19-1405; Rev 1; 4/99
RS-485/RS-422 Transceivers with Preemphasis
for High-Speed, Long-Distance Communication
________________General Description
The MAX3291/MAX3292 high-speed RS-485/RS-422
transceivers feature driver preemphasis circuitry, which
extends the distance and increases the data rate of reli-
able communication by reducing intersymbol interfer-
ence (ISI) caused by long cables. The MAX3291 is
programmable for data rates of 5Mbps to 10Mbps,
while the MAX3292 is programmable for data rates up
to 10Mbps by using a single external resistor.
The MAX3291/MAX3292 are full-duplex devices that
operate from a single +5V supply and offer a low-cur-
rent shutdown mode that reduces supply current to
100nA. They feature driver output short-circuit current
limiting and a fail-safe receiver input that guarantees a
logic-high output if the input is open circuit. A 1/4-unit-
load receiver input impedance allows up to 128 trans-
ceivers on the bus.
____________________________Features
o
Preemphasis Increases the Distance and Data
Rate of Reliable RS-485/RS-422 Communication
o
Data Rate
Optimized for 5Mbps to 10Mbps (MAX3291)
Programmable up to 10Mbps (MAX3292)
o
100nA Low-Current Shutdown Mode
o
Allow Up to 128 Transceivers on the Bus
o
-7V to +12V Common-Mode Input Voltage Range
o
Pin-Compatible with ’75180, MAX489, MAX491
MAX3080, MAX3083, MAX3086, MAX1482
MAX3291/MAX3292
_______________Ordering Information
PART
MAX3291CSD
TEMP. RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
14 SO
14 Plastic DIP
14 SO
14 Plastic DIP
14 SO
14 Plastic DIP
14 SO
14 Plastic DIP
________________________Applications
Long-Distance, High-Speed RS-485/RS-422
Communications
Telecommunications
Industrial-Control Local Area Networks
MAX3291CPD
MAX3291ESD
MAX3291EPD
MAX3292CSD
MAX3292CPD
MAX3292ESD
MAX3292EPD
Typical Operating Circuit and Functional Diagram
R
PSET
*
R
PSET
*
1µF
PEE
(PSET)
1
C
PSET
*
V
CC
14
(V
CCD
)
RO
RE
DE
DI
2
3
4
5
Z 10
Y 9
R = Z
O
R = Z
O
11
12
B
A
13
R = Z
O
R = Z
O
9
10
Y
Z
A 12
B 11
PEE
(PSET)
C
PSET
*
V
CC
14
(V
CCD
)
1µF
1
13
5
DI
4 DE
3
RE
2
RO
( ) ARE FOR MAX3292
* MAX3292 ONLY
Z
O
= THE CHARACTERISTIC
IMPEDANCE OF THE CABLE
MAX3291
MAX3292
7(6)
GND
MAX3291
MAX3292
7(6)
GND
Pin Configuration appears at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
RS-485/RS-422 Transceivers with Preemphasis
for High-Speed, Long-Distance Communication
MAX3291/MAX3292
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V
CC
, V
CCD
) .................................................+6V
Control Input Voltage (RE,
DE, PEE,
PSET, DI) .................................................-0.3V to (V
CC
+ 0.3V)
Driver Output Voltage (Y, Z) ................................-7.5V to +12.5V
Receiver Input Voltage (A, B)..............................-7.5V to +12.5V
Receiver Output Voltage (RO)....................-0.3V to (V
CC
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
14-Pin SO (derate 8.7mW/°C above +70°C).................695mW
14-Pin Plastic DIP (derate 10.0mW/°C above +70°C) ..800mW
Operating Temperature Ranges
MAX329_C_ D......................................................0°C to +70°C
MAX329_E_ D ...................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+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.
DC ELECTRICAL CHARACTERISTICS
(Typical Operating Circuit, V
CC
= +5V ±5%, R
PSET
= 0 (MAX3292), V
CC
= V
CCD
(MAX3292), T
A
= T
MIN
to T
MAX
, unless otherwise
noted. Typical values are at V
CC
= +5V and T
A
= +25°C.) (Note 1)
PARAMETER
DRIVER
Differential Driver Output
Differential Driver Output with
Preemphasis
Differential Driver
Preemphasis Ratio
Change in Magnitude of
Differential Output Voltage
(Normal and Preemphasis)
Driver Common-Mode Output
Voltage (Normal and
Preemphasis)
Change in Magnitude of
Common-Mode Voltage
(Normal and Preemphasis)
Change in Magnitude of
Common-Mode Output
Voltage (Normal to
Preemphasis)
Input High Voltage
Input Low Voltage
Input Current
PEE Input Current (MAX3291)
PSET Input Current (MAX3292)
Output Leakage (Y and Z)
Driver Short-Circuit Output
Current
2
V
OD
V
ODP
DPER
∆V
OD
,
∆V
ODP
Figure 1
R = 27Ω
Figure 1, R = 27Ω (Note 3)
R = 27Ω
No load (Note 2)
2.4
1.65
2.0
2.35
1.5
5.0
5.25
V
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Figure 1, R = 27Ω (Note 4)
0.2
V
V
OC
Figure 1, R = 27Ω
V
CC
/ 2
3
V
∆V
OC
Figure 1, R = 27Ω (Note 5)
0.3
V
∆V
NP
Figure 1, R = 27Ω
DE, DI,
RE
PEE
DE, DI,
RE,
PEE
DE, DI,
RE
-15
V
PSET
= V
CC
DE = GND,
V
CC
= GND or 5.25V
V
Y
= V
Z
= +12V
V
Y
= V
Z
= -7V
±30
50
mV
V
IH
V
IL
I
IN
I
PEE
I
PSET
I
O
I
OSD
2.4
3.75
0.8
±2
-30
70
-45
110
25
-25
±250
V
V
µA
µA
µA
µA
mA
-7V
≤
V
OUT
≤
+12V (Note 6)
_______________________________________________________________________________________
RS-485/RS-422 Transceivers with Preemphasis
for High-Speed, Long-Distance Communication
MAX3291/MAX3292
DC ELECTRICAL CHARACTERISTICS (continued)
(Typical Operating Circuit, V
CC
= +5V ±5%, R
PSET
= 0 (MAX3292), V
CC
= V
CCD
(MAX3292), T
A
= T
MIN
to T
MAX
, unless otherwise
noted. Typical values are at V
CC
= +5V and T
A
= +25°C.) (Note 1)
PARAMETER
RECEIVER
Input Current (A and B)
Receiver Differential
Threshold Voltage
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Three-State Output Current at
Receiver
Receiver Input Resistance
Receiver Output Short-Circuit
Current
SUPPLY CURRENT
No-Load Supply Current
Supply Current in Shutdown
Mode
I
CC +
I
CCD
RE
= GND, DE = V
CC
I
SHDN
RE
= V
CC,
DE = GND, V
Y
= V
Z
= 0 to V
CC
or
floating
2.0
0.1
3.0
1
mA
µA
I
A
,
B
V
TH
∆V
TH
V
OH
V
OL
I
OZR
R
IN
I
OSR
DE = GND,
V
CC
= GND or 5.25V
-7V
≤
V
CM
≤
+12V
V
A
= V
B
= 0
I
O
= -4mA, V
A
- V
B
= V
TH
I
O
= 4mA, V
A
- V
B
= -V
TH
0
≤
V
O
≤
V
CC
-7V
≤
V
CM
≤
+12V
0
≤
V
RO
≤
V
CC
48
±15
±95
0.1
3.5
0.4
±1
V
IN
= +12V
V
IN
= -7V
-200
35
250
-150
200
µA
mV
mV
V
V
µA
kΩ
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SWITCHING CHARACTERISTICS
(Typical Operating Circuit, V
CC
= +5V ±5%, R
PSET
= 0 (MAX3292), V
CC
= V
CCD
(MAX3292), T
A
= +25°C, unless otherwise noted.
Typical values are at V
CC
= +5V and T
A
= +25°C.)
PARAMETER
Driver Propagation Delay
Driver Differential Output
Rise or Fall Time
SYMBOL
t
DPLH
t
DPHL
t
HL
t
LH
CONDITIONS
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 50pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 50pF
Figures 3 and 10,
R
DIFF
= 54Ω,
C
L1
= C
L2
= 50pF
MAX3291/MAX3292,
R
PSET
= 0
MAX3292,
R
PSET
= 523kΩ
80
0.75
MIN
TYP
41
44
12
100
1
30
3
10
8
120
1.25
MAX
65
65
UNITS
ns
ns
ns
µs
ns
ns
Mbps
Driver Preemphasis Interval
t
PRE
Preemphasis Voltage Level to
Normal Voltage Level Delay
Differential Driver Output
Skew
t
DPLH
- t
DPHL
Maximum Data Rate
t
PTND
t
DSKEW
f
MAX
Figures 3 and 10, R
DIFF
= 54Ω,
C
L1
= C
L2
= 50pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 50pF
_______________________________________________________________________________________
3
RS-485/RS-422 Transceivers with Preemphasis
for High-Speed, Long-Distance Communication
MAX3291/MAX3292
SWITCHING CHARACTERISTICS (continued)
(Typical Operating Circuit, V
CC
= +5V ±5%, R
PSET
= 0 (MAX3292), V
CC
= V
CCD
(MAX3292), T
A
= +25°C, unless otherwise noted.
Typical values are at V
CC
= +5V and T
A
= +25°C.)
PARAMETER
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
Receiver Propagation Delay
Receiver Output Skew
t
RPLH
- t
RPHL
Receiver Enable to Output
Low
Receiver Enable to Output
High
Receiver Disable Time from
Low
Receiver Disable Time from
High
Time to Shutdown
Driver Enable from Shutdown
to Output High
Driver Enable from Shutdown
to Output Low
Receiver Enable from
Shutdown to Output High
Receiver Enable from
Shutdown to Output Low
SYMBOL
t
DZH
t
DZL
t
DLZ
t
DHZ
t
RPLH
t
RPHL
t
RSKEW
t
RZL
t
RZH
t
RLZ
t
RHZ
t
SHDN
t
DZH(SHDN)
t
DZL(SHDN)
t
RZH(SHDN)
t
RZL(SHDN)
CONDITIONS
Figures 2 and 6, S2 closed, R
L
= 500Ω,
C
L
= 100pF
Figures 2 and 6, S1 closed, R
L
= 500Ω,
C
L
= 100pF
Figures 2 and 6, S1 closed, R
L
= 500Ω,
C
L
= 15pF
Figures 2 and 6, S2 closed, R
L
= 500Ω,
C
L
= 15pF
Figures 7 and 9, C
L
= 50pF, V
ID
= 2V,
V
CM
= 0
Figures 7 and 9, C
L
= 100pF
Figures 2 and 8, R
L
= 1kΩ, C
L
= 100pF,
S1 closed
Figures 2 and 8, R
L
= 1kΩ, C
L
= 100pF,
S2 closed
Figures 2 and 8, R
L
= 1kΩ, C
L
= 15pF,
S1 closed
Figures 2 and 8, R
L
= 1kΩ, C
L
= 15pF,
S2 closed
Figures 4 and 11 (Note 7)
Figures 2 and 6, R
L
= 500Ω, C
L
= 100pF,
S2 closed
Figures 2 and 6, R
L
= 500Ω, C
L
= 100pF,
S1 closed
Figures 2 and 8, R
L
= 1kΩ, C
L
= 100pF,
S2 closed
Figures 2 and 8, R
L
= 1kΩ, C
L
= 100pF,
S1 closed
50
3
3
MIN
TYP
72
55
53
71
49
52
3
43
43
25
25
160
6000
6000
850
30
55
55
45
45
500
8750
8750
1500
1500
MAX
105
105
100
100
85
85
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
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:
Guaranteed by design.
Note 3:
DPER is defined as (V
ODP
/ V
OD
).
Note 4:
∆V
ODP
and
∆V
OC
are the changes in V
DD
and V
OC
, respectively, when the DI input changes. This specification reflects
constant operating conditions. When operating conditions shift, the maximum value may be momentarily exceeded.
Note 5:
∆V
ODP
and
∆V
OC
are the changes in V
OD
and V
OC
, respectively, when the DI input changes state.
Note 6:
Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during
current limiting.
Note 7:
Shutdown is enabled by bringing
RE
high and DE low. 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 500ns, the device is guaranteed to have
entered shutdown. Time to shutdown for the device (t
SHDN
) is measured by monitoring R0 as in Figure 4.
4
_______________________________________________________________________________________
RS-485/RS-422 Transceivers with Preemphasis
for High-Speed, Long-Distance Communication
__________________________________________Typical Operating Characteristics
(V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
TYPICAL PREEMPHASIS WAVEFORM
MAX3291/2-01
MAX3291/MAX3292
PREEMPHASIS INTERVAL vs. R
PSET
(C
PSET
= 0.1µF)
MAX3291/2-02
R
PRE
AND t
PRE
vs. t
BAUD
MAX3291/92 toc 03
2500
2250
PREEMPHASIS INTERVAL (ns)
2000
1750
1200
1000
800
R
PRE
(kΩ)
600
NOTE A
400
200
0
1500
1250
1000
750
500
250
0
NOTE A
V
Y
- V
Z
2V/
div
100ns/div
0 100 200 300 400 500 600 700 800 900 1000
R
PSET
(kΩ)
0
500
1000
t
BAUD
(ns)
1500
2000
DRIVER DIFFERENTIAL
OUTPUT VOLTAGE vs. R
DIFF
MAX3291/2-04
DRIVER DIFFERENTIAL
OUTPUT VOLTAGE vs. TEMPERATURE
MAX3291/2-05
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
C
L
= 50pF
57.5
PROPAGATION DELAY (ns)
55.0
52.5
50.0
47.5
45.0
42.5
MAX3291/2-06
DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
10
20
30
40
50
60
70
80
NORMAL
STRONG
4.25
DIFFERENTIAL OUTPUT VOLTAGE (V)
4.00
3.75
3.50
3.25
3.00
2.75
2.50
2.25
2.00
R
DIFF
= 54Ω
-40
-20
0
20
40
60
80
NORMAL (V
OD
)
STRONG (V
ODP
)
60.0
40.0
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
90 100
R
DIFF
(Ω)
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
MAX3291/2-07
RECEIVER PROPAGATION DELAY
MAX3291/2-08
50.0
47.5
PROPAGATION DELAY (ns)
45.0
42.5
40.0
37.5
35.0
32.5
30.0
-40
-20
0
20
40
60
80
C
L1
= C
L2
= 50pF
V
A
- V
B
2.5V/
div
5V/
div
RO
100
20ns/div
TEMPERATURE (°C)
Note A:
Dotted line represents region in which preemphasis may not work in systems with excessive power-supply noise. See
Preemphasis at Low Data Rates.
_______________________________________________________________________________________
5
京公网安备 11010802033920号
EEWORLD
