3
LT1507
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switch Frequency V
C
Set to Give 50% Duty Cycle 460 500 540 kHz
–25°C ≤ T
J
≤ 125°C 440 560 kHz
T
J
≤ –25°C 440 570 kHz
Switch Frequency Line Regulation 4.3V ≤ V
IN
≤ 15V ● 0.05 0.15 %/V
Frequency Shifting Threshold on F
B
Pin ∆f = 10kHz ● 0.8 1.0 1.3 V
Minimum Input Voltage (Note 2) ● 4 4.3 V
Minimum Boost Voltage (Note 3) I
SW
≤ 1.5A ● 3 3.5 V
Boost Current (Note 4) V
BOOST
= V
IN
+ 5V I
SW
= 500mA, –25°C ≤ T
J
≤ 125°C1222mA
T
J
≤ –25°C25mA
I
SW
= 1.5A, –25°C ≤ T
J
≤ 125°C2535mA
T
J
≤ –25°C40mA
Input Supply Current (Note 5) ● 3.8 5.4 mA
Shutdown Supply Current V
SHDN
= 0V, V
IN
≤ 12V 15 50 µA
V
SW
= 0V, V
C
Open ● 75 µA
Lockout Threshold V
C
Open ● 2.3 2.38 2.46 V
Shutdown Threshold V
C
Open Device Shutting Down ● 0.15 0.37 0.70 V
Device Starting Up ● 0.25 0.45 0.70 V
Minimum Synchronizing Amplitude ● 1.5 2.2 V
Synchronizing Frequency Range (Note 7) 580 1000 kHz
The
● 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.
T
J
= 25°C, V
IN
= 5V, V
C
= 1.5V, boost open, switch open unless otherwise specified.
V
C
Pin Shutdown Threshold
JUNCTION TEMPERATURE (°C)
–50
2.44
2.43
2.42
2.41
2.40
100
LT1507 • TPC03
–25 0 25 50 75 125
FEEDBACK VOLTAGE (V)
CURRENT (µA)
2.0
1.5
1.0
0.5
0
VOLTAGE
CURRENT
LOAD CURRENT (A)
0
EFFICIENCY (%)
100
90
80
70
60
50
1.00
LT1507 • TA02
0.25
0.50
0.75
1.25
V
IN
= 5V
V
OUT
= 3.3V
Switch Peak Current Limit Feedback Pin Voltage and Current
JUNCTION TEMPERATURE (°C)
–50
1.4
1.2
1.0
0.8
0.6
0.4
100
LT1507 • TPC01
–25 0 25 50 75 125
THRESHOLD VOLTAGE (V)
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
