MC34268 ON Semiconductor, MC34268 Datasheet - Page 3

• Manufacturer Part Number: MC34268
• Description: SCSI-2 Active Terminator Regulator
• Manufacturer: ON Semiconductor

application. The MC34268 is designed specifically to
provide 2.85 V required to drive a SCSI–2 bus. The output
current capability of the regulator is in excess of 800 mA;
enough to drive standard SCSI–2, fast SCSI–2, and some
wide SCSI–2 applications. The typical dropout voltage is
less than 1.0 V, allowing the IC to regulate to input voltages
less than 4.0 V. Internal protective features include current
and thermal limiting.
MC34268D
MC34268DR2
MC34268DT
MC34268DTRK
MC34268STT3
Figure 3 is a circuit of a typical SCSI terminator
180
160
120
80
40
0
0
Figure 4. SOP–8 Thermal Resistance versus
10
Device
L, LENGTH OF COPPER FLAGS (mm)
20
P.C.B. Copper Length
L
É É
P.C. Board Heatsink Example
É É
É É
30
5.0V
Copper
2.0 oz
L
9.0 mm
É É É
É É É
É É É
40
1N5819
L
50
Figure 3. Typical SCSI Application
10
ORDERING INFORMATION
60
SOT–223
Package
V in
DPAK
DPAK
SO–8
SO–8
http://onsemi.com
MC34268
70
MC34268
Regulator
3
SCSI
Gnd
an ESR of less than 10
With economical electrolytic capacitors, cold temperature
operation can pose a stability problem. As temperature
decreases, the capacitance also decreases and the ESR
increases, which could cause the circuit to oscillate.
Tantalum capacitors may be a better choice if small size is
a requirement. Also, the capacitance and ESR of a tantalum
capacitor is more stable over temperature.
The MC34268 requires an external 10 F capacitor with
90
80
70
60
50
40
0
V O
C O
Figure 5. DPAK Thermal Resistance
versus P.C.B. Copper Length
10
10
L, LENGTH OF COPPER (mm)
2500 Units / Tape & Reel
2500 Units / Tape & Reel
4000 Units / Tape & Reel
Shipping Information
98 Units / Rail
75 Units / Rail
110
for stability over temperature.
20
P.C. Board Heatsink Example
É É É É É
É É É É É
L
É É É É É
É É É É É
To SCSI Bus
Copper
2.0 oz
30
L
40