EVALUATION KIT AVAILABLE
Click here to ask about the production status of specific part numbers.
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
General Description
The MAX14782E is a half duplex RS-485/422 transceiver
that operates at either 3.3V or 5V rails with high ±35kV
ESD performance and up to 500kbps data rate.
Functional Diagram
VCC
Benefits and Features
●● Integrated Protection Increases End Equipment
Up-Time
• High ESD Protection
• ±35kV HBM ESD per JEDEC JS-001-2012
• ±20kV Air Gap ESD per IEC 61000-4-2
• ±12kV Contact ESD per IEC 61000-4-2
• ± 4kV EFT per IEC 61000-4-4
• Short-Circuit-Protected Outputs
• True Fail-Safe Receiver Prevents False Transitionon Receiver Input Short or Open Events
• Hot-Swap Capability Eliminates False Transitions
During Power-Up or Hot Insertion
●● 3V to 5.5V Supply Voltage Range
●● Data Rates up to 500kbps
MAX14782E
●● -40°C to +125°C Operating Temperature
RO
●● Allows Up to 32 Transceivers On the Bus
R
RE
B
SHUTDOWN
A
DE
DI
D
GND
Ordering Information/Selector Guide appear at end of data
sheet.
19-6776; Rev 2; 7/20
●● Low 10µA (max) Shutdown Current for Lower Power
Consumption
Applications
●●
●●
●●
●●
Motion Controllers
Field Bus Networks
Encoder Interfaces
Backplane Buses
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Absolute Maximum Ratings
(Voltages referenced to GND.)
VCC ......................................................................-0.3V to +6.0V
RO............................................................. -0.3V to (VCC + 0.3V)
RE, DE, DI.............................................................-0.3V to +6.0V
A, B (VCC ≥ 3.6V) ..............................................-8.0V to +13.0V
A, B (VCC < 3.6V) .............................................-9.0V to +13.0V
Short-Circuit Duration (RO, A, B) to GND..................Continuous
Operating Temperature Range
MAX14782EA_.............................................. -40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Continuous Power Dissipation (TA = +70°C)
SO (derate at 7.6mW/°C above +70°C).......................606mW
TDFN-EP (derate at 24.4mW/°C above +70°C).........1951mW
µMAX (derate at 4.8mW/°C above +70°C)..................387mW
Lead Temperature (soldering, 10s).................................. +300ºC
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 Information
PACKAGE TYPE: 8 SO
Package Code
S8+4
Outline Number
21-0041
Land Pattern Number
90-0096
THERMAL RESISTANCE, FOUR-LAYER BOARD
Junction to Ambient (θJA)
132°C/W
Junction to Case (θJC)
38°C/W
PACKAGE TYPE: 8 TDFN
Package Code
T833+2
Outline Number
21-0137
Land Pattern Number
90-0059
THERMAL RESISTANCE, FOUR-LAYER BOARD
Junction to Ambient (θJA)
41°C/W
Junction to Case (θJC)
8°C/W
PACKAGE TYPE: 8 µMAX
Package Code
U8+1
Outline Number
21-0036
Land Pattern Number
90-0092
THERMAL RESISTANCE, FOUR-LAYER BOARD
Junction to Ambient (θJA)
206°C/W
Junction to Case (θJC)
42°C/W
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 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.
www.maximintegrated.com
Maxim Integrated │ 2
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Electrical Characteristics
(VCC = +3.0V to +5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = +5V and TA = +25°C.) (Notes 1, 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
4
mA
10
µA
POWER SUPPLY
Supply Voltage
Supply Current
Shutdown Supply Current
3.0
VCC
ICC
ISHDN
DE = VCC, RE = GND, no load
1.9
DE = GND, RE = VCC
DRIVER
Differential Driver Output
Change in Magnitude of Differential
Output Voltage
Driver Common-Mode Output
Voltage
Change in Magnitude of CommonMode Voltage
VOD
ΔVOD
VOC
ΔVOC
VCC = 4.5V, RL = 54Ω, Figure 1
2.1
VCC = 3V, RL = 100Ω, Figure 1
2.0
VCC = 3V, RL = 54Ω, Figure 1
1.5
RL = 54Ω or 100Ω, Figure 1 (Note 3)
-0.2
RL = 54Ω or 100Ω, Figure 1
RL = 54Ω or 100Ω, Figure 1 (Note 3)
-0.2
2.2
Single-Ended Driver Output High
VOH
A or B output, IA or B = -20mA
Single-Ended Driver Output Low
VOL
A or B output, IA or B = 20mA
Differential Output Capacitance
COD
DE = RE = VCC, f = 4MHz
Driver Short-Circuit Output Current
|IOST|
V
0
+0.2
V
VCC / 2
3
V
+0.2
V
V
0.8
12
V
pF
0 ≤ VOUT ≤ +12V, output low
250
-7V ≤ VOUT ≤ VCC, output high
250
mA
RECEIVER
VIN = +12V
Input Current
IA, B
DE = GND, VCC = GND
or +5.5V
Differential Input Capacitance
CA, B
Between A and B, DE = GND, f = 4MHz
Receiver Differential Threshold
Voltage
VTH
-7V ≤ VCM ≤ +12V
VIN = -7V
400
-800
1000
+300
12
-200
pF
-10
ΔVTH
Receiver Input Resistance
RIN
-7V ≤ VCM ≤ +12V
12
kΩ
Input-Voltage High
VIH
DE, DI, RE
2.0
V
Input-Voltage Low
VIL
DE, DI, RE
VHYS
DE, DI, RE
IIN
DE, DI, RE
Input Hysteresis
Input Current
Input Impedance on First Transition
DE, RE
RO Output-Voltage High
VOHRO
RE = GND, IRO = -2mA,
(VA - VB) > 200mV
RO Output-Voltage Low
VOLRO
RE = GND, IRO = 2mA,
(VA - VB) < -200mV
www.maximintegrated.com
10
mV
Receiver Input Hysteresis
LOGIC INTERFACE (DI, DE, RE, RO)
VCM = 0V
-105
µA
mV
0.8
50
1
V
mV
±1
µA
10
kΩ
VCC - 0.4
V
0.4
V
Maxim Integrated │ 3
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Electrical Characteristics (continued)
(VCC = +3.0V to +5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = +5V and TA = +25°C.) (Notes 1, 2)
PARAMETER
Receiver Three-State Output
Current
SYMBOL
Receiver Output Short-Circuit
Current
CONDITIONS
IOZR
RE = VCC, 0 ≤ VRO ≤ VCC
IOSR
0 ≤ VRO ≤ VCC
MIN
TYP
MAX
UNITS
±1
µA
±110
mA
PROTECTION
Thermal-Shutdown Threshold
TSHDN
Temperature rising
+160
°C
15
°C
IEC 61000-4-2 Air-Gap Discharge to GND
±20
IEC 61000-4-2 Contact Discharge to GND
±12
Human Body Model
±35
Human Body Model
±2
Thermal-Shutdown Hysteresis
ESD Protection on A and B Pins
ESD Protection, All Other Pins
kV
kV
Switching Characteristics
(VCC = +3V to +5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = +5V and TA = +25°C.) (Notes 1, 2, 4)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRIVER
Driver Propagation Delay
tDPLH
tDPHL
20
RL = 54Ω, CL = 50pF,
Figures 2 and 3
Driver Differential Output Rise or
Fall Time
tHL, tLH
RL = 54Ω, CL = 50pF,
Figures 2 and 3
Differential Driver Output Skew
|tDPLH - tDPHL|
tDSKEW
RL = 54Ω, CL = 50pF,
Figures 2 and 3
Maximum Data Rate
DRMAX
20
200
ns
600
ns
140
ns
kbps
500
Driver Enable to Output High
tDZH
RL = 110Ω, CL = 50pF,
Figures 4 and 5 (Note 5)
2500
ns
Driver Enable to Output Low
tDZL
RL = 110Ω, CL = 50pF,
Figures 4 and 5 (Note 5)
2500
ns
Driver Disable Time from Low
tDLZ
RL = 110Ω, CL = 50pF,
Figures 4 and 5
100
ns
Driver Disable Time from High
tDHZ
RL = 110Ω, CL = 50pF,
Figures 4 and 5
100
ns
Driver Enable from Shutdown to
Output High
tDLZ(SHDN)
RL = 110Ω, CL = 15pF,
Figures 4 and 5 (Note 5)
5.5
µs
Driver Enable from Shutdown to
Output Low
tDHZ(SHDN)
RL = 110Ω, CL = 15pF,
Figures 4 and 5 (Note 5)
5.5
µs
700
ns
Time to Shutdown
www.maximintegrated.com
tSHDN
(Note 6)
50
340
Maxim Integrated │ 4
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Switching Characteristics MAX14782E (continued)
(VCC = +3V to +5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = +5V and TA = +25°C.) (Notes 1, 2, 4)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RECEIVER
Receiver Propagation Delay
tRPLH
tRPHL
Receiver Output Skew
tRSKEW
Maximum Data Rate
DRMAX
200
CL = 15pF, Figures 6 and 7
200
CL = 15pF, Figures 6 and 7 (Note 6)
30
500
ns
ns
kbps
Receiver Enable to Output High
tRZH
RL = 1kΩ, CL = 15pF, Figure 8
(Note 5)
Receiver Enable to Output Low
tRZL
RL = 1kΩ, CL = 15pF, Figure 8
(Note 5)
50
ns
Receiver Disable Time from Low
tRLZ
RL = 1kΩ, CL = 15pF, Figure 8
50
ns
Receiver Disable Time from High
tRHZ
RL = 1kΩ, CL = 15pF, Figure 8
50
ns
50
ns
Receiver Enable from Shutdown to
Output High
tRLZ(SHDN)
RL = 1kΩ, CL = 15pF,
Figure 8 (Note 5)
5.5
µs
Receiver Enable from Shutdown to
Output Low
tRHZ(SHDN)
RL = 1kΩ, CL = 15pF,
Figure 8 (Note 5)
5.5
µs
700
ns
Time to Shutdown
tSHDN
(Note 6)
50
340
Note 1: All devices 100% production tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 2: 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 3: ΔVOD and ΔVOC are the changes in VOD and VOC, respectively, when the DI input changes state.
Note 4: Capacitive load includes test probe and fixture capacitance.
Note 5: Guaranteed by design; not production tested.
Note 6: The timing parameter refers to the driver or receiver enable delay, when the device has exited the initial hot-swap protect
state and is in normal operating mode.
www.maximintegrated.com
Maxim Integrated │ 5
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Test and Timing Diagrams
A
VCC
DE
RL
2
DI
A
VOD
B
VOD
RL
2
RL
CL
VOC
B
Figure 1. Driver DC Test Load
Figure 2. Driver Timing Test Circuit
f = 1MHz, tLH = 3ns, tHL = 3ns
VCC
DI
1.5V
1.5V
0
tDPHL
tDPLH
B
A
VOD
VOD = [VA - VB]
VO
VOD
90%
0
-VO
90%
10%
10%
tLH
tHL
tDSKEW = |tDPLH - tDPHL|
Figure 3. Driver Propagation Delays
www.maximintegrated.com
Maxim Integrated │ 6
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
GND OR VCC DI D
A
B
S1
VCC
OUT
CL
50pF
RL = 110Ω
DE
1.5V
tDZH, tDZH(SHDN)
DE
GENERATOR
0
0.25V
OUT
50Ω
VOH
1.5V
0
tDHZ
Figure 4. Driver Enable and Disable Times (tDHZ, tDZH)
VCC
0 OR VCC DI D
A
RL = 110Ω
S1
VCC
OUT
B
VCC
OUT
DE
GENERATOR
DE
50Ω
1.5V
tDZL, tDZL(SHDN)
0
tDLZ
1.5V
VOL
0.25V
Figure 5. Driver Enable and Disable Times (tDZL, tDZL)
A
ATE
R
VID
RO
B
Figure 6. Receiver Propagation Delay Test Circuit
www.maximintegrated.com
Maxim Integrated │ 7
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
A
1V
B
-1V
tRPHL
VOH
RO
tRPLH
1.5V
1.5V
VOL
tRSKEW = |tRPHL - tRPLH|
Figure 7. Receiver Propagation Delays
+1.5V
S3
-1.5V
VID
R
RO
RE
GENERATOR
1.5V
tRZH, tRZH(SHDN)
RO
0
S1 OPEN
S2 CLOSED
S3 = +1.5V
VCC
1.5V
tRHZ
RO
0.25V
VCC
S2
CL
15pF
VCC
1.5V
RE
0
S1 CLOSED
S2 OPEN
S3 = -1.5V
tRZL, tRZL(SHDN)
VOH
VCC
2
0
RE
S1
50Ω
VCC
RE
R
1kΩ
0
VCC
2
VOL
RO
VCC
S1 OPEN
S2 CLOSED
S3 = +1.5V
1.5V
RE
tRLZ
0
S1 CLOSED
S2 OPEN
S3 = -1.5V
VCC
VOH
0
VCC
RO
0.25V
VOL
Figure 8. Receiver Enable and Disable Times
www.maximintegrated.com
Maxim Integrated │ 8
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Typical Operating Characteristics
(VCC = +5V, TA = +25°C, unless otherwise specified.)
1.5
VCC = 3.3V
1.0
VCC = 5V
VCC = 3.3V
3
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
MAX14782E toc03
60
VCC = 3.3V, 54Ω LOAD
50
40
VCC = 5V, NO LOAD
30
VCC = 3.3V, NO LOAD
20
10
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
100
0
200
300
400
500
RECEIVER-OUTPUT HIGH VOLTAGE
vs. OUTPUT CURRENT
RECEIVER-OUTPUT LOW VOLTAGE
vs. OUTPUT CURRENT
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
VCC = 3.3V
1
-10
-20
-30
-40
-60
-50
4
3
2
VCC = 3.3V
1
0
5.0
4.5
10
20
30
40
50
RL = 54Ω
CL = 50pF
VCC = 5V
3.5
3.0
2.5
2.0
1.5
VCC = 3.3V
1.0
60
120
VCC = 5V
80
40
0
VCC = 3.3V
0
1
2
3
4
5
DIFFERENTIAL OUTPUT VOLTAGE (V)
DIFFERENTIAL DRIVER OUTPUT
VOLTAGE vs. TEMPERATURE
4.0
-180
-160
DRIVER OUTPUT CURRENT
vs. OUTPUT HIGH VOLTAGE
VCC = 5V
-140
-120
-100
VCC = 3.3V
-80
-60
-40
-20
0.5
0
0
OUTPUT CURRENT (mA)
MAX14782E toc07
DIFFERENTIAL DRIVER OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
VCC = 5V
160
MAX14782E toc08
2
OUTPUT SINKING CURRENT
DRIVER OUTPUT CURRENT (mA)
VCC = 5V
3
OUTPUT LOW VOLTAGE (V)
4
5
MAX14782E toc06
DATA RATE (kbps)
MAX14782E toc05
TEMPERATURE (°C)
OUTPUT SOURCING CURRENT
0
VCC = 5V, 54Ω LOAD
TEMPERATURE (°C)
MAX14782E toc04
OUTPUT HIGH VOLTAGE (V)
5
1
5
0
6
2
0.5
0
7
4
DE = VCC
70
SUPPLY CURRENT (mA)
2.0
8
OUTPUT CURRENT (mA)
SUPPLY CURENT (mA)
VCC = 5V
DE = GND
RE = VCC
9
SUPPLY CURRENT vs. DATA RATE
80
MAX14782E toc02
DE = VCC
RE = GND
2.5
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
10
SUPPLY CURENT (µA)
3.0
MAX14782E toc01
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
www.maximintegrated.com
0
-7 -6 -5 -4 -3 -2 -1 0
1
2
3
4
5
OUTPUT HIGH VOLTAGE (V)
Maxim Integrated │ 9
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Typical Operating Characteristics (continued)
(VCC = +3.0V to +5.5V, TA = TMIN to TMAX, unless otherwise specified. Typical values are at VCC = +5V and TA = +25°C.) (Notes 1, 2)
VCC = 3.3V
80
60
40
450
400
350
250
0
200
6
8
10
12
14
VCC = 5V
12
10
8
6
4
2
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
DRIVER-OUTPUT RISE /FALL TIME
vs. TEMPERATURE
DRIVER-OUTPUT TRANSITION SKEW
vs. TEMPERATURE
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
tHL, VCC = 5V
tHL, VCC = 3.3V
tLH, VCC = 3.3V
-40 -25 -10 5 20 35 50 65 80 95 110 125
RL = 54Ω
CL = 50pF
2.5
200
180
2.0
1.5
VCC = 3.3V
1.0
0.5
0
120
100
80
tRPLH, VCC = 5V
40
CL = 15pF
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
DRIVER/RECEIVER
PROPAGATION DELAY
DIFFERENTIAL INPUT CAPACITANCE
vs. FREQUENCY
30
MAX14782E toc15
DE = GND
VCC = 3.3V
CL = 8pF
A /B
2V/div
RO
20
10
2V/div
400ns/div
www.maximintegrated.com
CAPACITANCE (pF)
2V/div
DI
tRPLH, VCC = 3.3V
60
0
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
tRPHL, VCC = 3.3V
140
20
VCC = 5V
tRPHL, VCC = 5V
160
MAX14782E toc16
tLH, VCC = 5V
3.0
MAX14782E toc13
RL = 54Ω
CL = 50pF
MAX14782E toc11
VCC = 3.3V
TEMPERATURE (°C)
100
0
16
RL = 54Ω
CL = 50pF
OUTPUT LOW VOLTAGE (V)
300
200
tDPHL, VCC = 3.3V
PROPAGATION DELAY (ns)
400
4
DRIVER-OUTPUT TRANSITION SKEW (ns)
500
2
tDPLH, VCC = 3.3V
300
20
0
tDPHL, VCC = 5V
tDPLH, VCC = 5V
18
DIFFERENTIAL DRIVER SKEW
vs. TEMPERATURE
MAX14782E toc14
100
500
DRIVER DIFFERENTIAL SKEW (ns)
120
RL = 54Ω
CL = 50pF
550
20
MAX14782E toc10
140
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
600
PROPAGATION DELAY (ns)
160
600
DRIVER-OUTPUT RISE/FALL TIME (ns)
VCC = 5V
MAX14782E toc12
DRIVER OUTPUT CURENT (mA)
180
MAX14782E toc09
DRIVER OUTPUT CURRENT
vs. OUTPUT LOW VOLTAGE
0
0
3
30
FREQUENCY (MHz)
Maxim Integrated │ 10
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Pin Configuration
TOP VIEW
VCC
B
A
GND
8
7
6
5
MAX14782E
+
8
VCC
7
B
3
6
A
4
5
GND
RO
1
RE
2
DE
DI
MAX14782E
*EP
+
1
2
3
4
RO
RE
DE
DI
µMAX/SO
TDFN-EP
*CONNECT EXPOSED PAD (EP) TO GND
Pin Description
PIN
NAME
1
RO
Receiver Output. See Function Tables.
2
RE
Receiver Output Enable. Drive RE low to enable RO. Drive RE high to disable the receiver. RO is high
impedance when RE is high. Drive RE high and pull DE low to enter low-power shutdown mode.
3
DE
Driver Output Enable. Drive DE high to enable the driver. Drive DE low to disable the driver. Driver
outputs are high-impedance when the driver is disabled. Drive RE high and pull DE low to enter lowpower shutdown mode.
4
DI
Driver Input. With DE high, a low on DI forces the A output low and the B output high. Similarly, a high
on DI forces the A output high and B output low.
5
GND
6
A
Noninverting RS-485/RS-422 Receiver Input and Driver Output
7
B
Inverting RS-485/RS-422 Receiver Input and Driver Output
8
VCC
—
EP
www.maximintegrated.com
FUNCTION
Ground
Positive Supply Voltage Input. Bypass VCC with a 0.1µF ceramic capacitor to ground.
Exposed Pad (TDFN only). Connect EP to GND.
Maxim Integrated │ 11
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Function Tables
TRANSMITTING
INPUTS
OUTPUTS
MODE
RE
DE
DI
B
A
X
1
1
0
1
Active
X
1
0
1
0
Active
0
0
X
High Impedance
Driver Disabled
1
0
X
High Impedance
Shutdown
RECEIVING
INPUTS
RE
DE
0
0
OUTPUTS
MODE
A-B
RO
X
≥ -10mV
1
Active
X
≤ -200mV
0
Active
0
X
Open/Shorted
1
Active
1
1
X
High Impedance
Receiver Disabled
0
X
High Impedance
Shutdown
1
X = Don’t care
www.maximintegrated.com
Maxim Integrated │ 12
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Detailed Description
Hot-Swap Capability
The MAX14782E is a 3.3V to 5V ESD-protected RS-485/
RS-422 transceiver intended for high-speed, half-duplex
communications. Integrated hot-swap functionality eliminates false transitions on the bus during power-up or hot
insertion.
The device features fail-safe receiver inputs guaranteeing
a logic-high receiver output when inputs are shorted or
open. The IC has a 1-unit load receiver input impedance,
allowing up to 32 transceivers on the bus.
True Fail Safe
The MAX14782E 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. If the differential receiver input voltage
(A–B) is greater than or equal to -10mV, RO is logic-high.
Driver Single-Ended Operation
The A and B outputs can either be used in the standard
differential operating mode, or can be used as singleended outputs. Since the A and B driver outputs swing
rail-to-rail, they can individually be used as standard TTL
logic outputs.
Hot-Swap Inputs
When circuit boards are inserted in a hot or powered
backplane, disturbances on the enable inputs and differential receiver inputs can lead to data errors. Upon
initial circuit board insertion, the processor undergoes its
power-up sequence. During this period, the processor
output drivers are high impedance and are unable to drive
the DE and RE inputs of the MAX14782E to a defined
logic level. Leakage currents up to 10µA from the highimpedance outputs of a controller could cause DE and RE
to drift to an incorrect logic state. Additionally, parasitic
circuit board capacitance could cause coupling of VCC
or GND to DE and RE. These factors could improperly
enable the driver or receiver. The MAX14782E features
integrated hot-swap inputs that help to avoid these potential problems.
When VCC rises, an internal pulldown circuit holds DE
low and RE high. After the initial power-up sequence, the
pulldown circuit becomes transparent, resetting the hotswap-tolerable inputs.
Hot-Swap Input Circuitry
The DE and RE enable inputs feature hot-swap capability. At the input, there are two nMOS devices, M1 and M2
(Figure 9). When VCC ramps from 0V, an internal 10µs
timer turns on M2 and sets the SR latch that also turns
VCC
10µs
TIMER
TIMER
DE
DRIVER
ENABLE
(HOT SWAP)
5kΩ (typ)
100µA
M1
500µA
M2
Figure 9. Simplified Structure of the Driver Enable (DE) Pin
www.maximintegrated.com
Maxim Integrated │ 13
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
on M1. Transistors M2 (a 500µA current sink) and M1 (a
100µA current sink) pull DE to GND through a 5kΩ (typ)
resistor. M2 is designed to pull DE to the disabled state
against an external parasitic capacitance up to 100pF that
can drive DE high. After 10µs, the timer deactivates M2
while M1 remains on, holding DE low against three-state
leakages that can drive DE high. M1 remains on until an
external source overcomes the required input current.
At this time, the SR latch resets and M1 turns off. When
M1 turns off, DE reverts to a standard, high-impedance
CMOS input. Whenever VCC drops below 1V, the hotswap input is reset.
● ±35kV HBM
A complementary circuit employing two pMOS devices
pulls RE to VCC.
Figure 10 shows the HBM, and Figure 11 shows the current waveform it generates when discharged into a lowimpedance state. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then
discharged into the test device through a 1.5kΩ resistor.
±35kV ESD Protection
ESD protection structures are incorporated on all pins
to protect against electrostatic discharges encountered
during handling and assembly. The driver outputs and
receiver inputs of the MAX14782E have extra protection
against static electricity. The ESD structures withstand
high ESD in all states: normal operation, shutdown, and
powered down. After an ESD event, the MAX14782E
keeps working without latch-up or damage.
ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the MAX14782E are
characterized for protection to the following limits:
RC
1MΩ
CHARGE CURRENTLIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
CS
100pF
RD
1.5kΩ
Figure 10. Human Body ESD Test Model
www.maximintegrated.com
● ±12kV using the Contact Discharge method specified
in 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)
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 MAX14782E helps
in designing equipment to meet IEC 61000-4-2 without the
need for additional ESD protection components.
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.
IP 100%
90%
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
● ±20kV using the Air-Gap Discharge method specified
in IEC 61000-4-2
IR
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
AMPERES
DEVICE
UNDER
TEST
36.8%
10%
0
0
tRL
TIME
tDL
CURRENT WAVEFORM
Figure 11. Human Body Current Waveform
Maxim Integrated │ 14
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
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.
Applications Information
RE and DE can be connected together and driven simultaneously. The MAX14782E is 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 800ns (max), the
device is guaranteed to enter shutdown.
Driver Output Protection
Typical Applications
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus connection. The first, a 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 exceeds +160°C (typ).
The MAX14782E transceiver is designed for bidirectional
data communications on multipoint bus transmission
lines. Figure 14 shows a typical network application circuit. To minimize reflections, terminate the line at both
ends with its characteristic impedance and keep stub
lengths off the main line as short as possible.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by bringing RE
high and DE low. In shutdown, the devices draw less than
10µA of supply current.
RC
50MΩ TO 100MΩ
HIGHVOLTAGE
DC
SOURCE
CS
150pF
I
100%
90%
DISCHARGE
RESISTANCE
IPEAK
CHARGE CURRENTLIMIT RESISTOR
RD
330Ω
DEVICE
UNDER
TEST
STORAGE
CAPACITOR
10%
tR = 0.7ns TO 1ns
t
30ns
60ns
Figure 12. IEC 61000-4-2 ESD Test Model
Figure 13. IED 61000-4-2 ESD Generator Current Waveform
120Ω
DI
DE
B
D
D
DI
DE
RO
120Ω
B
A
B
A
B
A
A
R
R
RE
R
R
D
MAX14782E
DI
RO
RE
D
DE
RO RE
DI
DE
RO RE
Figure 14. Typical Half-Duplex RS-485 Network
www.maximintegrated.com
Maxim Integrated │ 15
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Ordering Information/Selector Guide
PART
SUPPLY RANGE
DATA RATE (MAX)
TEMP RANGE
PIN-PACKAGE
MAX14782EASA+
3.0V to 5.5V
500kbps
-40°C to +125°C
8 SO
MAX14782EATA+
3.0V to 5.5V
500kbps
-40°C to +125°C
8 TDFN-EP*
MAX14782EAUA+
3.0V to 5.5V
500kbps
-40°C to +125°C
8 µMAX
µMax is a registered trademark of Maxim Integrated Products, Inc.
+Denotes lead(Pb)-free/RoHS-compliant package.
*EP = Exposed paddle.
Chip Information
PROCESS: BiCMOS
www.maximintegrated.com
Maxim Integrated │ 16
MAX14782E
500Kbps 3.3V to 5V RS-485/RS-422 Transceiver
with ±35kV HBM ESD Protection
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
8/13
Initial release
1
1/15
Updated page 1 content
2
7/20
Updated the Benefits and Features and Electrical Characteristics sections
DESCRIPTION
—
1
1, 3
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
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.
© 2020 Maxim Integrated Products, Inc. │ 17
工商网监
湘ICP备2023018690号
