MAXIM MAX3158EAI

19-2778; Rev 0; 2/03
High CMRR RS-485 Transceiver
with ±60V Isolation
Features
♦ ±60V Isolated Data Interface
♦ +5V Single Supply
♦ Low-Cost Replacement for Opto-Isolated
Transceivers
♦ True Fail-Safe Receiver While Maintaining
EIA/TIA-485 Compliance
♦ Pin-Selectable Full/Half-Duplex Operation
♦ Phase Controls to Correct for Twisted-Pair
Reversal
♦ 25µA Low-Power Shutdown Mode
♦ Thermal Shutdown for Driver Overload Protection
♦ 28-Pin SSOP Package
♦ Slew-Rate-Limited Reduced EMI
Ordering Information
________________________Applications
Industrial Controls
Telecommunications
Level Translators
Local Area Networks
PART
TEMP RANGE
PIN-PACKAGE
MAX3158CAI
0°C to +70°C
28 SSOP
MAX3158CPI
0°C to +70°C
28 PDIP
MAX3158EAI
-40°C to +85°C
28 SSOP
MAX3158EPI
-40°C to +85°C
28 PDIP
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
VCC
MICRO
ISOVCC
VCC
H/F
TXP
RXP
DE
DI
RE
RO
MAX3158
GND
C3
1µF
A
B
Y
Z
YR
ZR
AR
BR
RT = 100Ω
RS-485
NODE
REMOTE MICRO
0.1µF
RG
C1LO C1HI C2LO C2HI ISOCOM
±60V
C1
0.047µF
C2
0.047µF
C4
10nF
GND OFFSET
REMOTE GND
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX3158
General Description
The MAX3158 is a high CMRR RS-485/RS-422 data-communications interface providing ±60V isolation in a
hybrid microcircuit. A single +5V supply on the logic side
powers both sides of the interface, with external 100V
capacitors transferring power from the logic side to the
isolated side. Each MAX3158 contains one transmitter
and one receiver and is guaranteed to operate at data
rates up to 250kbps. Drivers are short-circuit current limited and 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 receiver
output if the inputs are open, shorted, or connected to a
terminated transmission line with all drivers disabled.
The MAX3158 typically draws 25mA of supply current
when unloaded or when fully loaded with the driver disabled. Supply current drops to 25µA when the device is
placed in shutdown mode. The device is pin selectable
between half- and full-duplex mode and also features
an independently programmable receiver and transmitter output phase through separate pins. The MAX3158
is a low-cost replacement for opto-isolated transceivers. For fully isolated RS-485/RS-422 transceivers,
refer to the MAX1480 family data sheet.
MAX3158
High CMRR RS-485 Transceiver
with ±60V Isolation
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
Supply Voltage (VCC).............................................................+7V
Cable Ground (ISOCOM) ....................................................±75V
Isolated Supply ISOVCC Relative to Cable Ground
(ISOCOM) ...........................................................................+7V
Digital Input, Output Voltage
(DI, DE, RE, TXP, RXP, RO).....................-0.3V to (VCC + 0.3V)
Digital Inputs (H/F) Relative to Cable Ground
(ISOCOM) .........................................-0.3V to (ISOVCC + 0.3V)
Driver Output Voltage (Y, Z) Relative to Cable Ground
(ISOCOM)............................................................-8V to +12.5V
Receiver Input Voltage (A, B) Relative to Cable Ground
(ISOCOM)............................................................-8V to +12.5V
Termination Connections (YR, ZR, AR, BR) Relative to Cable
Ground (ISOCOM)...............................................-8V to +12.5V
Charge-Pump Capacitance Low
(C1LO, C2LO) .........................................-0.3V to (VCC + 0.3V)
Charge-Pump Capacitance High (C1HI, C2HI) Relative
to Cable Ground (ISOCOM) .............-0.3V to (ISOVCC + 0.3V)
Continuous Power Dissipation (TA = +70°C)
28-Pin SSOP (derate 10.8mW/°C above +70°C) ..........860mW
28-Pin PDIP (derate 14.3mW/°C above +70°C)..........1143mW
Operating Temperature Ranges
MAX3158C_I .......................................................0°C to +70°C
MAX3158E_I ....................................................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................-65°C to +160°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%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF, 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
6
V
DRIVER
Differential Driver Output,
No Load
VOD1
Differential Driver Output,
Loaded
VOD2
Change in Magnitude of
Differential Output Voltage
(Note 2)
∆VOD
Figure 1, R = 50Ω or R = 27Ω
0.2
V
VOC
Figure 1, R = 50Ω or R = 27Ω,
VOC relative to ISOCOM
3.5
V
∆VOC
Figure 1, R = 50Ω or R = 27Ω
0.2
V
Driver Common-Mode Voltage
Change in Magnitude of
Common-Mode Voltage
(Note 2)
2
Figure 1, R = 10MΩ
Figure 1, R = 50Ω (RS-422)
2.0
Figure 1, R = 27Ω (RS-485)
1.5
Input High Voltage
VIH
DE, DI, RE, TXP, RXP, relative to GND,
H/F relative to ISOCOM
Input Low Voltage
VIL
DE, DI, RE, TXP, RXP, relative to GND,
H/F relative to ISOCOM
DI Input Hysteresis
VHYS
V
2.0
V
0.8
100
_______________________________________________________________________________________
V
mV
High CMRR RS-485 Transceiver
with ±60V Isolation
(VCC = +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF, TA = TMIN to TMAX, unless otherwise noted.
Typical values are at VCC = +5V and TA = +25°C.) (Note 1)
PARAMETER
Input Current
Input Current (A and B)
Output Leakage (Y and Z)
Full Duplex
Driver Short-Circuit Output
Current (Note 3)
SYMBOL
CONDITIONS
IIN1
DE, DI, RE
IIN2
H/F, TXP, RXP internal pulldown
MIN
TYP
MAX
±2
10
40
DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN VISOCOM) ≤ +12V, AR = BR = ISOCOM
-5.0
+8.0
DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN VISOCOM) ≤ +12V, AR open, BR open
-0.58
+1.0
DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN VISOCOM) ≤ +12V, YR = ZR = ISOCOM
-5.0
+8.0
DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN VISOCOM) ≤ +12V, YR open, ZR open
-0.58
+1.0
IOSD1
VISOCOM - 7V ≤ VOUT ≤ VISOVCC
-250
IOSD2
VISOCOM - 7V ≤ VOUT ≤ VISOCOM + 12V
IIN3
IO
UNITS
µA
mA
mA
250
mA
RECEIVER
Receiver Differential Threshold
Voltage
VTH
Receiver Input Hysteresis
∆VTH
Receiver Output High Voltage
VOH
-7V ≤ VCM - VISOCOM ≤ +12V
-200
-125
-50
25
IO = -4mA, VID = -50mV
mV
mV
V CC - 1.5
V
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
Receiver Output Short-Circuit
Current
-7V ≤ VCM - VISOCOM ≤ +12V, AR = BR =
ISOCOM
1.5
-7V ≤ VCM - VISOCOM ≤ +12V, AR open,
BR open
12
IOSR
0V ≤ VRO ≤ VCC
±7
ICC
No load, RE = DE = DI = GND or VCC
DE = GND, RE = VCC, VISOCOM = GND
RIN
kΩ
±100
mA
25
85
mA
25
60
SUPPLY CURRENT
Supply Current
Supply Current in Shutdown
Mode
ISHDN
Maximum Ground Differential
∆VGND
DE = GND, RE = VCC, VISOCOM = ±60V
DE = GND, RE = VCC,
| ISOCOM leakage | ≤ 650µA
±650
±60
µA
V
_______________________________________________________________________________________
3
MAX3158
ELECTRICAL CHARACTERISTICS (continued)
MAX3158
High CMRR RS-485 Transceiver
with ±60V Isolation
SWITCHING CHARACTERISTICS
(VCC = +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
tDPLH
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
400
1400
2000
tDPHL
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
400
Driver Output Skew
| tDPLH - tDPHL |
tDSKEW
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Driver Rise or Fall Time
tDR, tDF
Figures 3 and 5, RDIFF = 54Ω,
CL1 = CL2 =100pF
Driver Input to Output
UNITS
ns
200
1400
1200
2000
250
ns
2200
ns
Maximum Data Rate
fMAX
Driver Enable to Output High
tDZH
Figures 4 and 6, CL = 100pF, S2 closed
250
3500
kbps
ns
Driver Enable to Output Low
tDZL
Figures 4 and 6, CL = 100pF, S1 closed
3500
ns
Driver Disable Time from Low
tDLZ
Figures 4 and 6, CL = 15pF, S1 closed
300
ns
Driver Disable Time from High
tDHZ
Figures 4 and 6, CL = 15pF, S2 closed
300
ns
600
ns
Receiver Input to Output
tRPLH,
tRPHL
Figures 7 and 9; | VID | ≥ 2.0V
440
Differential Receiver Skew
| tRPLH - tRPHL |
tRSKEW
Figures 7 and 9; | VID | ≥ 2.0V
20
ns
Receiver Enable to Output Low
tRZL
Figures 2 and 8, CL = 100pF, S1 closed
20
50
Receiver Enable to Output High
tRZH
Figures 2 and 8, CL = 100pF, S2 closed
20
50
ns
Receiver Disable Time from Low
tRLZ
Figures 2 and 8, CL = 100pF, S1 closed
200
500
ns
tRHZ
Figures 2 and 8, CL = 100pF, S2 closed
200
500
ns
200
700
ns
Receiver Disable Time from High
Time to Shutdown
tSHDN
(Note 4)
50
ns
Driver Enable from Shutdown to
Output High
tDZH
(SHDN)
Figures 4 and 6, CL = 15pF, S2 closed
0.2
1
ms
Driver Enable from Shutdown to
Output Low
tDZL
(SHDN)
Figures 4 and 6, CL = 15pF, S1 closed
0.2
1
ms
Receiver Enable from Shutdown
to Output High
tRZH
(SHDN)
Figures 2 and 8, CL = 100pF, S2 closed
0.2
1
ms
Receiver Enable from Shutdown
to Output Low
tRZL
(SHDN)
Figures 2 and 8, CL = 100pF, S1 closed
0.2
1
ms
Charge-Pump Oscillating
Frequency
fOSC
1.3
MHz
Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referred 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: Current level applies to peak current just prior to foldback-current limiting.
Note 4: The device is put into shutdown 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 700ns, the device is guaranteed to have entered shutdown.
4
_______________________________________________________________________________________
High CMRR RS-485 Transceiver
with ±60V Isolation
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
100
80
60
40
VISOCOM = -50V
100
0
VISOCOM = 0V
-100
VISOCOM = +50V
NO LOAD
30
25
20
15
5
-300
0
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
TEMPERATURE (°C)
RECEIVER OUTPUT CURRENT
vs. RECEIVER OUTPUT HIGH VOLTAGE
14
12
10
8
6
IRO = 8mA
0.40
5
6
IRO = -8mA
4.35
4.30
0.35
0.30
0.25
0.20
0.15
4.25
4.20
4.15
4.10
4
0.10
4.05
2
0.05
4.00
0
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
4
4.40
OUTPUT VOLTAGE (V)
OUTPUT LOW VOLTAGE (V)
16
3
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
0.50
0.45
2
OUTPUT LOW VOLTAGE (V)
MAX3158 toc05
18
1
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX3158 toc04
20
0
MAX3158 toc06
0
3.95
-40
-20
0
20
40
60
80
-40
100
-20
0
20
40
60
80
100
OUTPUT HIGH VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
DRIVER OUTPUT CURRENT
vs. DRIVER OUTPUT LOW VOLTAGE
DRIVER OUTPUT CURRENT
vs. DRIVER OUTPUT HIGH VOLTAGE
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
OUTPUT CURRENT (mA)
120
-10
100
80
60
40
100
-20
-30
-40
-50
OUTPUT CURRENT (mA)
140
-60
-70
-80
-90
MAX3158 toc09
0
MAX3158 toc07
160
MAX3158 toc08
OUTPUT CURRENT (mA)
35
10
-200
20
OUTPUT CURRENT (mA)
40
OUTPUT CURRENT (mA)
SUPPY CURRENT (µA)
RL = 54Ω
120
200
45
MAX3158 toc02
140
SUPPY CURRENT (mA)
300
MAX3158 toc01
160
RECEIVER OUTPUT CURRENT
vs. RECEIVER OUTPUT LOW VOLTAGE
MAX3158 toc03
SUPPLY CURRENT vs. TEMPERATURE
10
1
0.1
-100
20
-110
-120
0
0
2
4
6
8
10
OUTPUT VOLTAGE (V)
12
14
0.01
-8
-6
-4
-2
0
2
OUTPUT HIGH VOLTAGE (V)
4
6
0
1
2
3
4
5
6
DIFFERENTIAL OUTPUT VOLTAGE (V)
_______________________________________________________________________________________
5
MAX3158
Typical Operating Characteristics
(VCC = +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, TA = +25°C, unless otherwise noted.)
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
1.92
1.90
1.88
1.86
470
460
450
440
1.84
430
1.82
420
1.80
410
RL = 54Ω
1.50
PROPAGATION DELAY (µs)
480
PROPAGATION DELAY (ns)
1.48
1.46
1.44
1.42
1.40
1.38
1.36
-40
-20
0
20
40
60
80
1.34
1.32
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
DRIVER ENABLE TIME
vs. TEMPERATURE
DRIVER DISABLE TIME
vs. TEMPERATURE
RECEIVER PROPAGATION DELAY
DRIVER DISABLE TIME (ns)
1.475
1.450
1.425
1.400
1.375
1.350
MAX3158 toc15
250
MAX3158 toc13
1.500
MAX3158 toc14
OUTPUT VOLTAGE (V)
1.94
1.52
MAX3158 toc11
RL = 54Ω
1.96
490
MAX3158 toc10
1.98
DRIVER PROPAGATION DELAY
vs. TEMPERATURE
MAX3158 toc12
DRIVER DIFFERENTIAL OUTPUT
VOLTAGE vs. TEMPERATURE
DRIVER ENABLE TIME (µs)
MAX3158
High CMRR RS-485 Transceiver
with ±60V Isolation
200
VA - VB
0V
5V/div
150
0V
RO
100
50
1.325
1.300
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
-40
-20
0
20
40
60
80
100
2µs/div
TEMPERATURE (°C)
POWER-UP DELAY
(VISOCOM = 0V)
DRIVER PROPAGATION DELAY
MAX3158 toc17
MAX3158 toc16
MAX3158 toc18
DE
10V/div
DI
0V
POWER-UP DELAY
(VISOCOM = -50V)
DE
5V/div
0V
2V/div
0V
VY
5V/div
VY - VZ
-50V
VY
10V/div
RDIFF = 54Ω
CL1 = CL2 = 100pF
2µs/div
6
40µs/div
100µs/div
_______________________________________________________________________________________
High CMRR RS-485 Transceiver
with ±60V Isolation
POWER-UP DELAY
(VISOCOM = +50V)
MAX3158 toc19
DE
5V/div
0V
+50V
VY
10V/div
COMMON-MODE VOLTAGE TO GROUND (V)
70
MAX3158 toc20
MAXIMUM COMMON-MODE VOLTAGE TO
GROUND vs. COMMON-MODE FREQUENCY
MAXIMUM COMMON-MODE
VOLTAGE TO ISOCOM
60
50
COMMON-MODE VOLTAGE TO
ISOCOM = 7V PEAK
40
30
20
10
0
100µs/div
0.1
1
10
COMMON-MODE FREQUENCY (kHz)
Test Circuits and Timing Diagrams
Y
3V
DE
CL1
R
Y
DI
VOD
RDIFF
VID
Z
R
VOC
CL2
Z
Figure 3. Driver Timing Test Circuit
Figure 1. Driver DC Test Load
RECEIVER
OUTPUT
1kΩ
TEST POINT
CL
100pF
VCC
S1
500Ω
S1
VCC
OUTPUT
UNDER TEST
1kΩ
CL
S2
Figure 2. Receiver Enable/Disable Timing Test Load
S2
Figure 4. Driver Enable/Disable Timing Test Load
_______________________________________________________________________________________
7
MAX3158
Typical Operating Characteristics (continued)
(VCC = +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, TA = +25°C, unless otherwise noted.)
High CMRR RS-485 Transceiver
with ±60V Isolation
MAX3158
Test Circuits and Timing Diagrams (continued)
3V
DI
1.5V
3V
1.5V
0V
tDPHL
tDPLH
RE
1.5V
tRZL(SHDN), tRZL
Z
VO
Y
1/2 VO
VO
VDIFF
0V
-VO
1.5V
0V
1/2 VO
10%
1.5V OUTPUT NORMALLY LOW
RO
1.5V
VDIFF = V (Y) - V (Z)
tDR
VOL + 0.5V
OUTPUT NORMALLY HIGH
90%
90%
tRLZ
VCC
RO
10%
VOH - 0.5V
0V
tDF
tDSKEW = | tDPLH - tDPHL |
tRZH(SHDN), tRZH
Figure 5. Driver Propagation Delays
tRHZ
Figure 8. Receiver Enable and Disable Times
3V
DE
1.5V
1.5V
0V
tDLZ
tDZL(SHDN), tDZL
Y, Z
B
2.3V OUTPUT NORMALLY LOW
VOL
VOL + 0.5V
VID
RR
A
OUTPUT NORMALLY HIGH
Y, Z
ATE
VOH - 0.5V
2.3V
0V
tDZH(SHDN), tDZH
tDHZ
Figure 6. Driver Enable and Disable Times
RO
Figure 9. Receiver Propagation Delay Test Circuit
VOH
VOL
1V
A
-1V
B
1.5V
OUTPUT
tRPHL
1.5V
tRPLH
INPUT
tRSKEW = | tRPLH - tRPHL |
Figure 7. Receiver Propagation Delays
8
_______________________________________________________________________________________
RECEIVER
OUTPUT
High CMRR RS-485 Transceiver
with ±60V Isolation
PIN
SSOP
PDIP
1
2
NAME
RO
FUNCTION
Receiver Output. When RE is low and A - B > -50mV, RO will be high; if A - B ≤ -200mV,
RO will be low.
2
3
RE
Receiver Output Enable. Drive RE low to enable RO.
3
4
DE
Driver Output Enable. Drive DE high to enable driver outputs.
4
5
DI
Driver Input. With DE high, a low on DI forces the noninverting output low and the inverting
output high; with DI high, outputs reverse.
5
6
C1LO
6, 7,
12, 22,
23
1, 12,
14, 15,
28
N.C.
8
7
C1HI
Connect to the negative terminal of C1 (0.047µF, 100V).
No Connection. Not internally connected.
Connect to the positive terminal of C1 (0.047µF, 100V).
9
8
ISOVCC
Internally generated power-supply voltage, referenced to the cable ground (ISOCOM).
Connect a 1µF capacitor to ISOCOM.
10
9
H/F
Half/Full-Duplex Selector Pin. Leave open, or connect to ISOCOM to select Full Duplex,
or connect to ISOVCC to select Half Duplex.
11
10
ZR
Connect to ISOCOM for a 1.5kΩ input impedance on Z. Leave open for a 12kΩ input
impedance on Z.
13
11
YR
Connect to ISOCOM for a 1.5kΩ input impedance on Y. Leave open for a 12kΩ input
impedance on Y.
14
13
ISOCOM
15
16
Z
16
17
Y
Noninverting Driver Output (and Noninverting Receiver Input in Half-Duplex Mode)
17
18
B
Inverting Receiver Input in Full-Duplex Mode
18
19
A
Noninverting Receiver Input in Full-Duplex Mode
19
20
BR
Connect to ISOCOM for a 1.5kΩ input impedance on B. Leave open for a 12kΩ input
impedance on B.
20
21
AR
Connect to ISOCOM for a 1.5kΩ input impedance on A. Leave open for a 12kΩ input
impedance on A.
21
22
C2HI
24
23
C2LO
Connect to the negative terminal of C2 (0.047µF, 100V).
25
24
GND
Ground
26
25
TXP
Transmitter Phase. Leave open, or connect to GND for normal transmitter polarity, or connect
to VCC to invert the transmitter polarity.
27
26
RXP
Receiver Phase. Leave open, or connect to GND for normal receiver polarity, or connect to
VCC to invert the receiver polarity.
28
27
VCC
+4.75V to +5.25V Positive Supply. Connect a 0.1µF capacitor to GND.
Cable Ground
Inverting Driver Output (and Inverting Receiver Input in Half-Duplex Mode)
Connect to the positive terminal of C2 (0.047µF, 100V).
_______________________________________________________________________________________
9
MAX3158
Pin Description
MAX3158
High CMRR RS-485 Transceiver
with ±60V Isolation
Detailed Description
The MAX3158 is a high CMRR RS-485/RS-422 datacommunications interface providing ±60V isolation in a
hybrid microcircuit. A single +5V supply on the logic
side powers both sides of the interface, with external
100V capacitors transferring power from the logic side
to the isolated side (see Block Diagram). The MAX3158
typically draws 25mA of supply current when unloaded
or when fully loaded with the driver disabled. Supply
current drops to 25µA when the device is placed in
shutdown mode (see Low-Power Shutdown Mode section). The MAX3158 transceiver for RS-485/RS-422
communication contains one driver and one receiver.
This device features 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 Fail-Safe section). The MAX3158 is selectable between half- and full-duplex communication by
connecting a selector pin to ISOVCC or ISOCOM,
respectively. 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 device also features
independently programmable receiver and transmitter
output phase through separate pins. The MAX3158 is a
low-cost replacement for opto-isolated transceivers.
connect it to VCC. To invert the receiver phase, drive
RXP high or connect it to VCC. Note that the receiver
threshold is positive when RXP is high.
The MAX3158 can operate in full- or half-duplex mode.
Connect H/F to ISOCOM for full-duplex mode, and connect it to ISOVCC for half-duplex operation. In halfduplex mode, the receiver inputs are switched to the
driver outputs, connecting outputs Y and Z to inputs A
and B, respectively. In half-duplex mode, the internal
full-duplex receiver input resistors are still connected to
pins A and B.
Low-Power Shutdown Mode
The low-power shutdown mode is initiated by bringing
both RE high and DE low. In shutdown, this device typically draws only 25µA of supply current, and no power
is transferred across the isolation capacitors in this
mode. 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 700ns, the parts are guaranteed
to enter shutdown. Enable times t_ZH and t_ZL in the
Switching Characteristics table assume the part was
not in a low-power shutdown state. Enable times
t_ZH(SHDN) and t_ZL(SHDN) assume the parts were shut
down. It takes drivers and receivers longer to become
enabled from low-power shutdown mode t_ZH(SHDN),
t_ ZL(SHDN) than from driver/receiver-disable mode
(t_ZH, t_ZL).
Fail-Safe
Driver Output Protection
The MAX3158 guarantees 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. The receiver threshold is fixed
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 MAX3158, this results in a logic high
with a 50mV minimum noise margin. Unlike competitor’s
fail-safe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA-485 standard.
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
Typical Operating Characteristics). The second, a thermal shutdown circuit, forces the driver outputs into a
high-impedance state if the die temperature becomes
excessive—typically around +150°C.
MAX3158 Programming
The MAX3158 has several programmable operating
modes. Occasionally, twisted-pair lines are reversed.
The MAX3158 has two pins that invert the phase of the
driver and the receiver to correct for this problem. For
normal operation, drive TXP and RXP low, connect
them to ground, or leave them unconnected (internal
pulldown). To invert the driver phase, drive TXP high or
10
Applications Information
Capacitor and Grounding Resistor
Selection
The value for the charge-pump capacitors C1 and C2
should be between 47nF and 100nF. Smaller values will
result in insufficient supply voltage on the isolated side.
Larger values are allowed but will not result in better
charge-pump capacity. The values for C1 and C2, as
well as that of C4, determine the maximum frequency
and amplitude of the voltage difference (under operating conditions) between the local and isolated ground.
Besides the capacitor values, this maximum frequency
______________________________________________________________________________________
High CMRR RS-485 Transceiver
with ±60V Isolation
Y
DI
Z
TXP
YR
DE
ZR
RO
A
B
RE
RXP
AR
BR
MAX3158
H/F
VCC
ISOVCC
POWER
OSC
GND
C1L
C2L
and amplitude are also determined by the resistance
between the remote ground and the ISOCOM pin. The
receiver input resistors will cause the isolated common
voltage to go to the mean voltage of the receiver inputs,
which will be a direct function of the remote ground
potential. The receiver input resistance and the capacitors C1, C2, and C4 set up a time constant that limits
how fast the ISOCOM pin can follow variations in the
remote ground voltage. Connecting YR and ZR in halfduplex operation, or AR and BR in full-duplex operation,
to ISOCOM results in a relatively low input impedance of
the MAX3158 receiver inputs (2kΩ). This allows for a
60Hz sine wave with a 60V maximum amplitude (see
Typical Operating Characteristics). If YR, ZR, AR, and
BR are left open, the receiver input impedance is 12kΩ
allowing up to 32 transceivers on the bus. To guarantee
the same low time constant under those conditions, use
a shielded cable with a 1kΩ resistor connected between
C1H C2H
ISOCOM
the shield and ISOCOM. Using a lower value for this
resistor is not recommended because this could trigger
a holding current in the internal ESD protection device if
the ±75V isolation limit is exceeded.
A single point hard-ground connection for the shield is
recommended.
Communication Between
Two MAX3158s
If two MAX3158 devices are used to communicate with
each other, one of the devices must have ISOCOM
connected to local ground. Failure to do so will result in
floating ISOCOM pins, with both devices trying to adapt
to the isolated ground of the other.
Chip Information
TRANSISTOR COUNT: 1309
______________________________________________________________________________________
11
MAX3158
Block Diagram
High CMRR RS-485 Transceiver
with ±60V Isolation
MAX3158
Pin Configurations
TOP VIEW
RO 1
28 VCC
N.C. 1
28 N.C.
RE 2
27 RXP
RO 2
27 VCC
DE 3
26 TXP
RE 3
26 RXP
DI 4
25 GND
DE 4
25 TXP
24 C2LO
DI 5
C1LO 5
N.C. 6
MAX3158
23 N.C.
C1LO 6
N.C. 7
22 N.C.
C1HI 7
C1HI 8
21 C2HI
23 C2LO
22 C2HI
ISOVCC 8
21 AR
ISOVCC 9
20 AR
H/F 9
20 BR
H/F 10
19 BR
ZR 10
19 A
ZR 11
18 A
YR 11
18 B
N.C. 12
17 B
N.C. 12
17 Y
YR 13
16 Y
ISOCOM 13
16 Z
ISOCOM 14
15 Z
N.C. 14
28 SSOP
12
24 GND
MAX3158
MAX3157
15 N.C.
28 PDIP
______________________________________________________________________________________
High CMRR RS-485 Transceiver
with ±60V Isolation
SSOP.EPS
2
1
INCHES
E
H
MILLIMETERS
DIM
MIN
MAX
MIN
MAX
A
0.068
0.078
1.73
1.99
A1
0.002
0.008
0.05
0.21
B
0.010
0.015
0.25
0.38
C
D
0.09
0.20
0.004 0.008
SEE VARIATIONS
E
0.205
e
0.212
0.0256 BSC
5.20
MILLIMETERS
INCHES
D
D
D
D
D
5.38
MIN
MAX
MIN
MAX
0.239
0.239
0.278
0.249
0.249
0.289
6.07
6.07
7.07
6.33
6.33
7.33
0.317
0.397
0.328
0.407
8.07
10.07
8.33
10.33
N
14L
16L
20L
24L
28L
0.65 BSC
H
0.301
0.311
7.65
7.90
L
0.025
0∞
0.037
8∞
0.63
0∞
0.95
8∞
N
A
C
B
e
A1
L
D
NOTES:
1. D&E DO NOT INCLUDE MOLD FLASH.
2. MOLD FLASH OR PROTRUSIONS NOT TO EXCEED .15 MM (.006").
3. CONTROLLING DIMENSION: MILLIMETERS.
4. MEETS JEDEC MO150.
5. LEADS TO BE COPLANAR WITHIN 0.10 MM.
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, SSOP, 5.3 MM
APPROVAL
DOCUMENT CONTROL NO.
21-0056
REV.
1
C
______________________________________________________________________________________
1
13
MAX3158
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
PDIPN.EPS
MAX3158
High CMRR RS-485 Transceiver
with ±60V Isolation
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.
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© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.