Datasheet

Reduced EMI and Reections
(MAX3293/MAX3294)
The MAX3293/MAX3294 are slew-rate limited, minimizing
EMI and reducing reflections caused by improperly ter-
minated cables. Figure 12 shows Fourier analysis of the
MAX3295 transmitting a 125kHz signal. High-frequency
harmonics with large amplitudes are evident. Figure 13
shows the same information, but for the slew-rate-limited
MAX3293, transmitting the same signal. The high-fre-
quency harmonics have much lower amplitudes, and the
potential for EMI is significantly reduced.
To minimize reflections, the line should be terminated at
both ends in its characteristic impedance, and stub lengths
off the main line should be kept as short as possible. The
slew-rate-limited MAX3293 and MAX3294 are more toler-
ant of imperfect termination.
Driver-Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus contention.
The first, a foldback current limit on the output stage,
provides immediate protection against short circuits over
the whole common-mode voltage range (see the Typical
Operating Characteristics). The second, a thermal-shut-
down circuit, forces the driver outputs into a high-imped-
ance state if the die temperature exceeds +160°C.
Figure 13. Driver-Output Waveform and FFT Plot of MAX3293
Transmitting a 125kHz Signal
Figure 12. Driver-Output Waveform and FFT Plot of MAX3295
Transmitting a 125kHz Signal
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
6 SOT23 U6CN+2 21-0058 90-0175
V
CC
ZDE
1 6 Y
+
5 GND
DI
MAX3293
MAX3294
MAX3295
SOT23-6
TOP VIEW
2
3 4
DRIVER-OUTPUT WAVEFORM AND
FFT PLOT OF MAX3293
10dB/div
DRIVER-OUTPUT WAVEFORM AND
FFT PLOT OF MAX3295
10dB/div
MAX3293–MAX3295 20Mbps, +3.3V, SOT23 RS-485/
RS-422 Transmitters
www.maximintegrated.com
Maxim Integrated │ 10
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Chip Information
PROCESS: BiCMOS
Pin Conguration