LT1375/LT1376
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. T
J
= 25°C, V
IN
= 15V, V
C
= 1.5V, boost open, switch open,
unless otherwise noted.
PARAMETER
Shutdown Thresholds
CONDITIONS
V
C
Open
V
C
Open
Device Shutting Down
Device Starting Up
LT1375HV/LT1376HV Device Shutting Down
LT1375HV/LT1376HV Device Starting Up
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
0.15
0.25
0.15
0.25
TYP
0.37
0.45
0.37
0.45
1.5
MAX
0.60
0.60
0.70
0.70
2.2
900
UNITS
V
V
V
V
V
kHz
kΩ
Minimum Synchronizing Amplitude (LT1375 Only)
Synchronizing Range (LT1375 Only)
SYNC Pin Input Resistance
V
IN
= 5V
q
580
40
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Gain is measured with a V
C
swing equal to 200mV above the low
clamp level to 200mV below the upper clamp level.
Note 3:
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 4:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
Note 5:
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 6:
Input supply current is the bias current drawn by the input pin
when the BIAS pin is held at 5V with switching disabled. Output supply
current is the current drawn by the BIAS pin when the bias pin is held at
5V. Total input referred supply current is calculated by summing input
supply current (I
SI
) with a fraction of output supply current (I
SO
):
I
TOT
= I
SI
+ (I
SO
)(V
OUT
/V
IN
)(1.15)
With V
IN
= 15V, V
OUT
= 5V, I
SI
= 0.9mA, I
SO
= 3.6mA, I
TOT
= 2.28mA.
For the LT1375, quiescent current is equal to:
I
TOT
= I
SI
+ I
SO
(1.15)
because the BIAS pin is internally connected to V
IN
.
Note 7:
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 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
Inductor Core Loss
1.0
V
OUT
= 5V, V
IN
= 10V, I
OUT
= 1A
TYPE 52
POWDERED IRON
Kool Mµ
®
PERMALLOY
µ
= 125
20
12
8
CORE LOSS (W)
0.1
2
1.2
0.8
0.4
FEEDBACK VOLTAGE (V)
4
SWITCH PEAK CURRENT (A)
0.01
CORE LOSS IS
INDEPENDENT OF LOAD
CURRENT UNTIL LOAD CURRENT FALLS
LOW ENOUGH FOR CIRCUIT TO GO INTO
DISCONTINUOUS MODE
0
5
10
15
INDUCTANCE (µH)
20
25
0.001
Kool Mµ is a registered trademark of Magnetics, Inc.
4
U W
1375/76 G01
Switch Peak Current Limit
2.5
TYPICAL
2.0
2.43
2.44
Feedback Pin Voltage and Current
2.0
CORE LOSS (% OF 5W LOAD)
1.5
CURRENT (µA)
1.5
GUARANTEED MINIMUM
2.42
VOLTAGE
1.0
1.0
0.2
0.12
0.08
0.04
0.02
CURRENT
2.41
0.5
0.5
0
0
20
60
40
DUTY CYCLE (%)
80
100
1375/76 G08
2.40
–50
–25
100
JUNCTION TEMPERATURE (°C)
0
25
50
75
0
125
1375/76 G09
LINER [ LINEAR TECHNOLOGY ]
