MAX3082 MAXIM [Maxim Integrated Products], MAX3082 Datasheet - Page 17

• Manufacturer Part Number: MAX3082
• Description: Fail-Safe, High-Speed 10Mbps, Slew-Rate-Limited RS-485/RS-422 Transceivers
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 13. Receiver Propagation Delay Test Circuit
Figure 15. Driver Output Waveform and FFT Plot of
MAX3083/MAX3084/MAX3085, and MAX3089
with SRL = V
components with large amplitudes are evident. Figure
15 shows the same signal displayed for a MAX3083/
MAX3084/MAX3085, and MAX3089 with SRL = V
transmitting under the same conditions. Figure 15’s
high-frequency harmonic components are much lower
in amplitude, compared with Figure 14’s, and the poten-
tial for EMI is significantly reduced. Figure 16
shows the same signal displayed for a MAX3080/
MAX3081/MAX3082, and MAX3089 with SRL = uncon-
nected, transmitting under the same conditions. Figure
16’s high-frequency harmonic components are even
lower.
20dB/div
Slew-Rate-Limited RS-485/RS-422 Transceivers
ATE
0Hz
CC,
Transmitting a 20kHz Signal
______________________________________________________________________________________
V
ID
100kHz/div
B
A
R
Fail-Safe, High-Speed (10Mbps),
R
1MHz
A
B
RECEIVER
OUTPUT
CC
),
In general, a transmitter’s rise time relates directly to the
length of an unterminated stub, which can be driven with
only minor waveform reflections. The following equation
expresses this relationship conservatively:
where t
For example, the MAX3080’s rise time is typically
1320ns, which results in excellent waveforms with a stub
length up to 90 feet. A system can work well with longer
unterminated stubs, even with severe reflections, if the
waveform settles out before the UART samples them.
Figure 14. Driver Output Waveform and FFT Plot of
MAX3086/MAX3087/MAX3088, and MAX3089 with
SRL = GND, Transmitting a 20kHz Signal
Figure 16. Driver Output Waveform and FFT Plot of
MAX3080/MAX3081/MAX3082, and MAX3089
with SRL = Unconnected, Transmitting a 20kHz Signal
20dB/div
20dB/div
RISE
0Hz
0Hz
is the transmitter’s rise time.
Length = t
RISE
100kHz/div
100kHz/div
/ (10 x 1.5ns/ft)
1MHz
1MHz
A
B
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