MAX1480 Maxim, MAX1480 Datasheet - Page 15

• Manufacturer Part Number: MAX1480
• Description: Complete / Isolated RS-485/RS-422 Data Interface
• Manufacturer: Maxim

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.
Figure 11. Driver Output Waveform and FFT Plot of
MAX1480A/MAX1490A Transmitting a 150kHz Signal
Figure 12. Driver Output Waveform and FFT Plot of
MAX1480B/MAX1480C/MAX1490B Transmitting a 150kHz
Signal
10dB/div
10dB/div
0Hz
MAX1480B/MAX1480C/MAX1490B:
0Hz
Reduced EMI and Reflections
______________________________________________________________________________________
500kHz/div
500kHz/div
Complete, Isolated RS-485/RS-422
5MHz
5MHz
_____________________Function Tables
Table 3. Transmitting
X = Don’t care
High-Z = High impedance
Table 4. Receiving
Table 5. Transmitting
* For DE
and Typical Application Circuit (Figure 1 for MAX1480A/B/C,
Figure 2 for MAX1490A/B).
Table 6. Receiving
DE
INPUT
1
1
0
(DI
´
DE
´
1
0
and DI
0
0
0
INPUTS*
´
(MAX1480A/MAX1480B/MAX1480C)
(V
´
)
≥ +0.2V
≤ -0.2V
INPUT
*
Open
A
- V
´
INPUTS*
pin descriptions, see Detailed Block Diagram
B
)
DI
1
0
X
Data Interface
´
V
≥ +0.2V
(MAX1490A/MAX1490B)
≤ -0.2V
Open
A
Z
0
1
- V
Half-Duplex Devices
Full-Duplex Devices
B
High-Z
OUTPUTS
B
0
1
OUTPUTS
OUTPUT
(RO)
1
0
1
OUTPUT
(RO)
High-Z
Y
1
0
0
1
0
A
1
0
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