Download MAX485 Low Power, Slew-Rate-Limited RS-485/RS

MAX485
MAX485
Low Power, Slew-Rate-Limited RS-485/RS-422
Transceiver
DESCRIPTION
The MAX485 is low-power transceivers for RS-485 and RS-422 communication. IC contains one driver and one
receiver.
The driver slew rates of the MAX485 is not limited, allowing them to transmit up to 2.5Mbps.
These transceivers draw between 120µA and 500µA of supply current when unloaded or fully loaded with disabled
drivers. All parts operate from a single 5V supply. Drivers are 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 fail-safe feature that guarantees a logic-high output if the input is open circuit. The MAX485 is
designed for half-duplex applications
FEATURES
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
APPLICATIONS
ƒ
ƒ
ƒ
ƒ
ƒ
Low Quiescent Current: 300µA
-7V to +12V Common-Mode Input Voltage Range
Three-State Outputs
30ns Propagation Delays, 5ns Skew
Full-Duplex and Half-Duplex Versions Available
Operate from a Single 5V Supply
Allows up to 32 Transceivers on the Bus
Data rate: 2,5 Mbps
Current-Limiting and Thermal Shutdown for Driver
Overload Protection
Low-Power RS-485 Transceivers
Low-Power RS-422 Transceivers
Level Translators
Transceivers for EMI-Sensitive Applications
Industrial-Control Local Area Networks
ORDERING INFORMATION
PART NO.
MAX485CPA
MAX485CSA
MAX485EPA
MAX485ESA
Temp. Range (°C)
0 to 70
0 to 70
-40 to 85
-40 to 85
PINOUT
Package
8 Pin DIP
8 Pin SOP
8 Pin DIP
8 Pin SOP
TYPICAL APPLICATION
TOP VIEW
RO1
RO 1
R
RE 2
DE 3
DI 4
D
8
VCC
7
B
6
A
5
GND
R
VCC1
RE1
Rt
DE1
DI1
D
GND1
DIP8 / SOP8
Rt
RO2
R
VCC2
RE2
DE2
DI2
1
D
GND2
MAX485
PIN DESCRIPTIONS
Pin No.
PIN NAME
01
RO
02
RE
03
DE
04
DI
05
06
07
08
GND
A
B
Vcc
DESCRIPTION
Receiver Output. If the receiver output is enabled(RE low), then if A > B by
200mV, RO will be high. If A < B by 200mV, then RO will be low.
Receiver Output Enable. A low enables the receiver output, RO. A high
input forces the receiver output into a high impedance state.
Driver Outputs Enable. A high on DE enables the driver output. A and B,
and the chip will function as a line driver. A low input will force the driver
outputs into a high impedance state and the chip will function as a line
receiver.
Driver Input. If the driver outputs are enabled (DE high), then a low on DI
forces the outputs A low and B high. A high on DI with the driver outputs
enabled will force A high and B low.
Ground Connection.
Driver Output/Receiver Input.
Driver Output/Receiver Input.
Positive Supply; 4.75 < Vcc < 5.25.
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) …………………………………………………………………………..…..12V
Control Input Voltage………………………………………………………......-0.5V to (VCC +0.5V)
Driver Input Voltage (DI)………………………………………………………-0.5V to (VCC +0.5V)
Driver Output Voltage (A, B)………………………………………………………..… -8V to +12.5V
Receiver Input Voltage (A, B)…………………………………………………………. -8V to +12.5V
Receiver Output Voltage (RO)…………………………………………….…-0.5V to (VCC +0.5V)
Continuous Power Dissipation…………………………………………………………. (TA= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) …………………………….………..727mW
8-Pin SO (derate 5.88mW/°C above +70°C) ………………………………………………471mW
Storage Temperature Range………………………………………………….……-65°C to +160°C
Lead Temperature (soldering, 10sec)……………………………………………….……… +300°C
DC ELECTRICAL CHARACTERISTICS
(VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)
PARAMETER
Differential Driver Output (no load)
Differential Driver Output (with load)
SYMBOL
VOD1
VOD2
Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States
Driver
Common-Mode
Output
Voltage
Change in Magnitude of Driver
Common-Mode Output Voltage for
Complementary Output States
Input High Voltage
Input Low Voltage
Input Current
Input Current
(A, B)
∆VOD
Receiver Differential Threshold
Voltage
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
VTH
CONDITIONS
R = 50Ω (RS-422)
R = 27Ω (RS-485), Figure 4
R = 27Ω or 50Ω, Figure 4
MIN
TYP
2
1.5
MAX
UNITS
5
V
V
5
0.2
V
VOC
R = 27Ω or 50Ω, Figure 4
3
V
∆VOD
R = 27Ω or 50Ω, Figure 4
0.2
V
VIH
VIL
IIN1
IIN2
∆VTH
VOH
VOL
DE, DI, RE
DE, DI, RE
DE, DI, RE
DE = 0V;
VCC = 0V or 5.25V,
-7V ≤ VCM ≤12V
2.0
VIN = 12V
VIN = -7V
VCM = 0V
IO = -4mA, VID = 200mV
IO = 4mA, VID = -200mV
2
0.8
±2
1.0
-0.8
0.2
-0.2
70
3.5
0.4
V
V
µA
mA
V
mV
V
V
MAX485
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)
PARAMETER
SYMBOL
Three-State
(high
impedance)
Output Current at Receiver
Receiver Input Resistance
No-Load Supply Current
(Note 3)
IOZR
0.4V ≤ VO ≤ 2.4V
RIN
ICC
-7V ≤ VCM ≤ 12V
Driver Short-Circuit Current,
VO = High
Driver Short-Circuit Current,
VO = Low
Receiver Short-Circuit Current
CONDITIONS
RE = 0V or VCC
MIN
TYP
MAX
UNITS
±1
µA
kΩ
12
DE = VCC
DE = 0V
IOSD1
-7V ≤ VO ≤ 12V (Note 4)
IOSD2
-7V ≤ VO ≤ 12V (Note 4)
IOSR
0V ≤ VO ≤ VCC
500
300
900
500
µA
35
250
mA
35
250
mA
7
95
mA
SWITCHING CHARACTERISTICS
(VCC = 5V ±5%, TA = TMIN to TMAX, unless otherwise noted.) (Notes 1, 2)
PARAMETER
Driver Input to Output
Driver Output Skew to Output
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
| tPLH - tPHL | Differential
Receiver Skew
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable Time from
Low
Receiver Disable Time from
High
Maximum Data Rate
SYMBOL
MIN
TYP
MAX
UNITS
10
30
60
ns
10
60
10
ns
tZH
tZL
tLZ
tHZ
RDIFF = 54Ω, CL1 = CL2 = 100pF
CL= 100pF, S2 closed
CL= 100pF, S1 closed
CL= 15pF, S1 closed
CL= 15pF, S2 closed
30
5
40
40
40
40
70
70
70
70
ns
ns
ns
ns
tSKD
RDIFF = 54Ω
13
tZL
tZH
tLZ
CRL = 15pF, S1 closed
CRL = 15pF, S2 closed
CRL = 15pF, S1 closed
20
20
20
50
50
50
ns
ns
ns
tHZ
CRL = 15pF, S2 closed
20
50
ns
tPLH
tPHL
tSKEW
CONDITIONS
RDIFF = 54Ω
CL1 = CL2 = 100pF
fMAX
2.5
ns
Mbps
Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device
ground unless otherwise specified.
Note 2: All typical specifications are given for VCC = 5V and TA = +25°C.
Note 3: Supply current specification is valid for loaded transmitters when DE = 0V.
Note 4: Applies to peak current. See Typical Operating Characteristics.
3
MAX485
TESTING CIRCUITS
A
S1
TEST POINT
R
1k
RECEIVER
OUTPUT
VOD
VCC
CRL
15pF
VOC
R
1k
S2
B
Figure 1. Driver DC Test Load
Figure 2. Receiver Timing Test Load
3V
DE
A
DI
S1
A
CL1
RO
RDIFF
B
B
CL2
S2
RE
CL
15pF
Figure 3. Driver/Receiver Timing Test Circuit
Figure 4. Driver Timing Test Load #2
SWITCHING TIME WAVEFORMS
3V
f = 1MHz, t r ≤ 10ns, t f ≤ 10ns
1.5V
DI
1.5V
0V
t PLH
1/2 VO
t PHL
B
VO
A
tSKEW
1/2 VO
VO
0V
–VO
80%
10%
t SKEW
90%
VDIFF = V(A) – V(B)
20%
tr
tf
Figure 5. Driver Propagation Delays
3V
1.5V
DE
f = 1MHz, t r ≤ 10ns, t f ≤ 10ns
1.5V
0V
5V
VCC
500Ω
OUTPUT
UNDER TEST
t ZL
A, B
t LZ
2.3V
OUTPUT NORMALLY LOW
0.5V
2.3V
OUTPUT NORMALLY HIGH
0.5V
VOL
VOH
A, B
0V
t HZ
t ZH
Figure 6. Driver Enable and Disable Times
4
MAX485
SWITCHING TIME WAVEFORMS
VOH
1.5V
R
f = 1MHz, t r ≤ 10ns, t f ≤ 10ns
t PHL
VOD2
A, B
–VOD2
1.5V
OUTPUT
VOL
0V
t PLH
INPUT
Figure 7. Receiver Propagation Delays
3V
1.5V
RE
f = 1MHz, t r ≤ 10ns, t f ≤ 10ns
1.5V
0V
t ZL
5V
t LZ
R
R
1.5V
OUTPUT NORMALLY LOW
0.5V
1.5V
OUTPUT NORMALLY HIGH
0.5V
0V
t HZ
t ZH
Figure 8. Receiver Enable and Disable Times
FUNCTION TABLES
Transmitting
Receiving
INPUTS
OUTPUTS
INPUTS
OUTPUTS
RE
DE
DI
LINE
CONDITION
B
A
RE
DE
A–B
R
X
1
1
No Fault
0
1
0
0
≥ 0.2V
1
X
1
0
No Fault
1
0
0
0
≤ – 0.2V
0
X
0
X
X
Z
Z
0
0
Inputs Open
1
X
1
X
Fault
Z
Z
1
0
X
Z
5
MAX485
PACKAGE
DIP8 Package
(Narrow .300 Inch)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
0.300 – 0.325
(7.620 – 8.255)
0.009 – 0.015
(0.229 – 0.381)
(
0.065
(1.651)
TYP
+0.035
0.325 –0.015
8.255
+0.889
–0.381
0.130 ± 0.005
(3.302 ± 0.127)
0.045 – 0.065
(1.143 – 1.651)
)
0.125
(3.175) 0.020
MIN (0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
0.100
(2.54)
BSC
SOP8 Package
(Narrow .150 Inch)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
6
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC