LT1268BCQ Linear Technology, LT1268BCQ Datasheet - Page 3

• Manufacturer Part Number: LT1268BCQ
• Description: IC SWITCHNG REG 7.5A 150KHZ 5-DD
• Manufacturer: Linear Technology
• Type: Step-Down (Buck), Inverting, Flybackr

Specifications of LT1268BCQ

• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 60 V
• Current - Output: 7.5A
• Frequency - Switching: 150kHz
• Voltage - Input: 3.5 ~ 30 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: D²Pak, TO-263 (5 leads + tab)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Internal Switch(s): -

The
temperature range.
Note 1: Measured with V
Note 2: For duty cycles (DC) between 50% and 65%, minimum guaranteed
switch current is given by I
Note 3: Minimum current limit is reduced by 0.5A at 125 C. 100 C test
limits are guaranteed by correlation to 125 C tests.
Note 4: LT1268B reference voltage is specified at 9mV to guarantee 1%
output voltage accuracy when 0.1% external resistors are used to set
output voltage. To maintain output accuracy under load, load current
should be taken from the case and the ground pin should be connected
separately to output ground. See AN19 for details.
Note 5: The Q package is intended for surface mount without a separate
heat sink. See graph for thermal resistance as a function of the mounting
area. This curve assumes no other heat dissipators adjacent to package.
Note 6: Maximum switch current may be limited by package power
dissipation, especially for the surface mount (Q) package. This package
SYMBOL
f
DC
TYPICAL PERFOR A CE CHARACTERISTICS
ELECTRICAL C
I
I
SW
IN
MAX
24
18
12
6
0
denotes specifications which apply over the full operating
Switch Current Limit vs Duty Cycle
0
10
20
PARAMETER
Supply Current Increase
During Switch-ON Time
Switching Frequency
Maximum Switch Duty Cycle
Shutdown Mode Supply Current
Shutdown Mode Threshold Voltage
30
DUTY CYCLE (%)
25°C
40
C
50
in hi clamp, V
LIM
HARA TERISTICS
60
= 6.25 (1.7 – DC).
125°C
70
–55°C
80
W U
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
LT1268 • TPC01
FB
90
C
= 0.8V.
100
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
Switch Saturation Voltage
0
CONDITIONS
3V V
3V V
T
J
1
= 25°C
IN
IN
2
V
IN
SWITCH CURRENT (A)
V
V
3
= 15V, V
MAX
MAX
4
, V
C
5
has a thermal resistance of 20 C/W to 50 C/W (see graph). The following
formula will allow an estimate of maximum continuous switch current as a
function of power loss and duty cycle. See AN19 for more details.
In a typical application where thermal resistance is 30 C/W, maximum
power might be limited to 2W and power allocated to switch loss is 1.5W.
For a duty cycle of 40%, this yields
Obviously, a combination of high thermal resistance and high duty cycle
may restrict switch current to a value well below the 7.5A electrical limit.
= 0.05V
C
I
I
6
P = Power dissipation due to switch current
R
DC = Switch duty cycle
= 0.5V, V
MAX
MAX
SW
7
=
=
= Switch-ON resistance 0.15
8
LT1268 • TPC02
0.15
R
SW
FB
9
1.5
P
= V
10
DC
0.4
REF
= 5A
, switch pin open, unless otherwise noted.
60
50
10
40
30
20
0
MIN
120
120
100
Q Package Thermal Resistance
0
65
50
LT1268B/LT1268
TOP SURFACE COPPER AREA (cm
5
DOUBLE-SIDED BOARD, 1oz COPPER
BOTTOM COPPER AREA >100cm
SINGLE-SIDED BOARD, 1oz COPPER
TYP
150
100
150
25
85
10
15
MAX
180
180
500
250
300
45
92
20
25
LT1268 • 603
2
)
UNITS
2
mA/A
3
kHz
kHz
mV
mV
30
%
A