DS2119M
as possible to the DS2119M. The DS2119M should be placed as close as possible to the SCSI connector
to minimize signal and power-trace length, thereby resulting in less input capacitance and reflections,
which can degrade the bus signals.
To maintain the specified regulation, a 4.7µF capacitor is required between the VREF pin (VREF) and
ground of each DS2119M. A high frequency cap (0.1µF ceramic recommended) can also be placed on the
VREF pin in applications that use fast rise/fall time drivers. A typical SCSI bus configuration is shown in
Figure 2.
DIFFSENS Noise Filtering: The DS2119M incorporates a digital filter to remove high-frequency
transients on the DIFFSENS control line, thereby eliminating erroneous switching between
modes. This filter eliminates the need for the external capacitor and resistor, which heretofore
performed this function.
NOTES:
1) DIFFSENS. Refers to the SCSI bus signal.
2) DIFFSENSE. Refers to the Dallas Semiconductor pin name and internal circuitry relating the
DIFFSENS driver.
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