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PDF MAX1490B Data sheet ( Hoja de datos )

Número de pieza MAX1490B
Descripción Complete / Isolated RS-485/RS-422 Data Interface
Fabricantes Maxim Integrated 
Logotipo Maxim Integrated Logotipo



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19-0259; Rev 5; 5/05
Complete, Isolated RS-485/RS-422
Data Interface
_________________General Description
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B are complete, electrically isolated, RS-485/
RS-422 data-communications interface solutions in a
hybrid microcircuit. Transceivers, optocouplers, and a
transformer provide a complete interface in a standard
DIP package. A single +5V supply on the logic side pow-
ers both sides of the interface.
The MAX1480B/MAX1480C/MAX1490B feature reduced-
slew-rate drivers that minimize EMI and reduce reflec-
tions caused by improperly terminated cables, allowing
error-free data transmission at data rates up to 250kbps.
The MAX1480A/MAX1490A driver slew rate is not limited,
allowing transmission rates up to 2.5Mbps. The
MAX1480A/B/C are designed for half-duplex communi-
cation, while the MAX1490A/B feature full-duplex com-
munication.
Drivers are short-circuit current limited and protected
against excessive power dissipation by thermal shut-
down circuitry that places the driver outputs into a high-
impedance state. The receiver input has a fail-safe
feature that guarantees a known output (RO low for the
MAX1480A/B/C, RO high for the MAX1490A/B) if the
input is open circuit.
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B typically withstand 1600VRMS (1 minute) or
2000VRMS (1 second). Their isolated outputs meet all
RS-485/RS-422 specifications. The MAX1480A/B/C are
available in a 28-pin DIP package, and the MAX1490A/B
are available in a 24-pin DIP package.
________________________Applications
Isolated RS-485/RS-422 Data Interface
Transceivers for EMI-Sensitive Applications
Industrial-Control Local Area Networks
Automatic Test Equipment
HVAC/Building Control Networks
Next-Generation Device Features
For Integrated ESD Protection
MAX1480E/MAX1490E: ±15kV ESD-Protected,
Isolated RS-485/RS-422 Data Interfaces
For Space-Constrained Applications
MAX3157: High CMRR, RS-485 Transceiver with
±50V Isolation
_______________Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX1480ACPI
0°C to +70°C
28 Wide Plastic DIP
MAX1480AEPI -40°C to +85°C
28 Wide Plastic DIP
Ordering Information continued at end of data sheet.
Data rate for “A” parts is up to 2.5Mbps. Data rate for “B” and
“C” parts is up to 250kbps.
_____________________Selection Table
PART
MAX1480A
MAX1480B
MAX1480C
MAX1490A
MAX1490B
HALF/
FULL
DUPLEX
Half
Half
Half
Full
Full
DATA
RATE
(MBPS)
2.5
0.25
0.25
2.5
0.25
SLEW-
RATE
LIMITED
No
Yes
Yes
No
Yes
DRIVER
ENABLE
TIME
(µs)
0.2
35
0.5
Pin Configurations
TOP VIEW
VCC1 1
VCC2 2
D1 3
D2 4
GND1 5
FS 6
SD 7
VCC3 8
DI 9
VCC4 10
RO 11
GND2 12
24 AC1 MAX1490A/B
23 AC2
22 ISO VCC1
21 ISO RO DRV
20 A
19 B
18 Z
17 Y
16 ISO COM1
15 ISO DI DRV
14 ISO VCC2
13 ISO RO LED
ISOLATION BARRIER
DIP
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

1 page




MAX1490B pdf
Complete, Isolated RS-485/RS-422
Data Interface
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B (continued)
(VCC_ = 5V ±10%, FS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = 5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Driver Disable Time from Low
(MAX1480C Only)
tLZ Figures 6 and 8, CL = 15pF, S1 closed
2.0 4.5
µs
Driver Disable Time from High
(MAX1480C Only)
tHZ Figures 6 and 8, CL = 15pF, S2 closed
2.0 4.5
µs
Receiver Input to Output
Propagation Delay
|tPLH - tPHL| Differential Receiver
Skew
Maximum Data Rate
Time to Shutdown
Shutdown to Driver Output High
Shutdown to Driver Output Low
tPLH
tPHL
tSKD
fMAX
tSHDN
tZH(SHDN)
tZL(SHDN)
Figures 5 and 10, RDIFF = 54Ω,
CL1 = CL2 = 100pF
Figures 5 and 10, RDIFF = 54Ω,
CL1 = CL2 = 100pF
tPLH, tPHL < 50% of data period
Figures 6 and 9, CL = 100pF, S2 closed
Figures 6 and 9, CL = 100pF, S1 closed
2 3.0
2 3.0
µs
1200
ns
0.25 Mbps
100 µs
35 100
µs
35 100
µs
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 (GND_), unless otherwise specified.
Note 2: For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480A/
MAX1480B/MAX1480C, Figure 2 for MAX1490A/MAX1490B).
Note 3: Shutdown supply current is the current at VCC1 and VCC2 when shutdown is enabled.
Note 4: Applies to peak current (see Typical Operating Characteristics). Although the MAX1480A/B/C and MAX1490A/B provide
electrical isolation between logic ground and signal paths, they do not provide isolation between external shields and the
signal paths (see Isolated Common Connection section).
_______________________________________________________________________________________ 5

5 Page





MAX1490B arduino
Complete, Isolated RS-485/RS-422
Data Interface
___________________________________________________Pin Description (continued)
PIN
MAX1480A/B/C MAX1490A/B
NAME
FUNCTION
PINS ON THE ISOLATED RS-485/RS-422 SIDE (continued)
— 17 Y Noninverting Driver Output
— 18 Z Inverting Driver Output
— 19 B Inverting Receiver Input
— 20 A Noninverting Receiver Input
21 — ISO DE IN Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation.
22 — ISO DI IN Isolated Driver Input. Connect to ISO DI DRV for normal operation.
23 — A Noninverting Driver Output and Noninverting Receiver Input
24
21
ISO RO DRV
Isolated Receiver-Output Drive. Connect to ISO RO LED through a resistor
(Table 1 of Figure 1 for MAX1480A/B/C, Table 2 of Figure 2 for MAX1490A/B).
25 — B Inverting Driver Output and Inverting Receiver Input
26
27, 28
22
23, 24
ISO VCC1
AC2, AC1
Isolated Supply Voltage Source
Internal Connections. Leave these pins unconnected.
Note: For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480A/B/C,
Figure 2 for MAX1490A/B).
Detailed Description
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B are complete, electrically isolated, RS-485/
RS-422 data-communications interface solutions.
Transceivers, optocouplers, a power driver, and a
transformer in one standard 28-pin DIP package (24-
pin for the MAX1490A/B) provide a complete interface.
Signals and power are internally transported across the
isolation barrier (Figures 1, 2). Power is transferred from
the logic side (nonisolated side) to the isolated side of
the barrier through a center-tapped transformer.
Signals cross the barrier through high-speed optocou-
plers. A single +5V supply on the logic side powers
both sides of the interface. The MAX1480A/B/C offer
half-duplex communications while the MAX1490A/B
feature full-duplex communication. The functional
input/output relationships are shown in Tables 3–6.
The MAX1480B/MAX1480C/MAX1490B feature reduced-
slew-rate drivers that minimize EMI and reduce reflec-
tions caused by improperly terminated cables, allowing
error-free transmission at data rates up to 250kbps. The
MAX1480A/MAX1490A driver slew rate is not limited,
allowing transmission rates up to 2.5Mbps.
The MAX1480B/MAX1480C/MAX1490B shutdown feature
reduces supply current to as low as 0.2µA by using the
SD pin (see the Low-Power Shutdown Mode section).
Use the FS pin to select between high and low switching
frequencies for the isolated power driver. The driver
switches at the lower frequency 535kHz when FS is low,
and at the higher frequency 725kHz when FS is high. The
FS pin has a weak internal pull-up that switches the
device to the high-frequency mode when FS is left
unconnected. With FS high or open, no-load supply
current is reduced by approximately 4mA, and by up to
8mA when fully loaded. For optimal performance and
minimal supply current, connect FS to VCC_ or leave
unconnected.
Drivers are short-circuit current limited and are protect-
ed against excessive power dissipation by thermal
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 RO (logic-low RO)
output if the input is open circuit.
On the MAX1480A/B/C, the driver outputs are enabled
by bringing DE´ high. Driver-enable times are typically
0.2µs for the MAX1480A, 35µs for the MAX1480B, and
0.5µs for the MAX1480C. Allow time for the devices to be
enabled before sending data (see the Driver Enable
Time vs. Temperature graph in the Typical Operating
Characteristics). When enabled, driver outputs function
as line drivers. Driver outputs are high impedance when
DE´ is low. While outputs are high impedance, they func-
tion as line receivers.
______________________________________________________________________________________ 11

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