ON MC34268D Scsi-2 active terminator regulator Datasheet

MC34268
SCSI-2 Active Terminator
Regulator
The MC34268 is a medium current, low dropout positive voltage
regulator specifically designed for use in SCSI–2 active termination
circuits. This device offers the circuit designer an economical
solution for precision voltage regulation, while keeping power losses
to a minimum. The regulator consists of a 1.0 V dropout composite
PNP/NPN pass transistor, current limiting, and thermal limiting.
These devices are packaged in the 8–pin SOP–8 and 3–pin DPAK
and SOT–223 surface mount power packages.
Applications include active SCSI–2 terminators and post
regulation of switching power supplies.
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MARKING
DIAGRAMS
8
SOP–8
D SUFFIX
CASE 751
8
1
34268
ALYW
1
2.85 V Output Voltage for SCSI–2 Active Termination
1.0 V Dropout
Output Current in Excess of 800 mA
Thermal Protection
Short Circuit Protection
Output Trimmed to 1.4% Tolerance
No Minimum Load Required
Space Saving DPAK, SOT–223 and SOP–8 Surface Mount Power
Packages
A
L
Y
W
= Assembly Location
= Wafer Lot
= Year
= Work Week
Gnd
1
8
2
7
3
6
4
5
Output
Input
NC
Output
NC
(Top View)
Simplified Block Diagram
DPAK
DT SUFFIX
CASE 369A
Input
1
34268
ALYWW
3
Thermal
Limiting
Control
Circuit
SOT–223
ST SUFFIX
CASE 318E
1
3
Current
Limit
AYW
268ST
Output
4
1
2
3
Pin 1. Ground
2. Output
3. Input
4. Output
(Top View)
Ground
Heatsink surface (shown as terminal 4 in
case outline drawing) is connected to Pin 2.
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 3 of this data sheet.
 Semiconductor Components Industries, LLC, 2000
April, 2000 – Rev. 1
1
Publication Order Number:
MC34268/D
MC34268
MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Vin
15
V
PD
RθJC
RθJA
Internally Limted
5.0
87
W
°C/W
°C/W
PD
RθJC
RθJA
Internally Limited
22
140
W
°C/W
°C/W
PD
RθJC
RθJA
Internally Limited
15
245
W
°C/W
°C/W
TJ
0 to +150
°C
Tstg
– 55 to +150
°C
Power Supply Input Voltage
Power Dissipation and Thermal Characteristics
DT Suffix, Plastic Package, Case 369A
TA = 25°C, Derate Above TA = 25°C
Thermal Resistance, Junction–to–Case
Thermal Resistance, Junction–to–Air
D Suffix, Plastic Package, Case 751
TA = 25°C, Derate Above TA = 25°C
Thermal Resistance, Junction–to–Case
Thermal Resistance, Junction–to–Air
ST Suffix, Plastic Package, Case 318E
TA = 25°C, Derate Above TA = 25°C
Thermal Resistance, Junction–to–Case
Thermal Resistance, Junction–to–Air
Operating Junction Temperature Range
Storage Temperature
ELECTRICAL CHARACTERISTICS
(Vin = 4.25 V, CO = 10 µF, for typical values TJ = 25°C, for min/max values TJ = 0°C to +125°C, unless otherwise noted.)
Symbol
Min
Typ
Max
Unit
VO
2.81
2.76
2.85
2.85
2.89
2.93
V
Line Regulation (Vin = 4.25 V to 15 V, IO = 0 mA, TJ = 25°C)
Regline
—
—
0.3
%
Load Regulation (IO = 0 mA to 800 mA, TJ = 25°C)
Regload
—
—
0.5
%
Dropout Voltage (IO = 490 mA)
Vin – VO
—
0.95
1.1
V
Characteristic
Output Voltage (TJ = 25°C, IO = 0 mA)
Output Voltage, over Line, Load, and Temperature (Vin = 3.9 V to 15 V,
IO = 0 mA to 490 mA)
Ripple Rejection (f = 120 Hz)
RR
55
—
—
dB
Maximum Output Current (Vin = 5.0 V)
I(max)
800
—
—
mA
Bias Current (Vin = 4.25 V, IO = 0 mA)
IB
—
5.0 to 3.0
8.0
mA
IL(min)
—
—
0
mA
I O , OUTPUT CURRENT
∆ VO , OUTPUT VOLTAGE DEVIATION
Minimum Load Current to maintain Regulation (Vin = 15 V)
Figure 1. Dropout Voltage versus
Output Load Current
V in–VO , DROPOUT VOLTAGE (V)
1.5
TJ = 25°C
1.3
1.1
0.9
0.7
0.5
0
200
400
600
800
1000
IO, OUTPUT LOAD CURRENT (mA)
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2
Figure 2. Transient Load Regulation
Vin = 5.0 V
CO = 10 µF
TA = 25°C
20 ms/DIV
MC34268
Figure 3. Typical SCSI Application
Vin
5.0V
1N5819
10
CO
Gnd
θ JA, THERMAL RESISTANCE JUNCTION-TO-AIR (° C/W)
θ JA, THERMAL RESISTANCE JUNCTION-TO-AIR (° C/W)
Figure 4. SOP–8 Thermal Resistance versus
P.C.B. Copper Length
ÉÉÉÉÉ
ÉÉÉÉÉ
ÉÉÉÉÉ
P.C. Board Heatsink Example
160
L
120
2.0 oz
Copper
L
9.0 mm
L
80
40
0
0
10
20
30
40
50
L, LENGTH OF COPPER FLAGS (mm)
60
10
To SCSI Bus
The MC34268 requires an external 10 µF capacitor with
an ESR of less than 10 Ω for stability over temperature.
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.
Figure 3 is a circuit of a typical SCSI terminator
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.
180
110Ω
VO
MC34268
SCSI
Regulator
70
Figure 5. DPAK Thermal Resistance
versus P.C.B. Copper Length
90
ÉÉÉÉÉ
ÉÉÉÉÉ
ÉÉÉÉÉ
ÉÉÉÉÉ
P.C. Board Heatsink Example
L
80
2.0 oz
Copper
70
L
60
50
40
0
10
20
30
L, LENGTH OF COPPER (mm)
ORDERING INFORMATION
Device
Package
Shipping Information
MC34268D
SO–8
98 Units / Rail
MC34268DR2
SO–8
2500 Units / Tape & Reel
MC34268DT
DPAK
75 Units / Rail
MC34268DTRK
DPAK
2500 Units / Tape & Reel
MC34268STT3
SOT–223
4000 Units / Tape & Reel
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3
40
MC34268
PACKAGE DIMENSIONS
SOP–8
D SUFFIX
CASE 751–06
ISSUE T
D
A
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
2. DIMENSIONS ARE IN MILLIMETER.
3. DIMENSION D AND E DO NOT INCLUDE MOLD
PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 PER SIDE.
5. DIMENSION B DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.127 TOTAL IN EXCESS
OF THE B DIMENSION AT MAXIMUM MATERIAL
CONDITION.
C
8
5
0.25
H
E
B
M
M
1
4
h
B
X 45 _
q
e
A
C
SEATING
PLANE
L
0.10
A1
B
0.25
M
C B
S
A
S
DIM
A
A1
B
C
D
E
e
H
h
L
q
MILLIMETERS
MIN
MAX
1.35
1.75
0.10
0.25
0.35
0.49
0.19
0.25
4.80
5.00
3.80
4.00
1.27 BSC
5.80
6.20
0.25
0.50
0.40
1.25
0_
7_
DPAK
DT SUFFIX
CASE 369A–13
ISSUE Z
–T–
C
B
V
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
SEATING
PLANE
E
R
4
Z
A
S
1
2
3
U
K
F
J
L
H
D
G
2 PL
0.13 (0.005)
M
T
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4
DIM
A
B
C
D
E
F
G
H
J
K
L
R
S
U
V
Z
INCHES
MIN
MAX
0.235
0.250
0.250
0.265
0.086
0.094
0.027
0.035
0.033
0.040
0.037
0.047
0.180 BSC
0.034
0.040
0.018
0.023
0.102
0.114
0.090 BSC
0.175
0.215
0.020
0.050
0.020
–––
0.030
0.050
0.138
–––
MILLIMETERS
MIN
MAX
5.97
6.35
6.35
6.73
2.19
2.38
0.69
0.88
0.84
1.01
0.94
1.19
4.58 BSC
0.87
1.01
0.46
0.58
2.60
2.89
2.29 BSC
4.45
5.46
0.51
1.27
0.51
–––
0.77
1.27
3.51
–––
MC34268
PACKAGE DIMENSIONS
SOT–223
ST SUFFIX
CASE 318E–04
ISSUE K
A
F
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
4
S
B
1
2
3
D
L
G
J
C
0.08 (0003)
H
M
K
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5
INCHES
DIM MIN
MAX
A
0.249
0.263
B
0.130
0.145
C
0.060
0.068
D
0.024
0.035
F
0.115
0.126
G
0.087
0.094
H 0.0008 0.0040
J
0.009
0.014
K
0.060
0.078
L
0.033
0.041
M
0_
10 _
S
0.264
0.287
MILLIMETERS
MIN
MAX
6.30
6.70
3.30
3.70
1.50
1.75
0.60
0.89
2.90
3.20
2.20
2.40
0.020
0.100
0.24
0.35
1.50
2.00
0.85
1.05
0_
10 _
6.70
7.30
MC34268
Notes
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6
MC34268
Notes
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7
MC34268
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MC34268/D
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