MAX1485CUB [MAXIM]
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package; 软件可选的，半/全双工，摆率限制， 12Mbps的， RS - 485 / RS - 422收发器，レMAX封装
| 型号： | MAX1485CUB |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in レMAX Package |
| 文件： | 总16页 (文件大小：186K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1312; Rev 0; 10/97
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
The MAX1481/MAX1484/MAX1485/MAX1486 provide
software-selectable, half-/full-duplex, low-power, slew-
rate-limited, and high-speed (12Mbps) RS-485/RS-422
operation in a 10-pin µMAX package—the smallest
10-pin package available.
♦ 10-Pin µMAX Package: Smallest 10-Pin Package
♦ Software-Selectable Half-/Full-Duplex Operation
(MAX1485/MAX1486)
♦ 0.1µA Low-Current Shutdown Mode (MAX1481)
The software-selectable, half-/full-duplex MAX1485/
MAX1486 make obsolete the normally larger and more
expensive solutions required for selectable half-/full-
d up le x RS-485/RS-422 op e ra tion: 1) a 14-p in, full-
duplex transceiver configured via jumpers between
receiver and transmitter lines, or 2) two 8-pin, half-
duplex transceivers, which require an additional invert-
er logic gate for software selectability.
♦ Slew-Rate Limiting Allows Error-Free Data
Transmission (MAX1481/MAX1485)
♦ 12Mbps High-Speed Operation
(MAX1484/MAX1486)
♦ Allow up to 256 Transceivers on the Bus
The MAX1481/MAX1484 are functionally equivalent to
the industry-standard MAX491 and 75180, and are
designed for space-constrained, full-duplex RS-422
applications.
______________Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
10 µMAX
10 µMAX
10 µMAX
10 µMAX
10 µMAX
10 µMAX
10 µMAX
MAX1481CUB
MAX1481EUB
MAX1484CUB
MAX1484EUB
MAX1485CUB
MAX1485EUB
MAX1486CUB
MAX1486EUB
All parts contain one driver and one receiver and fea-
ture a 1/8-unit-load receiver input impedance, allowing
up to 256 tra ns c e ive rs on the b us . The MAX1481/
MAX1485 feature reduced-slew-rate drivers that mini-
mize EMI and reduce reflections caused by improperly
terminated cables, allowing error-free data transmission
up to 250kbps. The MAX1484/MAX1486 driver slew
rates are not limited, allowing them to transmit up to
12Mbps.
The MAX1481/MAX1484/MAX1485/MAX1486 draw only
300µA of supply current. The MAX1481 has a low-power
shutdown mode that reduces supply current to only
0.1µA. All devices operate from a single 5V supply.
________________________Ap p lic a t io n s
Low-Power RS-422/RS-485 Communications
Level Translators
Drivers are output short-circuit current limited and are
p rote c te d a g a ins t e xc e s s ive p owe r d is s ip a tion b y
thermal-shutdown circuitry that places the driver outputs
into a high-impedance state. The receiver input has a fail-
safe feature that guarantees a logic-high output if the
input is open circuit.
Hand-Held Equipment
Battery-Powered Equipment
Transceiver for EMI-Sensitive Applications
Industrial-Control Local Area Networks
______________________________________________________________S e le c t io n Ta b le
Data
Rate
(Mbps)
Slew-
Rate
Limited
Low-
Power
Shutdown
Quiescent
Current
(µA)
Half/Full
Duplex
Driver
Enable
Receiver
Enable
Transceivers
on Bus
Pin-
Package
Part
MAX1481
MAX1484
MAX1485
MAX1486
Full
Full
0.250
12
Yes
No
Yes
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
No
300
300
300
300
256
256
256
256
10 µMAX
10 µMAX
10 µMAX
10 µMAX
Selectable
Selectable
0.250
12
Yes
No
No
________________________________________________________________ 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 408-737-7600 ext. 3468.
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V ) ............................................................+7V
Continuous Power Dissipation
CC
Control Input Voltage (RE, DE, H/F) ...........-0.3V to (V + 0.3V)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW
Operating Temperature Ranges
CC
Driver Input Voltage (DI).............................-0.3V to (V + 0.3V)
CC
Driver Output Voltage (A, B, Y, Z) ..........................-8V to +12.5V
Receiver Input Voltage, Half Duplex (Y, Z) ............-8V to +12.5V
Receiver Input Voltage, Full Duplex (A, B).............-8V to +12.5V
MAX148_C_ _ ......................................................0°C to +70°C
MAX148_E_ _....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Receiver Output Voltage (RO)....................-0.3V to (V + 0.3V)
CC
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
(V = +5V ±5%, T = T
to T
, unless otherwise noted. Typical values are at V = +5V and T = +25°C.) (Note 1)
CC
A
MIN
MAX
CC
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRIVER
V
OD1
No load, Figure 5
5
Differential Driver Output
R = 50Ω (RS-422), Figure 5
R = 27Ω (RS-485), Figure 5
2.0
1.5
V
V
V
OD2
5
Change in Magnitude of
Differential Output Voltage
(Note 2)
∆V
R = 50Ω or 27Ω, Figure 5
0.2
OD
Driver Common-Mode Output
Voltage
V
R = 50Ω or 27Ω, Figure 5
R = 50Ω or 27Ω, Figure 5
3
V
V
OC
Change in Magnitude of
Common-Mode Voltage (Note 2)
∆V
0.2
OC
Input High Voltage
Input Low Voltage
Input Current
V
2.0
V
V
DE, DI, RE, H/F
DE, DI, RE, H/F
DE, DI, RE, H/F
IH1
V
IL1
0.8
±2
I
IN1
µA
V
= 12V
= -7V
= 12V
= -7V
= 12V
= -7V
0.125
-0.1
10
IN
Input Current (Y and Z for Half
Duplex, A and B for Full Duplex)
DE = GND,
= GND or 5.25V
I
mA
µA
IN2
V
CC
V
IN
V
IN
Output Leakage (Y and Z)
(MAX1481/MAX1484 Only)
I
DE = GND
DE = GND
O
V
IN
-10
5/MAX1486
V
IN
125
-100
Output Leakage (Y and Z)
(MAX1485/MAX1486 Only)
I
µA
O
V
IN
Driver Output Short-Circuit
Current (Note 3)
I
-7V ≤ V
≤ 12V
35
250
mA
OSD
OUT
2
_______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
ELECTRICAL CHARACTERISTICS (continued)
(V = +5V ±5%, T = T
to T
, unless otherwise noted. Typical values are at V = +5V and T = +25ºC.) (Note 1)
CC
A
MIN
MAX
CC
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RECEIVER
Receiver Differential Threshold
Voltage
V
-7V ≤ V ≤ 12V
-200
3.5
200
mV
TH
CM
Receiver Input Hysteresis
∆V
70
mV
V
TH
Receiver Output High Voltage
Receiver Output Low Voltage
V
OH
I = -4mA, V = 200mV
O ID
V
OL
I
O
= 4mA, V = -200mV
0.4
±1
V
ID
Three-State Output Current at
Receiver
I
0.4V ≤ V ≤ 2.4V
µA
kΩ
OZR
O
Receiver Input Resistance
R
-7V ≤ V ≤ 12V
96
IN
CM
Receiver Output Short-Circuit
Current
I
0V ≤ V ≤ V
CC
±95
mA
OSR
RO
SUPPLY CURRENT
No-Load Supply Current
I
300
0.1
600
10
µA
µA
RE = GND, DE = V
CC
CC
Supply Current in Shutdown
Mode (MAX1481 Only)
I
DE = GND, RE = V
SHDN
CC
SWITCHING CHARACTERISTICS (MAX1484/MAX1486)
(V = 5V ±5%, T = T
to T
, unless otherwise noted. Typical values are at V = +5V and T = +25°C.)
CC
A
MIN
MAX
CC
A
PARAMETER
SYMBOL
CONDITIONS
= 54Ω, C = C = 100pF,
MIN
TYP
30
MAX
60
UNITS
Driver Input to Output
t
DPLH
DPHL
R
DIFF
L1
L2
ns
Figures 7 and 9
t
30
60
Driver Output Skew
R
= 54Ω, C = C = 100pF,
DIFF
L1
L2
t
5
10
35
ns
ns
DSKEW
Figures 7 and 9
| t
- t
|
DPLH DPHL
R
= 54Ω, C = C = 100pF,
DIFF
L1
L2
Driver Rise or Fall Time
t
, t
5
15
DR DF
Figures 7 and 9
Maximum Data Rate
f
12
Mbps
ns
MAX
Driver Enable to Output Low
Driver Enable to Output High
Driver Disable Time from Low
Driver Disable Time from High
t
C
C
C
C
= 100pF, S1 closed, Figures 8 and 10
= 100pF, S2 closed, Figures 8 and 10
= 15pF, S1 closed, Figures 8 and 10
= 15pF, S2 closed, Figures 8 and 10
40
40
40
40
70
70
70
70
DZL
L
L
L
L
t
t
ns
DZH
t
ns
DLZ
DHZ
ns
t
t
,
RPLH
Receiver Input to Output
Figures 11 and 13
Figures 11 and 13
90
5
150
ns
ns
RPHL
| t
RPLH
- tRPHL | Differential
t
RSKD
Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable Time from Low
Receiver Disable Time from High
t
C
C
C
C
= 100pF, S1 closed, Figures 6 and 12
= 100pF, S2 closed, Figures 6 and 12
= 100pF, S1 closed, Figures 6 and 12
= 100pF, S2 closed, Figures 6 and 12
20
20
20
20
50
50
50
50
ns
ns
ns
ns
RZL
L
L
L
L
t
RZH
t
RLZ
t
RHZ
_______________________________________________________________________________________
3
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
SWITCHING CHARACTERISTICS (MAX1481/MAX1485) (continued)
(V = 5V ±5%, T = T
to T
, unless otherwise noted. Typical values are at V = +5V and T = +25°C.)
CC
A
MIN
MAX
CC
A
PARAMETER
SYMBOL
CONDITIONS
= 54Ω, C = C = 100pF,
MIN
TYP
600
600
MAX
1000
1000
UNITS
t
t
DPLH
DPHL
R
DIFF
L1
L2
Driver Input to Output
ns
Figures 7 and 9
Driver Output Skew
R
= 54Ω, C = C = 100pF,
DIFF
L1
L2
t
10
200
ns
ns
DSKEW
Figures 7 and 9
| t
- t
|
DPLH DPHL
R
DIFF
= 54Ω, C = C = 100pF,
L1
L2
Driver Rise or Fall Time
t
, t
250
250
1000
DR DF
Figures 7 and 9
Maximum Data Rate
f
kbps
ns
MAX
Driver Enable to Output Low
Driver Enable to Output High
Driver Disable Time from Low
Driver Disable Time from High
t
C
C
C
C
= 100pF, S1 closed, Figures 8 and 10
= 100pF, S2 closed, Figures 8 and 10
= 15pF, S1 closed, Figures 8 and 10
= 15pF, S2 closed, Figures 8 and 10
3000
3000
200
DZL
L
L
L
L
t
t
ns
DZH
t
ns
DLZ
DHZ
200
ns
t
t
,
RPLH
Receiver Input to Output
Figures 11 and 13
Figures 11 and 13
90
15
150
ns
ns
RPHL
| t
RPLH
- tRPHL | Differential
t
RSKD
Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable Time from Low
Receiver Disable Time from High
Time to Shutdown
t
C
C
C
C
= 100pF, S1 closed, Figures 6 and 12
= 100pF, S2 closed, Figures 6 and 12
= 100pF, S1 closed, Figures 6 and 12
= 100pF, S2 closed, Figures 6 and 12
20
20
50
50
ns
ns
ns
ns
ns
RZL
L
L
L
L
t
RZH
t
20
50
RLZ
t
20
50
RHZ
t
MAX1481 only (Note 4)
50
200
600
SHDN
Driver Enable from Shutdown to
Output High
MAX1481 only, C = 15pF, S2 closed,
L
Figures 8 and 10
t
t
3000
3000
500
ns
ns
ns
ns
DZH(SHDN)
Driver Enable from Shutdown to
Output Low
MAX1481 only, C = 15pF, S1 closed,
L
Figures 8 and 10
t
DZL(SHDN)
Receiver Enable from Shutdown
to Output High
MAX1481 only, C = 100pF, S2 closed,
L
Figures 6 and 12
RZH(SHDN)
Receiver Enable from Shutdown
to Output Low
MAX1481 only, C = 100pF, S1 closed,
L
Figures 6 and 12
t
1000
RZL(SHDN)
5/MAX1486
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: ∆V and ∆V are the changes in V and V , respectively, when the DI input changes state.
OD
OC
OD
OC
Note 3: Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during
current limiting.
Note 4: Shutdown is enabled by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the MAX1481
is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the MAX1481 is guaranteed to
have entered shutdown.
4
_______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V = +5V, T = +25°C, unless otherwise noted.)
CC
A
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
OUTPUT CURRENT vs.
RECEIVER OUTPUT LOW VOLTAGE
OUTPUT CURRENT vs.
RECEIVER OUTPUT HIGH VOLTAGE
360
60
50
40
30
25
20
MAX1481/MAX1485
340
320
300
280
260
240
220
30
20
15
10
MAX1484/MAX1486
10
0
5
0
1
1
-60 -40 -20
0
20 40 60 80 100
0
2
3
4
5
0
2
3
4
5
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)
OUTPUT LOW VOLTAGE (V)
SHUTDOWN CURRENT
vs. TEMPERATURE
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
114
110
106
102
98
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
I
RO
= 8mA
I
RO
= 8mA
94
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX1481/MAX1485 RECEIVER
MAX1484/MAX1486 RECEIVER
MAX1481/MAX1485 DRIVER
PROPAGATION DELAY vs. TEMPERATURE
PROPAGATION DELAY vs. TEMPERATURE
PROPAGATION DELAY vs. TEMPERATURE
105
100
95
94
93
92
91
90
89
680
660
640
620
600
580
560
540
R
= 54Ω
C
C
LOAD
= 15pF
C
LOAD
= 15pF
DIFF
C
L1 = L2 = 100pF
90
85
88
87
86
80
75
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
-60 -40 -20
0
20 40 60 80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
_________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V = +5V, T = +25°C, unless otherwise noted.)
CC
A
OUTPUT CURRENT vs.
MAX1484/MAX1486 DRIVER
OUTPUT CURRENT vs.
DRIVER OUTPUT HIGH VOLTAGE
PROPAGATION DELAY vs. TEMPERATURE
DRIVER OUTPUT LOW VOLTAGE
120
100
80
60
40
20
0
38
140
R
= 54Ω
C
DIFF
C
L1 = L2 = 100pF
120
100
80
34
30
26
22
18
60
40
20
0
-8
-6
-4
-2
0
2
4
6
-60 -40 -20
0
20 40 60 80 100
0
2
4
6
8
10
12
OUTPUT HIGH VOLTAGE (V)
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
MAX1484/MAX1486
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
RECEIVER PROPAGATION DELAY
MAX1481/4/5/6-15
100
2.40
2.35
2.30
2.25
2.20
2.15
2.10
R
DIFF
= 54Ω
V - V
(2V/div)
A
B
10
1
RO
(5V/div)
0.1
0.01
-60 -40 -20
0
20 40 60 80 100
50ns/div
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
DIFFERENTIAL OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
5/MAX1486
MAX1484/MAX1486
MAX1481/MAX1485
MAX1481/MAX1485
DRIVER PROPAGATION DELAY
DRIVER PROPAGATION DELAY
RECEIVER PROPAGATION DELAY
MAX1481/4/5/6-18
MAX1481/4/5/6-17
MAX1481/4/5/6-16
DI
DI
V - V
(5V/div)
5V/div
A
B
(2V/div)
V - V
2V/div
V - V
(2V/div)
Y
Z
Y
Z
RO
(5V/div)
50ns/div
1µs/div
1µs/div
6
_______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
______________________________________________________________P in De s c rip t io n
PIN
MAX1485/MAX1486
NAME
FUNCTION
MAX1481/
MAX1484
H/F = 0
H/F = 1
Receiver Output. When RE is low and if A - B ≥ 200mV, RO goes high; if A - B ≤
-200mV, RO goes low.
1
1
1
RO
Half-/Full-Duplex Selector Input. Connect H/F to V for half-duplex mode, and
connect to GND for full-duplex mode.
CC
—
2
—
3
2
—
3
H/F
Receiver Output Enable Input. Drive RE low to enable RO; RO is high impedance
when RE is high. For MAX1481 only, drive RE high and DE low to enter the low-
power shutdown mode.
2
3
4
RE
DE
DI
Driver Output Enable Input. Drive DE high to enable driver outputs. These outputs
are high impedance when DE is low.
Driver Input. With DE high, a low on DI forces noninverting output low and invert-
ing output high. Similarly, a high on DI forces noninverting output high and invert-
ing output low.
4
4
5
6
5
6
5
—
6
GND
B
Ground
Inverting Receiver Input
—
7
—
7
B
Receiver Input Resistors*
—
7
Z
Inverting Driver Output
—
8
—
8
Z
Inverting Driver Output and Inverting Receiver Input
Noninverting Driver Output
—
8
Y
—
9
—
9
Y
Noninverting Driver Output and Noninverting Receiver Input
Noninverting Receiver Input
Receiver Input Resistors*
—
9
A
—
10
—
10
A
10
V
CC
Positive Supply; +4.75V ≤ V ≤ +5.25V
CC
*(MAX1485/MAX1486 only) In half-duplex mode, the driver outputs serve as receiver inputs. The full-duplex receiver inputs (A and B)
will still have a 1/8-unit load, but are not connected to the receiver.
_______________________________________________________________________________________
7
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
_____________________________________________________________Fu n c t io n Ta b le s
MAX1481
RECEIVING
INPUTS
TRANSMITTING
OUTPUT
INPUTS
OUTPUTS
DE
X
A-B
≥ 0.2V
≤ -0.2V
X
RO
RE
0
DE
1
DI
1
Z
0
1
Y
RE
X
X
0
1
0
1
0
0
X
1
0
1
1
High-Z
0
X
X
High-Z
High-Z
1
0
High-Z and Shutdown
High-Z and
Shutdown
1
0
X
MAX1484
TRANSMITTING
RECEIVING
INPUTS
OUTPUTS
INPUTS
OUTPUT
DE
1
DI
1
Z
Y
DE
X
A-B
≥ 0.2V
≤ -0.2V
X
RO
RE
X
RE
0
0
1
1
0
1
0
X
1
0
0
X
X
0
X
High-Z
High-Z
1
X
High-Z
MAX1485/MAX1486
TRANSMITTING
RECEIVING
INPUTS
OUTPUTS
INPUTS
OUTPUT
DE
1
DI
1
Z
Y
1
DE
X
X
0
A-B
≥ 0.2V
≤ -0.2V
X
Y-Z
X
RO
1
H/F
0
1
0
0
1
1
1
0
0
X
0
0
X
High-Z
High-Z
≥ 0.2V
1
0
5/MAX1486
0
X
≤ -0.2V
X = Don’t care
Note: In shutdown mode, driver and receiver outputs are high impedance.
8
_______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
TOP VIEW
MAX1481
MAX1484
MAX1481
MAX1484
0.1µF
0.1µF
MAX1481
MAX1484
10
10
V
CC
V
CC
9
6
A
B
R
t
8
7
Y
Z
1
4
RO
DI
RO
RE
1
2
3
4
5
10
9
V
CC
3
2
A
Y
Z
2
3
4
DE
RE
RE
DE
DI
DE
8
R
t
7
8
Z
6
9
B
A
DI
7
1
RO
GND
6
B
Y
5
GND
5
GND
µMAX
Figure 1. MAX1481/MAX1484 Pin Configuration and Typical Full-Duplex Operating Circuit
MAX1485
MAX1486
MAX1485
MAX1486
TOP VIEW
0.1µF
0.1µF
10
10
V
CC
V
9
6
A
B
R
t
CC
8
7
Y
Z
1
4
3
2
RO
DI
RO
H/F
DE
1
2
3
4
5
10
9
V
CC
H/F
DE
A
Y
Z
2
3
4
H/F
MAX1485
MAX1486
8
DE
DI
7
8
R
t
Z
6
9
B
A
DI
7
1
RO
GND
6
B
Y
5
GND
5
GND
µMAX
Figure 2. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Full-Duplex Operating Circuit
MAX1485
MAX1486
MAX1485
MAX1486
TOP VIEW
0.1µF
0.1µF
10
10
V
CC
V
CC
1
4
3
2
RO
DI
RO
H/F
DE
1
2
3
4
5
10
9
V
CC
8
8
Y
R
t
R
t
Y
H/F
DE
A
Y
Z
2
3
4
H/F
MAX1485
MAX1486
Z
7
9
Z
7
9
8
DE
DI
A
A
DI
7
1
RO
GND
6
B
6
B
B
6
5
GND
5
GND
µMAX
Figure 3. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Half-Duplex Operating Circuit
_______________________________________________________________________________________
9
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
MAX1 4 8 5 /MAX1 4 8 6
Ha lf-/Fu ll-Du p le x Mo d e Op e ra t io n
V
CC
The MAX1484/MAX1485 can operate in full- or half-
duplex mode. Drive the H/F pin low or connect it to
GND for full-duplex operation, or drive it high for half-
duplex operation. In full-duplex mode, the pin configu-
ra tion of the d rive r a nd re c e ive r is the s a me a s a
MAX1481 (Figure 1).
MAX1485
MAX1486
B
A
DI
DE
__________Ap p lic a t io n s In fo rm a t io n
RO
2 5 6 Tra n s c e ive rs o n t h e Bu s
The standard RS-485 receiver input impedance is 12kΩ
(1-unit load), and the standard driver can drive up to
32-unit loa d s . The MAX1481/MAX1484/MAX1485/
MAX1486 transceivers have a 1/8-unit-load receiver
input impedance (96kΩ), allowing up to 256 trans-
ceivers to be connected in parallel on one communica-
tion line. Connect any combination of these devices
and/or other RS-485 transceivers totaling 32-unit loads
or less.
H/F
Z
Y
GND
Figure 4. MAX1485/MAX1486 Functional Diagram
Re d u c e d EMI a n d Re fle c t io n s
The MAX1481/MAX1485 are slew-rate limited, minimiz-
ing EMI and reducing reflections caused by improperly
terminated cables. Figure 14 shows the driver output
waveform and its Fourier analysis of a 20kHz signal
transmitted by a MAX1484. High-frequency harmonic
components with large amplitudes are evident. Figure
15 shows the same signal displayed for a MAX1481
transmitting under the same conditions. Figure 15’s
high-frequency harmonic components are much lower
in amplitude compared to Figure 14’s, significantly
reducing potential EMI.
_______________De t a ile d De s c rip t io n
The MAX1481/MAX1484/MAX1485/MAX1486 hig h-
speed transceivers for RS-485/RS-422 communication
contain one driver and one receiver. The MAX1481/
MAX1485 feature reduced-slew-rate drivers that mini-
mize EMI and reduce reflections caused by improperly
terminated cables, allowing error-free data transmission
up to 250kbps. The MAX1484/MAX1486 driver slew
rates are not limited, making transmission speeds up to
12Mbps possible.
These transceivers are designed to operate on a +5V
single supply and typically draw 300µA of supply cur-
rent when unloaded or fully loaded with the drivers dis-
abled. The MAX1481 has a shutdown mode in which
supply current is typically reduced to 0.1µA.
In general, a transmitter’s rise time relates directly to
the length of an unterminated stub, which can be dri-
ven with only minor waveform reflections. The following
equation expresses this relationship conservatively:
5/MAX1486
Length = t
/ (10 x 1.5ns/ft)
RISE
Drivers are output short-circuit current limited and are
protected against excessive power dissipation by ther-
mal-shutdown circuitry that places the driver outputs
into a high-impedance state.
where t
is the transmitter’s rise time.
RISE
For e xa mp le , the MAX1481’s ris e time is typ ic a lly
500ns, which results in excellent waveforms with a stub
le ng th up to 33 fe e t. A s ys te m ma y work we ll with
longer unterminated stubs, even with severe reflec-
tions , if the wa ve form s e ttle s out b e fore the UART
samples them.
All devices have a 1/8-unit-load receiver input imped-
ance that allows up to 256 transceivers on the bus. The
MAX1481/MAX1484 are designed for full-duplex com-
munications. The H/F pin on the MAX1485/MAX1486
allows the user to select between half-duplex or full-
duplex operation (Figure 4).
10 ______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
Y
1k
TEST POINT
R
R
RECEIVER
OUTPUT
V
CC
S1
S2
V
OD
C
L
1k
V
OC
Z
Figure 5. Driver DC Test Load
Figure 6. Receiver Enable/Disable Timing Test Load
3V
DE
C
L1
V
CC
Y
S1
R
DIFF
DI
500Ω
V
ID
OUTPUT
UNDER TEST
Z
C
L
C
L2
S2
Figure 7. Driver Timing Test Circuit
Figure 8. Driver Enable/Disable Timing Test Load
3V
3V
DI
1.5V
1.5V
DE
1.5V
1.5V
0V
t
t
DPHL
0V
DPLH
1/2 V
O
t
t
, t
DLZ
DZL(SHDN) DPL
Z
Y, Z
V
O
2.3V
V
OL
+0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
Y
V
OL
1/2 V
O
V
DIFF
= V - V
Y Z
V
O
Y, Z
0V
V
DIFF
90%
90%
0V
-V
V
OH
-0.5V
2.3V
10%
10%
O
t
R
t
F
D
, D
D
HZ
ZH(SHDN) ZH
t
t
- t
SKEW = | PLH PHL |
Figure 9. Driver Propagation Delays
Figure 10. Driver Enable and Disable Times
______________________________________________________________________________________ 11
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
3V
RE
1.5V
1.5V
0V
V
OH
R
LZ
R
, R
RO
ZL(SHDN) ZL
1.5V
1.5V
V
OL
OUTPUT
V
CC
RO
1.5V
V
+ 0.5V
- 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
OL
R
R
PLH
PHL
A
B
1V
-1V
INPUT
RO
V
OH
1.5V
0V
R
, R
R
HZ
ZH(SHDN) ZH
Figure 11. Receiver Propagation Delays
Figure 12. Receiver Enable and Disable Times
(MAX1481/MAX1484 only)
B
A
RECEIVER
OUTPUT
20dB/div
V
ID
R
ATE
0Hz
250kHz/div
2.5MHz
Figure 13. Receiver Propagation Delay Test Circuit
Figure 14. Driver Output Waveform and FFT Plot of
MAX1484/MAX1486 Transmitting a 20kHz signal
longer to become enabled from the low-power shutdown
mod e (t_ZH(SHDN) t_ZL(SHDN) tha n from the
driver/receiver disable mode (t_ZH, t_ZL).
Lo w -P o w e r S h u t d o w n Mo d e
(MAX1 4 8 1 o n ly)
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the MAX1481 typi-
cally draws only 0.1µA of supply current.
5/MAX1486
,
)
Drive r Ou t p u t P ro t e c t io n
Excessive output current and power dissipation caused
by faults or by bus contention are prevented by two
mechanisms. A foldback current limit on the output
stage provides immediate protection against short cir-
cuits over the whole common-mode voltage range (see
Typical Operating Characteristics). In addition, a ther-
mal shutdown circuit forces the driver outputs into a
high-impedance state if the die temperature becomes
excessive.
RE and DE may be driven simultaneously; the parts 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 600ns, the parts are guaranteed to enter
shutdown.
Enable times t_ZH and t_ZL in the Switching Character-
istics tables assume the part was not in low-power shut-
down. Enable times t_ZH(SHDN) and t_ZL(SHDN) assume
the parts were shut down. It takes drivers and receivers
12 ______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
lines. Figures 19 and 20 show typical network applica-
tions circuits. These parts can also be used as line
repeaters with cable lengths longer than 4000 feet
(Figure 16).
Lin e Le n g t h vs . Da t a Ra t e
The RS-485/RS-422 standard covers line lengths up to
4000 feet. For line lengths greater than 4000 feet, use
the repeater application shown in Figure 16.
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-lim-
ited MAX1481/MAX1485 are more tolerant of imperfect
termination than the MAX1484/MAX1486.
Figures 17 and 18 show the system differential voltage
for the parts driving 4000 feet of 26AWG twisted-pair
wire into 120Ω loads.
Typ ic a l Ap p lic a t io n s
The MAX1485/MAX1486 are designed for bidirectional
data communications on multipoint bus transmission
MAX1481
MAX1484
MAX1485
MAX1486
A
120Ω
120Ω
RO
RE
R
DATA IN
B
20dB/div
DE
Z
DI
DATA OUT
D
Y
H/F
0Hz
250kHz/div
2.5MHz
NOTE: RE ON MAX1481 AND MAX1484 ONLY.
H/F ON MAX1485 AND MAX1486 ONLY.
Figure 16. Line Repeater
Figure 15. Driver Output Waveform and FFT Plot of
MAX1481/MAX1485 Transmitting a 20kHz Signal
MAX1481/4/5/6-fig18
MAX1481/4/5/6-fig17
DI
5V/div
DI
5V/div
4V/div
5V/div
V - V
4V/div
5V/div
V - V
A
B
A
B
RO
RO
1µs/div
5µs/div
Figure 18. MAX1484/MAX1486 System Differential Voltage at
200kHz Driving 4000 ft. of Unterminated Cable
Figure 17. MAX1481/MAX1485 System Differential Voltage at
50kHz Driving 4000 ft. of Unterminated Cable
______________________________________________________________________________________ 13
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5V
5V
V
V
CC
CC
H/F
H/F
D
120Ω
120Ω
DE
B
A
B
A
DI
D
DI
DE
RO
B
A
B
A
RO
R
R
5V
H/F
R
R
V
CC
D
D
V
CC
V
CC
MAX1485
MAX1486
DE
DI
RO
DI
RO
DE
Figure 19. Typical Half-Duplex RS-485 Network
5/MAX1486
14 ______________________________________________________________________________________
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
5/MAX1486
A
Y
120Ω
120Ω
120Ω
120Ω
RO
RE
R
DI
D
B
Z
Z
B
DE
DE
RE*
RO
DI
R
D
Y
A
Y
Z
B
A
Y
Z
B
A
H/F**
H/F**
R
R
H/F**
H/F**
D
DI
D
DI
MAX1481
MAX1484
MAX1485
MAX1486
DE RE* RO
DE RE* RO
*RE ON MAX1481 AND MAX1484 ONLY.
**H/F ON MAX1485 AND MAX1486 ONLY.
Figure 20. Typical Full-Duplex RS-485 Network
___________________Ch ip In fo rm a t io n
TRANSISTOR COUNT: 396
______________________________________________________________________________________ 15
Softw a re -Se le c ta ble , Ha lf-/Full-Duple x, Sle w -Ra te -Lim ite d,
12Mbps , RS-485/RS-422 Tra ns c e ive rs in µMAX Pa c ka ge
________________________________________________________P a c k a g e In fo rm a t io n
5/MAX1486
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 ____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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