BELLING BL3085E

BL3085E
General Description
TheBL3085E is a +/- 15kV electrostatic discharge (ESD) protected, high-speed transceiver for
RS-485 communication that contain 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 BL3085E features reduced slew-rate driver that minimizes EMI
and reduces reflections caused by improperly terminated cables, allowing error-free data
transmission up to 500kbps. All transmitter outputs and receiver inputs are protected to +/- 15kV
using the Human Body Model. The transceiver typically draws 500 micron ampere of supply
current when unloaded, or when fully loaded with the driver disabled. All devices have a
1/8-unit-load receiver input impedance that allows up to 256 transceivers on the bus. The BL3085E
is intended for half-duplex communications.
Applications

RS-485 Communications

Level Translators

Transceivers for EMI-Sensitive Applications

Industrial Control Local Area Networks

Energy Meter Networks

Power Inverters

Building Automation Networks

Telecommunications Equipment
I/O ESD
protection
Human Body Model: ±15kV
IEC 61000-4-2：
Contact discharge: ±15kV
Air discharge: ±20kV
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BL3085E
PIN Configuration
BL3085E
Pin figure
BL3085E logic figure
Ordering Information
PART
TEMP RANGE
PIN PACKAGE
BL3085E
-40℃～+85℃
SOP8
Pin Description
BL3085E PIN
NAME
FUNCTION
1
RO
Receiver Output. When RE is low and if A - B ≧-50mV, RO will be high; if A
- B ≦-200mV, RO will be low.
2
RE
Receiver Output Enable. Drive RE low to enable RO; RO is high impedance
when RE is high. Drive RE high and DE low to enter low-power
shutdown mode.
3
DE
Driver Output Enable. Drive DE high to enable driver outputs. These outputs
are high impedance when DE is low. Drive RE high and DE low to
enter low-power shutdown mode.
4
DI
Driver Input. With DE high, a low on DI forces non-inverting output low and
inverting output high. Similarly, a high on DI forces non-inverting output
high and inverting output 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
VCC
Positive Supply 4.75V ≦VCC ≦5.25V
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BL3085E
ABSOLUTE MAXIMUM RATINGS
PARAMETER
SYMBOL
NUM
UNITS
Supply Voltage (VCC)
VCC
+7
V
/RE, DE
-0.3~VCC+0.3
V
Driver Input Voltage (DI)
DI
-0.3~VCC+0.3
V
Driver Output Voltage (A, B)
A, B
±13
V
Receiver Input Voltage (A, B)
A, B
±13
V
Receiver Output Voltage (RO)
RO
-0.3~VCC+0.3
V
Continuous Power Dissipation
Pd
471
Operating Temperature Ranges
BL3085E
-40～+85
℃
Storage Temperature Range
-65～+150
℃
Lead Temperature (soldering, 10s)
300
℃
Control Input Voltage (RE, DE)
mW
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the
specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +5V ± 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Note
1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
SYMBOL
UNITS
DRIVER
Differential Driver
VOD1
Figure 1
5
V
Output (No Load)
Differential Driver
VOD2
Figure 1, R = 27
1.5
V
Output
Change-in-Magnitude
of Differential Output
0.2
V
Figure 1, R = 27
VOD
Voltage (Note 2)
Driver Common Mode
Figure 1, R = 27
VOC
3
V
Output Voltage
Change-in-Magnitude
of Common-Mode
VOC
0.2
V
Figure 1, R = 27
Voltage (Note 2)
of
Input High Voltage
DE, DI, RE
VIH1
2.0
V
Input Low Voltage
VIL1
DE, DI, RE
0.8
V
DI Input Hysteresis
VHYS
BL3085E
100
mV
DE =
GND,
VIN = 12V
125
VCC =
Input Current (A and B)
µA
IIN1
GND
Or
VIN = -7V
-75
5.25V
-7V ≦VOUT ≦VCC
-250
Driver Short-Circuit
Output Current
(Note 3)
Receiver
Differential
Threshold Voltage
Receiver Input
Hysteresis
Receiver Output
High Voltage
Receiver Output
Low Voltage
Three-State Output
Current at Receiver
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IOSD
VTH
VTH
Input
Output
VOH
Output
VOL
IOZR
0V ≦VOUT ≦12V
0V ≦VOUT≦VCC
RECEIVER
±25
-7V ≦VCM ≦12V
-200
-120
250
mA
-50
mV
30
IO = -4mA, VID = -50mV
mV
VCC-1.5
V
IO = 4mA, VID = -200mV
0.4
V
0.4V ≦VO≦2.4V
±1
µA
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BL3085E
Receiver
Input
Resistance
Receiver Output
Short
Circuit
Current
Input
RIN
-7V≦VCM ≦12V
IOSR
0V ≦VRO ≦VCC
kΩ
96
±7
±95
mA
900
µA
180
600
µA
DE = GND, VRE = VCC
0.001
10
µA
Human Body Model
±15
SUPPLY CURRENT
No load,
DE = VCC
RE = DI=
ICC
GND or
DE = GND
VCC
Supply Current
Supply Current in
Shutdown Mode
ESD Protection for A,
B
ISHDN
110
kV
SWITCHING CHARACTERISTICS—BL3085E
(VCC = +5V ± 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
Driver Input to
Output
t DPLH
CONDITIONS
MIN
TYP
MAX
UNITS
250
720
900
250
720
900
-3
±100
ns
530
750
ns
500
Kbps
t DPHL
Figure 3, RDIFF =54,
CL1 = CL2 =100pF
Driver Output Skew
| t DPLH – t DPHL |
t DSKEW
Figure 3, RDIFF =54
CL1 = CL2 =100pF
Driver Rise or Fall
Time
t DR, t DF
Figure 3, RDIFF =54
,CL1 = CL2 =100pF
Maximum Data Rate
f MAX
Driver Enable to
Output High
t DZH
Figure 4, CL =100pF,
S2 closed
2500
ns
Driver Enable to
Output Low
t DZL
Figure 4, CL =100pF,
S1 closed
2500
ns
Driver Disable Time
from Low
t DLZ
Figure 4, CL = 15pF,
S1 closed
100
ns
Driver Disable Time
from High
t DHZ
Figure 4, CL = 15pF,
S2 closed
100
ns
Receiver Input to
Output
t RPLH,
t RPHL
Figure 5, | VID |≧2.0V
rise and fall time of
VID≦15ns
127
200
ns
t RSKD
Figure 5, | VID |≧2.0V
rise and fall time of
VID≦15ns
3
±30
ns
Receiver Enable to
Output Low
t RZL
Figure 2, CL =100pF,
S1 closed
20
50
ns
Receiver Enable to
Output High
t RHZ
20
50
ns
Receiver Disable
Time from Low
t RLZ
20
50
ns
Receiver Disable
Time from High
t RHZ
20
50
ns
200
600
ns
4500
ns
| t RPLH – t RPHL|
Differential Receiver
Skew
200
Figure 2, CL =100pF,
S2 closed
Figure 2, CL =100pF,
S1 closed
Figure 2, CL =100pF,
S2 closed
ns
Time to Shutdown
t SHDN
Driver Enable from
Shutdown-to-Output
High
t DZH(SHDN)
Driver Enable from
Shutdown-to-Output
Low
t DZL(SHDN)
Figure 4, CL = 15pF,
S1 closed
4500
ns
Receiver Enable
t RZH(SHDN)
Figure 2, CL =100pF,
3500
ns
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(Note 4)
Figure 4, CL = 15pF,
S2 closed
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50
V1.0
BL3085E
from
Shutdown-to-Output
High
Receiver Enable
from
Shutdown-to-Output
Low
S2 closed
t RZL(SHDN)
Figure 2, CL =100pF,
3500
ns
S1 closed
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: ΔVOD and ΔVOC are the changes in VOD and VOC, respectively, when the DI input changes state.
Note 3: Maximum current level applies to peak current just prior to fold-back current limiting; minimum current level applies during
current limiting.
Note 4: The device is put into shutdown by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the
device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the device is guaranteed to
have entered shutdown.
Note 1:
Typical Operating Characteristics
Function Tables
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V1.0
BL3085E
TRANSMITTING
INPUTS
DE
1
1
0
0
RE
X
X
0
1
OUTPUTS
DI
1
0
X
X
RECEIVING
B
0
1
High-Z
A
1
0
High-Z
Shutdown
OUTPUTS
RO
1
0
1
High-Z
Shutdown
INPUTS
RE
0
0
0
1
1
A-B
≧-0.05V
≦-0.2V
Open/shorted
X
X
DE
X
X
X
1
0
X = Don’t care
Shutdown mode, driver and receiver outputs high impedance
Test Circuits
Figure1.
Driver DC Test Load
Figure3.
Driver Timing Test Load
Figure 2.
Figure 4.
Figure5. Receiver Propagation Delay Test Load
Receiver Enable/Disable Timing Test Load
Driver Enable/Disable Timing Test Load
Figure 6. Human Body ESD Test Model
Detailed Description
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V1.0
BL3085E
The BL3085E high - speed transceiver for RS-485 communication contains one driver and one
receiver.
These devices feature fail-safe circuitry, which guarantees a logic-high receiver output
when the receiver inputs are open or shorted, or when they are connected to a terminated
transmission line with all drivers disabled (see the Fail-Safe section).
The BL3085E feature
reduced slew-rate driver that minimizes EMI and reduces reflections caused by improperly
terminated cables, allowing error-free data transmission up to 500kbps (see the Reduced EMI and
Reflections section).
The BL3085E is a half-duplex transceiver. The voltage operates from a
single +5V supply. Drivers are output short-circuit current limited. Thermal shutdown circuitry
protects drivers against excessive power dissipation. When activated, the thermal shutdown
circuitry places the driver outputs into a high impedance state.
Receiver Input Filtering
The receiver of the BL3085E, when operating in 500kbps, incorporates input filtering in addition to
input hysteresis. This filtering enhances noise immunity with differential signals that have very
slow rise and fall times. Receiver propagation delay increases by 25% due to this filtering.
Fail-Safe
The BL3085E guarantees a logic-high receiver output when the receiver inputs are shorted or open,
or when they are connected to a terminated transmission line with all drivers disabled. This is done
by setting the receiver threshold between -50mV and -200mV. If the input voltage of differential
receiver (A-B) is greater than or equal to -50mV, RO is logic high. If A-B is less than or equal to
-200mV, RO is logic low. In the case of a terminated bus with all transmitters disabled, the receiver
differential input voltage is pulled to 0V by the termination. With the receiver threshold of the
BL3085E, this results in a logic high with a 50mV minimum noise margin. Unlike previous
fail-safe devices, the -50mV to -200mV threshold complies with the +/-200mV EIA/TIA-485
standard.
ESD Protection
As with BL3085E, ESD-protection structures are incorporated on all pins to protect against
electrostatic discharges encountered during handling and assembly. The driver output and receiver
input of theBL3085Ehave extra protection against static electricity. The ESD-protected pins are
tested with reference to the ground pin in a powered-down condition. They are tested to +/- 15kV
using the Human Body Model.
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V1.0
BL3085E
Power Usage In An RS-485 Transceiver
Power consumption is a concern in many applications.
Power supply current is delivered to the
bus load as well as to the transceiver circuitry. For a typical RS-485 bus configuration, the load that
an active driver must drive consists of all of the receiving nodes, plus the termination resistors at
each end of the bus. The load presented by the receiving nodes depends on the input impedance of
the receiver. The TIA/EIA-485-A standard defines a unit load as allowing up to 1 mA. With up to
32 unit loads allowed on the bus, the total current supplied to all receivers can be as high as 32 mA.
The BL3085E is rated as a 1/8 unit load device. the bus input current is less than 1/8 mA, allowing
up to 256 nodes on a single bus. Any combination of these devices and/or other RS-485 transceivers
with a total of 32 unit loads or less can be connected to the line. The current in the termination
resistors depends on the differential bus voltage. The standard requires active drivers to produce at
least 1.5 V of differential signal. For a bus terminated with one standard 145 ohm resistor at each
end, this sums to 25 mA differential output current whenever the bus is active.
BL3085E can drive more than 25 mA to a 60 ohm load,
Typically the
resulting in a differential output voltage
higher than the minimum required by the standard. Overall, the total load current can be 60 mA to a
loaded RS-485 bus. There is additional current required by the transceiver itself; the BL3085E
circuitry requires only about
0.3 mA with both driver and receiver enabled,
and below 0.3 mA
with either the driver enabled or with the receiver enabled. In low-power shutdown mode,
the driver nor receiver is active. And the supply current is very low.
neither
Supply current increases with
signaling rate primarily due to the totem pole outputs of the driver. When these outputs change
state, there is a moment when both the high-side and low-side output transistors are conducting and
this creates a short spike in the supply current. As the frequency of state changes increases, more
power is used.
Low-Power Shutdown Mode
When both the driver and receiver are disabled (DE low and RE high) the device is in shutdown
mode. If the enable inputs are in this state for less than 60 ns, the device does not enter shutdown
mode. This guards against inadvertently entering shutdown mode during driver/receiver enabling.
Only when the enable inputs are held in this state for 300 ns or more, the device is assured to be in
shutdown mode.
In this low-power shutdown mode, most internal circuitry is powered down
except over temperature protection circuit, and the supply current is typically 40 micron ampere.
When either the driver or the receiver is re-enabled, the internal circuitry becomes active. If only the
driver is re-enabled (DE changed to high) the driver outputs are driven according to the DI input
after the enable times given by tPZH(SHDN) and
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tPZL (SHDN) in the driver switching
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BL3085E
characteristics.
high and B low,
If the DI input is open when the driver is enabled, the driver outputs defaults to A
in accordance with the driver failsafe feature.
If only the receiver is re-enabled
(RE changed to low) the receiver output is driven according to the state of the bus inputs (A and B)
after the enable time given by tPZH(SHDN) and tPZL(SHDN) in the receiver switching characteristics.
If there is no valid state on the bus the receiver responds as described in the failsafe operation
section. If both the receiver and driver are re-enabled simultaneously, the receiver output is driven
according to the state of the bus inputs (A and B) and the driver output is driven according to the DI
input. Note that the state of the active driver affects the inputs to the receiver. Therefore, the
receiver outputs are valid as soon as the driver outputs are valid.
Driver Output Protection
Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus
contention. The first, a fold back current limit on the output stage, provides immediate protection
against short circuits over the whole common-mode voltage range. The second, a thermal shutdown
circuit, forces the driver outputs into a high-impedance state if the die temperature becomes
excessive.
Layout
Consideration
A ground plane is recommended when using a high frequency device like the BL3085E. A 0.1uF
ceramic bypass capacitor less than 1/4 inch away from the VDD pin is recommended. Good
bypassing is especially needed when operating at maximum frequency or when package to package
matching is very important. The PC board traces connected to the A and B outputs must be kept as
symmetrical and short as possible to obtain the same parasitic board capacitance. This maintains the
good matching characteristics of the low-to-high and high to low transitions of the BL3085E. Note
that output A to output B capacitance should also be minimized. If routed adjacent to each other on
the same layer, they should be separated by an amount at least as wide as the trace widths. If output
A and output B are routed on different signal planes, they should not be routed directly on top of
each other. A trace width lateral separation is also recommended. As mentioned before, care
should also be taken when routing the DI input. To achieve consistent board-to board propagation
delay, the ringing on this signal should be kept below a few hundred millivolts.
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