EVALUATION KIT AVAILABLE
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
General Description
The MAX14775E/MAX14776E fault-protected RS-485/
RS-422 transceivers feature ±65V protection for overvoltage
signal faults on communication bus lines, ensuring
communication in harsh industrial environments.
Each device contains one driver and one receiver and
operates over the 3V to 5.5V supply range. The
MAX14775E is optimized for high-speed data rates up
to 20Mbps. The MAX14776E features slew-rate limited
outputs for data rates up to 500kbps.
These transceivers are optimized for robust communication
in noisy environments. A large 200mV (typ) hysteresis on
receiver inputs ensure for high noise rejection and a failsafe feature guarantees a logic-high on the receiver output
when the inputs are open or shorted. Driver outputs are
protected against short-circuit conditions.
The MAX14775E/MAX14776E receivers feature a 1/3unit load input impedance, allowing up to 100 transceivers
on a bus.
The MAX14775E/MAX14776E are available in 8-pin
SOIC and 8-pin TDFN-EP packages and operate over the
-40°C to +125°C temperature range.
Benefits and Features
●● Integrated Protection Ensures for Robust
Communication
• ±65V Fault Protection Range on Driver Outputs/
Receiver Inputs
• ±25V Common Mode Range on the Receiver Inputs
• Large Receiver Hysteresis Increases Noise Tolerance
• Hot-Swap Protection
• Thermal Shutdown
●● High-Performance Transceiver Enables Flexible
Designs
• Compliant with RS-485 EIA/TIA-485 Standard
• 20Mbps (MAX14775E)/500kbps (MAX14776E)
Maximum Data Rate
• 3V to 5.5V Supply Range
• Up to 100 Devices on the Bus
Applications
●● Industrial Field Bus Networks
●● Motion Controllers
●● HVAC
Ordering Information appears at end of data sheet.
Selector Guide
PART NUMBER
MAX DATA RATE
MAX14775EASA+
20Mbps
8 SOIC
MAX14775EATA+
20Mbps
8 TDFN-EP
MAX14776EASA+
500kbps
8 SOIC
MAX14776EATA+
500kbps
8TDFN-EP
19-8614; Rev 0; 9/16
PIN-PACKAGE
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Absolute Maximum Ratings
(All voltages referenced to GND)
VCC .........................................................................-0.3V to +6V
RO.............................................................-0.3V to (VCC + 0.3V)
DE, DI, RE................................................................-0.3V to +6V
A, B (IMAX = ±1mA) ...............................................-70V to +70V
Short-Circuit Duration (RO, A, B)...............................Continuous
Continuous Power Dissipation (TA = +70°C)
8-pin SOIC (derate 7.60mW/°C above +70°C).........606.1mW
8-pin TDFN (derate 24.4mW/°C above +70°C).......1951.2mW
Operating Temperature Range.......................... -40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Lead Temperature (soldering, 10s).................................. +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.
Package Thermal Characteristics (Note 1)
SOIC
Junction-to-Ambient Thermal Resistance (θJA)........132°C/W
Junction-to-Case Thermal Resistance (θJC)..............38°C/W
TDFN
Junction-to-Ambient Thermal Resistance (θJA)..........41°C/W
Junction-to-Case Thermal Resistance (θJC)................8°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.
DC Electrical Characteristics
(VCC = 3.0V to 5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
5.3
mA
POWER
Supply Voltage
VCC
3.0
Supply Current
ICC
DE = high, RE = low, no load, no
switching
Shutdown Supply Current
ISH
DE = high, RE = low
Shutdown Short-Circuit Supply
Current
DRIVER
ISHDN_SHRT
Differential Driver Output
|VOD|
Change in Magnitude of Differential Driver Output Voltage
ΔVOD
Driver Common-Mode Output
Voltage
VOC
Change in Magnitude of
Common-Mode Voltage
ΔVOC
A or B shorted to ±65V, DE = high,
RE = low
RL = 54Ω, Figure 1a
1.5
RL = 100Ω, Figure 1a
2.0
RL = 100Ω or 54Ω, Figure 1a (Note 3)
-0.2
4
μA
240
μA
V
VCC/ 2
RL = 100Ω or 54Ω, Figure 1a
RL = 100Ω or 54Ω, Figure 1a (Note 3)
3
-0.2
+0.2
V
3
V
+0.2
V
Single-Ended Driver Output
Voltage High
VOH
A and B outputs, output is high,
ISOURCE = 3mA
Single-Ended Driver Output
Voltage Low
VOL
A and B outputs, output is low,
ISINK = 3mA
0.2
V
Driver Short-Circuit Output
Current
IOSD1
-65V ≤ VA or VB < 0V or VCC < VA or
VB ≤ +65V (Note 4)
200
mA
www.maximintegrated.com
VCC-0.2
V
Maxim Integrated │ 2
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
DC Electrical Characteristics (continued)
(VCC = 3.0V to 5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25°C.) (Note 2)
PARAMETER
Average Driver Short-Circuit
Output Current
SYMBOL
CONDITIONS
IOSD2
0V ≤ VA or VB ≤ VCC
IA, IB
DE = low,
0V ≤ VCC ≤ 5.5V
MIN
TYP
MAX
UNITS
250
mA
RECEIVER
Input Current (A, B)
Receiver Input Resistance
RIN
Common Mode Voltage Range
VCM
Receiver Differential Threshold
Voltage Rising
Receiver Differential Threshold
Voltage Falling
VCM = +12V
VCM = -7V
-7V ≤ VCM ≤ +12V
+280
-200
38
µA
kΩ
-25
+25
V
VTHH
-25V ≤ VCM ≤ +25V
+40
+200
mV
VTHL
-25V ≤ VCM ≤ +25V
-200
-40
mV
Receiver Input Hysteresis
ΔVTH
VCM = 0V, time from last transition
< tD_FS
Differential Input Fail-safe
Threshold
VTH_FSH
25V ≤ VCM ≤ +25V, time from last
transition > tD_FS
Differential Input Capacitance
250
-40
CA,B
Measured between A and B, f = 1MHz
RO Output Logic High Voltage
VOH
ISOURCE = 3mA, (VA - VB) ≥ +200mV VCC-0.4
RO Output Logic Low Voltage
VOL
ISINK = 3mA, (VA - VB) < +200mV
RO Leakage Current
IOZR
RE = high, 0V ≤ VRO ≤ VCC
RO Short-Circuit Current
IOSR
0V ≤ VRO ≤ VCC
Input Logic High Voltage
VIH
Input Logic Low Voltage
VIL
mV
+40
50
mV
pF
LOGIC OUTPUTS (RO)
LOGIC INPUTS (DE, DI, RE)
Input Hysteresis
Input Leakage Current
Input Impedance on First
Transition
V
-1
0.4
V
+1
μA
70
0.67 x
VCC
VHYS
mA
V
0.33 x
VCC
100
IIN
RIN_FT
DE, RE
Thermal-Shutdown Threshold
TSHDN
Temperature rising
Thermal-Shutdown Hysteresis
THYST
V
mV
-1
+1
μA
1
10
kΩ
PROTECTION
+162
°C
12
°C
ESD Protection
(A, B Pins to GND)
Human Body Model
±8
IEC 61000-4-2- Contact Discharge
±5
ESD Protection (All Other Pins)
Human Body Model
±2
Fault Protection Range (A, B
Pins to GND)
www.maximintegrated.com
-65
kV
kV
+65
V
Maxim Integrated │ 3
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Switching Electrical Characteristics (MAX14775E)
(VCC = 3.0V to 5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRIVER
tDPLH, tDPHL
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3
40
ns
Differential Driver Output Skew
|tDPLH - tDPHL|
tDSKEW
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3 (Note 7)
9
ns
Driver Differential Output Rise
or Fall Time
tLH, tHL
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3 (Note 7)
15
ns
Maximum Data Rate
DRMAX
Driver Propagation Delay
8
20
Mbps
Driver Enable to Output High
tDZH
RL = 110Ω, CL = 50pF, Figure 4
90
ns
Driver Enable to Output Low
tDZL
RL = 110Ω, CL = 50pF, Figure 5
90
ns
1000
ns
Driver Enable Time
tD
-20V ≤VCM ≤+25V, 4.5V ≤VCC ≤5.5V,
Figure 1a
Driver Disable Time From Low
tDLZ
RL = 110Ω, CL = 50pF, Figure 5
50
ns
Driver Disable Time From High
tDHZ
RL = 110Ω, CL = 50pF, Figure 4
50
ns
Driver Enable Time from
Shutdown to Output High
tDLZ(SHDN)
RL = 110Ω, CL = 50pF, Figure 4
(Note 5)
170
μs
Driver Enable Time from
Shutdown to Output Low
tDHZ(SHDN)
RL = 110Ω, CL = 50pF, Figure 4
(Note 5)
170
μs
800
ns
tRPLH, tRPHL CL = 15pF, Figure 6 and Figure 7
50
ns
tRSKEW
CL = 15pF, Figure 6 and Figure 7
(Note 7)
5
ns
Receiver Enable to Output
High
tRZH
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
50
ns
Receiver Enable to Output Low
tRZL
RL = 1kΩ, CL = 15pF, S1 closed,
Figure 8
50
ns
Receiver Disable Time From
Low
tRLZ
RL = 1kΩ, CL = 15pF, S1 closed,
Figure 8
50
ns
Receiver Disable Time From
High
tRHZ
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
50
ns
Receiver Enable from
Shutdown to Output Low
tRLZ(SHDN)
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8 (Note 5)
170
μs
Receiver Enable from
Shutdown to Output High
tRHZ(SHDN)
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8 (Note 5)
170
μs
800
ns
Time to Shutdown
tSHDN
(Note 5)
50
RECEIVER (Note 6)
Receiver Propagation Delay
Receiver Output Skew
Time to Shutdown
tSHDN
Delay to Fail-Safe Operation
tD_FS
www.maximintegrated.com
(Note 5)
50
10
μs
Maxim Integrated │ 4
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Switching Electrical Characteristics (MAX14776E)
(VCC = 3.0V to 5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
1000
ns
140
ns
DRIVER
tDPLH, tDPHL
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3
Differential Driver Output Skew
|tDPLH - tDPHL|
tDSKEW
RL = 54Ω, CL = 50pF, Figure 2 and
Figure 3 (Note 7)
Driver Differential Output Rise
or Fall Time
tLH, tHL
RL = 54Ω, CL =
50pF, Figure 2
and Figure 3
Maximum Data Rate
DRMAX
Driver Propagation Delay
100
3V ≤ VCC ≤ 3.6V
105
600
4.5V ≤ VCC ≤ 5.5V
105
600
500
ns
kbps
Driver Enable to Output High
tDZH
RL = 110Ω, CL = 50pF, Figure 4
2500
ns
Driver Enable to Output Low
tDZL
RL = 110Ω, CL = 50pF, Figure 5
-20V ≤ VCM ≤ +25V, 4.5V ≤ VCC ≤5.5V,
Figure 1a
2500
ns
3500
ns
Driver Enable Time
tD
Driver Disable Time From Low
tDLZ
RL = 110Ω, CL = 50pF, Figure 5
100
ns
Driver Disable Time From High
tDHZ
RL = 110Ω, CL = 50pF, Figure 4
100
ns
Driver Enable Time from
Shutdown to Output High
tDLZ(SHDN)
RL = 110Ω, CL = 50pF, Figure 4
(Note 5)
170
μs
Driver Enable Time from
Shutdown to Output Low
tDHZ(SHDN)
RL = 110Ω, CL = 50pF, Figure 4
(Note 5)
170
μs
800
ns
tRPLH, tRPHL CL = 15pF, Figure 6 and Figure 7
200
ns
CL = 15pF, Figure 6 and Figure 7
(Note 7)
30
ns
50
ns
50
ns
Time to Shutdown
RECEIVER (Note 6)
Receiver Propagation Delay
Receiver Output Skew
tSHDN
tRSKEW
(Note 5)
50
Receiver Enable to Output
High
tRZH
Receiver Enable to Output Low
tRZL
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
RL = 1kΩ, CL = 15pF, S1 closed,
Figure 8
Receiver Disable Time from
Low
tRLZ
RL = 1kΩ, CL = 15pF, S1 closed,
Figure 8
50
ns
Receiver Disable Time from
High
tRHZ
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
50
ns
Receiver Enable from Shutdown
to Output High
tRLZ(SHDN)
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
170
μs
Receiver Enable from Shutdown
to Output Low
tRHZ(SHDN)
RL = 1kΩ, CL = 15pF, S2 closed,
Figure 8
170
μs
Time to Shutdown
tSHDN
Delay to Fail-Safe Operation
tD_FS
www.maximintegrated.com
(Note 5)
50
800
10
ns
μs
Maxim Integrated │ 5
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Switching Electrical Characteristics (MAX14776E) (continued)
(VCC = 3.0V to 5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 3.3V and TA = +25°C.) (Note 2)
Note 2: All devices are 100% production tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 3: ΔVOD and ΔVOC are the changes in VOD and VOC, respectively, when the DI input changes state.
Note 4: The short-circuit current is 200mA (max) for a short period (35μs, typ). If the short circuit persists, the outputs are then set
to high impedance for 300ms (typ).
Note 5: Shutdown is enabled when RE is high and DE is 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 held in this state for at least 800ns, the device is guaranteed to
have entered shutdown.
Note 6: Capacitive load includes test probe and fixture capacitance.
Note 7: Guaranteed by design. Not production tested.
375Ω
A
A
RL
2
VOD
VOD
60Ω
+ VCM
-
VOC
RL
2
B
B
375Ω
(b)
(a)
Figure 1. Driver DC Test Load
DI
A
B
VOD
RL
CL
Figure 2. Driver Timing Test Circuit
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Maxim Integrated │ 6
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
tLH P 3ns, tHL P 3ns
VCC
50%
DI
50%
GND
1/2 VO
tDPHL
tDPLH
B
A
1/2 VO
VO
VDIFF = VA - VB
VO
80%
80%
VDIFF
0
20%
20%
tLH
-VO
tHL
tDSKEW = |tDPLH - tDPHL|
Figure 3. Driver Propagation Delays
A
GND OR VCC
DI
S1
B
DE
VCC
OUT
D
CL
50pF
RL = 110I
DE
tDZH
OUT
GENERATOR
50I
50%
250mV
50%
tDHZ
GND
VOH
GND
Figure 4. Driver Enable and Disable Times (tDHZ, tDZH)
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Maxim Integrated │ 7
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
VCC
GND OR VCC
A
DI
RL = 110I
S1
OUT
D
B
CL = 50pF
DE
GENERATOR
50I
VCC
DE
50%
GND
tDZL
tDLZ
VCC
50%
OUT
250mV
VOL
Figure 5. Driver Enable and Disable Times (tDZL, tDLZ)
A
ATE
R
VID
RECEIVER
OUTPUT
B
Figure 6. Receiver Propagation Delay Test Circuit
www.maximintegrated.com
Maxim Integrated │ 8
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
tLH P 3ns, tHL P 3ns
A
1V
B
-1V
tRPHL
tRPLH
VCC
2
RO
VOH
VCC
2
VOL
tRSKEW = |tRPHL - tRPLH|
Figure 7. Receiver Propagation Delays
+1.5V
S3
-1.5V
VID
GNDB
GENERATOR
R
RE
RO
RL
1kI
S1
VCC
S2
CL
15pF
GND
50I
VCC
VCC
50%
RE
GND
S1 OPEN
S2 CLOSED
S3 = +1.5V
50%
RE
GND
tRZL
tRZH
VOH
VCC
2
GND
RO
VCC
50%
RE
VCC
2
RO
S1 OPEN
S2 CLOSED
S3 = +1.5V
VCC
RE
50%
GND
GND
RO
VCC
VOL
S1 CLOSED
S2 OPEN
S3 = -1.5V
tRLZ
tRHZ
0.25V
S1 CLOSED
S2 OPEN
S3 = -1.5V
VCC
VOH
RO
GND
0.25V
VOL
Figure 8. Receiver Enable and Disable Times
www.maximintegrated.com
Maxim Integrated │ 9
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Typical Operating Characteristics
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. DRIVER DATA RATE
(VCC = 3.3V)
80
70
70
60
60
50
40
RL = 120Ω
30
10
10
No Load
0
70
60
RL = 120Ω
1
10
0
0.01
0.1
tDPLH, VCC = 5V
4
2
tDPHL, VCC = 5V
0
250
200
150
tDPLH, VCC = 5V
tDPHL, VCC = 5V
DRIVER DIFFERENTIAL OUTPUT
VOLTAGE vs. LOAD CURRENT
4.5
160
toc08
120
80
-120
-140
-160
2.5
VCC = 3.3V
toc09
VCC = 5V
2.5
2.0
1.5
VCC = 3.3V
1.0
1.0
0
0.5
0.5
-20
0.0
0.0
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DRIVER DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
3.0
3.0
20
-65 -55 -45 -35 -25 -15 -5 5 15 25 35 45 55 65
DRIVER VOLTAGE (V)
OUTPUT IS HIGH
3.5
1.5
40
-80
-100
4.0
2.0
60
-60
4.5
3.5
100
-40
-65 -55 -45 -35 -25 -15 -5 5 15 25 35 45 55 65
DRIVER VOLTAGE (V)
VCC = 5V
4.0
140
5.5
DRIVER OUTPUT SHORT CIRCUIT
CURRENT vs. VOLTAGE
toc06
-200
5.0
OUTPUT IS LOW
5.0
-20
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (ºC)
DRIVER OUTPUT SHORT CIRCUIT
CURRENT vs. VOLTAGE
toc07
4.0
4.5
VCC (V)
-180
100
VOD (V)
SHORT CIRCUIT CURRENT (mA)
180
tDPLH, VCC = 3.3V
300
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (ºC)
200
tDPHL, VCC = 3.3V
350
VOD (V)
6
20
3.5
0
400
PROPAGATION DELAY (ns)
PROPAGATION DELAY (ns)
10
3.0
450
tDPLH, VCC = 3.3V
12
10
MAX14776 DRIVER PROPAGATION
DELAY vs TEMPERATURE
toc05
500
tDPHL, VCC = 3.3V
14
1
DRIVER DATA RATE (Mbps)
MAX14775 DRIVER PROPAGATION
DELAY vs TEMPERATURE
toc04
16
8
10
No Load
DRIVER DATA RATE (Mbps)
18
40
20
SHORT CIRCUIT CURRENT (mA)
0.1
50
30
0
0.01
toc03
80
30
20
DRIVER CURRENT vs.
VCC VOLTAGE
90
RL = 60Ω
40
20
20
toc02
50
RL = 60Ω
ICC (mA)
ICC (mA)
toc01
ILOAD (mA)
80
SUPPLY CURRENT
vs. DRIVER DATA RATE
(VCC = 5V)
LOAD = 60Ω
0
25
50
75
100
LOAD CURRENT (mA)
125
150
RL = 54Ω
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated │ 10
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Typical Operating Characteristics (continued)
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
RO OUTPUT LOW
vs SINK CURRENT
1.00
toc10
RO OUTPUT HIGH
vs SOURCE CURRENT
6
0.90
VCC = 5V
5
0.80
0.70
4
0.60
VCC = 5V
VOH (V)
VOL (V)
toc11
0.50
VCC = 3.3V
0.40
3
2
0.30
0.20
VCC = 3.3V
1
0.10
0.00
0
0
50
10
20
30
SINK CURRENT (mA)
40
50
0
MAX14775 RECEIVER PROPAGATION
DELAY vs TEMPERATURE
toc12
200
20
30
40
SOURCE CURRENT (mA)
50
MAX14776 RECEIVER PROPAGATION
DELAY vs TEMPERATURE
toc13
180
40
35
tRPHL, VCC = 3.3V
tRPLH, VCC = 3.3V
30
25
20
15
tRPLH, VCC = 5V
tRPHL, VCC = 5V
PROPAGATION DELAY (ns)
PROPAGATION DELAY (ns)
45
10
160
tRPLH, VCC = 3.3V
120
100
80
60
10
40
5
20
0
tRPHL, VCC = 3.3V
140
tRPHL, VCC = 5V
tRPLH, VCC = 5V
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
www.maximintegrated.com
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated │ 11
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Pin Configurations
TOP VIEW
+
8
VCC
7
B
3
6
A
4
5
GND
RO
1
RE
2
DE
DI
MAX14775E
MAX14776E
VCC
B
A
GND
8
7
6
5
MAX14775E
MAX14776E
*
+
SOIC
1
2
3
4
RO
RE
DE
DI
TDFN-EP
3mm x 3mm
* Exposed Pad. Connect to GND
Pin Description
PIN
NAME
1
RO
Receiver Data Output. See the Function Tables for more information.
2
RE
Receiver Output Enable. Drive RE low or connect to GND to enable RO. Drive RE high to disable
the receiver. RO is high impedance when RE is high. Drive RE high and DE low to force the IC into
low-power shutdown mode.
3
DE
Driver Output Enable. Drive DE high to enable the driver. Drive DE low or connect to GND to disable
the driver. Drive DE low and RE high to force the IC into low-power shutdown mode.
4
DI
Driver Input. With DE high, a low on DI forces the noninverting output (A) low and the inverting output (B) high. Similarly, a high on DI forces the noninverting output high and the inverting output low.
5
GND
6
A
Noninverting Driver Output/Receiver Input
7
B
Inverting Driver Output/Receiver Input
8
VCC
–
EP
www.maximintegrated.com
FUNCTION
Ground
Power Supply Input. Bypass VCC to GND with a 0.1μF capacitor as close as possible to the device.
Exposed Pad. TDFN package only. Connect EP to GND. EP is not intended as the main ground
connection.
Maxim Integrated │ 12
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Function Tables
Transmitting
INPUTS
RE
OUTPUTS
DE
DI
B
A
X
1
1
0
1
X
1
0
1
0
0
0
X
High Impedance
High Impedance
1
0
X
Shutdown. A and B are high impedance.
Note: X = Don’t care.
RECEIVING
INPUTS
OUTPUTS
RE
DE
(VA - VB)
Time from Last
A-B Transition
0
X
≥ +200mV
Always
1
0
X
-200mV < (VA - VB) < +200mV
< tD_FS
Indeterminate.
RO is latched to previous value.
0
X
-40mV < (VA - VB) < +40mV
> tD_FS
1
0
X
≤ - 200mV
Always
0
0
X
Open/Shorted
> tD_FS
1
1
1
X
X
High impedance
1
0
X
X
Shutdown. RO is high impedance.
RO
Note: X = Don’t care.
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Maxim Integrated │ 13
MAX14775E/MAX14776E
Detailed Description
The MAX14775E/MAX14776E half-duplex transceivers
are optimized for RS-485/RS-422 applications that require
up to ±65V protection from faults on communication bus
lines. These devices contain one differential driver and
one differential receiver. The devices feature a 1/3 unit
load, allowing up to 100 transceivers on a single bus.
The MAX14775E supports data rates up to 20Mbps. The
MAX14776E supports data rates up to 500kbps.
Driver
The driver accepts a single-ended, logic-level input (DI) and
transfers it to a differential RS-485 level output on the A and
B driver outputs.
Set the driver enable input (DE) low to disable the driver. A
and B are high impedance when the driver is disabled.
Receiver
The receiver accepts a differential, RS-485 level input on
the A and B inputs and transfers it to a single-ended, logiclevel output (RO).
Drive the receiver enable input (RE) low to enable the
receiver. Driver RE high to disable the receiver. RO is high
impedance when RE is high.
Low-Power Shutdown
Drive DE low and RE high for at least 800ns to put
the MAX14775E/MAX14776E into low-power shutdown
mode. Supply current drops to 20μA when the device is
in shutdown mode.
A glitch protection feature ensures that the MAX14775E/
MAX14776E will not accidentally enter shutdown mode
due to logic skews between DE and RE when switching
between transmit and receive modes.
±65V Fault Protection
The driver outputs/receiver inputs of transceivers connected
to an industrial RS-485 network often experience faults
when shorted to voltages that exceed the -7V to +12V
input range specified in the EIA/TIA-485 standard. Under
such circumstances, ordinary RS-485 transceivers that
have a typical absolute maximum voltage rating of -8V to
+12.5V require costly external protection devices which
can compromise the RS-485 performance. To reduce
system complexity and the need for external protection,
the driver outputs/receiver inputs of the MAX14775E/
MAX14776E are designed to withstand voltage faults of up
to ±65V with respect to ground without damage. Protection
is guaranteed regardless whether the transceiver is active,
in shutdown or without power.
www.maximintegrated.com
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
When a fault is detected on A or B, the affected driver output is switched into a high-impedance state. After 300ms
(typ), the driver output is re-enabled for 30μs (typ). If the
fault condition persists, the driver output is again disabled.
If the fault has been removed, the driver outputs remain
on and the transceiver operates normally.
Driving a non-terminated cable may cause the voltage
seen at the driver outputs (A or B) to exceed the absolute
maximum voltage rating if the DI input is switched during
a ±65V fault on the A or B pins. Therefore, a termination resistor is recommended in order to maximize the
overvoltage fault protection while the DI input is being
switched.
If the DI input does not change state while the fault condition is present, the MAX14775E/MAX14776E will withstand up to ±65V on the RS-485 inputs, regardless of the
termination status of the data cable.
Fail-Safe
The devices’ receiver features symmetrical thresholds to
improve the duty cycle of the received signal, ensuring that
it is 50% when the received signal amplitude is small.
Additionally, a high input hysteresis (250mV, typ) increases
the resilience to noise on the receiver.
The MAX14775E/MAX14776E also include a fail-safe
feature that ensures the receiver output (RO) is high when
the receiver inputs are shorted or open, or when they are
connected to a differentially terminated transmission line
with all drivers disabled for longer than tD_FS (10μs, typ).
Hot-Swap Functionality
Hot-Swap Inputs
Inserting circuit boards into a hot, or powered backplane
may cause voltage transients on DE, RE, and receiver
inputs A and B that can lead to data errors. For example,
upon initial circuit board insertion, the processor undergoes a power-up sequence. During this period, the highimpedance state of the output drivers makes them unable
to drive the MAX14775E/MAX14776E enable inputs to
a defined logic level. Meanwhile, leakage currents of up
to 10μA from the high-impedance output, or capacitively
coupled noise from VCC or GND, could cause an input
to drift to an incorrect logic state. To prevent such a
condition from occurring, the MAX14775E/MAX14776E
features hot-swap input circuitry on DE and RE to safeguard against unwanted driver activation during hot-swap
situations. When VCC rises, an internal pulldown circuit
holds DE low and RE high for at least 10μs. After the
initial power-up sequence, the internal pulldown/pullup
circuitry becomes transparent, resetting the hot-swap
tolerable inputs.
Maxim Integrated │ 14
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Thermal Shutdown Protection
Power Considerations for the MAX14775E/
MAX14776E
The MAX14775E/MAX14776E feature thermal-shutdown
protection circuitry to protect the device. When the junction
temperature exceeds +165°C (typ), the driver outputs are
disabled and RO is high impedance. Driver and receiver
outputs are re-enabled when the junction temperature falls
below 150°C (typ).
At high data rates, the power dissipation of an RS-485
transceiver can be high. The power dissipation of a halfduplex transceiver is determined by a number of factors,
including:
●●
The data rate
●●
The time that the driver is transmitting
●●
The termination impedance
The MAX14775E/MAX14776E transceivers have 0.32unit load receiver, allowing up to 100 MAX14775E/
MAX14776E transceivers connected in parallel on a
shared communication line. Connect any combination of
these devices, and/or other RS-485 devices, for a maximum
of 32 unit loads to the line.
●●
The power supply voltage
Typical Application
Similarly, the power dissipation in a transceiver is much
higher when the driver is transmitting, compared to when
the transceiver is receiving. In half-duplex communication,
the period of transmission relative to the idle or receiving
intervals (i.e., the duty cycle) should be taken into consideration
when calculating the average power dissipation.
Applications Information
100 Transceivers on the Bus
The MAX14775E/MAX14776E half-duplex transceivers are
designed for bidirectional data communications on
multipoint bus transmission lines. Figure 9 shows a typical
network applications circuit. To minimize reflections, the bus
should be terminated at the receiver inputs in its characteristics
impedance, and stub lengths off the main line should be
kept as short as possible.
Higher data rates result in higher power dissipation due
to switching losses in the transceiver. Switching losses
increase even more when capacitance is applied to the A
and B pins. External capacitance should be kept to a minimum
to help reduce power dissipation at high data rates.
B
B
D
DE
RE
DE
RE
R
DE RE
RO
A
D
DI
R
D
A
B
R
MAX14775E
MAX14776E
DI
A
A
B
RO
D
120Ω
120Ω
RO
DI
R
DI
DE RE
RO
Figure 9. Typical RS-485 Network
www.maximintegrated.com
Maxim Integrated │ 15
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
The line termination resistance/impedance determines
the driver’s load current during transmission and the
differential output voltage (VOD) on the driver is
determined by the supply voltage. A higher supply voltage
results in a larger differential output voltage at the driver
driving the line, which in turn results in a higher current
draw from the supply (ICC).
The power dissipation in the chip is calculated as the
product of supply current times supply voltage, subtracting
the power dissipated in the external termination resistor2:
PDIS = (VCC x ICC) – (VOD2/RLOAD)
Use the Typical Operation Characteristics to determine
the supply current at a given supply voltage and data rate.
For example, assuming a data rate of 20Mbps with a 5V
supply on a fully loaded bus (RL = 60Ω), we can calculate
that the power dissipation (at room temperature) is:
PDIS = (5V x 70mA) – (4.3V2/60Ω) = 42mW
Ensure that power dissipation of the transceiver is kept
below the value listed in the Absolute Maximum Ratings
section to protect the device from entering thermal shutdown or from damage. If the calculated power dissipation
nears the specified limits, select a package with a lower
thermal resistance which also allows for higher power
dissipation.
RC
1MΩ
CHARGE-CURRENTLIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
Cs
100pF
RD
1500Ω
ESD protection can be tested in various ways. The
transmitter outputs and receiver inputs of the devices
are characterized for protection to the cable-side ground
(GNDB) to the following limits:
●●
±8kV HBM
●●
±5kV using the Contact Discharge method specified
in the IEC 61000-4-2
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents test
setup, test methodology, and test results.
Human Body Model (HBM)
Figure 10 shows the HBM test model and Figure 11
shows the current waveform it generates when
discharged in a low-impedance state. This model
consists of a 100pF capacitor charged to the ESD voltage of
interest, which is then discharged in to the test device
through a 1.5kΩ resistor.
IP 100%
90%
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
ESD Protection
ESD protection structures are incorporated on all pins
to protect against electrostatic discharge encountered
during handling and assembly. The driver outputs and
receiver inputs of the MAX14775E/MAX14776E have
extra protection against static electricity. The ESD structures
withstand high ESD in normal operation and when powered
down. After an ESD event, the devices keep working without
latch-up or damage.
Ir
AMPS
DEVICE
UNDER
TEST
36.8%
10%
0
0
Figure 10. Human Body ESD Test Model
www.maximintegrated.com
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
tRL
TIME
tDL
CURRENT WAVEFORM
Figure 11. Human Body Current Waveform
Maxim Integrated │ 16
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and
performance of finished equipment. However, it does not
specifically refer to integrated circuits. The MAX14775E/
MAX14776E help in designing equipment to meet IEC
61000-4-2 without the need for additional ESD protection
components.
CHARGE-CURRENTLIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
Cs
150pF
RD
330Ω
I
100%
90%
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
IPEAK
RC
50MΩ TO 100MΩ
The major difference between tests done using the HBM
and IEC 61000-4-2 is higher peak current in IEC 610004-2 because series resistance is lower in the IEC 610004-2 model. Hence, the ESD withstand voltage measured
to IEC 61000-4-2 is generally lower than that measured
using the HBM. Figure 12 shows the IEC 61000-4-2
model and Figure 13 shows the current waveform for IEC
61000-4-2 ESD Contact Discharge Test.
DEVICE
UNDER
TEST
10%
tr = 0.7ns TO 1ns
t
30ns
60ns
Figure 12. IEC 61000-4-2 ESD Test Model
www.maximintegrated.com
Figure 13. IEC 61000-4-2 ESD Generator Current Waveform
Maxim Integrated │ 17
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Functional Diagram
R
RO
SHUTDOWN
DE
DI
PROTECTION
RE
A
B
D
MAX14775E
MAX14776E
www.maximintegrated.com
Maxim Integrated │ 18
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Ordering Information
PART
Package Information
TEMP RANGE
PIN-PACKAGE
MAX14775EASA+
-40°C to +125°C
8 SOIC
MAX14775EASA+T
-40°C to +125°C
8 SOIC
MAX14775EATA+
-40°C to +125°C
8 TDFN-EP
MAX14775EATA+T
-40°C to +125°C
8 TDFN-EP
MAX14776EASA+
-40°C to +125°C
8 SOIC
MAX14776EASA+T
-40°C to +125°C
8 SOIC
MAX14776EATA+
-40°C to +125°C
8 TDFN-EP
MAX14776EATA+T
-40°C to +125°C
8 TDFN-EP
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND PATTERN
NO.
8 SOIC
S8+4
21-0041
90-0096
8 TDFN-EP
T833+2
21-0137
90-0059
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and Reel
Chip Information
PROCESS: BiCMOS
www.maximintegrated.com
Maxim Integrated │ 19
MAX14775E/MAX14776E
±65V Fault Protected 500kpbs/20Mbps
Half-Duplex RS-485/RS-422 Transceivers
Revision History
REVISION
NUMBER
REVISION
DATE
0
9/16
DESCRIPTION
Initial release
PAGES
CHANGED
—
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2016 Maxim Integrated Products, Inc. │ 20
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