Datasheet

MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
16 ______________________________________________________________________________________
MAX1480B/MAX1480C/MAX1490B:
Reduced EMI and Reflections
The MAX1480B/MAX1480C/MAX1490B are slew-rate-
limited, minimizing EMI and reducing reflections
caused by improperly terminated cables. Figure 11
shows both the driver output waveform of a
MAX1480A/MAX1490A transmitting a 150kHz signal
and the Fourier analysis of that waveform. High-fre-
quency harmonics with large amplitudes are evident.
Figure 12 shows the same information for the slew-rate-
limited MAX1480B/MAX1480C/MAX1490B transmitting
the same signal. The high-frequency harmonics have
much lower amplitudes, and therefore the potential for
EMI is significantly reduced.
Table 3. Transmitting
Table 4. Receiving
Table 5. Transmitting
Table 6. Receiving
1
X
INPUTS*
1
High-Z
OUTPUTS
0
High-Z
1
0
Figure 11. Driver Output Waveform and FFT Plot of
MAX1480A/MAX1490A Transmitting a 150kHz Signal
10dB/div
0Hz 5MHz
500kHz/div
Figure 12. Driver Output Waveform and FFT Plot of
MAX1480B/MAX1480C/MAX1490B Transmitting a 150kHz
Signal
10dB/div
0Hz 5MHz
500kHz/div
_____________________Function Tables
Half-Duplex Devices
(MAX1480A/MAX1480B/MAX1480C)
Full-Duplex Devices
(MAX1490A/MAX1490B)
DI´
AB
DE´
0 011
≥ +0.2V
Open
INPUTS*
0
0
V
A
- V
B
OUTPUT
(RO)
DE´
≤ -0.2V 10
0
0
0 1
Z Y
1 00
1
1
1
OUTPUT
(RO)
0≤ -0.2V
≥ +0.2V
Open
INPUT
(V
A
- V
B
)
X = Don’t care
High-Z = High impedance
* 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).
OUTPUTS
INPUT*
(DI´)