The MAX14781E +5V, half-duplex ±25kV ESD-protected
RS-485 transceiver features integrated automatic polar-
ity correction to ensure that miswired A and B lines are
autonomously corrected, simplifying equipment and net-
work installation.
The MAX14781E includes slew-rate limited drivers that
minimize EMI, allowing for error-free data transmission
up to 370kbps.
This device includes fail-safe circuitry, guaranteeing a
logic-high receiver output when the receiver inputs are
shorted or open. Hot-swap functionality on the receiver
and driver enable inputs also eliminates false transitions
on the bus during power-up or live insertion.
The MAX14781E features a 1/8-unit load receiver input
impedance, allowing up to 256 transceivers on the bus. All
driver outputs are protected up to ±25kV ESD using the
Human Body Model. The MAX14781E is available in an
8-pin SO package and operates over the extended -40°C
to +85°C temperature range.
Benefits and Features
• High ESD Protection
●
Automatic Polarity Correction
●
Integrated Protection Increases Robustness
±25kV HBM ESD
±15kV IEC 61000-4-2 Air Gap Discharge ESD
±9kV IEC 61000-4-2 Contact Discharge ESD
• True Fail-Safe Receiver
• Hot-Swap Functionality
●
+5V Operation
●
Low 10µA (max) Shutdown Current
●
Extended -40°C to +85°C Operating Temperature
Ordering Information
appears at end of data sheet.
Applications
For related parts and recommended products to use with this part, refer
to
www.maximintegrated.com/MAX14781E.related.
●
Power Meter Networks
●
HVAC Networks
●
Control Systems
Functional Diagram
RO
RE
DE
DI
MAX14781E
R
POLARITY
CORRECT
A
D
B
19-6859; Rev 0; 12/13
MAX14781E
Half-Duplex RS-485 Transceiver
with Polarity Correction
Absolute Maximum Ratings
(All voltages referenced to GND)
V
CC
.......................................................................-0.3V to +6.0V
RE,
RO ..................................................... -0.3V to (V
CC
+ 0.3V)
DE, DI ..................................................................-0.3V to +6.0V
A, B........................................................................-8.0V to +13V
Short-Circuit Duration (RO, A, B) to GND .................Continuous
Continuous Power Dissipation (T
A
= +70°C)
8-Pin SO (derate at 7.6mW/°C above +70°C) ..............606mW
Operating Temperature Range ............................-40ºC to +85ºC
Junction Temperature ...................................................... +150ºC
Storage Temperature Range .............................-65ºC to +150°C
Lead Temperature (soldering 10 sec) ............................. +300°C
Soldering Temperature (reflow) .......................................+260°C
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.
Junction-to-Ambient Thermal Resistance (θ
JA
) ............132°C/W
Package Thermal Characteristics
(Note 1)
Junction-to-Case Thermal Resistance (θ
JC
) ...................38°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to
www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
PARAMETER
DRIVER
Supply Voltage
Differential Driver Output
Change in Magnitude of
Differential Output Voltage
Driver Common-Mode Output
Voltage
Change in Magnitude of
Common-Mode Otput Voltage
Input Voltage High
Input Voltage Low
Input Current
Input Impedance Until First
Transition at Power-Up (DE,
RE)
Input Impedance Until First
Transition After POR Delay (DE,
RE)
Driver Short-Circuit Output
Current
(V
CC
= 5V ±10%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
= 5V and T
A
= +25°C.)(Notes 2, 3)
SYMBOL
V
CC
R
L
= 100Ω, Figure 1
V
OD
ΔV
OD
V
OC
ΔV
OC
V
IH
V
IL
I
IN
R
FTPU
R
L
= 54Ω, Figure 1
No load, Figure 1
R
L
= 100Ω or 54Ω, Figure 1
R
L
= 100Ω or 54Ω, Figure 1 (Note 4)
R
L
= 54Ω, Figure 1 (Note 4)
DE, DI,
RE
DE, DI,
RE
DE,
RE
Until the first DE/RE
transition occurs,
Figure 9 (Note 7)
Until the first DE/RE
transition occurs,
Figure 9
Output low, 0V ≤
Driver is in short V
OUT ≤
12V
circuit (Note 5)
Output high, -7V ≤
V
OUT ≤
V
CC
-1
3.65
3.0
0.8
+1
8.8
V
CC
/2
CONDITIONS
MIN
4.5
3
2
TYP
MAX
5.5
V
CC
V
CC
V
CC
0.2
3
0.2
V
V
V
V
V
μA
kΩ
V
UNITS
V
R
FTPOR
7
60
kΩ
+40
-250
+250
mA
-40
I
OSD
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Maxim Integrated
│
2
MAX14781E
Half-Duplex RS-485 Transceiver
with Polarity Correction
Electrical Characteristics (continued)
PARAMETER
Driver Short-Circuit Foldback
Ouptut Current
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
Input Current (A and B)
RECEIVER
Receiver Differential Threshold
Voltages
Receiver Input Hysteresis
Receiver Output Voltage High
Receiver Output Voltage Low
Receiver Three-State Output
Current
Receiver Output Short Circuit
Current
POLARITY DETECTION
Maximum A-B Voltage
Difference for Inverted Polarity
Minimum A-B Voltage
Difference for Normal Polarity
Polarity Monitoring Interval
SUPPLY CURRENT
Supply Current
Shutdown Supply Current
PROTECTION
I
CC
I
SHDN
V
PI
V
PN
t
PM
V
TH1
V
TH2
ΔV
TH
V
OH
V
OL
I
OZR
I
OSR
SYMBOL
(V
CC
= 5V ± 10%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
= 5V and T
A
= +25°C.)(Notes 2, 3)
CONDITIONS
Output low, (V
CC
-1V) ≤
V
OUT ≤
12V
Driver is in short
circuit (Note 5)
Output high, -7V ≤
V
OUT ≤
+1V
Temperature rising
DE = low, V
CC
= V
IN
= 12V
0V or 5V
V
IN
= -7V
Normal/
noninverted mode
Inverted mode
MIN
20
mA
-20
+175
15
125
-100
°C
°C
μA
TYP
MAX
UNITS
I
OSDF
T
SHDN
T
HYST
I
A,B
-7V ≤
V
CM
≤
+12V
V
A
+ V
B
= 0V
-200
+50
V
CC
- 0.6
-125
+125
15
-50
+200
mV
mV
V
RE
= low, I
SOURCE
= -1mA
RE
= low, I
SINK
= 1mA
RE
= high, 0V ≤
V
RO
≤ V
CC
0V ≤
V
RO
≤ V
CC
0.4
-1
-110
+1
+110
V
μA
mA
(V
A
- V
B
) for at least t
PM
(V
A
- V
B
) for at least t
PM
(Note 6)
DE = high,
RE
= low, no load
DE = low,
RE
= high
Human Body Model
±25
±15
±9
±2
+200
8.3
1.2
-200
mV
mV
20
1.8
10
ms
mA
μA
ESD Protection (A and B Pins)
IEC 61000-4-2 Air Gap Discharge to
GND
IEC 61000-4-2- Contact Discharge
to GND
kV
ESD Protection (All Other Pins)
Human Body Model
kV
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Maxim Integrated
│
3
MAX14781E
Half-Duplex RS-485 Transceiver
with Polarity Correction
Switching Characteristics
(V
CC
= 5V ± 10%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
= 5V and T
A
= +25°C.)(Notes 2, 3)
PARAMETER
DRIVER
Driver Propagation Delay
Differential Driver Output Skew
|t
DPLH
- t
DPHL
|
Driver Differential Output Rise or
Fall Time
Maximum Data Rate
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
Driver Enable from Shutdown to
Output High
Driver Enable from Shutdown to
Output Low
Time to Shutdown
RECEIVER
Receiver Propagation Delay
Receiver Output Skew
Maximum Data Rate
Receiver Enable to Output High
t
RPLH
t
RPLH
t
RSKEW
DR
MAX
t
RZH
R
L
= 1kΩ, C
L
= 15pF, Figure 8
(Note 9)
C
L
= 15pF, Figures 6, 7
C
L
= 15pF, Figures 6, 7
0.125
200
200
30
500
50
ns
ns
kbps
ns
t
DPLH
t
DPHL
t
DSKEW
t
R,
t
F
DR
MAX
t
DZH
t
DZL
t
DLZ
t
DHZ
t
DZH(SHDN)
t
DZL(SHDN)
t
SHDN
R
L
= 500Ω, C
L
= 50pF, Figures 4,
5 (Note 9)
R
L
= 500Ω, C
L
= 50pF, Figures 4,
5 (Note 9)
R
L
= 500Ω, C
L
= 50pF, Figures 4,
5 (Note 9)
R
L
= 500Ω, C
L
= 50pF, Figures 4,
5 (Note 9)
R
L
= 1kΩ, C
L
= 15pF, Figures 4, 5
(Note 9)
R
L
= 1kΩ, C
L
= 15pF, Figures 4, 5
(Note 9)
(Note 10)
50
340
R
L
= 54Ω, C
L
= 50pF, Figures 2, 3
R
L
= 54Ω, C
L
= 50pF, Figures 2, 3
R
L
= 54Ω, C
L
= 50pF, Figures 2, 3
250
370
2500
2500
100
100
5.5
5.5
700
200
200
1000
1000
140
900
ns
ns
ns
kbps
ns
ns
ns
ns
μs
μs
ns
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
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Maxim Integrated
│
4
MAX14781E
Half-Duplex RS-485 Transceiver
with Polarity Correction
Switching Characteristics (continued)
(V
CC
= 5V ± 10%, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
= 5V and T
A
= +25°C.)(Notes 2, 3)
PARAMETER
Receiver Enable to Output Low
Receiver Disable Time from Low
Receiver Disable Time from High
Receiver Enable from Shutdown
to Output High
Receiver Enable from Shutdown
to Output Low
Time to Shutdown
SYMBOL
t
RZL
t
RLZ
t
RHZ
t
RZH(SHDN)
t
RZL(SHDN)
t
SHDN
CONDITIONS
R
L
= 1kΩ, C
L
= 15pF, Figure 8
(Note 9)
R
L
= 1kΩ, C
L
= 15pF, Figure 8
(Note 9)
R
L
= 1kΩ, C
L
= 15pF, Figure 8
(Note 9)
R
L
= 1kΩ, C
L
= 15pF, Figure 8
(Note 9)
R
L
= 1kΩ, C
L
= 15pF, Figure 8
(Note 9)
(Note 10)
50
340
MIN
TYP
MAX
50
50
50
5.5
5.5
700
UNITS
ns
ns
ns
μs
μs
ns
Note 2:
All devices are 100% production tested at T
A
= +25°C. Spefications over temperature are guaranteed by design.
Note 3:
All currents into the device are positive. All currents out of the device are negative. All voltages are referenced to ground,
unless otherwise noted.
Note 4:
ΔV
OD
and ΔV
OC
are the changes in V
OD
and V
OC
, respectively, when the DI input changes state.
Note 5:
The short-circuit output current applies to the peak current just prior to foldback current limiting. The short-circuit foldback
output current applies during current limiting to allow recovery from a bus contention.
Note 6:
t
PM
is the interval, with no A/B switching activity, after which the internal logic circuitry records the polarity. t
PM
includes the
correction delay, after which the polarity is changed.
Note 7:
Not production tested. Guaranteed by design.
Note 8:
Capacitive loads include test probe and fixture capacitance.
Note 9:
This parameter refers to the driver/receiver enable delay when the device has exited the initial hot-swap state and is in nor-
mal operating mode.
Note 10:
Shutdown is enabled by driving
RE
high and DE low. The device is guaranteed to have entered shutdown after t
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