General Description
The MAX13485E/MAX13486E +5V, half-duplex, ±15kV
ESD-protected RS-485 transceivers feature one driver
and one receiver. These devices include fail-safe circuitry,
guaranteeing a logic-high receiver output when receiver
inputs are open or shorted. The receiver outputs a logic-
high if all transmitters on a terminated bus are disabled
(high impedance). The MAX13485E/MAX13486E include
a hot-swap capability to eliminate false transitions on the
bus during power-up or live-insertion.
The MAX13485E features reduced slew-rate drivers
that minimize EMI and reduce reflections caused by
improperly terminated cables, allowing error-free trans-
mission up to 500kbps. The MAX13486E driver slew
rate is not limited, allowing transmit speeds up to
16Mbps.
The MAX13485E/MAX13486E feature a 1/4-unit load
receiver input impedance, allowing up to 128 transceivers
on the bus. These devices are intended for half-duplex
communications. All driver outputs are protected to ±15kV
ESD using the Human Body Model. The MAX13485E/
MAX13486E are available in 8-pin SO and space-saving
8-pin µDFN packages. The devices operate over the
extended -40°C to +85°C temperature range.
Applications
Utility Meters
Industrial Controls
Industrial Motor Drives
Automated HVAC Systems
Features
♦+5V Operation
♦True Fail-Safe Receiver While Maintaining
EIA/TIA-485 Compatibility
♦Hot-Swappable for Telecom Applications
♦Enhanced Slew-Rate Limiting Facilitates Error-
Free Data Transmission (MAX13485E)
♦High-Speed Version (MAX13486E) Allows for
Transmission Speeds Up to 16Mbps
♦Extended ESD Protection for RS-485/RS-422 I/O
Pins ±15kV Using Human Body Model
♦1/4 Unit Load, Allowing Up to 128 Transceivers on
the Bus
♦Available in Space-Saving 8-Pin μDFN or Industry
Standard 8-Pin SO Packages
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
________________________________________________________________
Maxim Integrated Products
1
19-0742; Rev 0; 1/07
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Ordering Information/
Selector Guide
PART PIN-
PACKAGE
SLEW-RATE
LIMITED
PKG
CODE
MAX13485EELA+T 8 µDFN Yes L822-1
MAX13485EESA+ 8 SO Yes S8-2
MAX13486EELA+T 8 µDFN No L822-1
MAX13486EESA+ 8 SO No S8-2
+
Denotes a lead-free package.
Note: All devices are specified over the -40°C to +85°C operating
temperature range.
Rt
RE
RO
B
AA
B
Rt
R
D
RO
DI
8
7
6
5
1
2
3
4
RE
DE
R
DI
D
DE
+
123
87
4
65
VCC A GNDB
RO DIDERE
MAX13485E
MAX13486E
DFN
+
A
GNDDI
1
2
8
7
VCC
BRE
DE
RO
SO
SO
3
4
6
5
R
D
+
TOP VIEW
GND
VCC
0.1μF
MAX13485E
MAX13486E
Pin Configurations
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
(All voltages referenced to GND.)
VCC ........................................................................................+6V
DE, RE, DI.................................................................-0.3V to +6V
A, B ..............................................................................-8V to 13V
Short-Circuit Duration (RO, A, B) to GND ..................Continuous
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW
8-Pin µDFN (derate 4.8mW/°C above +70°C) ..........380.6mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(VCC = +5V ±5%, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA= +25°C.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DRIVER
RDIFF = 100Ω, Figure 1 2.0 VCC
RDIFF = 54Ω, Figure 1 1.5Differential Driver Output VOD
No load VCC
V
Change in Magnitude of
Differential Output Voltage ΔVOD RDIFF = 100Ω or 54Ω, Figure 1 (Note 3) 0.2 V
Driver Common-Mode Output
Voltage VOC RDIFF = 100Ω or 54Ω, Figure 1 VCC
/ 2 3V
Change in Magnitude of
Common-Mode Voltage ΔVOC RDIFF = 100Ω or 54Ω, Figure 1 (Note 3) 0.2 V
Input-High Voltage VIH DI, DE, RE 2.0 V
Input-Low Voltage VIL DI, DE, RE 0.8 V
Input Current IIN DI, DE, RE ±1 µA
0V < VOUT < +12V +50 +250
Driver Short-Circuit Output
Current (Note 4) IOSD -7V < VOUT < 0V -250 -50 mA
(VCC - 1V) < VOUT < +12V 20
Driver Short-Circuit Foldback
Output Current Note 3) IOSDF -7V < VOUT < 0V -20 mA
RECEIVER
VIN = +12V 250
Input Current (A and B) IA, B DE = GND, VCC = GND
or +5V VIN = -7V -200 µA
Receiver-Differential-Threshold
Voltage VTH -7V < VCM < +12V -200 -50 mV
Receiver Input Hysteresis ΔVTH VA + VB = 0V 25 mV
Output-High Voltage VOH IO = -1.6mA, VA - VB > VTH VCC -
1.5 V
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +5V ±5%, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA= +25°C.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Output-Low Voltage VOL IO = 1mA, VA - VB < -VTH 0.4 V
Tri-State Output Current at
Receiver IOZR 0V < VO < VCC ±1 µA
Receiver Input Resistance RIN -7V < VCM < +12V 48 kΩ
Receiver-Output Short-Circuit
Current IOSR 0V < VRO < VCC ±7 ±95 mA
POWER SUPPLY
Supply Voltage VCC 4.75 5.25 V
Supply Current ICC DE = 1, RE = 0, no load 4.5 mA
Shutdown Supply Current ISHDN DE = 0, RE = 1 10 µA
ESD PROTECTION
Air Gap Discharge IEC61000-4-2
(MAX13485E) ±15
ESD Protection (A, B)
Human Body Model ±15
kV
ESD Protection (All Other Pins) Human Body Model ±2 kV
SWITCHING CHARACTERISTICS—MAX13485E
(VCC = +5V ±5%, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA= +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DRIVER
tDPLH 200 1000
Driver Propagation Delay tDPHL
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3 200 1000 ns
tHL 250 900
Driver-Differential Output Rise or
Fall Time tLH
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3 250 900 ns
Driver-Differential Output Skew
|tDPLH - tDPHL|tDSKEW RDIFF = 54Ω, CL = 50pF, Figures 2 and 3 140 ns
Maximum Data Rate 500 kbps
Driver Enable to Output High tDZH Figures 4 and 5 2500 ns
Driver Enable to Output Low tDZL Figures 4 and 5 2500 ns
Driver Disable Time from High tDHZ Figures 4 and 5 100 ns
Driver Disable Time from Low tDLZ Figures 4 and 5 100 ns
Driver Enable from Shutdown to
Output High tDZH
(
SHDN
)
Figures 4 and 5 5500 ns
Driver Enable from Shutdown to
Output Low tDZL
(
SHDN
)
Figures 4 and 5 5500 ns
Time to Shutdown tSHDN 50 340 700 ns
RECEIVER
tRPLH 80
Receiver Propagation Delay tRPHL
CL = 15pF, Figures 6 and 7 80 ns
Receiver Output Skew tRSKEW CL = 15pF, Figure 7 13 ns
Maximum Data Rate 500 kbps
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
4 _______________________________________________________________________________________
SWITCHING CHARACTERISTICS—MAX13485E (continued)
(VCC = +5V ±5%, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA= +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Receiver Enable to Output High tRZH Figure 8 50 ns
Receiver Enable to Output Low tRZL Figure 8 50 ns
Receiver Disable Time from High tRHZ Figure 8 50 ns
Receiver Disable Time from Low tRLZ Figure 8 50 ns
Receiver Enable from Shutdown
to Output High tRZH
(
SHDN
)
Figure 8 2200 ns
Receiver Enable from Shutdown
to Output Low tRZL
(
SHDN
)
Figure 8 2200 ns
Time to Shutdown tSHDN 50 340 700 ns
SWITCHING CHARACTERISTICS—MAX13486E
(VCC = +5V ±5%, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA= +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DRIVER
tDPLH 50
Driver Propagation Delay tDPHL
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3 50 ns
tHL 15
Driver Differential Output Rise or
Fall Time tLH
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3 15 ns
Differential Driver Output Skew
|tDPLH - tDPHL|tDSKEW RDIFF = 54Ω, CL = 50pF, Figures 2 and 3 8 ns
Maximum Data Rate 16 Mbps
Driver Enable to Output High tDZH Figures 4 and 5 50 ns
Driver Enable to Output Low tDZL Figures 4 and 5 50 ns
Driver Disable Time from High tDHZ Figures 4 and 5 50 ns
Driver Disable Time from Low tDLZ Figures 4 and 5 50 ns
Driver Enable from Shutdown to
Output High tDZH
(
SHDN
)
Figures 4 and 5 2200 ns
Driver Enable from Shutdown to
Output Low tDZL
(
SHDN
)
Figures 4 and 5 2200 ns
Time to Shutdown tSHDN 50 340 700 ns
RECEIVER
tRPLH 80
Receiver Propagation Delay tRPHL
CL = 15pF, Figures 6 and 7 80 ns
Receiver Output Skew tRSKEW CL = 15pF, Figure 7 13 ns
Maximum Data Rate 16 Mbps
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
_______________________________________________________________________________________ 5
SWITCHING CHARACTERISTICS—MAX13486E (continued)
(VCC = +5V ±5%, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA= +25°C.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Receiver Enable to Output High tRZH Figure 8 50 ns
Receiver Enable to Output Low tRZL Figure 8 50 ns
Receiver Disable Time from High tRHZ Figure 8 50 ns
Receiver Disable Time from Low tRLZ Figure 8 50 ns
Receiver Enable from Shutdown
to Output High tRZH
(
SHDN
)
Figure 8 2200 ns
Receiver Enable from Shutdown
to Output Low tRZL
(
SHDN
)
Figure 8 2200 ns
Time to Shutdown tSHDN 50 340 700 ns
Note 1: µDFN devices production tested at +25°C. Overtemperature limits are generated by design.
Note 2: All currents into the device are positive. All currents out of the device are negative. All voltages referred to device ground,
unless otherwise noted.
Note 3: ΔVOD and ΔVOC are the changes in VOD and VOC when the DI input changes states.
Note 4: The short-circuit output current applied 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.
Typical Operating Characteristics
(VCC = +5V, TA = +25°C, unless otherwise noted.)
3.0
3.2
3.6
3.4
3.8
4.0
-40 10-15 35 60 85
SUPPLY CURRENT vs. TEMPERATURE
MAX13485-86E toc01
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
NO LOAD
0
7
21
14
28
35
021345
OUTPUT CURRENT vs. RECEIVER
OUTPUT HIGH VOLTAGE
MAX13485-86E toc02
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
0
20
10
40
30
50
60
021345
OUTPUT CURRENT vs. RECEIVER
OUTPUT LOW VOLTAGE
MAX13485-86E toc03
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
4.0
4.4
4.2
4.8
4.6
5.2
5.0
5.4
-40 10-15 35 60 85
RECEIVER OUTPUT HIGH
VOLTAGE vs. TEMPERATURE
MAX13485-86E toc04
TEMPERATURE (°C)
OUTPUT HIGH VOLTAGE (V)
IO = 1mA
0
0.1
0.3
0.2
0.4
0.5
-40 10-15 35 60 85
RECEIVER OUTPUT LOW
VOLTAGE vs. TEMPERATURE
MAX13485-86E toc05
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)
IO = 1mA
DIFFERENTIAL OUPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX13485-86E toc06
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
4321
20
40
60
80
0
05
0
1.0
0.5
2.0
1.5
2.5
3.0
-40 10-15 35 60 85
DRIVER-DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
MAX13485-86E toc07
TEMPERATURE (°C)
DIFFERENTIAL OUTPUT VOLTAGE (V)
RDIFF = 54Ω
0
40
20
80
60
100
120
-7 -5 -4 -3-6 -2 0-1 12345
OUTPUT CURRENT vs. TRANSMITTER
OUTPUT HIGH VOLTAGE
MAX13485-86E toc08
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
0
40
20
80
60
100
120
0462 8 10 12
OUTPUT CURRENT vs. TRANSMITTER
OUTPUT LOW VOLTAGE
MAX13485-86E toc09
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
0
3
2
1
4
5
6
7
8
9
10
-40 10-15 35 60 85
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX13485-86E toc10
TEMPERATURE (°C)
SHUTDOWN CURRENT (μA)
300
400
350
500
450
550
600
-40 10-15 35 60 85
DRIVER PROPAGATION
vs. TEMPERATURE (MAX13485E)
MAX13485-86E toc11
TEMPERATURE (°C)
DRIVER PROPAGATION DELAY (ns)
tDPLH
tDPHL
0
10
5
20
15
25
30
-40 10-15 35 60 85
DRIVER PROPAGATION DELAY
vs. TEMPERATURE (MAX13486E)
MAX13485-86E toc12
TEMPERATURE (°C)
DRIVER PROPAGATION DELAY (ns)
tDPLH
tDPHL
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
_______________________________________________________________________________________
7
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
RECEIVER PROPAGATION
vs. TEMPERATURE (MAX13485E)
MAX13485-86E toc13
TEMPERATURE (°C)
PROPAGATION DELAY (ns)
603510-15
20
40
60
80
0
-40 85
tRPHL
tRPLH
RECEIVER PROPAGATION
vs. TEMPERATURE (MAX13486E)
MAX13485-86E toc14
TEMPERATURE (°C)
RECEIVER PROPAGATION (ns)
603510-15
10
20
30
40
0
-40 85
tRPHL
tRPLH
400ns/div
DRIVER PROPAGATION (500kbps)
(MAX13485E)
DI
2V/div
MAX13485/86E toc15
A-B
5V/div
10ns/div
DRIVER PROPAGATION (16Mbps)
(MAX13486E)
DI
2V/div
MAX13485/86E toc16
A-B
5V/div
10ns/div
RECEIVER PROPAGATION (16Mbps)
(MAX13486E)
B
2V/div
MAX13485/86E toc17
RO
2V/div
A
2V/div
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
8 _______________________________________________________________________________________
VOC
A
B
RDIFF 2
RDIFF
VOD CL
2
Figure 1. Driver DC Test Load
A
B
DE
DI
5V
RDIFF CL
VID
Figure 2. Driver Timing Test Circuit
1.5V 1.5V
0
DI
B
A
tDPLH tDPHL
1/2 VO
1/2 VO
VO
10%
90%
10%
90%
0
VO
-VO
VDIFF
tDSKEW = |tDPLH - tDPHL|
VDIFF = V(A) - V(B)
tHLtLH
VCC f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns
Figure 3. Driver Propagation Delays
Test Circuits and Waveforms
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
_______________________________________________________________________________________ 9
1.5V 1.5V
A, B
0
0
OUTPUT NORMALLY LOW
DE
OUTPUT NORMALLY HIGH
tDZL(SHDN),tDZL
tDZH(SHDN),tDZH
tDLZ
tDHZ
2.3V
2.3V
VOL + 0.5V
VOH + 0.5V
A, B
VOL
VCC
Figure 4. Driver Enable and Disable Times
ATE VID
A
B
RRECEIVER
OUTPUT
Figure 6. Receiver Propagation Delay Test Circuit
OUTPUT
UNDER TEST
500ΩS1
S2
VCC
CL
Figure 5. Driver-Enable and -Disable-Timing Test Load
1.5V 1.5V
1V
-1V
f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns
tRPHL tRPLH
VOH
VOL
RO
A
B
tRSKEW = |tRPHL - tRPLH|
Figure 7. Receiver Propagation Delays
Test Circuits and Waveforms (continued)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
10 ______________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 RO Receiver Output
2RE
Receiver Output Enable. Drive RE low to enable RO. RO is high impedance when RE is high. Drive
RE high and DE low to enter low-power shutdown mode. RE is a hot-swap input (see the Hot-Swap
Capability section for more details).
3DE
Driver Output Enable. Drive DE high to enable the driver outputs. These outputs are high-impedance
when DE is low. Drive RE high and DE low to enter low-power shutdown mode. DE is a hot-swap input
(see the Hot-Swap Capability section for more details).
4DI
Driver Input. Drive DI low to force noninverting output low and inverting output high. Drive DI high to
force noninverting output high and inverting output low (see the Function Tables).
5 GND Ground
6 A Noninverting Receiver Input and Noninverting Driver Output
7 B Inverting Receiver Input and Inverting Driver Output
8V
CC Positive Supply, VCC = +5V ±5%. Bypass VCC to GND with a 0.1µF capacitor.
TRANSMITTING
INPUT OUTPUT
RE DE DI B A
X11 0 1
X10 1 0
0 0 X HIGH IMPEDANCE HIGH IMPEDANCE
1 0 X SHUTDOWN
RECEIVING
INPUT OUTPUT
RE DE A-B RO
0X > -50mV 1
0X < -200mV 0
0 X OPEN/SHORT 1
1 1 X HIGH IMPEDANCE
1 0 X SHUTDOWN
Function Tables
X = Don’t care, shutdown mode, driver, and receiver outputs
are in high impedance.
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
__________________________________________________________________________
+1V
-1V
GENERATOR
VID
S3
S2
S1
1kΩ
CL
15pF
50Ω
VCC
RO
RE RE
RO
RE
RO
RO
RE
VCC/2
VCC
VCC
VCC
VOL
0
0
0
0
00
VOH
VOH
0.25V
0.25V
VOH/2
S1 OPEN
S2 CLOSED
S3 = +1V
S1 CLOSED
S2 OPEN
S3 = -1V
S1 OPEN
S2 CLOSED
S3 = +1V
S1 CLOSED
S2 OPEN
S3 = -1V
tRZH, tRZH(SHDN) tRZL, tRZL(SHDN)
tRLZ
tRHZ
VCC/2
VCC/2
VCC
(VOL + VCC)/2
VCC
VCC
VOL
VCC/2
Figure 8. Receiver Enable and Disable Times
Test Circuits and Waveforms (continued)
MAX13485E/MAX13486E
Detailed Description
The MAX13485E/MAX13486E half-duplex, high-speed
transceivers for RS-485/RS-422 communication contain
one driver and one receiver. These devices feature fail-
safe circuitry that guarantees a logic-high receiver out-
put when receiver inputs are open or shorted, or when
they are connected to a terminated transmission line
with all drivers disabled (see the
Fail-Safe
section). The
MAX13485E/MAX13486E also feature a hot-swap capa-
bility allowing line insertion without erroneous data
transfer (see the
Hot-Swap Capability
section). The
MAX13485E features reduced slew-rate drivers that
minimize EMI and reduce reflections caused by
improperly terminated cables, allowing error-free trans-
mission up to 500kbps. The MAX13486E driver slew
rate is not limited, making transmit speeds up to
16Mbps possible.
Fail-Safe
The MAX13485E/MAX13486E guarantee 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. This is done by
setting the receiver input threshold between -50mV and
-200mV. If the differential receiver input voltage (A - B) is
greater than or 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 terminated bus with all transmitters disabled,
the receiver’s differential input voltage is pulled to 0V by
the termination. With the receiver thresholds of the
MAX13485E/MAX13486E, this results is 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
backplane, differential disturbances to the data bus
can lead to data errors. Upon initial circuit-board inser-
tion, the data communication processor undergoes its
own power-up sequence. During this period, the
processor’s logic-output drivers are high impedance
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.
Additionally, parasitic circuit-board capacitance could
cause coupling of VCC or GND to the enable inputs.
Without the hot-swap capability, these factors could
improperly enable the transceiver’s driver or receiver.
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
hot-swap tolerable input.
Hot-Swap Input Circuitry
The enable inputs feature hot-swap capability. At the
input there are two nMOS devices, M1 and M2 (Figure
9). When VCC ramps from zero, an internal 7µs timer
turns on M2 and sets the SR latch, which also turns on
M1. Transistors M2, a 1.5mA current sink, and M1, a
500µA current sink, pull DE to GND through a 5kΩ
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 7µs, the timer deactivates
M2 while M1 remains on, holding DE low against tri-
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 hot-swap input is reset.
For RE there is a complementary circuit employing two
pMOS devices pulling RE to VCC.
Half-Duplex RS-485/RS-422 Transceivers in µDFN
12 ______________________________________________________________________________________
DE DE
(HOT SWAP)
5kΩ
TIMER
TIMER
VCC
10μs
M2M1
500μA
100μA
SR LATCH
Figure 9. Simplified Structure of the Driver Enable Pin (DE)
+15V ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges encountered during handling and
assembly. The driver outputs and receiver inputs of the
MAX13485E/MAX13486E have extra protection against
static electricity. Maxim’s engineers have developed
state-of-the-art structures to protect these pins against
ESD of ±15kV without damage. The ESD structures
withstand high ESD in all states: normal operation, shut-
down, and powered down. After an ESD event, the
MAX13485E/MAX13486E keep working without latchup
or damage.
ESD protection can be tested in various ways. The trans-
mitter outputs and receiver inputs of the MAX13485E/
MAX13486E are characterized for protection to the follow-
ing limits:
• ±15kV using the Human Body Model
• ±15kV using the Air Gap Discharge Method specified
in IEC 61000-4-2 (MAX13485E only)
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
Figure 10a shows the Human Body Model, and Figure
10b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the test device
through a 1.5kΩresistor.
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
MAX13485E/MAX13486E help equipment designs to
meet IEC 61000-4-2, without the need for additional
ESD-protection components.
The major difference between tests done using the
Human Body Model and IEC 61000-4-2 is higher peak
current in IEC 61000-4-2 because series resistance is
lower in the IEC 61000-4-2 model. Hence, the ESD
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
______________________________________________________________________________________ 13
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC
1MΩ
RD
1500Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 10a. Human Body ESD Test Model
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
0
0
AMPS
Figure 10b. Human Body Current Waveform
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
150pF
RC
50MΩ TO 100MΩ
RD
330Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 10c. IEC 61000-4-2 ESD Test Model
tr = 0.7ns TO 1ns 30ns
60ns
t
100%
90%
10%
I
PEAK
I
Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform
MAX13485E/MAX13486E
withstand voltage measured to IEC 61000-4-2 is gener-
ally lower than that measured using the Human Body
Model. Figure 10c shows the IEC 61000-4-2 model,
and Figure 10d shows the current waveform for the IEC
61000-4-2 ESD Contact Discharge test.
Machine Model
The machine model for ESD tests all pins using a 200pF
storage capacitor and zero discharge resistance.
The objective is to emulate the stress caused when I/O
pins are contacted by handling equipment during test
and assembly. Of course, all pins require this protec-
tion, not just RS-485 inputs and outputs.
The air-gap test involves approaching the device with a
charged probe. The contact-discharge method connects
the probe to the device before the probe is energized.
Applications Information
128 Transceivers on the Bus
The standard RS-485 receiver input impedance is 12kΩ
(1-unit load), and the standard driver can drive up to
32-unit loads. The MAX13485E/MAX13486E have a 1/4-
unit load receiver input impedance (48kΩ), allowing up
to 128 transceivers to be connected in parallel on one
communication line. Any combination of these devices,
as well as other RS-485 transceivers with a total of 32-
unit loads or fewer, can be connected to the line.
Reduced EMI and Reflections
The MAX13485E features reduced slew-rate drivers
that minimize EMI and reduce reflections caused by
improperly terminated cables, allowing error-free data
transmission up to 500kbps.
Low-Power Shutdown Mode
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the devices draw a
maximum of 10µA of supply current.
RE and DE can be driven simultaneously. The devices
are guaranteed not to enter shutdown if RE is high and
DE is low for less than 50ns. If the inputs are in this
state for at least 700ns, the devices are guaranteed to
enter shutdown.
Enable times tZH and tZL (see the
Switching Character-
istics
) assume the devices were not in a low-power shut-
down state. Enable times tZH(SHDN) and tZL(SHDN)
assume the devices were in shutdown state. It takes dri-
vers and receivers longer to become enabled from low-
power shutdown mode (tZH(SHDN), tZL(SHDN)) than from
driver-/receiver-disable mode (tZH, tZL).
Line Length
The RS-485/RS-422 standard covers line lengths up to
4000ft.
Typical Applications
The MAX13485E/MAX13486E transceivers are
designed for half-duplex, bidirectional data communi-
cations on multipoint bus transmission lines. Figure 11
shows typical network applications circuits. To mini-
mize reflections, terminate the line at both ends in its
characteristic impedance, and keep stub lengths off
the main line as short as possible. The slew-rate-limited
MAX13485E is more tolerant of imperfect termination.
Chip Information
PROCESS: BiCMOS
Half-Duplex RS-485/RS-422 Transceivers in µDFN
14 ______________________________________________________________________________________
R
R
R
DD
D
DI DI
RO RO
RE
RE
RtRt
R
D
DI RO RE DI RO RE
DE
DE
DE
DE
MAX13485E
MAX13486E
Figure 11. Typical Half-Duplex RS-485 Network
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
______________________________________________________________________________________ 15
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
SOICN .EPS
PACKAGE OUTLINE, .150" SOIC
1
1
21-0041 B
REV.DOCUMENT CONTROL NO.APPROVAL
PROPRIETARY INFORMATION
TITLE:
TOP VIEW
FRONT VIEW
MAX
0.010
0.069
0.019
0.157
0.010
INCHES
0.150
0.007
E
C
DIM
0.014
0.004
B
A1
MIN
0.053A
0.19
3.80 4.00
0.25
MILLIMETERS
0.10
0.35
1.35
MIN
0.49
0.25
MAX
1.75
0.050
0.016L0.40 1.27
0.3940.386D
D
MINDIM
D
INCHES
MAX
9.80 10.00
MILLIMETERS
MIN MAX
16 AC
0.337 0.344 AB8.758.55 14
0.189 0.197 AA5.004.80 8
N MS012
N
SIDE VIEW
H 0.2440.228 5.80 6.20
e 0.050 BSC 1.27 BSC
C
HE
eBA1
A
D
0∞-8∞
L
1
VARIATIONS:
6, 8, 10L UDFN.EPS
EVEN TERMINAL
L
C
ODD TERMINAL
L
C
L
e
L
A
e
E
D
PIN 1
INDEX AREA
b
e
A
b
N
SOLDER
MASK
COVERAGE
A A
1
PIN 1
0.10x45∞
LL1
(N/2 -1) x e)
XXXX
XXXX
XXXX
SAMPLE
MARKING
A1
A2
7
A
1
2
21-0164
PACKAGE OUTLINE,
6, 8, 10L uDFN, 2x2x0.80 mm
-DRAWING NOT TO SCALE-
COMMON DIMENSIONS
SYMBOL MIN. NOM.
A0.70 0.75
A1
D1.95 2.00
E1.95 2.00
L0.30 0.40
PKG. CODE N e b
PACKAGE VARIATIONS
L1
6L622-1 0.65 BSC 0.30±0.05
0.25±0.050.50 BSC8L822-1
0.20±0.030.40 BSC10L1022-1
2.05
0.80
MAX.
0.50
2.05
0.10 REF.
(N/2 -1) x e
1.60 REF.
1.50 REF.
1.30 REF.
A2
-
-DRAWING NOT TO SCALE-
A
2
2
21-0164
PACKAGE OUTLINE,
6, 8, 10L uDFN, 2x2x0.80 mm
0.15 0.20 0.25
0.020 0.025 0.035
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Boblet
