MAX3480EBCPI [MAXIM]
+-15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces; + -15kV ESD保护，隔离， 3.3V的RS - 485 / RS - 422数据接口
| 型号： | MAX3480EBCPI |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | +-15kV ESD-Protected, Isolated, 3.3V RS-485/RS-422 Data Interfaces |
| 文件： | 总16页 (文件大小：277K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1941; Rev 0; 4/01
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
General Description
____________________________Features
The MAX3480EA/MAX3480EB are electrically isolated
RS-485/RS-422 data-communications interfaces. The
RS-485/RS-422 I/O pins are protected against ±±5ꢀk
electrostatic discharge (ESD) shocꢀs, without latchup.
Transceivers, optocouplers, and a transformer are all
included in one low-cost, 28-pin DIP pacꢀage. A single
+3.3k supply on the logic side powers both sides of the
interface.
ꢀ Isolated Data Interface Guaranteed to 1260V
RMS
(1min)
ꢀ
15kV ESD Protection for I/O Pins
ꢀ Slew-Rate-Limited Data Transmission (160kbps for
MAX3480EB)
ꢀ High-Speed, Isolated, 2.5Mbps RS-485 Interface
(MAX3480EA)
The MAX3480EB features reduced-slew-rate drivers
that minimize EMI and reduce reflections caused by
improperly terminated cables, allowing error-free data
transmission at data rates up to ±60ꢀbps. The
MAX3480EA’s driver slew rate is not limited, allowing
transmission rates up to 2.5Mbps.
ꢀ Single +3.3V Supply
ꢀ Current Limiting and Thermal Shutdown for
Driver Overload Protection
ꢀ Standard 28-Pin DIP Package
Drivers are short-circuit current limited and are protect-
ed 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.
ꢀ Allows Up to 128 Transceivers on the Bus
The MAX3480EA/MAX3480EB are guaranteed to with-
stand ±260k
(±min) or ±520k
(±s). Their isolated
RMS
RMS
-in Configuration
inputs and outputs meet RS-485/RS-422 specifications.
TOP VIEW
________________________Applications
Isolated RS-485/RS-422 Data Interface
Transceivers for EMI-Sensitive Applications
Industrial-Control Local Area Networꢀs
Automatic Test Equipment
MAX3480EA
MAX3480EB
V
V
AC1
AC2
ISO V
B
CC1
1
2
28
27
26
25
24
23
22
21
CC2
D1
3
CC1
HkAC/Building Control Networꢀs
Telecom
D2
4
ISO RO DRV
GND1
5
MAX845
MAX485E
MAX487E
6
FS
A
Ordering Information
SD
ISO DI IN
7
DATA
RATE
(kbps)
V
V
8
ISO DE IN
ISO COM1
CC3
DI
PIN-
PACKAGE*
TEMP.
RANGE
PART
9
20
19
18
17
10
ISO DI DRV
CC4
MAX3480EACPI
0°C to +70°C 28 Plastic DIP
2500
2500
250
ISO V
CC2
DE 11
MAX3480EAEPI -40°C to +85°C 28 Plastic DIP
MAX3480EBCPI 0°C to +70°C 28 Plastic DIP
ISO DE DRV
GND2
RO
12
13
14
MAX3480EBEPI -40°C to +85°C 28 Plastic DIP
250
16 ISO COM2
ISO RO LED
V
CC5
15
*See Reliability section at end of data sheet.
ISOLATION BARRIER
DIP
________________________________________________________________ Maxim Integrated Products
1
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.
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
ABSOLUTE MAXIMUM RATINGS
With Respect to GND
LED Forward Current (DI, DE, ISO RO LED) ......................50mA
Supply Voltage (V
Supply Voltage (V
Control Input Voltage (SD, FS) ............-0.3V to (V
Receiver Output Voltage (RO).............-0.3V to (V
With Respect to ISO COM
V
V
V
) .......-0.3V to +3.8V
CC
5
Continuous Power Dissipation (T = +70°C)
28-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ..727mW
Operating Temperature Ranges
MAX3480E_CPI..................................................0°C to +70°C
MAX3480E_EPI...............................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
CC
CC3
CC
CC
A
1,
2,
4,
) ........................................-0.3V to +7V
+ 0.3V)
+ 0.3V)
CC3
CC5
Control Input Voltage (ISO DE _)......-0.3V to (ISO V
Driver Input Voltage (ISO DI _) .....-0.3V to (ISO V
Receiver Output Voltage (ISO RO _) ..-0.3V to (ISO V
+ 0.3V)
+ 0.3V)
+ 0.3V)
CC_
CC_
CC_
Driver Output Voltage (A, B)..............................-8V to +12.5V
Receiver Input Voltage (A, B)............................-8V to +12.5V
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
= V
= V
= V
= V
= +3.0V to +3.6V, FS = 0, T = T
to T
, unless otherwise noted. Typical values are at V
=
CC
CC1
CC2
CC4
CC5
A
MIN
MAX
CC
+3.3V and T = +25°C.) (Notes 1, 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
60
MAX
UNITS
f
FS = 0
FS = V
SWL
Switch Frequency
kHz
f
or open
CC
900
130
220
80
SWH
R = ∞
250
200
MAX3480EA,
DE´ = V or open
L
CC
R = 54Ω
L
Operating Supply Current
I
mA
CC
R = ∞
L
MAX3480EB,
DE´ = V
or open
CC
R = 54Ω
L
180
0.2
Shutdown Supply Current (Note 3)
FS Input Threshold
I
SD = V
High
µA
V
SHDN
CC3
V
2.4
FSH
V
Low
0.8
50
FSL
FSL
FS Input Pullup Current
FS Input Leakage Current
Input High Voltage
Input Low Voltage
I
FS low
µA
pA
V
I
FS high
10
FSM
V
DE´, DI´, Figure 1
DE´, DI´, Figure 1
V
- 0.4
CC
IH
V
0.4
0.8
V
IL
Isolation Voltage
V
ISO
SDH
T
= +25°C, 1min (Note 4)
1260
2.4
V
A
RMS
V
High
Low
1
1
Shutdown Input Threshold
V
V
SDL
Isolation Resistance
Isolation Capacitance
R
T
= +25°C, V =
ISO
50VDC
100
10,000
10
MΩ
ISO
ISO
A
C
ƒ = 1MHz
pF
A, B, Y, and Z pins, tested at Human Body
Model
ESD Protection
ESD
15
kV
V
Differential Driver Output
(No Load)
V
8
OD1
OD2
R = 50Ω (RS-422)
R = 27Ω (RS-485), Figure 3
2
Differential Driver Output
V
V
1.5
5
Change in Magnitude of Driver
Output Voltage for
Complementary Output States
Differential
0.3
R = 27Ω or 50Ω,
Figure 3
∆V
V
OD
Common mode
0.3
2
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= V
= V
= V
= +3.0V to +3.6V, FS = 0, T = T
to T
, unless otherwise noted. Typical values are at V
=
CC
CC1
CC2
CC4
CC5
A
MIN
MAX
CC
+3.3V and T = +25°C.) (Notes 1, 2)
A
PARAMETER
SYMBOL
CONDITIONS
R = 27Ω or 50Ω, Figure 4
MIN
TYP
MAX
4
UNITS
Driver Common-Mode Output
V
V
OC
V
V
V
V
= +12V
= -7V
0.25
-0.2
0.25
-0.2
IN
IN
IN
IN
MAX3480EA
MAX3480EB
DE´ = 0,
= 0 or
+3.6V
Input Current (A, B)
ISO I
V
mA
IN
CC
= +12V
= -7V
MAX3480EA
MAX3480EB
48
48
-7V ≤ V
12V
≤
CM
Receiver Input Resistance
R
kΩ
IN
Receiver Differential Threshold
Receiver Input Hysteresis
V
-7V ≤ V
≤ 12V
-0.2
0.2
V
TH
CM
∆V
V
= 0
CM
70
mV
V
TH
Receiver Output Low Voltage
Receiver Output High Current
Driver Short-Circuit Current
V
DI´ = V
0.4
OL
CC
I
V
= +3.6V, DI´ = 0
OUT
250
µA
mA
OH
ISO I
-7V ≤ V ≤ 12V (Note 5)
100
OSD
O
SWITCHING CHARACTERISTICS—MAX3480EA
(V
= V
= V
= V
= V
= +3.0V to +3.6V, FS = 0, T = T
to T
, unless otherwise noted. Typical values are at
MAX
CC
CC1
CC2
CC4
CC5
A
MIN
V
CC
= +3.3V and T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
t
t
PLH
PHL
100
100
275
275
Driver Input to Output
Propagation Delay
Figures 4, 6; R
= 54Ω,
DIFF
ns
C
L1
= C = 100pF
L2
Figures 4, 6; R
= 54Ω,
DIFF
t
Driver Output Skew
SKEW
25
15
100
50
ns
ns
C
L1
= C = 100pF (Note 5)
L2
Figures 4, 6; R
= 54Ω,
DIFF
t , t
R F
Driver Rise or Fall Time
C
L1
= C = 100pF
L2
t
t
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from High
Driver Disable Time from Low
ZH
Figures 5, 7; C = 100pF, S2 closed
0.5
0.5
0.6
0.6
100
120
1.8
1.8
1.8
1.8
225
225
µs
µs
µs
µs
L
t
ZL
Figures 5, 7; C = 100pF, S1 closed
L
HZ
Figures 5, 7; C = 15pF, S2 closed
L
t
LZ
Figures 5, 7; C = 15pF, S1 closed
L
t
PLH
PHL
Receiver Input to Output
Propagation Delay
Figures 4, 8; R
= 54Ω,
DIFF
ns
C
L1
= C = 100pF
t
L2
t
t
PLH - PHL Differential
Figures 4, 8; R
DIFF
= 54Ω,
t
SKD
MAX
20
100
ns
C
L1
= C = 100pF
Receiver Skew
L2
f
t
t
Maximum Data Rate
SKEW, SKD ≤ 25% of data period
2.5
Mbps
_______________________________________________________________________________________
3
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
SWITCHING CHARACTERISTICS—MAX3480EB
(V
= V
= V
= V
= V
= +3.0V to +3.6V, FS = 0, T = T
to T
, unless otherwise noted. Typical values are at
MAX
CC
CC1
CC2
CC4
CC5
A
MIN
V
CC
= +3.3V and T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
t
t
1.5
1.2
3.0
3.0
PLH
Driver Input to Output
Propagation Delay
Figures 4, 6; R
= 54Ω,
= 54Ω,
= 54Ω,
DIFF
µs
C
L1
= C = 100pF
L2
PHL
Figures 4, 6; R
DIFF
Driver Output Skew
t
300
1.0
1200
2.0
ns
µs
SKEW
C
L1
= C = 100pF
L2
Figures 4, 6; R
DIFF
Driver Rise or Fall Time
t , t
R
F
C
L1
= C = 100pF
L2
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
t
Figures 5, 7; C = 100pF, S2 closed
1.2
1.0
1.5
2.0
0.6
1.4
4.5
4.5
4.5
4.5
3.0
3.0
µs
µs
µs
µs
L
ZH
t
Figures 5, 7; C = 100pF, S1 closed
L
ZL
t
Figures 5, 7; C = 15pF, S1 closed
L
LZ
t
Figures 5, 7; C = 15pF, S2 closed
L
HZ
t
PLH
PHL
Receiver Input to Output
Propagation Delay
Figures 4, 8; R
= 54Ω,
DIFF
µs
C
L1
= C = 100pF
L2
t
t
t
PLH - PHL Differential
Figures 4, 8; R
DIFF
= 54Ω,
t
f
750
1500
ns
SKD
C
L1
= C = 100pF
Receiver Skew
L2
Maximum Data Rate
t
, t
≤ 25% of data period
160
kbps
SKEW SKD
MAX
Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to
logic-side ground (GND1, GND2), unless otherwise specified.
Note 2: For DE and DI pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for
´
´
MAX3480EA/MAX3480EB).
Note 3: Shutdown supply current is the current at V
when shutdown is enabled.
CC1
Note 4: Limit guaranteed by applying 1520V
for 1s. Test voltage is applied between all pins on one side of the package to all
RMS
pins on the other side of the package. For example, between pins 1 and 14, and 15 and 28.
Note 5: Applies to peak current. See Typical Operating Characteristics and Applications Information.
4
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
__________________________________________Typical Operating Characteristics
(V
= +3.3V, T = +25°C, Figure 1, unless otherwise noted.)
CC_
A
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
OUTPUT CURRENT
vs. DRIVER OUTPUT HIGH VOLTAGE
OUTPUT CURRENT
vs. DRIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
3.0
2.9
-100
-90
180
160
140
120
100
80
DI´ = HIGH OR OPEN
R = 54Ω
L
2.8
2.7
2.6
-80
-70
-60
2.5
2.4
2.3
2.2
-50
-40
-30
-20
60
40
20
0
2.1
2.0
-10
0
-40
-20
0
20
40
60
80
-6
-4
-2
0
2
4
6
0
2
4
6
8
10
12
TEMPERATURE (°C)
OUTPUT HIGH VOLTAGE (V)
OUTPUT LOW VOLTAGE (V)
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
0.8
0.7
0.6
0.5
0.4
0.3
0.2
5.00
4.75
4.50
4.25
4.00
3.75
3.50
MEASURED AT ISO RO DRV
MEASURED AT ISO RO DRV
I
RO
= 8mA
I
RO
= 8mA
0.1
0
3.25
3.00
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT CURRENT
OUTPUT CURRENT
vs. RECEIVER OUTPUT LOW VOLTAGE
vs. RECEIVER OUTPUT HIGH VOLTAGE
80
70
60
50
40
30
20
80
MEASURED AT ISO RO DRV
MEASURED AT ISO RO DRV
70
60
50
40
30
20
10
0
10
0
0
1.0
2.0
3.0
4.0
5.0
0
1.0
2.0
3.0
4.0
5.0
OUTPUT LOW VOLTAGE (V)
DIFFERENTIAL OUTPUT VOLTAGE (V)
_______________________________________________________________________________________
5
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
Typical Operating Characteristics (continued)
(V
= +3.3V, T = +25°C, Figure 1, unless otherwise noted.)
A
CC_
MAX3480EA DRIVER INPUT (AB)
AND RECEIVER OUTPUT (RO)
MAX3480EA DRIVER ENABLE (AB)
AND RECEIVER OUTPUT (RO)
MAX3480EA
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX3480EA/EB toc08
MAX3480EA/EB toc09
350
300
250
200
150
100
50
DI´ INPUT,
DE´ INPUT,
DE´ HIGH, 50Ω LOAD
2V/div
1V/div
DE
´ HIGH, 100Ω LOAD
A
A, 1V/div
B, 2V/div
2V/div
DE´
LOW, DI
´
LOW, R = ∞
L
B
RO,
74HC240,
2V/div
DE´ LOW, DI´ HIGH, R = ∞
L
0
100ns/div
3.0
3.2
3.4
3.6
3.8
100ns/div
CIRCUIT OF FIGURE 2, TERMINATION: 100Ω
SUPPLY VOLTAGE (V)
CIRCUIT OF FIGURE 2, TERMINATION: 100Ω
MAX3480EB DRIVER ENABLE (DE´)
MAX3480EB DRIVER INPUT (AB)
MAX3480EB
SUPPLY CURRENT vs. SUPPLY VOLTAGE
AND DRIVER OUTPUT (AB)
AND RECEIVER OUTPUT (RO)
MAX3480EA/EB toc12
MAX3480EA/EB toc11
300
250
DI´ INPUT,
DE´
DE´ HIGH, 50Ω LOAD
2V/div
1V/div
DE´ HIGH,
A
200
150
100
50
100Ω LOAD
2V/div
B
A
2V/div
DE´ LOW, DI´ LOW, R = ∞
L
B
2V/div
DE´ LOW, DI´ HIGH, R = ∞
L
RO,
74HC240,
2V/div
0
20µs/div
3.0
3.2
3.4
3.6
3.8
1µs/div
SUPPLY VOLTAGE (V)
DRIVER ENABLE TIME
vs. TEMPERATURE
DRIVER ENABLE TIME
vs. TEMPERATURE
2.5
2.0
1.5
1.0
0.5
0
2.0
1.5
MAX3480EB
MAX3480EB
R = 54Ω, DI´ = 0
L
R = 54Ω, DI´ = 0V MEASURED FROM
L
MEASURED FROM DE´
DE´ TO VALID OUTPUT
TO VALID OUTPUT
1.0
0.5
MAX3480EA
MAX3480EA
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
6
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
______________________________________________________________-in Description
PIN
NAME
FUNCTION
PINS ON THE NONISOLATED SIDE
1
2
V
V
Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 2, 10, and 14.
Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 10, and 14.
Boost-Voltage Generator Outputs. See Figures 1 and 2.
CC1
CC2
3, 4
D1, D2
GND1,
GND2
5, 12
6
Logic-Side Ground Inputs. Must be connected; not internally connected.
Frequency Switch Input. If V = V , switch frequency is high; if FS = 0, switch frequency is low
FS
CC
FS
(normal connection).
7
8
SD
Power-Supply Shutdown Input. Must be connected to logic ground.
V
Boosted V+ Voltage Input. Must be connected as shown in Figures 1 and 2.
CC3
DI
Driver Input. With DE´ high, a low on DI´ forces output A low and output B high. Similarly, a high on
DI´ forces output A high and output B low. Drives internal LED cathode through R1 (Table 1).
9
10
V
Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 2, and 14.
CC4
Driver-Enable Input. The driver outputs, A and B, are enabled by bringing DE´ high. The driver
outputs are high impedance when DE´ is low. If the driver outputs are enabled, the device functions
as a line driver. While the driver outputs are high impedance, the device functions as a line receiver.
Drives internal LED cathode through R2 (Table 1).
11
DE
Receiver Output. If A > B by 200mV, RO is low; if A < B by 200mV, RO is high. Open collector; must
13
14
RO
have pullup (R3) to V
(Table 1).
CC
V
Logic-Side (Nonisolated Side) +3.3V Supply Voltage Input. Connect to pins 1, 2, and 10.
CC5
_______________________________________________________________________________________
7
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
_________________________________________________-in Description (continued)
PIN
NAME
FUNCTION
PINS ON THE ISOLATED RS-485/RS-422 SIDE
ISO RO
LED
Isolated Receiver-Output LED Anode (Input). If A > B by 200mV, ISO RO LED is high; if A < B by
200mV, ISO RO LED is low.
15
16
ISO COM2
Isolated-Supply Common Input. Connect to ISO COM1.
Isolated Driver-Enable Drive Input. The driver outputs, A and B, are enabled by bringing DE´ high.
The driver outputs are high impedance when DE´ is low. If the driver outputs are enabled, the
device functions as a line driver. While the driver outputs are high impedance, the device functions
as a line receiver. Open collector output; must have pullup (R4 in Figure 1) to ISO VCC and be
connected to ISO DE IN for normal operation (Table 1).
ISO DE
DRV
17
18
19
ISO V
Isolated-Supply Positive Input Voltage. Connect to ISO V
.
CC1
CC2
Isolated Driver-Input Drive. With DE´ high, a low on DI´ forces output A low and output B high.
Similarly, a high on DI´ forces output A high and output B low. Open-collector output; must have
pullup (R5 in Figure 1) to ISO VCC and be connected to ISO DI IN for normal operation (Table 1).
ISO DI DRV
Isolated-Supply Common Output. Connect to ISO COM2. If RS-485 wires have a shield, connect
ISO COM1 to shield through 100Ω resistor.
20
ISO COM1
21
22
ISO DE IN
ISO DI IN
A
Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation.
Isolated Driver Input. Connect to ISO DI DRV for normal operation.
Noninverting Driver Output and Noninverting Receiver Input
23
24
ISO RO DRV Isolated Receiver-Output Drive. Connect to ISO RO LED through R6 (Table 1 and Figure 1).
25
B
Inverting Driver Output and Inverting Receiver Input
Isolated Supply Positive Output Voltage. Connect to ISO V
Internal Connections. Leave these pins unconnected.
26
ISO V
.
CC2
CC1
27, 28
AC2, AC1
Note: For DE and DI pin descriptions, see Detailed Block Diagram.
´
´
8
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
isolation barrier (Figure 1). Power is transferred from the
_______________Detailed Description
logic side (nonisolated side) to the isolated side of the
barrier through a center-tapped transformer. Signals
cross the barrier through high-speed optocouplers. A
single +3.3V supply on the logic side powers both
sides of the interface.
The MAX3480EA/MAX3480EB are electrically isolated,
RS-485/RS-422 data-communications interface solu-
tions. Transceivers, optocouplers, a power driver, and a
transformer are in one standard 28-pin DIP package.
Signals and power are internally transported across the
ISO V
CC1
V
CC3
D1
D2
MAX3480EA: MAX485E
MAX3480EB: MAX487E
MAX845
Q
B
N
ISO DI IN
D
OSC
1.1MHz/
1.6MHz
T
F/F
FS
A
ISO DE IN
Q
N
ISO RO DRV
R
RE
GND1
SD
ISO COM1
EXTERNAL RS-485/RS-422 WIRING
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
MAX3480EA/EB
V
IN
V
V
CC1
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
TWISTED PAIR
TO OTHER TRANSCEIVERS
+3.0V TO +3.6V
CC2
D1
D2
C1
22µF
D1, D2
1N914
C2
0.1µF
ISO V
CC1
R
R
L
L
3
B
B
4
BOOSTED V+
R7*
SHIELD (OPTIONAL)
ISO RO DRV
GND1
FS
C3
5
A
0.01µF
TWISTED PAIR
TO OTHER TRANSCEIVERS
MAX485E
MAX487E
MAX845
A
6
R6*
SD
ISO DI IN
SH
7
V
CC3
DI
ISO DE IN
ISO COM1
ISO DI DRV
8
R1*
R2*
SHIELD (OPTIONAL)
R4*
R5*
9
DI´
V
CC4
DE
10
11
12
13
14
NOTE: RESISTOR R8 PROTECTS THE
MAX3480E FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
A AND B.
LOGIC
I/O
ISO V
CC2
DE´
R8
100Ω
GND2
RO
ISO DE DRV
ISO COM2
ISO RO LED
RO
R3*
V
CC5
ISOLATION BARRIER
ISOLATION COMMON
C4
270pF
4kV
*SEE TABLE 1.
LOGIC GROUND
Figure 1. Detailed Block Diagram
Table 1. Pullup and LED Drive Resistors
PART
R1 (Ω)
R2 (Ω)
R3 (Ω)
R4 (Ω)
3600
R5 (Ω)
1000
R6 (Ω)
R7 (Ω)
Open
430
MAX3480EA
MAX3480EB
100
100
680
200
200
100
100
2000
3600
3600
_______________________________________________________________________________________
9
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
The MAX3480EB features reduced-slew-rate drivers
that minimize EMI and reduce reflections caused by
improperly terminated cables, allowing error-free trans-
mission at data rates up to 160kbps. The MAX3480EA’s
driver slew rates are not limited, allowing transmission
rates up to 2.5Mbps.
shutdown circuitry that puts 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 driver outputs are enabled by bringing DE´ high.
Driver-enable times are typically 500ns for the
MAX3480EA and 1µs for the MAX3480EB. Allow time
for the devices to be enabled before sending data.
When enabled, driver outputs function as line drivers.
Driver outputs are high impedance when DE´ is low.
While outputs are high impedance, they function as line
receivers.
The frequency-select FS is connected to GND_ in normal
operation, which selects a switching frequency of
approximately 600kHz. Connect to high for a higher
900kHz switching frequency.
Drivers are short-circuit current limited and are protect-
ed against excessive power dissipation by thermal
EXTERNAL RS-485/RS-422 WIRING
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
MAX3480EA/EB
V
IN
V
V
CC1
CC2
D1
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
TWISTED PAIR
TO OTHER TRANSCEIVERS
+3.0V TO +3.6V
C1
22µF
6V
D1, D2
1N914
C2
0.1µF
ISO V
CC1
R
R
L
3
B
B
D2
4
BOOSTED V+
SHIELD (OPTIONAL)
R7*
GND1
ISO RO DRV
C3
0.01µF
5
A
TWISTED PAIR
TO OTHER TRANSCEIVERS
MAX485E
MAX487E
MAX845
FS
A
6
74HC240
16
14
4
6
SD
ISO DI IN
SH
7
L
R6*
V
CC3
DI
V
ISO DE IN
ISO COM1
ISO DI DRV
8
R1*
R2*
18
2
R4*
R5*
SHIELD (OPTIONAL)
8
DRIVER INPUT
12
5
DI
9
3
CC4
DE
17
15
10
11
12
13
14
DE
DRIVER ENABLE
NOTE: RESISTOR R8 PROTECTS
THE MAX3480E FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
A AND B.
ISO V
CC2
13
7
R8
100Ω
GND2
RO
ISO DE DRV
ISO COM2
ISO RO LED
20
9
R3*
V
11
RECEIVER OUTPUT
CC5
RO
10
ISOLATION COMMON
ISOLATION BARRIER
*SEE TABLE 1.
C4
270pF
4kV
LOGIC GROUND
Figure 2. Typical Application Circuit
10 ______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
_________________________________________________________________Test Circuits
ISOLATION BARRIER
ISOLATION BARRIER
+3.3V
A
+3.3V
DE
C
´
L1
R
R
R3
A
A
R
DIFF
V
OD
D
R
RO
V
DI
ID
´
B
B
V
OC
C
L2
B
Figure 3. Driver DC Test Load
Figure 4. Driver/Receiver Timing Test Circuit
ISO V
ISO V
CC1,
CC2
S1
S2
500Ω
OUTPUT
UNDER TEST
C
L
Figure 5. Driver Timing Test Load
_______________________________________________________ꢀwitching Waveforms
V
_ - 0.4V
CC
V
_ - 0.4V
CC
V
CC
_ - 0.4V
2
V
_ - 0.4V
2
CC
V
CC
_ - 0.4V
2
V
_ - 0.4V
2
CC
DE
´
DI
´
0
0
t
t
PHL
PLH
1/2 V
O
t
t
LZ
ZL
A, B
B
A
2.3V
V
V
+ 0.5V
- 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
OL
V
O
V
OL
1/2 V
O
A, B
V
= V - V
A B
DIFF
V
O
2.3V
OH
V
DIFF
90%
90%
0
0
10%
10%
-V
O
t
t
HZ
ZH
t
R
t
F
t
t
- t
SKEW = | PLH PHL |
Figure 6. Driver Propagation Delays and Transition Times
Figure 7. Driver Enable and Disable Times
______________________________________________________________________________________ 11
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
The MAX3480EA/MAX3480EB withstand 1260V
__ꢀwitching Waveforms (continued)
RMS
(1 min) or 1560V
(1s). The isolated outputs of these
RMS
devices meet all RS-485/RS-422 specifications.
Boost koltage
The MAX3480EA/MAX3480EB require external diodes
on the primary of the transformer to develop the boost
voltage for the power oscillator. In normal operation,
whenever one of the oscillator outputs (D1 and D2)
goes low, the other goes to approximately double the
supply voltage. Since the circuit is symmetrical, the two
outputs can be combined with diodes, filtered, and
used to power the oscillator itself.
V
OH
RO
1.5V
1.5V
0
V
OUTPUT
OL
t
t
PLH
PHL
V
ID
ID
V - V
B
A
0
-V
INPUT
= |t - t
t
|
SKD
PLH PHL
The diodes on the primary side may be any fast-switch-
ing, small-signal diodes, such as the 1N914, 1N4148,
or CMPD2838. The nominal value of the primary filter
capacitor C3 is 0.01µF.
Figure 8. Receiver Propagation Delays
Driver Output -rotection
There are two mechanisms to prevent excessive output
current and power dissipation caused by faults or by
bus contention. 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 rises
excessively.
Function Tables
Table 2. Transmitting
INPUTS
OUTPUTS
B
A
DE´
DI´
1
1
0
1
1
0
Resistor R8 (Figures 1 and 2) provides additional pro-
tection by current limiting between the shield and the
two signal wires. In the event that shielded cable is
used and an external voltage or transient is inadver-
tently applied between the shield and the signal wires,
the MAX3480EA/MAX3480EB can be damaged.
Although unlikely, this condition can occur during
installation.
1
0
0
X
High-Z
High-Z
X = Don't care
High-Z = High impedance
Table 3. Receiving
The MAX3480EA/MAX3480EB provide electrical iso-
lation between logic ground and signal paths; they
do not provide isolation from external shields and
the signal paths. When in doubt, do not connect the
shield. The MAX3480EA/MAX3480EB can be dam-
aged if resistor R8 is shorted out.
INPUTS
OUTPUT
–—–
A-B
RO
DE´
0
≥ +0.2V
≤ -0.2V
0
1
0
0
Applications Information
The MAX3480EA/MAX3480EB provide extra protection
against ESD. The MAX3480EA/MAX3480EB are intend-
ed for harsh environments where high-speed commu-
nication is important. These devices eliminate the
need for transient suppressor diodes or the use of
discrete protection components. The standard (non-E)
MAX3480A/MAX3480B are recommended for applica-
tions where cost is critical.
0
Inputs open
12 ______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
R
R
D
1500Ω
C
1MΩ
I 100%
P
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
AMPERES
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
C
STORAGE
CAPACITOR
s
36.8%
100pF
SOURCE
10%
0
TIME
0
t
RL
t
DL
CURRENT WAVEFORM
Figure 9. Human Body ESD Test Model
Figure 10. Human Body Model Current Waveform
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the test device through a
1.5kΩ resistor.
±±15k EꢀD -rotection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges encountered during handling and
assembly. The driver outputs and receiver inputs have
extra protection against static electricity. Maxim’s engi-
neers developed state-of-the-art structures to protect
these pins against ESD of 15kV without damage. The
ESD structures withstand high ESD in all states: normal
operation, shutdown, and power-down. After an ESD
event, Maxim’s MAX3480EA/MAX3480EB keep working
without latchup. An isolation capacitor of 270pF 4kV
should be placed between ISO COM and logic ground
for optimal performance against an ESD pulse with
respect to logic ground.
Machine Model
The Machine Model for ESD tests all pins using a 200pF
storage capacitor and zero discharge resistance. Its
objective is to simulate the stress caused by contact that
occurs with handling and assembly during manufactur-
ing. Of course, all pins require this protection during
manufacturing—not just inputs and outputs. Therefore,
after PC board assembly, the Machine Model is less rel-
evant to l/O ports.
The MAX3480EA/MAX3480EB are designed for bidirec-
tional data communications on multipoint bus-transmis-
sion lines. Figure 11 shows a typical network application
circuit. To minimize reflections, terminate the line at both
ends with its characteristic impedance, and keep stub
lengths off the main line as short as possible. The slew-
rate-limited MAX3480EB is more tolerant of imperfect ter-
mination and stubs off the main line.
ESD protection can be tested in various ways; the
transmitter outputs and receiver inputs of this product
family are characterized for protection to 15kV using
the Human Body Model.
The MAX3480EA/MAX3480EB are specified and char-
acterized using the resistor values shown in Table 1.
Altering the recommended values can degrade perfor-
mance.
EꢀD Test Conditions
The +15kV ESD test specifications apply only to the A, B,
Y, and Z I/O pins. The test surge may be referenced to
either the ISO COM or to the nonisolated GND (this pre-
supposes that a bypass capacitor is installed between
The DI and DE inputs are the cathodes of LEDs whose
anodes are connected to V . These points are best
CC
V
and the nonisolated GND).
CC2
driven by a +3.3V CMOS-logic gate with a series
resistor to limit the current. The resistor values shown
in Table 1 are recommended when the 74HC240 gate
or equivalent is used. DI and DE are intended to be
Human Body Model
Figure 9 shows the Human Body Model, and Figure 10
shows the current waveform it generates when dis-
charged into a low impedance. This model consists of a
______________________________________________________________________________________ 13
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
driven through a series current-limiting resistor.
Directly grounding these pins destroys the device.
closely represent those of discrete optocouplers, rather
than the more robust characteristics of monolithic sili-
con ICs. The reliability testing programs for these multi-
component devices may be viewed on the Maxim
website (www.maxim-ic.com) under Technical Support,
Technical Reference, Multichip Products.
Reliability
These products contain transformers, optocouplers,
and capacitors, in addition to several monolithic ICs
and diodes. As such, the reliability expectations more
Table 4. Maxim’s 15kV ESD-Protected Isolated RS-485 Product Family
GUARANTEED
DATA RATE
(Mbps)
SUPPLY
VOLTAGE
(V)
NO. OF
Tx/Rx
FULL/HALF
DUPLEX
SLEW-RATE
LIMITED
NO. OF Tx/Rx
ON BUS
PART
MAX1480EA
MAX1480EC
MAX1490EA
MAX1490EB
MAX3480EA
MAX3480EB
1/1
1/1
1/1
1/1
1/1
1/1
2.50
0.25
2.50
0.25
2.50
0.25
Half
Half
Full
Full
Half
Half
No
Yes
No
32
32
5.0
5.0
5.0
5.0
3.3
3.3
32
Yes
No
32
32
Yes
128
14 ______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
B
DI
D
120Ω
DE
A
A
B
A
B
RO
R
RE
R
R
RE
RE
D
D
RO DE
DI
RO DE
DI
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
MAX3480EA/EB
V
IN
V
V
CC1
CC2
D1
AC1 (MAKE NO CONNECTION)
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
+3.0V TO +3.6V
C2
C1
22µF
6V
0.1µF
D1, D2
1N914
AC2 (MAKE NO CONNECTION)
ISO V
CC1
3
B
D2
B
4
BOOSTED V+
R7*
ISO RO DRV
A
GND1
FS
C3
0.01µF
120Ω
5
A
MAX485E
MAX487E
MAX845
6
74HC240
16
14
4
6
8
R6*
ISO DI IN
ISO DE IN
ISO COM1
ISO DI DRV
SD
SH
7
SHIELD
(OPTIONAL)
R4*
V
CC3
8
18
2
R1*
R2*
DRIVER INPUT
12
5
DI
DI
9
R5*
3
V
CC4
DE
17
15
13
10
11
12
13
14
DE
DRIVER ENABLE
ISO V
CC2
7
R8
100Ω
GND2
RO
ISO DE DRV
ISO COM2
20
R3*
V
CC5
RECEIVER OUTPUT
9
11
ISO RO LED
RO
NOTE: RESISTOR R8
PROTECTS THE MAX3480E
FROM TRANSIENT
CURRENTS BETWEEN
SHIELD AND A AND B.
10
ISOLATION
COMMON
ISOLATION BARRIER
C4
270pF
4kV
*SEE TABLE 1.
LOGIC GROUND
Figure 11. Typical RS-485/RS-422 Network
______________________________________________________________________________________ 15
±±15k EꢀDꢁ-rotected, Isolated, 3.3k
Rꢀꢁ481/Rꢀꢁ422 Data Interfaces
-ac5age Information
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 -roducts, ±20 ꢀan Gabriel Drive, ꢀunnyvale, CA 94086 408ꢁ737ꢁ7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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