LT1507
ELECTRICAL CHARACTERISTICS
T
J
= 25°C, V
IN
= 5V, V
C
= 1.5V, boost open, switch open unless otherwise specified.
PARAMETER
Switch Frequency
CONDITIONS
V
C
Set to Give 50% Duty Cycle
– 25°C
≤
T
J
≤
125°C
T
J
≤
–25°C
4.3V
≤
V
IN
≤
15V
∆f
= 10kHz
I
SW
≤
1.5A
V
BOOST
= V
IN
+ 5V
MIN
460
440
440
q
q
q
q
TYP
500
Switch Frequency Line Regulation
Frequency Shifting Threshold on F
B
Pin
Minimum Input Voltage (Note 2)
Minimum Boost Voltage (Note 3)
Boost Current (Note 4)
0.8
I
SW
= 500mA, –25°C
≤
T
J
≤
125°C
T
J
≤
–25°C
I
SW
= 1.5A, –25°C
≤
T
J
≤
125°C
T
J
≤
–25°C
q
0.05
1.0
4
3
12
25
3.8
15
Input Supply Current (Note 5)
Shutdown Supply Current
Lockout Threshold
Shutdown Threshold
Minimum Synchronizing Amplitude
Synchronizing Frequency Range (Note 7)
V
SHDN
= 0V, V
IN
≤
12V
V
SW
= 0V, V
C
Open
V
C
Open
V
C
Open
Device Shutting Down
Device Starting Up
q
q
q
q
q
2.3
0.15
0.25
580
2.38
0.37
0.45
1.5
MAX
540
560
570
0.15
1.3
4.3
3.5
22
25
35
40
5.4
50
75
2.46
0.70
0.70
2.2
1000
UNITS
kHz
kHz
kHz
%/V
V
V
V
mA
mA
mA
mA
mA
µA
µA
V
V
V
V
kHz
The
q
denotes specifications which apply over the operating temperature
range.
Note 1:
Gain is measured with a V
C
swing equal to 200mV above the low
clamp level to 200mV below the upper clamp level.
Note 2:
Minimum input voltage is not measured directly, but is guaranteed
by other tests. It is defined as the voltage where internal bias lines are still
regulated, so that the reference voltage and oscillator frequency remain
constant. Actual minimum input voltage to maintain a regulated output will
depend on output voltage and load current. See Applications Information.
Note 3:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
Note 4:
Boost current is the current flowing into the BOOST pin with the
pin held 5V above input voltage. It flows only during switch ON time.
Note 5:
Input supply current is the bias current drawn by the V
IN
pin when
the SHDN pin is held at 1V (switching disabled).
Note 6:
Switch ON resistance is calculated by dividing V
IN
to V
SW
voltage
by the forced current (1.5A). See Typical Performance Characteristics for
the graph of switch voltage at other currents.
Note 7:
For synchronizing frequency above 700kHz, with duty cycles
above 50%, external slope compensation may be needed. See Applications
Information.
Note 8:
Transconductance and voltage gain refer to the internal amplifier
exclusive of the voltage divider. To calculate gain and transconductance
refer to SENSE pin on fixed voltage parts. Divide values shown by the ratio
V
OUT
/2.42.
TYPICAL PERFORMANCE CHARACTERISTICS
V
C
Pin Shutdown Threshold
1.4
THRESHOLD VOLTAGE (V)
FEEDBACK VOLTAGE (V)
1.2
EFFICIENCY (%)
1.0
0.8
0.6
0.4
–50
–25
100
JUNCTION TEMPERATURE (°C)
0
25
50
75
U W
LT1507 • TPC01
Switch Peak Current Limit
100
V
IN
= 5V
V
OUT
= 3.3V
90
2.43
2.44
Feedback Pin Voltage and Current
2.0
1.5
CURRENT (µA)
80
2.42
VOLTAGE
1.0
70
CURRENT
2.41
0.5
60
50
125
0
0.25
0.75
1.00
0.50
LOAD CURRENT (A)
1.25
2.40
–50
–25
100
JUNCTION TEMPERATURE (°C)
0
25
50
75
0
125
LT1507 • TA02
LT1507 • TPC03
3
LINER [ LINEAR TECHNOLOGY ]
