DS21T07S Maxim Integrated Products, DS21T07S Datasheet - Page 2

• Manufacturer Part Number: DS21T07S
• Description: IC TERMINATOR SCSI 16-SOIC
• Manufacturer: Maxim Integrated Products
• Type: SCSI, LVD, SEr

Specifications of DS21T07S

• Number Of Terminations: 9
• Voltage - Supply: 4 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DS21T07
FUNCTIONAL DESCRIPTION
The DS21T07 consists of a bandgap reference, buffer amplifier, and nine termination resistors (Figure 1).
The bandgap reference circuit produces a precise 2.55V level which is fed to a buffer amplifier. The
buffer produces a 2.85V 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 2.85V (quiescent state). To handle actively negated SCSI signals,
the buffer can sink at least 200 mA, and V
will move less than 60 mV. When all lines settle in the
REF
quiescent state, the regulator will consume about 5 mA. When the DS21T07 is put into power-down
mode by bringing
low, the power-down circuitry will turn off the transistors on each signal line. This
PD
will isolate the DS21T07 from the signal lines and effectively remove it from the circuit. The power-
) has an internal 50K =pullup resistor. To place the DS21T07 into an active state, the
down pin (
PD
PD
pin should be left open circuited. When installed on disk drives or RAID system components, the
DS21T07 will not affect the SCSI bus during a hot plug operation.
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
DS21T07 requires a 4.7 µF capacitor connected between the VREF pins and ground. Figure 2 details a
typical SCSI bus configuration. In an 8-bit wide SCSI bus arrangement, two DS21T07’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, three DS21T07’s would be needed at each end of the SCSI cable in order to terminate the
27 active signal lines.
DS21T16 BLOCK DIAGRAM Figure 1
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