Maxim MAX13485EESA+ Half-duplex rs-485/rs-422 transceivers in udfn Datasheet

19-0742; Rev 0; 1/07
Half-Duplex RS-485/RS-422 Transceivers in µDFN
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 logichigh 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 transmission 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
Features
♦ +5V Operation
♦ True Fail-Safe Receiver While Maintaining
EIA/TIA-485 Compatibility
♦ Hot-Swappable for Telecom Applications
♦ Enhanced Slew-Rate Limiting Facilitates ErrorFree Data Transmission (MAX13485E)
♦ High-Speed Version (MAX13488E) 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
Ordering Information/
Selector Guide
PART
PINPACKAGE
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.
Industrial Motor Drives
Automated HVAC Systems
Pin Configurations
TOP VIEW
VCC
B
A
GND
8
7
6
5
MAX13485E
MAX13486E
DE
+
0.1µF
1
2
RO
3
RE
DE
4
RO
DI
+
RO
MAX13485E
MAX13486E
1
8
R
2
7
B
DE
3
6
A
5
GND
D
8
R
7
DE 3
4
DI
6
5
D
VCC
D
B
Rt
A
R
SO
DI
B
Rt
A
VCC
RE
DI 4
+
2
RE
DFN
1
RO
GND
RE
SO
________________________________________________________________ Maxim Integrated Products
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.
1
MAX13485E/MAX13486E
General Description
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
ABSOLUTE MAXIMUM RATINGS
(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
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.
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
Differential Driver Output
VOD
RDIFF = 100Ω, Figure 1
2.0
RDIFF = 54Ω, Figure 1
1.5
VCC
V
No load
VCC
0.2
V
3
V
0.2
V
Change in Magnitude of
Differential Output Voltage
∆VOD
RDIFF = 100Ω or 54Ω, Figure 1 (Note 3)
Driver Common-Mode Output
Voltage
VOC
RDIFF = 100Ω or 54Ω, Figure 1
Change in Magnitude of
Common-Mode Voltage
∆VOC
RDIFF = 100Ω or 54Ω, Figure 1 (Note 3)
VCC
/2
Input-High Voltage
VIH
DI, DE, RE
Input-Low Voltage
VIL
DI, DE, RE
0.8
V
Input Current
IIN
DI, DE, RE
±1
µA
Driver Short-Circuit Output
Current (Note 4)
IOSD
Driver Short-Circuit Foldback
Output Current Note 3)
IOSDF
2.0
V
0V < VOUT < +12V
+50
+250
-7V < VOUT < 0V
-250
-50
(VCC - 1V) < VOUT < +12V
20
-7V < VOUT < 0V
-20
mA
mA
RECEIVER
Input Current (A and B)
IA, B
DE = GND, VCC = GND
or +5V
Receiver-Differential-Threshold
Voltage
VTH
-7V < VCM < +12V
Receiver Input Hysteresis
∆VTH
VA + VB = 0V
Output-High Voltage
2
VOH
IO = -1.6mA, VA - VB > VTH
VIN = +12V
VIN = -7V
250
-200
-200
-50
25
VCC 1.5
_______________________________________________________________________________________
µA
mV
mV
V
Half-Duplex RS-485/RS-422 Transceivers in µDFN
ELECTRICAL CHARACTERISTICS (continued)
MAX
UNITS
Output-Low Voltage
PARAMETER
SYMBOL
VOL
IO = 1mA, VA - VB < -VTH
CONDITIONS
MIN
TYP
0.4
V
Tri-State Output Current at
Receiver
IOZR
0V < VO < VCC
±1
µA
Receiver Input Resistance
RIN
-7V < VCM < +12V
48
Receiver-Output Short-Circuit
Current
IOSR
0V < VRO < VCC
±7
±95
4.75
kΩ
mA
POWER SUPPLY
Supply Voltage
VCC
Supply Current
ICC
Shutdown Supply Current
ISHDN
5.25
V
DE = 1, RE = 0, no load
4.5
mA
DE = 0, RE = 1
10
µA
ESD PROTECTION
ESD Protection (A, B)
ESD Protection (All Other Pins)
Air Gap Discharge IEC61000-4-2
(MAX13485E)
±15
Human Body Model
±15
Human Body Model
±2
kV
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
Driver Propagation Delay
Driver-Differential Output Rise or
Fall Time
Driver-Differential Output Skew
|tDPLH - tDPHL|
tDPLH
tDPHL
tHL
tLH
tDSKEW
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3
200
1000
200
1000
250
900
250
900
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3
Maximum Data Rate
140
500
ns
ns
ns
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
700
ns
Time to Shutdown
tSHDN
50
340
RECEIVER
Receiver Propagation Delay
Receiver Output Skew
Maximum Data Rate
tRPLH
tRPHL
tRSKEW
80
CL = 15pF, Figures 6 and 7
80
CL = 15pF, Figure 7
13
500
ns
ns
kbps
_______________________________________________________________________________________
3
MAX13485E/MAX13486E
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) (Notes 1, 2)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
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
700
ns
Time to Shutdown
tSHDN
50
340
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
Driver Propagation Delay
Driver Differential Output Rise or
Fall Time
Differential Driver Output Skew
|tDPLH - tDPHL|
tDPLH
tDPHL
tHL
tLH
tDSKEW
50
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3
50
15
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3
15
RDIFF = 54Ω, CL = 50pF, Figures 2 and 3
Maximum Data Rate
8
16
ns
ns
ns
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
700
ns
Time to Shutdown
tSHDN
50
340
RECEIVER
Receiver Propagation Delay
Receiver Output Skew
Maximum Data Rate
4
tRPLH
tRPHL
tRSKEW
80
CL = 15pF, Figures 6 and 7
80
CL = 15pF, Figure 7
13
16
_______________________________________________________________________________________
ns
ns
Mbps
Half-Duplex RS-485/RS-422 Transceivers in µDFN
(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
700
ns
Time to Shutdown
tSHDN
50
340
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: ∆VOD and ∆VOC 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.)
OUTPUT CURRENT vs. RECEIVER
OUTPUT HIGH VOLTAGE
3.6
3.4
28
21
14
7
3.2
-40
-15
10
35
TEMPERATURE (°C)
60
85
50
40
30
20
10
0
0
3.0
60
MAX13485-86E toc03
35
OUTPUT CURRENT (mA)
SUPPLY CURRENT (mA)
3.8
OUTPUT CURRENT vs. RECEIVER
OUTPUT LOW VOLTAGE
MAX13485-86E toc02
NO LOAD
OUTPUT CURRENT (mA)
4.0
MAX13485-86E toc01
SUPPLY CURRENT vs. TEMPERATURE
0
1
2
3
OUTPUT HIGH VOLTAGE (V)
4
5
0
1
2
3
4
5
OUTPUT LOW VOLTAGE (V)
_______________________________________________________________________________________
5
MAX13485E/MAX13486E
SWITCHING CHARACTERISTICS—MAX13486E (continued)
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
RECEIVER OUTPUT HIGH
VOLTAGE vs. TEMPERATURE
4.8
4.6
4.4
0.4
0.3
0.2
80
MAX13485-86E toc06
IO = 1mA
OUTPUT CURRENT (mA)
5.0
MAX13485-86E toc05
OUTPUT HIGH VOLTAGE (V)
5.2
DIFFERENTIAL OUPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
0.5
OUTPUT LOW VOLTAGE (V)
IO = 1mA
RECEIVER OUTPUT LOW
VOLTAGE vs. TEMPERATURE
MAX13485-86E toc04
5.4
60
40
20
0.1
4.2
4.0
-15
10
35
60
85
-40
-15
10
35
60
0
85
2
3
DRIVER-DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
OUTPUT CURRENT vs. TRANSMITTER
OUTPUT HIGH VOLTAGE
OUTPUT CURRENT vs. TRANSMITTER
OUTPUT LOW VOLTAGE
1.5
1.0
0.5
80
60
40
100
35
60
-7 -6 -5 -4 -3 -2 -1 0
85
60
40
0
0
10
80
20
20
-15
MAX13485-86E toc09
MAX13485-86E toc08
100
120
OUTPUT CURRENT (mA)
2.0
120
OUTPUT CURRENT (mA)
2.5
MAX13485-86E toc07
OUTPUT VOLTAGE (V)
0
1
2
3
4
5
0
2
4
6
8
10
TEMPERATURE (°C)
OUTPUT HIGH VOLTAGE (V)
OUTPUT LOW VOLTAGE (V)
SHUTDOWN CURRENT
vs. TEMPERATURE
DRIVER PROPAGATION
vs. TEMPERATURE (MAX13485E)
DRIVER PROPAGATION DELAY
vs. TEMPERATURE (MAX13486E)
6
5
4
3
2
500
tDPHL
450
400
350
12
MAX13485-86E toc12
7
tDPLH
550
30
DRIVER PROPAGATION DELAY (ns)
8
600
MAX13485-86E toc11
9
DRIVER PROPAGATION DELAY (ns)
MAX13485-86E toc10
10
25
20
15
10
tDPLH
5
1
tDPHL
300
0
-40
-15
10
35
TEMPERATURE (°C)
6
5
4
TEMPERATURE (°C)
RDIFF = 54Ω
-40
1
TEMPERATURE (°C)
3.0
DIFFERENTIAL OUTPUT VOLTAGE (V)
0
0
-40
SHUTDOWN CURRENT (µA)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
60
85
0
-40
-15
10
35
TEMPERATURE (°C)
60
85
-40
-15
10
35
TEMPERATURE (°C)
_______________________________________________________________________________________
60
85
Half-Duplex RS-485/RS-422 Transceivers in µDFN
RECEIVER PROPAGATION
vs. TEMPERATURE (MAX13485E)
tRPHL
40
20
MAX13485-86E toc14
60
DRIVER PROPAGATION (500kbps)
(MAX13485E)
MAX13485/86E toc15
40
RECEIVER PROPAGATION (ns)
MAX13485-86E toc13
PROPAGATION DELAY (ns)
80
RECEIVER PROPAGATION
vs. TEMPERATURE (MAX13486E)
30
DI
2V/div
tRPLH
20
tRPHL
A-B
5V/div
10
tRPLH
0
0
-40
-15
10
35
60
85
-40
TEMPERATURE (°C)
-15
10
35
60
85
400ns/div
TEMPERATURE (°C)
DRIVER PROPAGATION (16Mbps)
(MAX13486E)
RECEIVER PROPAGATION (16Mbps)
(MAX13486E)
MAX13485/86E toc16
MAX13485/86E toc17
B
2V/div
DI
2V/div
A
2V/div
A-B
5V/div
10ns/div
RO
2V/div
10ns/div
_______________________________________________________________________________________
7
MAX13485E/MAX13486E
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
Test Circuits and Waveforms
A
5V
RDIFF
DE
2
A
DI
VOD
VID
CL
RDIFF
B
RDIFF
VOC
2
B
Figure 2. Driver Timing Test Circuit
Figure 1. Driver DC Test Load
f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns
VCC
DI
1.5V
1.5V
0
1/2 VO
tDPHL
tDPLH
B
A
1/2 VO
VO
VDIFF = V(A) - V(B)
VO
VDIFF
90%
90%
0
10%
10%
-VO
tHL
tLH
tDSKEW = |tDPLH - tDPHL|
Figure 3. Driver Propagation Delays
8
_______________________________________________________________________________________
CL
Half-Duplex RS-485/RS-422 Transceivers in µDFN
VCC
DE
1.5V
1.5V
0
tDLZ
tDZL(SHDN),tDZL
A, B
2.3V
VOL + 0.5V
OUTPUT NORMALLY LOW
VOL
OUTPUT NORMALLY HIGH
A, B
2.3V
VOH + 0.5V
0
tDZH(SHDN),tDZH
tDHZ
Figure 4. Driver Enable and Disable Times
500Ω
S1
VCC
B
OUTPUT
UNDER TEST
R
VID
ATE
CL
RECEIVER
OUTPUT
A
S2
Figure 5. Driver-Enable and -Disable-Timing Test Load
Figure 6. Receiver Propagation Delay Test Circuit
f = 1MHz, tLH ≤ 3ns, tHL ≤ 3ns
A
1V
B
-1V
tRPHL
tRPLH
VOH
RO
1.5V
VOL
1.5V
tRSKEW = |tRPHL - tRPLH|
Figure 7. Receiver Propagation Delays
_______________________________________________________________________________________
9
MAX13485E/MAX13486E
Test Circuits and Waveforms (continued)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
Pin Description
PIN
NAME
FUNCTION
1
RO
Receiver Output
2
RE
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).
3
DE
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).
4
DI
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
6
A
Noninverting Receiver Input and Noninverting Driver Output
7
B
Inverting Receiver Input and Inverting Driver Output
8
VCC
Ground
Positive Supply, VCC = +5V ±5%. Bypass VCC to GND with a 0.1µF capacitor.
Function Tables
TRANSMITTING
INPUT
OUTPUT
RE
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
RECEIVING
INPUT
OUTPUT
RE
DE
0
X
> -50mV
1
0
X
< -200mV
0
0
X
OPEN/SHORT
1
A-B
RO
1
1
X
HIGH IMPEDANCE
1
0
X
SHUTDOWN
X = Don’t care, shutdown mode, driver, and receiver outputs
are in high impedance.
10
______________________________________________________________________
Half-Duplex RS-485/RS-422 Transceivers in µDFN
S1
+1V
S3
VCC
1kΩ
-1V
VID
CL
15pF
GENERATOR
S2
50Ω
S1 OPEN
S2 CLOSED
S3 = +1V
S1 CLOSED
S2 OPEN
S3 = -1V
VCC
VCC
VCC/2
VCC/2
RE
RE
0
0
tRZH, tRZH(SHDN)
tRZL, tRZL(SHDN)
VOH
RO
VCC
VOH/2
(VOL + VCC)/2
RO
0
S1 OPEN
S2 CLOSED
S3 = +1V
VOL
S1 CLOSED
S2 OPEN
S3 = -1V
VCC
VCC/2
VCC/2
RE
0
RE
VCC
0
tRLZ
tRHZ
VCC
VOH
RO
0.25V
0
RO
0.25V
Figure 8. Receiver Enable and Disable Times
__________________________________________________________________________
VOL
MAX13485E/MAX13486E
Test Circuits and Waveforms (continued)
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
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 failsafe circuitry that guarantees a logic-high receiver output 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 capability 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 transmission up to 500kbps. The MAX13486E driver slew
rate is not limited, making transmit speeds up to
16Mbps possible.
VCC
10µs
TIMER
SR LATCH
TIMER
5kΩ
DE
(HOT SWAP)
DE
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 insertion, 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 processor’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.
12
100µA
500µA
M1
M2
Figure 9. Simplified Structure of the Driver Enable Pin (DE)
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 tristate 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 highimpedance 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
CHARGE-CURRENT
LIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
Cs
100pF
RC
50MΩ TO 100MΩ
RD
1500Ω
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
DEVICE
UNDER
TEST
STORAGE
CAPACITOR
Figure 10a. Human Body ESD Test Model
IP 100%
90%
Cs
150pF
RD
330Ω
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 10c. ICE 61000-4-2 ESD Test Model
I
100%
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
IPEAK
Ir
HIGHVOLTAGE
DC
SOURCE
MAX13485E/MAX13486E
RC
1MΩ
AMPS
36.8%
10%
0
10%
0
tRL
TIME
tr = 0.7ns TO 1ns
tDL
CURRENT WAVEFORM
Figure 10b. Human Body Current Waveform
+15V ESD Protection
As with all Maxim devices, 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
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, shutdown, 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 transmitter outputs and receiver inputs of the MAX13485E/
MAX13486E are characterized for protection to the following limits:
• ±15kV using the Human Body Model
• ±15kV using the Air Gap Discharge Method specified
in IEC 61000-4-2 (MAX13485E only)
t
30ns
60ns
Figure 10d. IEC 61000-4-2 ESD Generator Current Waveform
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 discharged into a low impedance. 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.
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
______________________________________________________________________________________
13
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
DI
D
Rt
D
Rt
DE
RO
RE
DI
DE
R
R
R
MAX13485E
MAX13486E
R
D
D
DI
RO
RE
DE
RO
RE
DI
DE
RO
RE
Figure 11. Typical Half-Duplex RS-485 Network
withstand voltage measured to IEC 61000-4-2 is generally 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 protection, 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.
Enable times tZH and tZL (see the Switching Characteristics) assume the devices were not in a low-power shutdown state. Enable times t ZH(SHDN) and t ZL(SHDN)
assume the devices were in shutdown state. It takes drivers and receivers longer to become enabled from lowpower shutdown mode (tZH(SHDN), tZL(SHDN)) than from
driver-/receiver-disable mode (tZH, tZL).
Applications Information
Line Length
128 Transceivers on the Bus
The RS-485/RS-422 standard covers line lengths up to
4000ft.
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 1/4unit 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 32unit 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.
14
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.
Typical Applications
The MAX13485E/MAX13486E transceivers are
designed for half-duplex, bidirectional data communications on multipoint bus transmission lines. Figure 11
shows typical network applications circuits. To minimize 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
N
E
H
INCHES
MILLIMETERS
MAX
MIN
0.069
0.053
0.010
0.004
0.014
0.019
0.007
0.010
0.050 BSC
0.150
0.157
0.228
0.244
0.016
0.050
MAX
MIN
1.35
1.75
0.10
0.25
0.35
0.49
0.19
0.25
1.27 BSC
3.80
4.00
5.80
6.20
0.40
SOICN .EPS
DIM
A
A1
B
C
e
E
H
L
1.27
VARIATIONS:
1
INCHES
TOP VIEW
DIM
D
D
D
MIN
0.189
0.337
0.386
MAX
0.197
0.344
0.394
MILLIMETERS
MIN
4.80
8.55
9.80
MAX
5.00
8.75
10.00
N MS012
8
AA
14
AB
16
AC
D
A
B
e
C
0 -8
A1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL
DOCUMENT CONTROL NO.
21-0041
REV.
B
1
1
______________________________________________________________________________________
15
MAX13485E/MAX13486E
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.)
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.)
A
D
XXXX
XXXX
XXXX
b
e
6, 8, 10L UDFN.EPS
MAX13485E/MAX13486E
Half-Duplex RS-485/RS-422 Transceivers in µDFN
N
SOLDER
MASK
COVERAGE
E
PIN 1
0.10x45
L
L1
1
SAMPLE
MARKING
PIN 1
INDEX AREA
A
A
(N/2 -1) x e)
7
CL
CL
b
L
L
A
A2
e
EVEN TERMINAL
A1
e
ODD TERMINAL
PACKAGE OUTLINE,
6, 8, 10L uDFN, 2x2x0.80 mm
21-0164
-DRAWING NOT TO SCALE-
A
1
2
COMMON DIMENSIONS
SYMBOL
MIN.
NOM.
MAX.
A
0.70
0.75
0.80
A1
0.15
0.20
0.25
A2
0.020
0.025
0.035
D
1.95
2.00
E
1.95
2.00
L
0.30
0.40
L1
-
2.05
2.05
0.50
0.10 REF.
PACKAGE VARIATIONS
PKG. CODE
N
e
b
(N/2 -1) x e
L622-1
6
0.65 BSC
0.30–0.05
1.30 REF.
L822-1
8
0.50 BSC
0.25–0.05
1.50 REF.
L1022-1
10
0.40 BSC
0.20–0.03
1.60 REF.
PACKAGE OUTLINE,
6, 8, 10L uDFN, 2x2x0.80 mm
-DRAWING NOT TO SCALE-
21-0164
A
2
2
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
Boblet
is a registered trademark of Maxim Integrated Products, Inc.
Similar pages