MAXIM MAX1481EUB

19-1312; Rev 0; 10/97
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
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.
Drivers are output short-circuit current limited and are
protected against excessive power dissipation by
thermal-shutdown circuitry that places the driver outputs
into a high-impedance state. The receiver input has a failsafe feature that guarantees a logic-high output if the
input is open circuit.
____________________________Features
♦ 10-Pin µMAX Package: Smallest 10-Pin Package
♦ Software-Selectable Half-/Full-Duplex Operation
(MAX1485/MAX1486)
♦ 0.1µA Low-Current Shutdown Mode (MAX1481)
♦ Slew-Rate Limiting Allows Error-Free Data
Transmission (MAX1481/MAX1485)
♦ 12Mbps High-Speed Operation
(MAX1484/MAX1486)
♦ Allow up to 256 Transceivers on the Bus
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1481CUB
0°C to +70°C
10 µMAX
MAX1481EUB
MAX1484CUB
MAX1484EUB
MAX1485CUB
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
10 µMAX
10 µMAX
10 µMAX
10 µMAX
MAX1485EUB
MAX1486CUB
MAX1486EUB
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
10 µMAX
10 µMAX
10 µMAX
________________________Applications
Low-Power RS-422/RS-485 Communications
Level Translators
Hand-Held Equipment
Battery-Powered Equipment
Transceiver for EMI-Sensitive Applications
Industrial-Control Local Area Networks
______________________________________________________________Selection Table
Part
Half/Full
Duplex
Data
Rate
(Mbps)
SlewRate
Limited
LowPower
Shutdown
Driver
Enable
Receiver
Enable
Quiescent
Current
(µA)
Transceivers
on Bus
PinPackage
MAX1481
Full
0.250
Yes
Yes
Yes
Yes
300
256
10 µMAX
MAX1484
Full
12
No
No
Yes
Yes
300
256
10 µMAX
MAX1485
Selectable
0.250
Yes
No
Yes
No
300
256
10 µMAX
MAX1486
Selectable
12
No
No
Yes
No
300
256
10 µMAX
________________________________________________________________ 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.
MAX1481/MAX1484/MAX1485/MAX1486
_______________General Description
The MAX1481/MAX1484/MAX1485/MAX1486 provide
software-selectable, half-/full-duplex, low-power, slewrate-limited, and high-speed (12Mbps) RS-485/RS-422
operation in a 10-pin µMAX package—the smallest
10-pin package available.
The software-selectable, half-/full-duplex MAX1485/
MAX1486 make obsolete the normally larger and more
expensive solutions required for selectable half-/fullduplex RS-485/RS-422 operation: 1) a 14-pin, fullduplex transceiver configured via jumpers between
receiver and transmitter lines, or 2) two 8-pin, halfduplex transceivers, which require an additional inverter logic gate for software selectability.
The MAX1481/MAX1484 are functionally equivalent to
the industry-standard MAX491 and 75180, and are
designed for space-constrained, full-duplex RS-422
applications.
All parts contain one driver and one receiver and feature a 1/8-unit-load receiver input impedance, allowing
up to 256 transceivers on the bus. The MAX1481/
MAX1485 feature reduced-slew-rate drivers that minimize 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.
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) ............................................................+7V
Control Input Voltage (RE, DE, H/F) ...........-0.3V to (VCC + 0.3V)
Driver Input Voltage (DI).............................-0.3V to (VCC + 0.3V)
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
Receiver Output Voltage (RO)....................-0.3V to (VCC + 0.3V)
Continuous Power Dissipation
10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW
Operating Temperature Ranges
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
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
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRIVER
VOD1
Differential Driver Output
Change in Magnitude of
Differential Output Voltage
(Note 2)
VOD2
No load, Figure 5
5
R = 50Ω (RS-422), Figure 5
2.0
R = 27Ω (RS-485), Figure 5
1.5
V
5
∆VOD
R = 50Ω or 27Ω, Figure 5
0.2
V
VOC
R = 50Ω or 27Ω, Figure 5
3
V
Change in Magnitude of
Common-Mode Voltage (Note 2)
∆VOC
R = 50Ω or 27Ω, Figure 5
0.2
V
Input High Voltage
VIH1
DE, DI, RE, H/F
Input Low Voltage
VIL1
DE, DI, RE, H/F
Input Current
IIN1
DE, DI, RE, H/F
Driver Common-Mode Output
Voltage
Input Current (Y and Z for Half
Duplex, A and B for Full Duplex)
IIN2
DE = GND,
VCC = GND or 5.25V
Output Leakage (Y and Z)
(MAX1481/MAX1484 Only)
IO
DE = GND
Output Leakage (Y and Z)
(MAX1485/MAX1486 Only)
IO
DE = GND
Driver Output Short-Circuit
Current (Note 3)
IOSD
2
-7V ≤ VOUT ≤ 12V
2.0
V
0.8
V
±2
µA
VIN = 12V
0.125
VIN = -7V
-0.1
VIN = 12V
10
VIN = -7V
-10
VIN = 12V
125
VIN = -7V
-100
35
_______________________________________________________________________________________
250
mA
µA
µA
mA
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
(VCC = +5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25ºC.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
200
mV
RECEIVER
Receiver Differential Threshold
Voltage
VTH
-7V ≤ VCM ≤ 12V
-200
Receiver Input Hysteresis
∆VTH
Receiver Output High Voltage
VOH
IO = -4mA, VID = 200mV
Receiver Output Low Voltage
VOL
IO = 4mA, VID = -200mV
0.4
V
Three-State Output Current at
Receiver
IOZR
0.4V ≤ VO ≤ 2.4V
±1
µA
Receiver Input Resistance
RIN
-7V ≤ VCM ≤ 12V
Receiver Output Short-Circuit
Current
IOSR
0V ≤ VRO ≤ VCC
ICC
RE = GND, DE = VCC
ISHDN
DE = GND, RE = VCC
70
mV
3.5
V
96
kΩ
±95
mA
300
600
µA
0.1
10
µA
TYP
MAX
UNITS
30
60
30
60
5
10
ns
15
35
ns
SUPPLY CURRENT
No-Load Supply Current
Supply Current in Shutdown
Mode (MAX1481 Only)
SWITCHING CHARACTERISTICS (MAX1484/MAX1486)
(VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
Driver Input to Output
Driver Input to Output
SYMBOL
tDPLH
tDPHL
CONDITIONS
MIN
RDIFF = 54Ω, CL1 = CL2 = 100pF,
Figures 7 and 9
Driver Output Skew
| tDPLH - tDPHL |
tDSKEW
RDIFF = 54Ω, CL1 = CL2 = 100pF,
Figures 7 and 9
Driver Rise or Fall Time
tDR, tDF
RDIFF = 54Ω, CL1 = CL2 = 100pF,
Figures 7 and 9
5
12
ns
Maximum Data Rate
fMAX
Driver Enable to Output Low
tDZL
CL = 100pF, S1 closed, Figures 8 and 10
40
70
Mbps
ns
Driver Enable to Output High
tDZH
CL = 100pF, S2 closed, Figures 8 and 10
40
70
ns
Driver Disable Time from Low
tDLZ
CL = 15pF, S1 closed, Figures 8 and 10
40
70
ns
Driver Disable Time from High
tDHZ
CL = 15pF, S2 closed, Figures 8 and 10
40
70
ns
150
ns
Receiver Input to Output
tRPLH,
tRPHL
Figures 11 and 13
90
| tRPLH - tRPHL | Differential
Receiver Skew
tRSKD
Figures 11 and 13
5
ns
Receiver Enable to Output Low
tRZL
CL = 100pF, S1 closed, Figures 6 and 12
20
50
ns
Receiver Enable to Output High
tRZH
CL = 100pF, S2 closed, Figures 6 and 12
20
50
ns
Receiver Disable Time from Low
tRLZ
CL = 100pF, S1 closed, Figures 6 and 12
20
50
ns
Receiver Disable Time from High
tRHZ
CL = 100pF, S2 closed, Figures 6 and 12
20
50
ns
_______________________________________________________________________________________
3
MAX1481/MAX1484/MAX1485/MAX1486
ELECTRICAL CHARACTERISTICS (continued)
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
SWITCHING CHARACTERISTICS (MAX1481/MAX1485) (continued)
(VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
Driver Input to Output
SYMBOL
tDPLH
tDPHL
CONDITIONS
MIN
RDIFF = 54Ω, CL1 = CL2 = 100pF,
Figures 7 and 9
Driver Output Skew
| tDPLH - tDPHL |
tDSKEW
RDIFF = 54Ω, CL1 = CL2 = 100pF,
Figures 7 and 9
Driver Rise or Fall Time
tDR, tDF
RDIFF = 54Ω, CL1 = CL2 = 100pF,
Figures 7 and 9
TYP
MAX
600
1000
600
1000
10
200
ns
1000
ns
250
250
UNITS
ns
Maximum Data Rate
fMAX
Driver Enable to Output Low
tDZL
CL = 100pF, S1 closed, Figures 8 and 10
3000
kbps
ns
Driver Enable to Output High
tDZH
CL = 100pF, S2 closed, Figures 8 and 10
3000
ns
Driver Disable Time from Low
tDLZ
CL = 15pF, S1 closed, Figures 8 and 10
200
ns
Driver Disable Time from High
tDHZ
CL = 15pF, S2 closed, Figures 8 and 10
200
ns
150
ns
Receiver Input to Output
tRPLH,
tRPHL
Figures 11 and 13
90
| tRPLH - tRPHL | Differential
Receiver Skew
tRSKD
Figures 11 and 13
15
ns
Receiver Enable to Output Low
tRZL
CL = 100pF, S1 closed, Figures 6 and 12
20
50
ns
Receiver Enable to Output High
tRZH
CL = 100pF, S2 closed, Figures 6 and 12
20
50
ns
Receiver Disable Time from Low
tRLZ
CL = 100pF, S1 closed, Figures 6 and 12
20
50
ns
tRHZ
CL = 100pF, S2 closed, Figures 6 and 12
20
50
ns
200
600
ns
Receiver Disable Time from High
Time to Shutdown
tSHDN
MAX1481 only (Note 4)
50
Driver Enable from Shutdown to
Output High
tDZH(SHDN)
MAX1481 only, CL = 15pF, S2 closed,
Figures 8 and 10
3000
ns
Driver Enable from Shutdown to
Output Low
tDZL(SHDN)
MAX1481 only, CL = 15pF, S1 closed,
Figures 8 and 10
3000
ns
Receiver Enable from Shutdown
to Output High
tRZH(SHDN)
MAX1481 only, CL = 100pF, S2 closed,
Figures 6 and 12
500
ns
Receiver Enable from Shutdown
to Output Low
tRZL(SHDN)
MAX1481 only, CL = 100pF, S1 closed,
Figures 6 and 12
1000
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: ∆VOD and ∆VOC are the changes in VOD and VOC, respectively, when the DI input changes state.
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
_______________________________________________________________________________________
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
300
280
MAX1484/MAX1486
260
40
30
20
220
-20
0
20
40
60
80
100
2
3
4
5
2
3
4
5
OUTPUT LOW VOLTAGE (V)
SHUTDOWN CURRENT
vs. TEMPERATURE
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
IRO = 8mA
0.45
0.40
IRO = 8mA
4.4
OUTPUT VOLTAGE (V)
102
4.5
MAX1481/4/5/6-05
MAX1481/4/5/6-04
106
0.50
98
0.35
0.30
0.25
0.20
94
0
20
40
60
80
100
4.2
4.1
4.0
3.8
0.10
-20
4.3
3.9
0.15
-60
-40
-20
0
20
40
60
80
-60
100
-40
-20
0
20
40
60
80
100
MAX1481/MAX1485 RECEIVER
PROPAGATION DELAY vs. TEMPERATURE
MAX1484/MAX1486 RECEIVER
PROPAGATION DELAY vs. TEMPERATURE
MAX1481/MAX1485 DRIVER
PROPAGATION DELAY vs. TEMPERATURE
95
90
85
80
CLOAD = 15pF
93
92
91
90
89
88
86
-60
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
100
RDIFF = 54Ω
CL1 = CL2 = 100pF
660
640
620
600
580
560
87
75
680
PROPAGATION DELAY (ns)
100
94
PROPAGATION DELAY (ns)
CLOAD = 15pF
MAX1481/4/5/6-09
TEMPERATURE (°C)
MAX1481/4/5/6-08
TEMPERATURE (°C)
MAX1481/4/5/6-07
TEMPERATURE (°C)
105
PROPAGATION DELAY (ns)
1
0
OUTPUT LOW VOLTAGE (V)
110
-40
10
TEMPERATURE (°C)
114
-60
15
0
1
0
OUTPUT LOW VOLTAGE (V)
-40
20
5
0
-60
MAX1481/4/5/6-03
25
10
240
SHUTDOWN CURRENT (nA)
MAX1481/4/5/6-02
50
30
MAX1481/4/5/6-06
320
OUTPUT CURRENT vs.
RECEIVER OUTPUT HIGH VOLTAGE
60
OUTPUT CURRENT (mA)
MAX1481/MAX1485
340
SUPPLY CURRENT (µA)
MAX1481/4/5/6-01
360
OUTPUT CURRENT vs.
RECEIVER OUTPUT LOW VOLTAGE
OUTPUT CURRENT (mA)
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
540
-60
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
100
-60
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX1481/MAX1484/MAX1485/MAX1486
__________________________________________Typical Operating Characteristics
(VCC = +5V, TA = +25°C, unless otherwise noted.)
_________________________________Typical Operating Characteristics (continued)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
30
26
120
100
80
60
40
22
-40
-20
0
20
40
60
80
100
80
60
40
0
0
0
2
4
6
8
10
-8
12
-6
-4
-2
0
2
4
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)
OUTPUT HIGH VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX1484/MAX1486
RECEIVER PROPAGATION DELAY
RDIFF = 54Ω
2.35
2.30
2.25
2.20
6
MAX1481/4/5/6-15
100
MAX1481/4/5/6-14
MAX1481/4/5/6-13
2.40
OUTPUT CURRENT (mA)
-60
100
20
20
18
120
MAX1481/4/5/6-12
34
140
MAX1481/4/5/6-11
PROPAGATION DELAY (ns)
RDIFF = 54Ω
CL1 = CL2 = 100pF
OUTPUT CURRENT (mA)
MAX1481/4/5/6-10
38
OUTPUT CURRENT vs.
DRIVER OUTPUT HIGH VOLTAGE
OUTPUT CURRENT vs.
DRIVER OUTPUT LOW VOLTAGE
OUTPUT CURRENT (mA)
MAX1484/MAX1486 DRIVER
PROPAGATION DELAY vs. TEMPERATURE
OUTPUT VOLTAGE (V)
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
10
VA - VB
(2V/div)
1
RO
(5V/div)
0.1
2.15
2.10
0.01
-60
-40
-20
0
20
40
60
80
100
0
DIFFERENTIAL OUTPUT VOLTAGE (V)
MAX1481/MAX1485
RECEIVER PROPAGATION DELAY
MAX1481/MAX1485
DRIVER PROPAGATION DELAY
RO
(5V/div)
1µs/div
6
MAX1484/MAX1486
DRIVER PROPAGATION DELAY
MAX1481/4/5/6-18
MAX1481/4/5/6-17
MAX1481/4/5/6-16
VA - VB
(2V/div)
50ns/div
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
TEMPERATURE (°C)
DI
(5V/div)
DI
5V/div
VY - VZ
(2V/div)
VY - VZ
2V/div
1µs/div
50ns/div
_______________________________________________________________________________________
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
PIN PIN
MAX1481/
MAX1484
MAX1485/MAX1486
NAME
FUNCTION
H/F = 0
H/F = 1
1
1
1
RO
Receiver Output. When RE is low and if A - B ≥ 200mV, RO goes high; if A - B ≤
-200mV, RO goes low.
—
2
2
H/F
Half-/Full-Duplex Selector Input. Connect H/F to VCC for half-duplex mode, and
connect to GND for full-duplex mode.
2
—
—
RE
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 lowpower shutdown mode.
3
3
3
DE
Driver Output Enable Input. Drive DE high to enable driver outputs. These outputs
are high impedance when DE is low.
4
4
4
DI
Driver Input. With DE high, a low on DI forces noninverting output low and inverting output high. Similarly, a high on DI forces noninverting output high and inverting output low.
5
5
5
GND
6
6
—
B
Inverting Receiver Input
—
—
6
B
Receiver Input Resistors*
7
7
—
Z
Inverting Driver Output
—
—
7
Z
Inverting Driver Output and Inverting Receiver Input
8
8
—
Y
Noninverting Driver Output
—
—
8
Y
Noninverting Driver Output and Noninverting Receiver Input
Ground
9
9
—
A
Noninverting Receiver Input
—
—
9
A
Receiver Input Resistors*
10
10
10
VCC
Positive Supply; +4.75V ≤ VCC ≤ +5.25V
*(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
MAX1481/MAX1484/MAX1485/MAX1486
______________________________________________________________Pin Description
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
_____________________________________________________________Function Tables
MAX1481
RECEIVING
TRANSMITTING
INPUTS
INPUTS
OUTPUTS
OUTPUT
RE
DE
DI
Z
Y
RE
DE
A-B
RO
X
1
1
0
1
0
X
≥ 0.2V
1
X
1
0
1
0
0
X
≤ -0.2V
0
0
0
X
High-Z
High-Z
1
1
X
High-Z
1
0
X
1
0
X
High-Z and
Shutdown
High-Z and Shutdown
MAX1484
TRANSMITTING
RECEIVING
INPUTS
OUTPUTS
INPUTS
OUTPUT
RE
DE
DI
Z
Y
RE
DE
A-B
RO
X
1
1
0
1
0
X
≥ 0.2V
1
X
1
0
1
0
0
X
≤ -0.2V
0
X
0
X
High-Z
High-Z
1
X
X
High-Z
MAX1485/MAX1486
TRANSMITTING
INPUTSINPUTS
RECEIVING
OUTPUTS
INPUTS
DE
DI
Z
Y
H/F
DE
1
1
0
1
0
1
0
1
0
0
0
X
High-Z
High-Z
OUTPUT
OUTPUT
A-B
Y-Z
RO
X
≥ 0.2V
X
1
X
≤ -0.2V
X
0
1
0
X
≥ 0.2V
1
1
0
X
≤ -0.2V
0
X = Don’t care
Note: In shutdown mode, driver and receiver outputs are high impedance.
8
_______________________________________________________________________________________
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
MAX1481
MAX1484
RO 1
MAX1481
MAX1484
0.1µF
MAX1481
MAX1484
10 VCC
RE
2
9
A
DE
3
8
Y
DI
4
7
Z
GND
5
6
B
RO
RE
DE
DI
1
10
VCC
9 A
0.1µF
Rt
Y 8
7
Z
6 B
2
10
VCC
Rt
7 Z
8 Y
5
µMAX
B 6
9
A
1
5
GND
4
DI
3 DE
2
RE
3
4
MAX1481/MAX1484/MAX1485/MAX1486
TOP VIEW
RO
GND
Figure 1. MAX1481/MAX1484 Pin Configuration and Typical Full-Duplex Operating Circuit
MAX1485
MAX1486
TOP VIEW
MAX1485
MAX1486
0.1µF
0.1µF
10
RO 1
10 VCC
RO
9
A
H/F 2
8
Y
H/F
2
DE
3
DI
4
7
Z
GND
5
6
B
MAX1485
MAX1486
1
DE
DI
VCC
9 A
Rt
Y 8
7
Z
6 B
10
CC
VCC
DI
3 DE
2 H/F
3
Rt
7 Z
4
8 Y
5
µMAX
B 6
9
A
1
5
GND
4
RO
GND
Figure 2. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Full-Duplex Operating Circuit
MAX1485
MAX1486
TOP VIEW
MAX1485
MAX1486
0.1µF
10 VCC
RO 1
H/F
2
DE
3
MAX1485
MAX1486
9
A
8
Y
DI
4
7
Z
GND
5
6
B
µMAX
RO
1
10
VCC
DI
10
VCC
8 Y
H/F 2
DE
0.1µF
Rt
Rt
3
7 Z
Z 7
4
9 A
A 9
6 B
B 6
5
GND
4
DI
3 DE
2 H/F
Y 8
1
5
RO
GND
Figure 3. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Half-Duplex Operating Circuit
_______________________________________________________________________________________
9
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
MAX1485/MAX1486
Half-/Full-Duplex Mode Operation
VCC
MAX1485
MAX1486
B
DI
A
DE
The MAX1484/MAX1485 can operate in full- or halfduplex mode. Drive the H/F pin low or connect it to
GND for full-duplex operation, or drive it high for halfduplex operation. In full-duplex mode, the pin configuration of the driver and receiver is the same as a
MAX1481 (Figure 1).
__________Applications Information
RO
256 Transceivers on the Bus
H/F
Z
Y
GND
Figure 4. MAX1485/MAX1486 Functional Diagram
_______________Detailed Description
The MAX1481/MAX1484/MAX1485/MAX1486 highspeed transceivers for RS-485/RS-422 communication
contain one driver and one receiver. The MAX1481/
MAX1485 feature reduced-slew-rate drivers that minimize 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 current when unloaded or fully loaded with the drivers disabled. The MAX1481 has a shutdown mode in which
supply current is typically reduced to 0.1µA.
Drivers are output short-circuit current limited and are
protected against excessive power dissipation by thermal-shutdown circuitry that places the driver outputs
into a high-impedance state.
All devices have a 1/8-unit-load receiver input impedance that allows up to 256 transceivers on the bus. The
MAX1481/MAX1484 are designed for full-duplex communications. The H/F pin on the MAX1485/MAX1486
allows the user to select between half-duplex or fullduplex operation (Figure 4).
10
The standard RS-485 receiver input impedance is 12kΩ
(1-unit load), and the standard driver can drive up to
32-unit loads. The MAX1481/MAX1484/MAX1485/
MAX1486 transceivers have a 1/8-unit-load receiver
input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on one communication line. Connect any combination of these devices
and/or other RS-485 transceivers totaling 32-unit loads
or less.
Reduced EMI and Reflections
The MAX1481/MAX1485 are slew-rate limited, minimizing 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.
In general, a transmitter’s rise time relates directly to
the length of an unterminated stub, which can be driven with only minor waveform reflections. The following
equation expresses this relationship conservatively:
Length = tRISE / (10 x 1.5ns/ft)
where tRISE is the transmitter’s rise time.
For example, the MAX1481’s rise time is typically
500ns, which results in excellent waveforms with a stub
length up to 33 feet. A system may work well with
longer unterminated stubs, even with severe reflections, if the waveform settles out before the UART
samples them.
______________________________________________________________________________________
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
MAX1481/MAX1484/MAX1485/MAX1486
Y
R
RECEIVER
OUTPUT
VOD
1k
TEST POINT
VCC
S1
CL
R
1k
VOC
S2
Z
Figure 5. Driver DC Test Load
Figure 6. Receiver Enable/Disable Timing Test Load
3V
DE
CL1
Y
DI
RDIFF
VID
VCC
S1
500Ω
OUTPUT
UNDER TEST
Z
CL
CL2
S2
Figure 7. Driver Timing Test Circuit
Figure 8. Driver Enable/Disable Timing Test Load
3V
DI
1.5V
0V
3V
1.5V
tDPHL
tDPLH
DE
1/2 VO
1.5V
tDZL(SHDN), tDPL
Z
tDLZ
Y, Z
VO
Y
VOL
1/2 VO
VO
VDIFF 0V
-VO
1.5V
0V
10%
2.3V OUTPUT NORMALLY LOW
VDIFF = VY - VZ
90%
90%
tR
tF
tSKEW = | tPLH - tPHL |
Figure 9. Driver Propagation Delays
OUTPUT NORMALLY HIGH
Y, Z
10%
VOL +0.5V
VOH -0.5V
2.3V
0V
DZH(SHDN), DZH
DHZ
Figure 10. Driver Enable and Disable Times
______________________________________________________________________________________
11
3V
RE
1.5V
1.5V
0V
RO
VOH
1.5V
VOL
1V
A
-1V
B
RPHL
RZL(SHDN), RZL
1.5V
OUTPUT
RPLH
RLZ
VCC
RO
1.5V OUTPUT NORMALLY LOW
RO
1.5V
INPUT
VOL + 0.5V
OUTPUT NORMALLY HIGH
VOH - 0.5V
0V
RZH(SHDN), RZH
Figure 11. Receiver Propagation Delays
RHZ
Figure 12. Receiver Enable and Disable Times
(MAX1481/MAX1484 only)
MAX1481/4/5/6-fig14
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
B
ATE
VID
RR
RECEIVER
OUTPUT
20dB/div
A
0Hz
Figure 13. Receiver Propagation Delay Test Circuit
Low-Power Shutdown Mode
(MAX1481 only)
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the MAX1481 typically draws only 0.1µA of supply current.
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 Characteristics tables assume the part was not in low-power shutdown. Enable times t_ZH(SHDN) and t_ZL(SHDN) assume
the parts were shut down. It takes drivers and receivers
12
250kHz/div
2.5MHz
Figure 14. Driver Output Waveform and FFT Plot of
MAX1484/MAX1486 Transmitting a 20kHz signal
longer to become enabled from the low-power shutdown
mode (t_ ZH (SHDN) , t_ Z L(SHDN) ) than from the
driver/receiver disable mode (t_ZH, t_ZL).
Driver Output Protection
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 circuits over the whole common-mode voltage range (see
Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a
high-impedance state if the die temperature becomes
excessive.
______________________________________________________________________________________
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
Figures 17 and 18 show the system differential voltage
for the parts driving 4000 feet of 26AWG twisted-pair
wire into 120Ω loads.
Typical Applications
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 MAX1481/MAX1485 are more tolerant of imperfect
termination than the MAX1484/MAX1486.
MAX1481/4/5/6-fig15
The MAX1485/MAX1486 are designed for bidirectional
data communications on multipoint bus transmission
lines. Figures 19 and 20 show typical network applications circuits. These parts can also be used as line
repeaters with cable lengths longer than 4000 feet
(Figure 16).
MAX1481
MAX1484
MAX1485
MAX1486
A
RO
RE
R
120Ω
B
DATA IN
DE
20dB/div
Z
DI
D
H/F
0Hz
250kHz/div
2.5MHz
Figure 15. Driver Output Waveform and FFT Plot of
MAX1481/MAX1485 Transmitting a 20kHz Signal
120Ω
Y
DATA OUT
NOTE: RE ON MAX1481 AND MAX1484 ONLY.
H/F ON MAX1485 AND MAX1486 ONLY.
Figure 16. Line Repeater
MAX1481/4/5/6-fig18
MAX1481/4/5/6-fig17
DI
5V/div
DI
5V/div
VA - VB
4V/div
VA - VB
4V/div
RO
5V/div
RO
5V/div
5µs/div
Figure 17. MAX1481/MAX1485 System Differential Voltage at
50kHz Driving 4000 ft. of Unterminated Cable
1µs/div
Figure 18. MAX1484/MAX1486 System Differential Voltage at
200kHz Driving 4000 ft. of Unterminated Cable
______________________________________________________________________________________
13
MAX1481/MAX1484/MAX1485/MAX1486
Line Length vs. Data Rate
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.
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
5V
VCC
5V
H/F
120Ω
H/F
DE
B
B
DI
VCC
120Ω
D
D
DI
DE
RO
A
B
A
B
R
A
A
R
5V
R
H/F
R
VCC
D
D
VCC
VCC
MAX1485
MAX1486
DI
DE
RO
DI
DE
RO
Figure 19. Typical Half-Duplex RS-485 Network
14
______________________________________________________________________________________
RO
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
Y
120Ω
R
RO
RE
120Ω
D
B
Z
Z
B
DI
DE
DI
MAX1481/MAX1484/MAX1485/MAX1486
A
DE
120Ω
D
Y
120Ω
Z
Y
B
A
Y
Z
B
A
RE*
RO
R
A
H/F**
H/F**
R
H/F**
D
DI
R
DE RE* RO
H/F**
D
DI
DE RE* RO
MAX1481
MAX1484
MAX1485
MAX1486
*RE ON MAX1481 AND MAX1484 ONLY.
**H/F ON MAX1485 AND MAX1486 ONLY.
Figure 20. Typical Full-Duplex RS-485 Network
___________________Chip Information
TRANSISTOR COUNT: 396
______________________________________________________________________________________
15
________________________________________________________Package Information
10LUMAXB.EPS
MAX1481/MAX1484/MAX1485/MAX1486
Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,
12Mbps, RS-485/RS-422 Transceivers in µMAX Package
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
© 1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.