BOOST Pin Voltage ................................................. 38V
BOOST Pin Above Input Voltage ............................. 15V
SHDN Pin Voltage ..................................................... 7V
BIAS Pin Voltage ...................................................... 7V
FB Pin Voltage (Adjustable Part) ............................ 3.5V
PACKAGE/ORDER I FOR ATIO
FRONT VIEW
7
6
5
4
3
2
1
R PACKAGE
7-LEAD PLASTIC DD
FB OR SENSE*
BOOST
V
IN
GND
V
SW
SYNC OR SHDN*
V
C
ORDER
PART NUMBER
LT1374CR
LT1374CR-5
LT1374CR-SYNC
LT1374CR-5 SYNC
LT1374HVCR
LT1374IR
LT1374IR-5
LT1374IR-SYNC
LT1374IR-5 SYNC
LT1374HVIR
ORDER
PART NUMBER
16 GND
15 V
SW
14 V
SW
13 SYNC
12 SHDN
11 V
C
10 BIAS
9
GND
TAB IS
GND
FRONT VIEW
7
6
5
4
3
2
1
T7 PACKAGE
7-LEAD PLASTIC TO-220
FB OR SENSE*
BOOST
V
IN
GND
V
SW
SHDN
V
C
TAB
IS
GND
T
JMAX
= 125°C,
θ
JA
= 30°C/ W
WITH PACKAGE SOLDERED TO 0.5 SQUARE INCH
COPPER AREA OVER BACKSIDE GROUND PLANE
OR INTERNAL POWER PLANE.
θ
JA
CAN VARY
FROM 20°C/W TO > 40°C/W DEPENDING ON
MOUNTING TECHNIQUES
TOP VIEW
GND
NC
V
IN
V
IN
BOOST
FB/SENSE
NC
GND
1
2
3
4
5
6
7
8
LT1374CFE
LT1374IFE
FE16 PACKAGE
16-LEAD PLASTIC TSSOP
θ
JA
= 40°C/ W
EXPOSED PAD SOLDERED TO
GROUND PLANE
*Default is the adjustable output voltage device with FB pin and shutdown function. Option -5 replaces FB with SENSE pin for fixed 5V output applications.
-SYNC replaces SHDN with SYNC pin for applications requiring synchronization. Consult LTC Marketing for parts specified with wider operating
temperature ranges.
2
U
U
W
W W
U
W
(Note 1)
FB Pin Current (Adjustable Part) ............................ 1mA
SENSE Voltage (Fixed 5V Part) ................................. 7V
SYNC Pin Voltage ..................................................... 7V
Operating Junction Temperature Range
LT1374C ............................................... 0°C to 125° C
LT1374I ........................................... – 40°C to 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER
PART NUMBER
LT1374CS8
LT1374CS8-5
LT1374CS8-SYNC
LT1374CS8-5 SYNC
LT1374HVCS8
LT1374IS8
LT1374IS8-5
LT1374IS8-SYNC
LT1374IS8-5 SYNC
LT1374HVIS8
S8 PART MARKING
1374
1374I
13745 1374I5
1374SN 374ISN
3745SN 74I5SN
1374HV 1374HVI
ORDER
PART NUMBER
LT1374CT7
LT1374CT7-5
LT1374IT7
LT1374IT7-5
TOP VIEW
V
IN
1
BOOST 2
FB OR
3
SENSE*
FGND 4
8 V
SW
SYNC
7
OR SHDN*
6 V
C
5 BIAS
S8 PACKAGE
8-LEAD PLASTIC SO
θ
JA
= 80°C/ W WITH FUSED (FGND)
GROUND PIN CONNECTED TO GROUND
PLANE OR LARGE LANDS
T
JMAX
= 125°C,
θ
JA
= 50°C/ W,
θ
JC
= 4°C/ W
1374fb
LT1374
ELECTRICAL CHARACTERISTICS
PARAMETER
Feedback Voltage (Adjustable)
Sense Voltage (Fixed 5V)
All Conditions
SENSE Pin Resistance
Reference Voltage Line Regulation
Feedback Input Bias Current
Error Amplifier Voltage Gain
Error Amplifier Transconductance
V
C
Pin to Switch Current Transconductance
Error Amplifier Source Current
Error Amplifier Sink Current
V
C
Pin Switching Threshold
V
C
Pin High Clamp
Switch Current Limit
Slope Compensation (Note 9)
Switch On Resistance (Note 7)
Maximum Switch Duty Cycle
Switch Frequency
Switch Frequency Line Regulation
Frequency Shifting Threshold on FB Pin
Minimum Input Voltage (Note 3)
Minimum Boost Voltage (Note 4)
Boost Current (Note 5)
V
IN
Supply Current (Note 6)
BIAS Supply Current (Note 6)
Shutdown Supply Current
CONDITIONS
All Conditions
The
q
denotes specifications which apply over the full operating tempera-
ture range, otherwise specifications are at T
J
= 25°C. V
IN
= 15V, V
C
= 1.5V, Boost = V
IN
+ 5V, switch open, unless otherwise noted.
MIN
2.39
2.36
4.94
4.90
7
TYP
2.42
5.0
10
0.01
0.5
400
2000
5.3
225
225
0.9
2.1
6
0.8
0.07
93
93
500
0
1.0
5.0
2.3
20
90
0.9
3.2
20
30
q
q
q
q
q
q
q
5V
≤
V
IN
≤
25V (5V
≤
V
IN
≤
32V for LT1374HV)
q
MAX
2.45
2.48
5.06
5.10
14
0.03
2
2700
3100
320
320
UNITS
V
V
V
V
kΩ
%/V
µA
µMho
µMho
A/ V
µA
µA
V
V
A
A
Ω
Ω
%
%
kHz
kHz
%/ V
V
V
V
mA
mA
mA
mA
µA
µA
µA
µA
V
V
V
V
kHz
kΩ
(Notes 2, 8)
∆I
(V
C
) =
±10µA
(Note 8)
q
200
1500
1000
140
140
V
FB
= 2.1V or V
SENSE
= 4.4V
V
FB
= 2.7V or V
SENSE
= 5.6V
Duty Cycle = 0
V
C
Open, V
FB
= 2.1V or V
SENSE
= 4.4V, DC
≤
50%
DC = 80%
I
SW
= 4.5A
V
FB
= 2.1V or V
SENSE
= 4.4V
q
q
q
4.5
8.5
0.1
0.13
q
q
V
C
Set to Give 50% Duty Cycle
q
90
86
460
440
0.8
5V
≤
V
IN
≤
25V, (5V
≤
V
IN
≤
32V for LT1374HV)
∆f
= 10kHz
I
SW
≤
4.5A
I
SW
= 1A
I
SW
= 4.5A
V
BIAS
= 5V
V
BIAS
= 5V
V
SHDN
= 0V, V
IN
≤
25V, V
SW
= 0V, V
C
Open
V
SHDN
= 0V, V
IN
≤
32V, V
SW
= 0V, V
C
Open
q
q
q
q
q
q
q
q
q
Lockout Threshold
Shutdown Thresholds
Synchronization Threshold
Synchronizing Range
SYNC Pin Input Resistance
V
C
Open
V
C
Open Device Shutting Down
Device Starting Up
2.3
0.13
0.25
580
2.38
0.37
0.45
1.5
40
540
560
0.15
1.3
5.5
3.0
35
140
1.4
4.0
50
75
75
100
2.46
0.60
0.7
2.2
1000
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
switching threshold 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.
1374fb
3
LT1374
ELECTRICAL CHARACTERISTICS
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:
V
IN
supply current is the current drawn when the BIAS pin is held
at 5V and switching is disabled. If the BIAS pin is unavailable or open
circuit, the sum of V
IN
and BIAS supply currents will be drawn by the V
IN
pin.
Note 7:
Switch on resistance is calculated by dividing V
IN
to V
SW
voltage
by the forced current (4.5A). 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 the SENSE pin on the fixed voltage parts. Divide values shown by
the ratio V
OUT
/2.42.
Note 9:
Slope compensation is the current subtracted from the switch
current limit at 80% duty cycle. See Maximum Output Load Current in the
Applications Information section for further details.
