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Linear Technology Electronic Components Datasheet

LT1950 Datasheet

Single Switch PWM Controller

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FEATURES
s Wide Input Range: 3V to 25V
s Programmable Volt-Second Clamp
s Output Power Levels from 25W to 500W
s Auxiliary Boost Converter Provides 10V Gate Drive
from VIN as Low as 3V
s Programmable Operating Frequency (100kHz to
500kHz) with One External Resistor
s Programmable Slope Compensation
s Programmable Leading Edge Blanking
s ±2% Internal 1.23V Reference
s Accurate Shutdown Pin Threshold with
Programmable Hysteresis
s 60ns Current Sense Delay
s 2.5V Auxiliary Reference Output
s Synchronizable to an External Clock up to 1.5 • fOSC
s Current Mode Control
s Small 16-Pin SSUOP Package
APPLICATIO S
s Telecom Power Supplies
s Automotive Power Supplies
s Portable Electronic Equipment
s Isolated and Nonisolated DC/DC Converters
LT1950
Single Switch PWM
Controller with Auxiliary
Boost Converter
DESCRIPTIO
The LT®1950 is a wide input range, forward, boost, flyback
and SEPIC controller that drives an N-channel power
MOSFET with few external components required.
A resistor programmable duty cycle clamp can be used to
generate a volt-second clamp for forward converter appli-
cations. An internal boost switcher is available for creating
a separate supply for the output gate driver, allowing 10V
gate drive from input voltages as low as 3V. The LT1950’s
operating frequency can be set with an external resistor
over a 100kHz to 500kHz range and a SYNC pin allows the
part to be synchronized to an external clock. Additional
programmability exists for leading edge blanking and
slope compensation.
A fast current sense comparator achieves 60ns current
sense delay and the error amplifier is a true voltage mode
error amplifier, allowing a wide range of compensation
networks. An accurate shutdown pin with programmable
hysteresis is available for undervoltage lockout and shut-
down. The LT1950 is available in a small 16-Pin SSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
36V to 72V DC to 26V/5A (Single Switch) Forward Converter
2.5V
0.1µF
249k
4.99k
SLOPE
VIN
VREF
VIN2
BOOST VSEC
ROSC
SHDN
LT1950
BLANK GATE
SYNC
GND
ISENSE
PGND
FB COMP
10VBIAS
VIN
470k
MBRB20200 47µH
47µF
1µF 18k
Si7450
0.015
4.7k
0.022µF 100k
1950 TA01a
VOUT
26V
5A
Efficiency vs Load Current
95
VIN = 36V
90 VIN = 48V
VIN = 72V
85
80
75
70
0.5
1.5 2.5 3.5 4.5
LOAD CURRENT (A)
5.5
s19n501T9A5010b 1950fs
1


Linear Technology Electronic Components Datasheet

LT1950 Datasheet

Single Switch PWM Controller

No Preview Available !

www.DataSheet.in
LT1950
ABSOLUTE AXI U RATI GS
(Note 1)
BOOST ....................................................... –0.3V to 35V
VIN, VIN2, SHDN ......................................... –0.3V to 25V
FB, SYNC, VSEC ........................................... –0.3V to 6V
COMP, BLANK .......................................... –0.3V to 3.5V
SLOPE ...................................................... –0.3V to 2.5V
ISENSE ......................................................... –0.3V to 1V
ROSC .................................................................... –50µA
VREF .................................................................... –10mA
Operating Junction Temperature Range
LT1950EGN/LT1950IGN (Notes 2, 5) ... – 40°C to 125°C
Storage Temperature Range ..................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
COMP 1
FB 2
ROSC 3
SYNC 4
SLOPE 5
VREF 6
SHDN 7
GND 8
16 VSEC
15 VIN
14 BOOST
13 PGND
12 GATE
11 VIN2
10 ISENSE
9 BLANK
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
TJMAX = 125°C, θJA = 110°C/W,
θJC (PIN 8) = 30°C/W
ORDER PART
NUMBER
LT1950EGN
LT1950IGN
GN PART MARKING
1950E
1950I
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. COMP = open, FB = 1.4V, ROSC = 249k, SYNC = 0V, SLOPE = open, VREF
= 0.1µF, SHDN = VIN, BLANK = 0V, ISENSE = 0V, VIN2 = 15V, GATE = 1nF, BOOST = open, VIN = 15V, VSEC = 0V, unless otherwise
specified.
PARAMETER
PWM Controller
Operating Input Voltage
Minimum Start-Up Voltage
VIN Quiescent Current
VIN Shutdown Current
Shutdown Threshold
Shutdown Pin Current
Shutdown Pin Current Hysteresis
VIN2 Quiescent Current
VIN2 Shutdown Current
VREF (External Output)
Output Voltage
Line Regulation
Load Regulation
Oscillator
Frequency: fOSC
Minimum Programmable fOSC
Maximum Programmable fOSC
SYNC Input Resistance
SYNC Switching Threshold
SYNC Frequency/fOSC
fOSC Line Reg
VROSC
CONDITIONS
MIN TYP MAX UNITS
IVREF = 0µA
IVREF = 0µA
IVREF = 0µA, FB = 1V, ISENSE = 0.2V
SHDN = 0V
q 3.0
25
q 2.6 3.0
2.3 3.0
5 20
3V < VIN < 25V
SHDN = 70mV Above Threshold
q 1.261 1.32 1.379
–7 –10 –13
SHDN = 100mV Below Threshold
4 7 10
I(VREF) = 0µA, FB = 1V, ISENSE = 0.2V
SHDN = 0V, VIN2 = 2.7V (Boost Diode from VIN = 3V)
1.7 2.5
500 700
V
V
mA
µA
V
µA
µA
mA
µA
IVREF = 0µA
IVREF = 0µA, 3V < VIN < 25V
0µA < IVREF < 2.5mA
q 2.425
2.500
1
1
2.575
5
5
V
mV
mV
ROSC = 249k, FB = 1V
ROSC = 499k
ROSC = 90.9k
(ROSC = 249k, fOSC =200kHz), FB = 1V (Note 7)
3V < VIN < 25V
9.5V < VIN2 < 25V
q 170 200 230
kHz
85 100 115
kHz
440 500 560
kHz
20 k
1.5 2.2
V
1.25 1.5
0.05 0.15
%/V
0.05 0.25
%/V
1V
sn1950 1950fs
2


Part Number LT1950
Description Single Switch PWM Controller
Maker Linear Technology
PDF Download

LT1950 Datasheet PDF






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