Maxim MAX3466EPD 5v, fail-safe, 40mbps, profibus rs-485/rs-422 transceiver Datasheet

19-3038; Rev 2; 8/09
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
The MAX3465–MAX3469 are high-speed differential
bus transceivers for RS-485 and RS-422 communications. They are designed to meet TIA/EIA-422-B,
TIA/EIA-485-A, V.11, and X.27 standards. The transceiver complies with the Profibus specification providing +2.1V minimum output level with a 54Ω load,
40Mbps data rate, and output skew less than 2ns. Each
part contains one three-state differential line driver and
one differential input line receiver. The devices operate
from a +5V supply and feature true fail-safe circuitry,
which guarantees a logic-high receiver output when the
receiver inputs are open or shorted. This enables all
receiver outputs on a terminated bus to output logic
highs when all transmitters are disabled.
All devices feature a 1/4-standard-unit load receiver
input impedance that allows 128 transceivers on the
bus. Driver and receiver propagation delays are guaranteed under 20ns for multidrop, clock distribution
applications. Drivers are short-circuit current limited
and are protected against excessive power dissipation
by thermal-shutdown circuitry. The driver and receiver
feature active-high and active-low enables, respectively, that can be connected together externally to serve
as a direction control.
Features
♦ Recommended for Profibus Applications
♦ Up to 40Mbps Data Rate
♦ 15ns Transmitter Propagation Delay
♦ 20ns Receiver Propagation Delay
♦ 2ns Transmitter and Receiver Skew
♦ High Differential Driver Output Level (2.1V on 54Ω)
♦ Hot-Swap Versions
♦ 1µA Shutdown Supply Current
♦ Low Supply Current Requirements (2.5mA, typ)
♦ Allow Up to 128 Transceivers on the Bus
♦ True Fail-Safe Receiver while Maintaining EIA/TIA485 Compatibility
♦ Designed for Multipoint Transmissions on Long
or Noisy Bus Lines
♦ Full-Duplex and Half-Duplex Versions Available
♦ Phase Controls to Correct for Twisted-Pair
Reversal for 14-Pin Versions
♦ Current-Limiting and Thermal Shutdown for
Driver Overload Protection
Ordering Information
Applications
High-Speed RS-485 Communications
PART
TEMP RANGE
PIN-PACKAGE
High-Speed RS-422 Communications
MAX3465CSD
Level Translators
MAX3465CPD
0°C to +70°C
Industrial-Control Local Area Networks
MAX3465ESD
-40°C to +85°C
14 SO
Profibus Applications
MAX3465EPD
-40°C to +85°C
14 Plastic DIP
0°C to +70°C
14 SO
14 Plastic DIP
Ordering Information continued at end of data sheet.
Pin Configurations appear at end of data sheet.
Selector Guide
MAX3465
Full
RECEIVER/
DRIVER
ENABLE
Yes
MAX3466
Full
Yes
PART
NUMBER
HALF/FULL
DUPLEX
LOWPOWER
SHUTDOWN
Yes
Yes
Yes
RECEIVER/
DRIVER PHASE
SELECT
Yes
No
Yes
HOT SWAP
INDEPENDENT
SHDN PIN
PIN COUNT
Yes
14
Yes
14
MAX3467
Full
No
No
No
No
No
8
MAX3468
Half
Yes
Yes
Yes
No
No
8
MAX3469
Half
Yes
Yes
No
No
No
8
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX3465–MAX3469
General Description
MAX3465–MAX3469
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) to GND ..................................-0.3V to +6V
Control Input Voltage (RE, DE, DI, SHDN, TXP, RXP)
to GND....................................................-0.3V to (VCC + 0.3V)
Driver Output Voltage (Y, Z) to GND .........................-8V to +13V
Receiver Input Voltage (A, B) to GND.......................-8V to +13V
Differential Driver Output Voltage (Y - Z) ...............................±8V
Differential Receiver Input (A - B) ..........................................±8V
Receiver Output Voltage (RO) to GND.......-0.3V to (VCC + 0.3V)
Output Driver Current (Y, Z) ...........................................±250mA
Continuous Power Dissipation (TA = +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin DIP (derate 9.09mW/°C above +70°C) ...............727mW
14-Pin SO (derate 8.33mW/°C above +70°C)..............667mW
14-Pin DIP (derate 10mW/°C above +70°C) ................800mW
Operating Temperature Range
MAX346_C__ ......................................................0°C to +70°C
MAX346_E__....................................................-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.) (Note 1)
PARAMETER
Power-Supply Range
SYMBOL
CONDITIONS
VCC
MIN
TYP
4.75
MAX
UNITS
5.25
V
VCC
V
DRIVER
Differential Driver Output
(No Load)
VOD
Figure 5, R = ∞
Differential Driver Output
VOD
Figure 5, R = 27Ω
Change in Magnitude of
Differential Output Voltage
ΔVOD
Figure 5, R = 50Ω or 27Ω (Note 2)
Driver Common-Mode Output
Voltage
VOC
Figure 5, R = 50Ω or 27Ω
Change in Magnitude of
Common-Mode Voltage
ΔVOC
Figure 5, R = 50Ω or 27Ω (Note 2)
Input High Voltage
VIH
DE, DI, RE, SHDN
Input Low Voltage
VIL
DE, DI, RE, SHDN
VHYS
DE, DI, RE, SHDN
Output Leakage (Y and Z) Full
Duplex
IO
DE = GND, VCC =
GND or +5.25V
Input Current
IIN
DI, RE, DE, SHDN
Input Hysteresis
2.1
V
0.2
V
3
V
0.2
V
2.0
V
0.8
50
VIN = +12V
VIN = -7V
Pulldown Current
RXP = TXP = VCC
Driver Short-Circuit Output
Current (Note 3)
IOSD
0 ≤ VOUT ≤ +12V, output low
Driver Short-Circuit Foldback
Output Current (Note 3)
IOSFD
+125
-100
5
15
-250
(VCC - 1V) ≤ VOUT ≤ +12V, output low
+25
-7V ≤ VOUT ≤ +1V, output high
µA
30
µA
-25
Thermal Shutdown Threshold
µA
±1
+250
-7V ≤ VOUT ≤ VCC, output high
V
mV
mA
mA
°C
140
RECEIVER
Differential Input Capacitance
Input Current (A and B) Full
Duplex
2
CA, B
IA, B
Between A and B
DE = GND,
VCC = GND or +5.25V
8
VIN = +12V
VIN = -7V
pF
+250
-200
_______________________________________________________________________________________
µA
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
(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
-200
-125
-50
mV
Receiver Differential Threshold
Voltage
VTH
-7V ≤ VCM ≤ +12V
Receiver Input Hysteresis
ΔVTH
VCM = 0
Receiver Output High Voltage
VOH
IO = -4mA, VA - VB = VTH
Receiver Output Low Voltage
VOL
IO = 4mA, VB - VA = VTH
0.4
V
Three-State Output Current at
Receiver
IOZR
0 ≤ VO ≤ VCC
±1
µA
Receiver Input Resistance
RIN
-7V ≤ VCM ≤ +12V
48
Receiver Output Short-Circuit
Current
IOSR
0 ≤ VRO ≤ VCC
±7
ESD Protection
20
mV
VCC - 1.5
V
kΩ
±95
mA
A, B, Y, and Z pins
(MAX3467/MAX3468/MAX3469)
±6
No load, DI = VCC or DI = GND
2.5
4
mA
1
10
µA
Figures 6 and 7, RDIFF = 54Ω,
CL = 50pF
15
ns
Figures 6 and 7, RDIFF = 54Ω,
CL = 50pF
10
ns
Figures 6 and 7, RDIFF = 54Ω,
CL = 50pF, TXP = GND or open
2
ns
kV
SUPPLY CURRENT
Normal Operation
(Static Condition)
IQ
Supply Current in SHDN
ISHDN
DE = GND and RE = VCC, or SHDN = VCC
SWITCHING CHARACTERISTICS
Driver Propagation Delay
tPLH
tPHL
Driver Differential Output Rise or
Fall Time
tR
Driver Output Skew |tPLH - tPHL|
tSKEW
tF
Driver Output Transition Skew
Guaranteed by design
Maximum Data Rate
1
30
40
ns
Mbps
Driver Enable to Output High
tZH
Figures 8 and 9, S2 closed, RL = 500Ω,
CL = 50pF
30
ns
Driver Enable to Output Low
tZL
Figures 8 and 9, S1 closed, RL = 500Ω,
CL = 50pF
30
ns
Driver Disable Time from Low
tLZ
Figures 8 and 9, S1 closed, RL = 500Ω,
CL = 50pF
30
ns
Driver Disable to Output High
tHZ
Figures 8 and 9, S2 closed, RL = 500Ω,
CL = 50pF
30
ns
Driver Enable Skew Time
|tZL - tZH|
RL = 500Ω, CL = 50pF, S1 closed (Figures
8 and 9), output low
5
ns
Driver Disable Skew Time
|tZL - tZH|
RL = 500Ω, CL = 50pF, S2 closed (Figures
8 and 9), output high
5
ns
Figure 10, CL = 15pF (Note 4)
20
ns
Receiver Propagation Delay
tPLH
tPHL
_______________________________________________________________________________________
3
MAX3465–MAX3469
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (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
|tPLH tPHL|
Receiver Output Skew
MIN
TYP
MAX
UNITS
Figure 10, CL = 15pF, RXP = GND or open
(Note 4)
2
ns
Receiver Enable to Output Low
tZL
Figures 8 and 11, RL = 1kΩ, CL = 15pF,
S1 closed (Note 4)
30
ns
Receiver Enable to Output High
tZH
Figures 8 and 11, RL = 1kΩ, CL = 15pF,
S2 closed (Note 4)
30
ns
Receiver Disable Time from Low
tLZ
Figures 8 and 11, RL = 1kΩ, CL = 15pF,
S1 closed (Note 4)
30
ns
Receiver Disable Time from High
tHZ
Figures 8 and 11, RL = 1kΩ, CL = 15pF,
S2 closed (Note 4)
30
ns
Time to Shutdown
tSHDN
800
ns
tZH (SHDN)
Figures 8 and 9, RL = 500Ω, CL = 50pF,
S2 closed (Note 5)
4
µs
Driver Enable from Shutdown to
Output Low
tZL (SHDN)
Figures 8 and 9, RL = 500Ω, CL = 50pF,
S1 closed (Note 5)
4
µs
Receiver Enable from Shutdown to
Output High
tZH (SHDN)
Figures 8 and 11, RL = 1kΩ, CL = 15pF,
S2 closed (Notes 4, 5)
4
µs
Receiver Enable from Shutdown to
Output Low
tZL (SHDN)
Figures 8 and 11, RL = 1kΩ, CL = 15pF,
S1 closed (Notes 4, 5)
4
µs
Driver Enable from Shutdown to
Output High
(Note 5)
50
Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referenced 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.
Note 4: Capacitive load includes test probe and fixture capacitance.
Note 5: Shutdown is enabled by bringing RE high and DE low or by bringing SHDN high. If the enable inputs are in this state for less
than 50ns, the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 800ns, the device
is guaranteed to have entered shutdown.
Typical Operating Characteristics
(VCC = +5V, TA = +25°C, unless otherwise noted.)
OUTPUT CURRENT
vs. RECEIVER OUTPUT LOW VOLTAGE
2.35
2.30
DE = GND
2.25
40
30
20
2.20
10
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
25
20
15
10
5
0
0
2.10
30
OUTPUT CURRENT (mA)
2.40
50
OUTPUT CURRENT (mA)
DE = VCC
35
MAX3465 toc02
2.45
2.15
4
60
MAX3465 toc01
2.50
OUTPUT CURRENT
vs. RECEIVER OUTPUT HIGH VOLTAGE
MAX3465 toc03
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
NO-LOAD SUPPLY CURRENT (mA)
MAX3465–MAX3469
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT LOW VOLTAGE (V)
0
1
2
3
OUTPUT HIGH VOLTAGE (V)
_______________________________________________________________________________________
4
5
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
200
150
100
50
0
-15
10
35
60
150
125
100
75
4.90
4.80
4.75
4.70
4.65
4.60
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
12
10
RDIFF = 54Ω
OUTPUT VOLTAGE (V)
10
8
10
35
60
3.0
2.5
6
2.0
4
-15
MAX3465 toc09
RDIFF = 54Ω
PROPAGATION DELAY (ns)
14
3.5
MAX3465 toc08
12
MAX3465 toc07
16
85
-40
-15
10
35
60
-40
85
-15
10
35
60
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
OUTPUT CURRENT vs. DRIVER OUTPUT
LOW VOLTAGE (TA = +25°C)
OUTPUT CURRENT
vs. DRIVER OUTPUT HIGH VOLTAGE
1
OUTPUT CURRENT (mA)
120
80
0
1
2
3
4
DIFFERENTIAL OUTPUT VOLTAGE (V)
5
-120
-80
-40
40
0.1
85
MAX3465 toc12
160
OUTPUT CURRENT (mA)
10
-160
MAX3465 toc11
200
MAX3465 toc10
100
0
IO = 4mA
4.85
TEMPERATURE (°C)
18
-40
MAX3465 toc06
175
85
20
PROPAGATION DELAY (ns)
IO = -4mA
50
-40
OUTPUT CURRENT (mA)
MAX3465 toc05
250
200
RECEIVER OUTPUT LOW VOLTAGE (mV)
MAX3465 toc04
SHUTDOWN SUPPLY CURRENT (nA)
300
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
RECEIVER OUTPUT HIGH VOLTAGE (mV)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
0
0
3
6
9
OUTPUT LOW VOLTAGE (V)
12
-7
-5
-3
-1
1
3
5
OUTPUT HIGH VOLTAGE (V)
_______________________________________________________________________________________
5
MAX3465–MAX3469
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
MAX3465–MAX3469
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
DRIVER AND RECEIVER
PROPAGATION DELAYS
EYE DIAGRAM
ENABLE RESPONSE TIME
MAX3465 toc13
MAX3465 toc15
MAX3465 toc14
DI
5V/div
5V/div
DE
Y, Z
2V/div
Y, Z
1V/div
Y, Z
1V/div
RO
5V/div
RDIFF = 54Ω
RDIFF = 54Ω
RDIFF = 54Ω
DATA RATE = 20Mbps
10ns/div
DATA RATE = 20Mbps
10ns/div
20ns/div
Pin Description
PIN
FULL DUPLEX
6
HALF
DUPLEX
MAX3465/
MAX3466
MAX3467
MAX3468/
MAX3469
1
—
—
NAME
SHDN
FUNCTION
Shutdown. Drive SHDN high to enter low-power shutdown mode.
2
2
1
RO
Receiver Output. When RE is low and (A - B) ≥ -50mV, RO is high; if (A - B) ≤
-200mV, RO is low.
3
—
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.
Driver Output Enable. Drive DE high to enable driver output. The driver
outputs are high impedance when DE is low. Drive RE high and DE low to
enter low-power shutdown mode. Do not leave RE unconnected when using
the MAX3466 or MAX3469.
4
—
3
DE
5
3
4
DI
6, 7
4
5
GND
8
—
—
TXP
9
10
11
12
5
6
7
8
—
—
—
—
Y
Z
B
A
13
—
—
RXP
14
—
—
1
—
—
8
7
6
VCC
B
A
Driver Input. With DE high, a low on DI forces the noninverting output low and
the inverting output high. Similarly, a high on DI forces the noninverting output
high and the inverting output low.
Ground
Transmitter Phase. Connect TXP to GND, or leave unconnected for normal
transmitter phase/polarity. Connect TXP to VCC to invert the transmitter
phase/polarity. TXP has an internal 15µA pulldown.
Noninverting Driver Output
Inverting Driver Output
Inverting Receiver Input
Noninverting Receiver Input
Receiver Phase. Connect RXP to GND, or leave unconnected for normal
receiver phase/polarity. Connect RXP to VCC to invert the receiver
phase/polarity. RXP has an internal 15µA pulldown.
Positive Supply: +4.75V ≤ VCC ≤ +5.25V. Bypass VCC to GND with a 0.1µF capacitor.
Inverting Receiver Input and Inverting Driver Output
Noninverting Receiver Input and Noninverting Driver Output
_______________________________________________________________________________________
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
MAX3465/MAX3466
MAX3467
TRANSMITTING
TRANSMITTING
INPUTS
OUTPUTS
INPUT
OUTPUTS
RE
DE
DI
SHDN
Z
Y
DI
Z
Y
X
1
1
0
0
1
1
0
1
X
1
0
0
1
0
0
1
0
0
0
X
0
High-Z
High-Z
1
0
X
X
Shutdown
X
X
X
1
Shutdown
RECEIVING
OUTPUT
A-B
RO
≥ -0.05V
1
OUTPUT
≤ -0.2V
0
Open/Shorted
1
RECEIVING
INPUTS
INPUTS
RE
DE
A-B
SHDN
RO
0
X
≥ -0.05V
0
1
0
X
≤ -0.2V
0
0
0
X
Open/Shorted
0
1
1
1
X
0
High-Z
1
0
X
X
Shutdown
X
X
X
1
Shutdown
MAX3468/MAX3469
TRANSMITTING
INPUTS
OUTPUTS
RE
DE
DI
B
A
X
1
1
0
1
X
1
0
1
0
0
0
X
High-Z
High-Z
1
0
X
Shutdown
RECEIVING
INPUTS
OUTPUT
RE
DE
A-B
RO
0
X
≥ -0.05V
1
0
X
≤ -0.2V
0
0
X
Open/Shorted
1
1
1
X
High-Z
1
0
X
Shutdown
_______________________________________________________________________________________
7
MAX3465–MAX3469
Function Tables
MAX3465–MAX3469
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
Pin Configurations and Typical Operating Circuit
VCC
DE
TOP VIEW
4
SHDN 1
VCC RE
0.1μF
14
14 VCC
13 RXP
RO
2
RE
3
12 A
DE 4
11 B
R
DI 5
9
DI
5
D
GND 6
9
GND 7
8
Y
TXP
Y
Rt
10
RO
R
Z
A
12
10 Z
D
MAX3465
MAX3466
RO
TXP
RXP
2
R
8
Rt
11
D
DI
B
13
3 6, 7 GND
DIP/SO
RE
DE
GND
Figure 1. MAX3465/MAX3466 Pin Configuration and Typical Full-Duplex Operating Circuit
0.1μF
TOP VIEW
VCC
MAX3467
VCC 1
5
VCC 1
RO
2
DI
3
R
8
A
DI
D
Y
Rt
6
RO
R
Z
7
B
6
Z
5
Y
A
8
D
GND 4
3
RO
2
R
Rt
7
D
DI
B
DIP/SO
4 GND
GND
Figure 2. MAX3467 Pin Configuration and Typical Full-Duplex Operating Circuit
TOP VIEW
0.1μF
RO 1
R
8 VCC
RO 1
RE 2
7 B
RE 2
DE 3
6 A
DE 3
5 GND
DI 4
DI 4
D
R
VCC
8
7 B
A
5
DI
D
RO
Rt
A
GND
DIP/SO
NOTE: PIN LABELS Y AND Z ON TIMING, TEST, AND WAVEFORM DIAGRAMS REFER TO PINS A AND B WHEN DE IS HIGH.
Figure 3. MAX3468/MAX3469 Pin Configuration and Typical Full-Duplex Operating Circuit
8
R
B
Rt
6
D
DE
MAX3468
MAX3469
_______________________________________________________________________________________
RE
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
The MAX3465–MAX3469 high-speed transceivers for
RS-485/RS-422 communication contain one driver and
one receiver. These devices feature true fail-safe circuitry, which guarantees a logic-high receiver output
when the receiver inputs are open or shorted, or when
they are connected to a terminated transmission line
with all drivers disabled (see the True Fail-Safe section). The MAX3465–MAX3469’s driver slew rates allow
transmit speeds up to 40Mbps.
The MAX3468 and MAX3469 are half-duplex transceivers, while the MAX3465, MAX3466, and MAX3467
are full-duplex transceivers. All of these parts operate
from a single +5V supply. Drivers are output short-circuit current limited. Thermal-shutdown circuitry protects
drivers against excessive power dissipation. When activated, the thermal-shutdown circuitry places the driver
outputs into a high-impedance state. The MAX3465
and MAX3468 devices have a hot-swap input structure
that prevents disturbances on the differential signal
lines when a circuit board is plugged into a hot backplane (see the Hot-Swap Capability section). All
devices have output levels that are compatible with
Profibus standards.
True Fail-Safe
The MAX3465–MAX3469 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 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 MAX3465–MAX3469, this results in a logic high with
a 50mV minimum noise margin. Unlike previous true
fail-safe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA-485 standard.
defined logic level. Leakage currents up to 10µA from the
high-impedance output could cause DE to drift to an
incorrect logic state. Additionally, parasitic circuit board
capacitance could cause coupling of VCC or GND to DE.
These factors could improperly enable the driver.
When VCC rises, an internal pulldown circuit holds DE
low for around 15µs. After the initial power-up
sequence, the pulldown circuit becomes transparent,
resetting the hot-swap-tolerable input.
Hot-Swap Input Circuitry
The MAX3465/MAX3468 enable inputs feature hot-swap
capability. At the input there are two NMOS devices, M1
and M2 (Figure 4). When VCC ramps from 0, an internal
15µs timer turns on M2 and sets the SR latch, which
also turns on M1. Transistors M2, a 2mA current sink,
and M1, a 100µA current sink, pull DE to GND through a
5.6kΩ 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 15µs, 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 hot-swap input is reset.
For RE there is a complementary circuit employing two
PMOS devices pulling to VCC.
VCC
15μs
TIMER
TIMER
Hot-Swap Capability
Hot-Swap Inputs
When circuit boards are inserted into a “hot” or powered backplane, disturbances to the enable 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 input of the MAX3465/MAX3468 to a
5.6kΩ
DE
(HOT SWAP)
EN
100μA
M1
2mA
M2
Figure 4. Simplified Structure of the Driver Enable Pin (DE)
_______________________________________________________________________________________
9
MAX3465–MAX3469
Detailed Description
MAX3465–MAX3469
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
3V
Y
DE
1.5V
1.5V
0V
R
tLZ
tZL(SHDN), tZL
VOD
Y, Z
R
50%
VOL
VOC
Z
VOL + 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
Y, Z
50%
VOH - 0.5V
0V
tHZ
tZH(SHDN), tZH
Figure 5. Driver DC Test Load
Figure 9. Driver Enable and Disable Times
3V
DE
DI
Y
VID
RDIFF
CL
f = 1MHz, tR ≤ 3ns, tF ≤ 3ns
Z
VOH
RO
1.5V
1V
A
-1V
B
1.5V
OUTPUT
VOL
tPHL
tPLH
INPUT
Figure 6. Driver Timing Test Circuit
Figure 10. Receiver Propagation Delays
f = 1MHz, tR ≤ 3ns, tF ≤ 3ns
3V
DI
1.5V
0V
1.5V
tPLH
tPHL
1/2 VO
Z
3V
VO
1.5V
RE
Y
1.5V
0V
1/2 VO
VDIFF = V (Y) - V (Z)
VO
VDIFF 0V
-VO
tZL(SHDN), tZL
90%
90%
10%
10%
tR
VCC
RO
1.5V
RO
1.5V
tLZ
OUTPUT NORMALLY LOW
VOL + 0.5V
tF
OUTPUT NORMALLY HIGH
tSKEW = | tPLH - tPHL |
RL
OUTPUT
UNDER TEST
VOH - 0.5V
0V
Figure 7. Driver Propagation Delays
tZH(SHDN), tZH
S1
VCC
tHZ
Figure 11. Receiver Enable and Disable Times
CL
S2
Figure 8. Enable/Disable Timing Test Load
10
______________________________________________________________________________________
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
B
ATE
R
VID
RECEIVER
OUTPUT
A
Figure 12. Receiver Propagation Delay Test Circuit
Applications Information
128 Transceivers on the Bus
The standard RS-485 receiver input impedance is 12kΩ
(one unit load), and the standard driver can drive up to
32 unit loads. The MAX3465–MAX3469 family of transceivers has 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 and/or other RS-485 transceivers
with a total of 32 unit loads or less can be connected to
the line.
Low-Power Shutdown Mode
(Except MAX3467)
Low-power shutdown mode is initiated by bringing
SHDN high (MAX3465/MAX3466), or both RE high and
DE low. In shutdown, the devices typically draw only
1µA 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 800ns, the devices
are guaranteed to enter shutdown.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus contention. The first, a foldback current limit on the output
stage, provides immediate protection against short circuits over the whole common-mode voltage range (see
the Typical Operating Characteristics). The second, a
thermal-shutdown circuit, forces the driver outputs into
a high-impedance state if the die temperature exceeds
+140°C.
Typical Applications
The MAX3465–MAX3469 transceivers are designed for
bidirectional data communications on multipoint bus
transmission lines. Figures 13 and 14 show typical network applications circuits. To minimize reflections, the
line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line
should be kept as short as possible.
Profibus Termination
The MAX3465–MAX3469 are designed for driving
Profibus termination networks. With a worst-case loading of two termination networks with 220Ω termination
impedance and 390Ω pullups and pulldowns, the drivers can drive VA-B > 2.1V output.
Chip Information
TRANSISTOR COUNT: 610
PROCESS: BiCMOS
Ordering Information (continued)
PART
TEMP RANGE
PIN-PACKAGE
MAX3466CSD
0°C to +70°C
14 SO
MAX3466CPD
0°C to +70°C
14 Plastic DIP
MAX3466ESD
-40°C to +85°C
14 SO
MAX3466EPD
-40°C to +85°C
14 Plastic DIP
MAX3467CSA
0°C to +70°C
8 SO
MAX3467CPA
0°C to +70°C
8 Plastic DIP
MAX3467ESA
-40°C to +85°C
8 SO
MAX3467EPA
-40°C to +85°C
8 Plastic DIP
MAX3468CSA
0°C to +70°C
8 SO
MAX3468CPA
0°C to +70°C
MAX3468ESA
-40°C to +85°C
8 SO
8 Plastic DIP
MAX3468EPA
-40°C to +85°C
8 Plastic DIP
MAX3469CSA
0°C to +70°C
8 SO
MAX3469CPA
0°C to +70°C
8 Plastic DIP
MAX3469ESA
-40°C to +85°C
8 SO
MAX3469EPA
-40°C to +85°C
8 Plastic DIP
______________________________________________________________________________________
11
MAX3465–MAX3469
Propagation Delay
Many digital encoding schemes depend on the difference
between the driver and receiver propagation delay times.
Typical propagation delays are shown in the Typical
Operating Characteristics. The difference in receiver delay
times, |tPLH - tPHL|, is a maximum of 2ns. The driver skew
time |tPLH - tPHL| is also a maximum of 2ns.
MAX3465–MAX3469
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
120Ω
120Ω
B
DI
B
DE
D
D
DE
A
B
A
B
A
DI
A
R
RO
R
RO
RE
RE
R
R
D
MAX3468
MAX3469
(HALF-DUPLEX)
D
DI
DE
RO
DI
RE
DE
RO
RE
Figure 13. Typical Half-Duplex RS-485 Network
A
Y
120Ω
120Ω
R
RO
D
B
RE
DE
Z
Z
DI
DI
120Ω
D
DE
RE
B
120Ω
R
Y
RO
A
Y
Z
B
A
B
Y
Z
B
R
MAX3465
MAX3466
MAX3467
(FULL-DUPLEX)
R
D
DI
A
D
DE RE
RO
DI
DE RE
RO
NOTE: RE AND DE ON MAX3465/MAX3466/MAX3467 ONLY.
Figure 14. Typical Full-Duplex RS-485 Network
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
12
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
14 SO
—
21-0041
14 PDIP
—
21-0043
______________________________________________________________________________________
+5V, Fail-Safe, 40Mbps, Profibus RS-485/
RS-422 Transceivers
REVISION
NUMBER
REVISION
DATE
0
10/09
1
2
DESCRIPTION
PAGES
CHANGED
Initial release.
—
1/04
Updated the description for the DE pin in the Pin Description table.
6
8/09
Replaced TOC 11.
5
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX3465–MAX3469
Revision History
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