MAX14780E

+5.0V, ±30kV ESD-Protected, Fail-Safe,

Hot-Swap, RS-485/RS-422 Transceiver
General Description Benefits and Features
The MAX14780E is a +5V, ±30kV HBM ESD half duplex Integrated Protection Increases Robustness
RS-485/422 transceiver. S ±30kV HBM ESD per JEDEC JS-001-2012
The MAX14780E features reduced slew-rate drivers that S ±12kV Contact ESD per IEC 61000-4-2
minimize EMI and reduce reflections caused by improp- S ±15kV Air Gap ESD per IEC 61000-4-2
erly terminated cables, allowing error-free data transmis- S True Fail-Safe Receiver Prevents False
sion up to 500kbps. Transitions on Receiver Input Short or Open
S Hot Swap Eliminates False Transitions During
The MAX14780E is available in an 8-pin SO and PDIP Power-Up or Hot Insertion
packages operating over a temperature range from S Short-Circuit Protected Outputs Low Current
-40°C to +85°C. Reduces Power Consumption
Applications Low Current Reduces Power Consumption
S 10µA Shutdown Current
Utility Meters
S 1.2mA of Supply Current When Unloaded
Lighting Systems
Industrial Control
Ordering Information
PART TEMP RANGE PIN-PACKAGE
Telecom
MAX14780EESA+ -40NC to +85NC 8 SO
Security Systems
MAX14780EEPA+ -40NC to +85NC 8 PDIP
Instrumentation +Denotes a lead(Pb)-free/RoHS-compliant package.

Typical Operating Circuit

0.1µF
MAX14780E DE
+
1 8 VCC DI
RO R D
2 7 B B
RE Rt Rt
3 6
DE
A A
4 5 RO
DI D R
GND

RE
TYPICAL HALF-DUPLEX OPERATING CIRCUIT

For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com. 19-5652; Rev 3; 1/15
MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.) Continuous Power Dissipation (TA = +70°C)
Supply Voltage (VCC)............................................................ +6V SO (derate 5.9mW/°C above +70°C)...........................471mW
Control Input Voltage (RE, DE)................................-0.3V to +6V PDIP (derate 9.1mW/°C above +70°C) .....................727.3mW
Driver Input Voltage (DI)..........................................-0.3V to +6V Operating Temperature Range........................... -40°C to +85°C
Driver Output Voltage (A, B).....................................-8V to +13V Junction Temperature......................................................+150°C
Receiver Input Voltage (A, B)...................................-8V to +13V Storage Temperature Range............................. -65°C to +150°C
Receiver Output Voltage (RO).................. -0.3V to (VCC + 0.3V) Lead Temperature (soldering, 10s).................................+300°C
Driver Output Current..................................................... ±250mA 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.

DC ELECTRICAL CHARACTERISTICS
(VCC = +5.0V ±10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DRIVER
VCC Supply-Voltage Range VCC 4.5 5.5 V
RL = 100I (RS-422), Figure 1 3 VCC
Differential Driver Output VOD RL = 54I (RS-485), Figure 1 2 VCC V
No load VCC
Change in Magnitude of
DVOD RL = 100I or 54I, Figure 1 (Note 2) 0.2 V
Differential Output Voltage
Driver Common-Mode Output
VOC RL = 100I or 54I, Figure 1 VCC/2 3 V
Voltage
Change in Magnitude of
DVOC RL = 100I or 54I, Figure 1 (Note 2) 0.2 V
Common-Mode Voltage
Input-High Voltage VIH DE, DI, RE 3 V
Input-Low Voltage VIL DE, DI, RE 0.8 V
Input Hysteresis VHYS DE, DI, RE 100 mV
Input Current IIN1 DE, DI, RE Q1 FA
Input Impedance First Transition
RPWUP DE, RE = RE = 2V 3.65 8.8 kI
at Power-Up
Input Impedance on First
Rft DE = RE = 2V 7 60 kΩ
Transition after POR Delay
Driver Short-Circuit Output 0 P VOUT P +12V (Note 3) 40 250
IOSD mA
Current -7V P VOUT P VCC (Note 3) -250 -40
Driver Short-Circuit Foldback (VCC - 1V) P VOUT P +12V (Note 3) 20
IOSDF mA
Output Current -7V P VOUT P +1V (Note 3) -20
Thermal-Shutdown Threshold TTS 175 NC
Thermal-Shutdown Hysteresis TTSH 15 NC
VDE = 0V, VIN = +12V 125
Input Current (A and B) IA, B FA
VCC = 0V or VCC VIN = -7V -100
RECEIVER
Receiver Differential Threshold
VTH -7V P VCM P +12V -200 -125 -50 mV
Voltage
Receiver Input Hysteresis DVTH VA + VB = 0V 15 mV

2   Maxim Integrated

 MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5.0V ±10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCC -
RO Output-High Voltage VOH IO = -1mA V
0.6
RO Output-Low Voltage VOL IO = 1mA 0.4 V
Three-State Output Current at
IOZR 0 P VO P VCC P1 FA
Receiver
Receiver Input Resistance RIN -7V P VCM P +12V 96 kI
Receiver Output Short-Circuit
IOSR 0V P VRO P VCC P 110 mA
Current
SUPPLY CURRENT
No load, VRE = 0V, DE = VCC 1.2 1.8
Supply Current ICC No load, RE = VCC, DE = VCC 1.2 1.8 mA
No load, VRE = 0V, VDE = 0V 1.2 1.8
Supply Current in Shutdown
ISHDN RE = VCC, VDE = 0V 2.8 10 FA
Mode
ESD PROTECTION
Human Body Model Q30
Contact Discharge
Q12
ESD Protection for A and B IEC 61000-4-2 kV
Air-Gap Discharge
Q15
IEC 61000-4-2

DRIVER SWITCHING CHARACTERISTICS WITH INTERNAL SRL (500kbps)

(VCC = +5.0V ±10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
tDPLH 200 1000
Driver Propagation Delay CL = 50pF, RL = 54I, Figures 2 and 3 ns
tDPHL 200 1000
Driver Differential Output Rise or
tR , tF CL = 50pF, RL = 54I, Figures 2 and 3 250 900 ns
Fall Time
Differential Driver Output Skew
tDSKEW CL = 50pF, RL = 54I, Figures 2 and 3 140 ns
|tDPLH - tDPHL|
Maximum Data Rate 500 kbps
Driver Enable to Output High tDZH Figure 4 2500 ns
Driver Enable to Output Low tDZL Figure 5 2500 ns
Driver Disable Time from Low tDLZ Figure 5 100 ns
Driver Disable Time from High tDHZ Figure 4 100 ns
Driver Enable from Shutdown to
tDZH(SHDN) Figure 4 5500 ns
Output High
Driver Enable from Shutdown to
tDZL(SHDN) Figure 5 5500 ns
Output Low
Time to Shutdown tSHDN 50 340 700 ns

Maxim Integrated   3

MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
RECEIVER SWITCHING CHARACTERISTICS WITH INTERNAL SRL (500kbps)
(VCC = +5.0V ±10%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5.0V and TA = +25NC.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
tRPLH 200
Receiver Propagation Delay CL = 15pF, Figures 6 and 7 ns
tRPHL 200
Receiver Output Skew
tRSKEW CL = 15pF, Figures 6 and 7 30 ns
|tRPLH - tRPHL|
Maximum Data Rate 500 kbps
Receiver Enable to Output Low tRZL Figure 8 50 ns
Receiver Enable to Output High tRZH Figure 8 50 ns
Receiver Disable Time from Low tRLZ Figure 8 50 ns
Receiver Disable Time from High tRHZ Figure 8 50 ns
Receiver Enable from Shutdown
tRZH(SHDN) Figure 8 5500 ns
to Output High
Receiver Enable from Shutdown
tRZL(SHDN) Figure 8 5500 ns
to Output Low
Time to Shutdown tSHDN 50 340 700 ns
Note 1: 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: The short-circuit output current applies to peak current just prior to foldback current limiting. The short-circuit foldback
output current applies during current limiting to allow a recovery from bus contention.

Test Circuits and Waveforms

B
VCC
RL/2 DI VCC/2
0
tDPLH tDPHL 1/2 VO
VOD
Z
RL/2 VOC
VO
Y
A
1/2 VO
VDIFF = V (B) - V (A)
VO
Figure 1. Driver DC Test Load VDIFF 0 90% 90%
10% 10%
-VO
tR tF

VCC
tSKEW = | tDPLH - tDPHL |
DE

B Figure 3. Driver Propagation Delays

DI VOD RL CL
A

Figure 2. Driver Timing Test Circuit

4   Maxim Integrated

 MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Test Circuits and Waveforms (continued)

S1
0 OR VCC D OUT

CL RL = 500Ω
50pF

GENERATOR
50Ω

VCC
DE VCC/2
tDZH, tDZH(SHDN)
0

0.25V VOH

OUT VOM = (0 + VOH)/2

0
tDHZ

Figure 4. Driver Enable and Disable Times (tDHZ, tDZH, tDZH(SHDN))

VCC

RL = 500Ω
S1
0 OR VCC D OUT

CL
50pF

GENERATOR 50Ω

VCC
DE VCC/2
tDZL, tDZL(SHDN)
0

tDLZ
VCC
OUT VOM = (VOL + VCC)/2
VOL 0.25V

Figure 5. Driver Enable and Disable Times (tDZL, tDLZ, tDLZ(SHDN))

Maxim Integrated   5

MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Test Circuits and Waveforms (continued)
A +1V

B -1V
B RECEIVER
OUTPUT
ATE VID R tRPLH
VOH
tRPHL
A VCC/2
VOL
RO
THE RISE TIME AND FALL TIME OF INPUTS A AND B < 4ns

Figure 6. Receiver Propagation Delay Test Circuit Figure 7. Receiver Propagation Delays

S1
+1.5V S3
VCC
1kΩ
-1.5V VID

CL
15pF S2

GENERATOR 50Ω

S1 OPEN S1 CLOSED
S2 CLOSED S2 OPEN
VS3 = +1.5V VS3 = -1.5V
VCC VCC

VCC/2
RE RE
0 0

tRZH, tRZH(SHDN)
tRZL, tRZL(SHDN)
VOH VCC
RO
VOH / 2
(VOL + VCC)/2
RO
0 VOL

S1 OPEN S1 CLOSED
S2 CLOSED S2 OPEN
VS3 = +1.5V VS3 = -1.5V
VCC VCC

50% VCC/2 50% VCC/2

RE
0 RE
0
tRHZ

tRLZ

VCC
VOH
10%
0.25V
RO
RO 10% 0.25V
0 VOL

Figure 8. Receiver Enable and Disable Times

6   Maxim Integrated
 MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Typical Operating Characteristics
(VCC = +5.0V, TA = +25°C, unless otherwise noted.)

OUTPUT CURRENT OUTPUT CURRENT

SUPPLY CURRENT vs. TEMPERATURE vs. RECEIVER OUTPUT-HIGH VOLTAGE vs. RECEIVER OUTPUT-LOW VOLTAGE
1.60 60 70

MAX14780E toc02
MAX14780E toc01

MAX14780E toc03
NO LOAD
1.50 60
50
1.40
OUTPUT CURRENT (mA)

OUTPUT CURRENT (mA)

SUPPLY CURRENT (mA)

50
40
1.30
40
1.20 DE = VCC 30
30
1.10
DE = 0 20
20
1.00
10 10
0.90

0.80 0 0
-40 -25 -10 5 20 35 50 65 80 95 110 125 0 1 2 3 4 5 0 1 2 3 4 5
TEMPERATURE (°C) OUTPUT HIGH VOLTAGE (V) OUTPUT LOW VOLTAGE (V)

RECEIVER OUTPUT-HIGH VOLTAGE RECEIVER OUTPUT-LOW VOLTAGE DRIVER DIFFERENTIAL OUTPUT CURRENT
vs. TEMPERATURE vs. TEMPERATURE vs. DIFFERENTIAL OUTPUT VOLTAGE
5.4 0.8 160
MAX14780E toc04

MAX14780E toc06
MAX14780E toc05

IO = -1mA IO = 1mA
0.7 DIFFERENTIAL OUTPUT CURRENT (mA) 140
5.2
OUTPUT HIGH VOLTAGE (V)

OUTPUT LOW VOLTAGE (V)

0.6 120
5.0
0.5 100
4.8
0.4 80
4.6
0.3 60
4.4
0.2 40
4.2 0.1 20

4.0 0 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 0 1 2 3 4 5
TEMPERATURE (°C) TEMPERATURE (°C) DIFFERENTIAL OUTPUT VOLTAGE (V)

DRIVER DIFFERENTIAL OUTPUT OUTPUT CURRENT vs. TRANSMITTER OUTPUT CURRENT vs. TRANSMITTER
VOLTAGE vs. TEMPERATURE OUTPUT-HIGH VOLTAGE OUTPUT-LOW VOLTAGE
4.8 200 200
MAX14780E toc07

MAX14780E toc09
MAX14780E toc08

RL = 54Ω
180 180
4.4
DIFFERENTIAL OUTPUT VOLTAGE (V)

160 160
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)

4.0 140 140

120 120
3.6
100 100
3.2 80
80
2.8 60 60
40 40
2.4
20 20
2.0 0 0
-40 -25 -10 5 20 35 50 65 80 95 110 125 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 0 2 4 6 8 10 12
TEMPERATURE (°C) OUTPUT HIGH VOLTAGE (V) OUTPUT-LOW VOLTAGE (V)

Maxim Integrated   7

MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Typical Operating Characteristics (continued)
(VCC = +5.0V, TA = +25°C, unless otherwise noted.)

SHUTDOWN CURRENT DRIVER PROPAGATION DELAY RECEIVER PROPAGATION DELAY

vs. TEMPERATURE vs. TEMPERATURE (500kbps) vs. TEMPERATURE (500kbps)
10 600 180

MAX14780E toc12
MAX14780E toc10

MAX14780E toc11
9 160

RECEIVER PROPAGATION DELAY (ns)

DRIVER PROPAGATION DELAY (ns) 550
8 140
SHUTDOWN CURRENT (µA)

7 tDPHL
500 120
6
100
tDPLH tDPLH
5 450
80
4
400 60 tDPHL
3
2 40
350
1 20
0 300 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 -40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C)

RECEIVER
PROPAGATION
DELAY
(500kbps) DRIVERPROPAGATION
DELAY(500kbps)
M AX14780E toc13 M AX14780E toc14

RL = 0
10
 RL = 0
10

DI
VA -VB 2V/div
5V/
div

RO
2V/div VY -VZ
5V/
div

200ns/
div 400ns/
div

8   Maxim Integrated

 MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Pin Configuration

+
RO 1 R 8 VCC

RE 2 7 B
DE 3 6 A
DI 4 D 5 GND

SO/PDIP

Pin Description
PIN NAME FUNCTION
1 RO Receiver Output. When RE is low and if (A - B) R -50mV, RO is high; if (A - B) P -200mV, RO is low.
Receiver Output Enable. Drive RE low to enable RO; RO is high impedance when RE is high. Drive
2 RE RE high and DE low to enter low-power shutdown mode. RE is a hot-swap input (see the Hot-Swap
Capability section for details).
Driver Output Enable. Drive DE high to enable driver outputs. These outputs are high impedance
3 DE 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 details).
Driver Input. With DE high, a low on DI forces noninverting output low and inverting output high.
4 DI
Similarly, a high on DI forces noninverting output high and inverting output low.
5 GND Ground
6 A Noninverting Receiver Input and Noninverting Driver Output
7 B Inverting Receiver Input and Inverting Driver Output
8 VCC Positive Supply VCC = +5.0V Q10%. Bypass VCC to GND with a 0.1FF capacitor.

Function Tables
TRANSMITTING RECEIVING
INPUTS OUTPUTS INPUTS OUTPUTS
RE DE DI B A RE DE A-B RO
X 1 1 0 1 0 X R -50mV 1
X 1 0 1 0 0 X P -200mV 0
0 0 X High-Z High-Z 0 X Open/shorted 1
1 0 X Shutdown 1 1 X High-Z
1 0 X Shutdown

Maxim Integrated   9

MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Detailed Description Additionally, parasitic circuit board capacitance could
cause coupling of VCC or GND to the enable inputs.
The MAX14780E high-speed transceiver for RS-485/ Without the hot-swap capability, these factors could
RS-422 communication contains one driver and one improperly enable the transceiver’s driver or receiver.
receiver. This device features fail-safe circuitry, which
guarantees a logic-high receiver output when the receiv- When VCC rises, an internal pulldown circuit holds DE
er inputs are open or shorted, or when they are con- low and RE high. After the initial power-up sequence,
nected to a terminated transmission line with all drivers the pulldown circuit becomes transparent, resetting the
disabled (see the Fail-Safe section). The MAX14780E hot-swap tolerable input.
also features a hot-swap capability allowing line inser- Hot-Swap Input Circuitry
tion without erroneous data transfer (see the Hot-Swap The enable inputs feature hot-swap capability. At the
Capability section). The MAX14780E features reduced input there are two nMOS devices, M1 and M2 (Figure 9).
slew-rate drivers that minimize EMI and reduce reflec- When VCC ramps from zero, an internal 7μs timer turns
tions caused by improperly terminated cables, allowing on M2 and sets the SR latch, which also turns on M1.
error-free data transmission up to 500kbps. Transistors M2, a 500μA current sink, and M1, a 100μA
The MAX14780E is a half-duplex transceiver and oper- current sink, pull DE to GND through a 5kΩ resistor.
ates from a single +5.0V supply. Drivers are output M2 is designed to pull DE to the disabled state against
short-circuit current limited. Thermal-shutdown circuitry an external parasitic capacitance up to 100pF that can
protects drivers against excessive power dissipation. drive DE high. After 7μs, the timer deactivates M2 while
When activated, the thermal-shutdown circuitry places M1 remains on, holding DE low against three-state leak-
the driver outputs into a high-impedance state. ages that can drive DE high. M1 remains on until an
external source overcomes the required input current.
Fail-Safe At this time, the SR latch resets and M1 turns off. When
The MAX14780E guarantees a logic-high receiver output M1 turns off, DE reverts to a standard, high-impedance
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
input threshold between -50mV and -200mV. If the dif-
ferential receiver input voltage (A - B) is greater than or VCC
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 ter- 10µs
TIMER
minated bus with all transmitters disabled, the receiver’s
SR LATCH
differential input voltage is pulled to 0V by the termina-
tion. With the receiver threshold of the MAX14780E, TIMER
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.
Hot-Swap Capability
Hot-Swap Inputs
When circuit boards are inserted into a hot or powered 5kΩ
backplane, differential disturbances to the data bus DE
DE
(HOT SWAP)
can lead to data errors. Upon initial circuit board inser-
tion, the data communication processor undergoes 100µA
its own power-up sequence. During this period, the 500µA
processor’s logic-output drivers are high impedance M1 M2
and are unable to drive the DE and RE inputs of these
devices to a defined logic level. Leakage currents up
to ±10μA from the high-impedance state of the proces-
sor’s logic drivers could cause standard CMOS enable
inputs of a transceiver to drift to an incorrect logic level. Figure 9. Simplified Structure of the Driver Enable Pin (DE)

10   Maxim Integrated

 MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
CMOS input. Whenever VCC drops below 1V, the hot- Human Body Model
swap input is reset. Figure 10a shows the Human Body Model, and Figure 10b
For RE there is a complementary circuit employing two shows the current waveform it generates when dis-
pMOS devices pulling RE to VCC. charged into a low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
±30kV ESD Protection which is then discharged into the test device through a
As with all Maxim devices, ESD-protection structures are 1.5kΩ resistor.
incorporated on all pins to protect against electrostatic
IEC 61000-4-2
discharges encountered during handling and assembly.
The IEC 61000-4-2 standard covers ESD testing and
The driver output and receiver input of the MAX14780E
performance of finished equipment. However, it does not
have extra protection against static electricity. Maxim’s
specifically refer to integrated circuits. The MAX14780E
engineers have developed state-of-the-art structures to
helps you design equipment to meet IEC 61000-4-2, with-
protect these pins against ESD of ±30kV without dam-
out the need for additional ESD-protection components.
age. The ESD structures withstand high ESD in all states:
normal operation, shutdown, and powered down. After The major difference between tests done using the
an ESD event, the MAX14780E keeps working without Human Body Model and IEC 61000-4-2 is higher peak
latchup or damage. current in IEC 61000-4-2 because series resistance
is lower in the IEC 61000-4-2 model. Hence, the ESD
ESD protection can be tested in various ways. The trans-
withstand voltage measured to IEC 61000-4-2 is gen-
mitter output and receiver input of the MAX14780E are
erally lower than that measured using the Human
characterized for protection to the following limits:
Body Model. Figure 10c shows the IEC 61000-4-2
• ±30kV using the Human Body Model model, and Figure 10d shows the current waveform for
• ±12kV using the Contact Discharge method specified IEC 61000‑4‑2 ESD Contact Discharge test.
in IEC 61000-4-2 Machine Model
• ±15kV using the Air-Gap Discharge method specified The machine model for ESD tests all pins using a 200pF
in IEC 61000-4-2 storage capacitor and zero discharge resistance. The
ESD Test Conditions objective is to emulate the stress caused when I/O pins
ESD performance depends on a variety of conditions. are contacted by handling equipment during test and
Contact Maxim for a reliability report that documents test assembly. Of course, all pins require this protection, not
setup, test methodology, and test results. just RS-485 inputs and outputs.

RC RD
1MΩ 1500Ω
IP 100% Ir PEAK-TO-PEAK RINGING
90% (NOT DRAWN TO SCALE)
CHARGE-CURRENT- DISCHARGE
LIMIT RESISTOR RESISTANCE
AMPS
HIGH- DEVICE 36.8%
VOLTAGE Cs STORAGE UNDER
DC 100pF CAPACITOR TEST 10%
SOURCE
0
0 TIME
tRL
tDL
CURRENT WAVEFORM

Figure 10a. Human Body ESD Test Model Figure 10b. Human Body Current Waveform

Maxim Integrated   11

MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
RC RD I
50MΩ TO 100MΩ 330Ω 100%
90%
CHARGE-CURRENT- DISCHARGE
LIMIT RESISTOR RESISTANCE

IPEAK
HIGH- DEVICE
VOLTAGE Cs STORAGE UNDER
DC 150pF CAPACITOR TEST
SOURCE 10%

tr = 0.7ns TO 1ns t
30ns
60ns

Figure 10c. IEC 61000-4-2 ESD Test Model Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform

Applications Information Enable times tZH and tZL (see the Switching
Characteristics section) assume the devices were not in
The standard RS-485 receiver input impedance is 12kΩ a low-power shutdown state. Enable times tZH(SHDN) and
(1-unit load), and the standard driver can drive up tZL(SHDN) assume the devices were in shutdown state.
to 32-unit loads. The MAX14780E has a 1/8-unit load It takes drivers and receivers longer to become enabled
receiver input impedance (96kΩ), allowing up to 256 from low-power shutdown mode (tZH(SHDN), tZL(SHDN))
transceivers to be connected in parallel on one commu- than from driver/receiver-disable mode (tZH, tZL).
nication line. Any combination of the MAX14780E, as well
as other RS-485 transceivers with a total of 32-unit loads Driver Output Protection
or fewer, can be connected to the line. Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus conten-
Reduced EMI and Reflections tion. The first, a foldback current limit on the output
The MAX14780E features reduced slew-rate drivers that stage, provides immediate protection against short cir-
minimize EMI and reduce reflections caused by improp- cuits over the whole common-mode voltage range (see
erly terminated cables, allowing error-free data transmis- the Typical Operating Characteristics). The second, a
sion up to 500kbps. thermal-shutdown circuit, forces the driver outputs into
Low-Power Shutdown Mode a high-impedance state if the die temperature exceeds
Low-power shutdown mode is initiated by bringing both +175°C (typ).
RE high and DE low. In shutdown, the devices typically Line Length
draw only 2.8μA of supply current. The RS-485/RS-422 standard covers line lengths up to
RE and DE can be driven simultaneously; the devices 4000ft. For line lengths greater than 4000ft, it may be
are guaranteed not to enter shutdown if RE is high and necessary to implement a line repeater.
DE is low for less than 50ns. If the inputs are in this state
for at least 700ns, the devices are guaranteed to enter
shutdown.

12   Maxim Integrated

 MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
120Ω 120Ω
DE
B B
DI
D D
DI
DE A B A B A A

RO R R RO
RE RE

R R
D D
MAX14780E

DI DE RO RE DI DE RO RE

Figure 11. Typical Half-Duplex RS-485 Network

Typical Applications Package Information

The MAX14780E transceiver is designed for bidirectional
For the latest package outline information and land patterns (foot-
data communications on multipoint bus transmission prints), go to www.maximintegrated.com/packages. Note that
lines. Figure 11 shows a typical network applications a “+”, “#”, or “-” in the package code indicates RoHS status only.
circuit. Package drawings may show a different suffix character, but the
To minimize reflections, terminate the line at both ends in drawing pertains to the package regardless of RoHS status.
its characteristic impedance, and keep stub lengths off
LAND
the main line as short as possible. The slew-rate-limited PACKAGE PACKAGE OUTLINE
PATTERN
MAX14780E is more tolerant of imperfect termination. TYPE CODE NO.
NO.

Chip Information 8 SO S8+4 21-0041 90-0096

8 PDIP P8+2 21-0043 —
PROCESS: BiCMOS

Maxim Integrated   13

MAX14780E
+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
Revision History
REVISION REVISION PAGES
DESCRIPTION
NUMBER DATE CHANGED
0 12/10 Initial release —
1 7/11 Added PDIP package information to data sheet 1, 2 , 9, 13
Updated DC Electrical Characteristics including adding new row for Input
2 10/11 Impedance on First Transition after POR Delay, updated Hot-Swap Input Circuitry 2, 10
section

3 1/15 Updated General Description and Benefits and Features sections 1

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.

14 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
©  2015 Maxim Integrated Products, Inc. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.