-0.3 to VCC+0.3
V
-40 to +85
℃
Power Supply
Control Input Voltage
Transmitter Input Voltage
Operating Temperature
DC Electrical Characteristics
（VCC=+5V±5℅,TA=-40℃～+85℃，Typical Values are VCC=+5V and TA＝25℃）
（Note 1）
Parameter
Power Supply
Symbol
Conditions
Vcc
MIN
4.5
TYP
MAX
UNITS
5.5
V
Driver
Differential
Driver
Output(no load)
VOD1
Figure 1
Differential
Output
VOD2
Figure 1，R=27Ω
∆VOD
Figure 1，R=27Ω
0.2
V
VOC
Figure 1，R=27Ω
3
V
Change
in
Magnitude
of
Common-Mode
Voltage（Note 2）
∆VOC
Figure 1，R=27Ω
0.2
V
Input High Voltage
VIH1
DE,DI,/RE
Input Low Voltage
VIL1
DE,DI,/RE
Driver
Change in Magnitude
of
Differential
Output
Voltage
（Note 2）
Driver
Common-mode
Output Voltage
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5
1.5
V
V
2.0
V
0.8
V
V1.2
BL3085B
DI Input Hysteresis
VHYS
Input Current(A and
B)
Driver Short-Circuit
Output Current
IIN4
100
DE=GND
VCC=GND
5.25V
or
VIN=12V
125
VIN=-7V
-75
-7V≦VOUT≦VCC
IOSD
mV
µA
-100
0V≦VOUT≦12V
100
mA
Receiver
Receiver Differential
Threshold Voltage
Receiver
Hysteresis
VTH
-7V≦VCM≦12V
-200
Input
-125
-50
40
mV
mV
Receiver
Output
High Voltage
VOH
IO=-4mA,VID=-50mV
Receiver Output Low
Voltage
VOL
IO=4mA,VID=-200mV
0.4
V
Three-State Output
Current at Receiver
IOZR
0.4V≦VO≦2.4V
±1
µA
Receiver
Resistance
RIN
-7V≦VCM≦12V
96
IOSR
0V≦VRO≦VCC
±7
ICC
No load ,/RE=DI=
GND or VCC
Input
Receiver
Output
Short-Circuit Current
VCC-1.5
V
KΩ
±95
mA
Supply Current
Supply Current
Supply Current
Shutdown Mode
in
ISHDN
DE=VCC
150
600
DE=GND
185
600
µA
10
µA
DE=GND, /RE=VCC，DI=VCC
or GND
µA
Note 1：All currents into the device are positive. All currents out of the device are negative. All voltages are referred
to device ground unless otherwise noted.
Note 2：△VOD and △VOC are the changes in VOD and VOC, respectively, when the DI input changes state.
Switching Characteristics
（VCC=+5V±5℅,TA=-40℃～+85℃，Typical values are at VCC=+5V，TA＝25℃）
Parameter
Driver Input to Output
Page4
Symbol
T DPLH
T DPHL
Conditions
Figure 3 and 5，RDIFF=54Ω
CL1=CL2=100pF
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MIN
TYP
MAX
450
800
450
800
UNITS
ns
V1.2
BL3085B
Driver Output
|TDPLH – TDPHL|
Skew
Driver Rise or Fall Time
T DSKEW
Figure 3 and 5，RDIFF=54Ω
CL1=CL2=100pF
TDR, TDF
Figure 3 and 5，RDIFF=54Ω
CL1=CL2=100pF
150
100
ns
500
ns
Maximum Data Rate
F MAX
Driver Enable to Output
High
T DZH
Figure 4 and 6，CL=100pF S2
Closed
200
ns
Driver Enable to Output
Low
T DZL
Figure 4 and 6，CL=100pF S1
Closed
200
ns
Driver Disable
from Low
Time
T DLZ
Figure 4 and 6，CL=15pF S1
Closed
300
ns
Driver Disable
from High
Time
T DHZ
Figure 4 and 6，CL=15pF S2
Closed
300
ns
T RPLH
T RPHL
Figure 7 and 9，
; rise and fall
VID≦15ns
time
of
450
800
ns
T RSKD
Figure 7 and 9，
; rise and fall
VID≦15ns
time
of
30
T RZL
Figure 2 and 8，CL=100pF S1
Closed
20
50
ns
T RZH
Figure 2 and 8，CL=100pF S2
Closed
20
50
ns
Receiver Disable Time
from Low
T RLZ
Figure 2 and 8，CL=100pF S1
Closed
80
150
ns
Receiver Disable Time
from High
T RHZ
Figure 2 and 8，CL=100pF S2
Closed
80
150
ns
Time to Shutdown
T SHDN
50
300
ns
Receiver
Output
|TRPLH
–
Differential
Skew
Input
to
TRPHL|
Receiver
Receiver Enable
Output Low
to
Receiver Enable
Output High
to
250
kbps
ns
Driver Enable from
Shutdown to Output
High
T DZH(SHDN)
Figure 4 and 6，CL=15pF S2
Closed
200
ns
Driver Enable from
Shutdown to Output
Low
T DZL(SHDN)
Figure 4 and 6，CL=15pF S1
Closed
200
ns
Receiver Enable from
Shutdown to Output
High
T RZH(SHDN)
Figure 2 and 8，CL=100pF S2
Closed
300
ns
Receiver Enable from
Shutdown to Output
Low
T RZL(SHDN)
Figure 2 and 8，CL=100pF S1
Closed
300
ns
Page5
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V1.2
BL3085B
Test Circuits and Timing Diagrams
Figure 1：Driver DC Test Load
Figure 2：Receiver Enable/Disable Timing Test Load
Figure 3：Driver Timing Test Circuit
Figure 4：Driver Enable/Disable Timing test Load
Figure 5：Driver Propagation Delays
Page6
Figure 6：Driver Enable and Disable Times
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V1.2
BL3085B
Figure 7：Receiver Propagation Delays
Figure 8：Receiver Enable and Disable Times
Figure 9：Receiver Propagation Delay Test Circuit
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V1.2
BL3085B
Package Information SOP8L
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V1.2