HG3085E
General Description
Features
The HG3085E +5V, half-duplex, ±15kV ESDprotected
RS-485/RS-422-compatible
transceivers feature one driver and one receiver.
The HG3085E include a hot-swap capability to
eliminate false transitions on the bus during
power-up or live insertion.
TheHG3085E features reduced slew-rate drivers
that minimize EMI and reduce reflections caused
by improperly terminated cables, allowing errorfree transmission up to 500kbps.
The HG3085E feature a 1/8-unit load receiver
input impedance, allowing up to 256 transceivers
on the bus. These devices are intended for halfduplex communications. All driver outputs are
protected to ±15kV ESD using the Human Body
Model.
Applications
TheHG3085 is available in an 8-pin SO package.
The devices operate over the extended -40°C to
+85°C temperature range.
+5V Operation
Hot-Swappable for Telecom Applications
Enhanced Slew-Rate Limiting Facilitates
ErrorFree Data Transmission
Extended ESD Protection for RS-485 I/O
Pins ±15kV Human Body Model
1/8Unit
Load , Allowing Up to
256Transceivers on the Bus
8 Pin-SOP/DIP Package
Isolated RS-485 Interfaces
Utility Meters
Industrial Controls
Industrial Motor Drives
Automated HVAC Systems
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
Supply Voltage VCC...............................................................+6V
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.
DE, RE, DI..............................................................-0.3V to +6
A, B........................................................................... -8V to +13V
Short-Circuit Duration (RO, A, B) to GND ..................Continuous
Continuous Power Dissipation (TA = +70°C)
8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering 10s) ..................................+300°C
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HG3085E
DC ELECTRICAL CHARACTERICS
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
Differential Driver Output (no load)
VOD1
Figure1
Differential Driver Output
VOD2
Figure1,R = 50Ω (RS422)
Figure1,R = 27Ω (RS485)
TYP
MAX
UNITS
5
V
DRIVER
2.0
V
1.5
Change in Magnitude of Differential
Output Voltage (Note 2)
∆VOD
Figure1,R =50Ωor R=
27Ω
0.2
V
Driver Common-Mode Output
Voltage
VOC
Figure1,R=50Ωor R =
27Ω
3
V
Change In Magnitude of
Common-Mode Voltage (Note 2)
∆VOC
Figure1,R=50Ωor R =
27Ω
0.2
V
Input High Voltage
VIH1
DE, DI, RE,
2.0
V
Input Low Voltage
VIL1
DE, DI, RE,
0.8
V
DI Input Hysteresis
VHYS
WS3085
100
mV
Input Current
IIN1
DE, DI, RE
±2
µA
Input Current (A and B)
IIN4
Driver Short-Circuit Output
Current (Note 3)
VOD1
DE = GND,
VCC=GND or 5.25V
VIN=12V
125
VIN = -7V
-75
-7V ≤ VOUT ≤ VCC
µA
mV
-250
RECEIVER
Receiver Differential Threshold
Voltage
VTH
Receiver Input Hysteresis
∆VTH
Receiver Output High Voltage
VOH
Receiver Output Low Voltage
-7V ≤ VCM ≤ +12V
-125 -50
mV
25
mV
IO = 4mA, VID = -200mV;
Vcc-1.5
V
VOL
IO = -4mA, VID = -50mV
0.4
V
Three-State Output Current at
Receiver
IOZR
0.4V ≤ VO ≤ 2.4V
±1
µA
Receiver Input Resistance
RIN
-7V ≤ VCM ≤ +12V
96
kΩ
Receiver Output Short-Circuit
Current
IOSR
0V ≤ VRO ≤ VCC
-200
±7
±95
mA
SUPPLY CURRENT
Supply Current
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ICC
No load,
RE =DI=GND or VCC
2
DE = VCC
530
900
DE =
GND
500
600
µA
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HG3085E
SWITCHING CHARACTERISTICS
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
Driver Input to Output
SYMBOL
tDPLH
tDPHL
CONDITIONS
Figures3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Driver Output Skew
| tDPLH - tDPHL |
tDSKEW
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Driver Rise or Fall Time
tDR, tDF
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Maximum Data Rate
fMAX
Driver Enable to Output High
tDZH
Driver Enable to Output Low
tDZL
Driver Disable Time from Low
tDLZ
Driver Disable Time from High
tDHZ
Receiver Input to Output
tRPLH,
tRPHL
| tRPLH - tRPHL | Differential
tRSKD
Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output
High
Receiver Disable Time from
Low
tRZL
tRZH
tRLZ
MIN TYP MAX
250 720 1000
250 720 1000
-3
200
±100
530
UNITS
ns
ns
750
ns
500
kbps
Figures4 and 6, CL =
100pF, S2 closed
2500
ns
Figures4 and 6,CL=
100pF, S1 closed
2500
ns
100
ns
100
ns
Figures 4 and 6, CL =
15pF, S1 closed
Figures 4 and 6, CL =
15pF, S2 closed
Figures 7 and 9; | VID | ≥
2.0V;rise and fall time of
VID ≤ 15ns
Figures 7 and 9; | VID | ≥
2.0V;rise and fall time of
VID ≤ 15ns
Figures 2 and 8, CL =
100pF, S1 closed
Figures 2 and 8, CL =
100pF, S2 closed
Figures 2 and 8 , CL =
100pF, S1 closed
Figures 2 and 8, CL =
100pF, S2 closed
127
200
ns
3
±30
ns
20
50
ns
20
50
ns
20
50
ns
20
50
ns
Receiver Disable Time from
High
tRHZ
Time to Shutdown
Driver Enable from Shutdown
to
tSHDN
(Note 4)
tDZH(SHD
Figures 4 and 6, CL =
15pF, S2 closed
4500
ns
Figures 4 and 6, CL =
15pF, S1 closed
4500
ns
Figures 2 and 8, CL =
100pF, S2 closed
3500
ns
Figures 2 and 8, CL =
100pF, S1 closed
3500
ns
N)
Output High
Driver Enable from Shutdown
to
tDZL(SHDN
)
50
200
600
ns
Output Low
Receiver Enable from
Shutdown to Output High
tRZH(SHD
Receiver Enable from
Shutdown to Output Low
tRZL(SHDN
N)
)
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
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Pin Description
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
3
DE
4
DI
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.
DE is a hot-swap input (see the Hot-Swap Capability section for more details).
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, VCC = +5V ±5%. Bypass VCC to GND with a 0.1µF capacitor.
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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.
RE is a hot-swap input (see the Hot-Swap Capability section for more details).
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HG3085E
Function Table
TRANSMITTING
INPUTS
RE
X
X
0
1
OUTPUTS
DE
1
1
0
0
DI
1
0
X
X
B/Z
0
1
High-Z
A/Y
1
0
High-Z
Shutdown
RECEIVING
RE
0
0
0
1
1
INPUTS
DE
X
X
X
1
0
A-B
≥ -0.05V
≤ -0.2V
Open/shorted
X
X
OUTPUTS
RO
1
0
1
High-Z
Shutdown
Applications Information
256 Transceivers on the Bus
The standard RS-485 receiver input impedance is
12kΩ (one-unit load), and the standard driver can
drive up to 32 unit loads. The HG3085 E family
of transceivers have a 1/8-unit-load receiver
input impedance (96kΩ), allowing up to 256
transceivers to be connected in parallel on one
communication line. 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.
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 (see Typical
Operating Characteristics). The second, a thermal
shutdown circuit, forces the driver outputs into a
high-impedance state if the die temperature
becomes excessive.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by
bringing both RE high and DE low. In shutdown,
the devices typically draw only 2uA of supply
current.
RE and DE may be driven simultaneously; the
parts are guaranteed not to enter shutdown if RE
is high and DE is low for less than 50ns. If the
inputs are in this state for at least 600ns, the parts
are guaranteed to enter shutdown.
Reduced EMI and Reflections
HG3085E is slew-rate limited, minimizing EMI
and reducing reflections caused by improperly
terminated cables.
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HG3085E
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