ds2114 Maxim Integrated Products, Inc., ds2114 Datasheet - Page 2

• Manufacturer Part Number: ds2114
• Description: Ds2114 Scsi Terminator
• Manufacturer: Maxim Integrated Products, Inc.

FUNCTIONAL DESCRIPTION
The DS2114 consists of a bandgap reference, buffer
amplifier, and nine termination resistors (Figure 1). The
bandgap reference circuit produces a precise 2.55 volts
level which is fed to a buffer amplifier. The buffer pro-
duces a 2.85 volts level and is capable of sourcing at
least 24 mA into each of the termination resistors when
the signal line is low (active). When the driver for a given
signal line turns off, the terminator will pull the signal line
to 2.85 volts (quiescent state). To handle actively ne-
gated SCSI signals, the buffer can sink at least 200 mA
and V
in the quiescent state, the regulator will consume about
2.5 mA.
DS2114 BLOCK DIAGRAM Figure 1
DS2114
070198 2/6
ref
TERMPWR1
TERMPWR2
will move less than 60 mV. When all lines settle
GND
REFERENCE
BANDGAP
+
–
To ensure proper operation, both the TERMPWR1 and
TERMPWR2 pins must be connected to the SCSI bus
TERMPWR line and both the VREF1 and VREF2 pins
must be tied together externally. Each DS2114 requires
a 4.7 F capacitor connected between the VREF pins
and ground. Figure 2 details a typical SCSI bus configu-
ration. In an 8–bit wide SCSI bus arrangement (“A”
Cable), two DS2114’s would be needed at each end of
the SCSI cable in order to terminate the 18 active signal
lines. In a 16–bit wide SCSI bus arrangement (“P”
Cable), three DS2114’s would be needed at each end of
the SCSI cable in order to terminate the 27 active signal
lines.
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
110 ohms
VREF1
VREF2
R1
R3
R2
R4
R5
R6
R7
R8
R9