Datasheet

5
LT1507
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
Inductor Core Loss for 3.3V Output
INDUCTANCE (µH)
1
0.001
CORE LOSS (W)
0.1
0.01
1.0
246810
LT1507 • TPC17
TYPE 52 POWDERED IRON
Kool Mµ
®
PERMALLOY
µ = 125
Metglas
®

CORE LOSS IS INDEPENDENT OF LOAD CURRENT
UNTIL LOAD CURRENT FALLS LOW ENOUGH 
FOR CIRCUIT TO GO INTO DISCONTINUOUS MODE
V
OUT
= 3.3V
V
IN
= 5V
I
OUT
= 1A


Kool Mµ is a registered trademark of Magnetics, Incorporated.
Metglas is a registered trademark of AlliedSignal Incorporated.
BOOST (Pin 1): The BOOST pin is used to provide a drive
voltage, higher than the input voltage, to the internal
bipolar NPN power switch. Without this added voltage the
typical switch voltage loss would be about 1.5V. The
additional boost voltage allows the switch to saturate and
voltage loss approximates that of a 0.3Ω FET structure,
but with a much smaller die area. Efficiency improves from
PIN FUNCTIONS
UUU
70% for conventional bipolar designs to greater than 85%
for these new parts.
V
IN
(Pin 2): Input Pin. The LT1507 is designed to operate
with an input voltage between 4.5V and 15V. Under certain
conditions, input voltage may be reduced down to 4V.
Actual minimum operating voltage will always be higher
than the output voltage. It may be limited by switch
OUTPUT VOLTAGE (%)
0
OUTPUT CURRENT (A)
2.5
2.0
1.5
1.0
0.5
0
80
LT1507 • TPC13
20
40
60
100
MOS LOAD
RESISTOR LOAD
CURRENT
SOURCE LOAD
FOLDBACK 
CHARACTERISTICS
*POSSIBLE
UNDESIRED
STABLE POINT 
FOR CURRENT 
SOURCE LOAD
*SEE "MORE THAN JUST VOLTAGE FEEDBACK"
IN APPLICATIONS INFORMATION SECTION
Current Limit Foldback
INPUT VOLTAGE (V)
4
0
CURRENT (A)
0.25
0.50
0.75
1.00
1.25
1.50
6 8 10 12
LT1507 • TPC14
14
L = 10µH
L = 5µH
L = 3µH
L = 2µH
V
OUT
= 3.3V
Maximum Load Current
at V
OUT
= 3.3V
INPUT VOLTAGE (V)
0
0
CURRENT (A)
0.25
0.50
0.75
1.00
1.25
1.50
36912
LT1507 • TPC15
15
L = 10µH
L = 5µH
L = 20µH
Maximum Load Current
at V
OUT
= 5V
Boost Pin Current
SWITCH CURRENT (A)
0
BOOST PIN CURRENT (mA)
12
10
8
6
4
2
0
0.25 0.50 0.75 1.00
LT1507 • TPC16
1.25
T
J
= 25°C
Switch Voltage Drop
SWITCH CURRENT (A)
0
SWITCH VOLTAGE (V)
0.8
0.6
0.4
0.2
0
0.25 0.50 0.75 1.00
LT1507 • TPC18
1.25 1.50
T
J
= 25°C