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LT1950IGN#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
LT1950
1
1950fa
■
Wide Input Range: 3V to 25V
■
Programmable Volt-Second Clamp
■
Output Power Levels from 25W to 500W
■
Auxiliary Boost Converter Provides 10V Gate Drive
from V
IN
as Low as 3V
■
Programmable Operating Frequency (100kHz to
500kHz) with One External Resistor
■
Programmable Slope Compensation
■
Programmable Leading Edge Blanking
■
±2% Internal 1.23V Reference
■
Accurate Shutdown Pin Threshold with
Programmable Hysteresis
■
60ns Current Sense Delay
■
2.5V Auxiliary Reference Output
■
Synchronizable to an External Clock up to 1.5 • f
OSC
■
Current Mode Control
■
Small 16-Pin SSOP Package
■
Telecom Power Supplies
■
Automotive Power Supplies
■
Portable Electronic Equipment
■
Isolated and Nonisolated DC/DC Converters
Single Switch PWM
Controller with Auxiliary
Boost Converter
, LTC and LT are registered trademarks of Linear Technology Corporation.
SLOPE
V
REF
BOOST
R
OSC
BLANK
SYNC
GND
FB
V
IN
V
IN2
V
SEC
SHDN
GATE
I
SENSE
PGND
COMP
LT1950
1950 TA01a
0.1µF
249k
4.99k
4.7k
0.022µF
1µF
470k
18k
10V
BIAS
100k
V
IN
MBRB20200
47µH
47µF
V
OUT
26V
5A
0.015Ω
Si7450
2.5V
PA0581
Efficiency vs Load Current
LOAD CURRENT (A)
0.5
EFFICIENCY (%)
95
90
85
80
75
70
4.5
1950 TA01b
1.5
2.5
3.5
5.5
V
IN
= 48V
V
IN
= 36V
V
IN
= 72V
36V to 72V DC to 26V/5A (Single Switch) Forward Converter
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.
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
LT1950
2
1950fa
ORDER PART
NUMBER
GN PART MARKING
T
JMAX
= 125°C, θ
JA
= 110°C/W,
θ
JC
(PIN 8) = 30°C/W
1950E
1950I
LT1950EGN
LT1950IGN
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. COMP = open, FB = 1.4V, R
OSC
= 249k, SYNC = 0V, SLOPE = open, V
REF
= 0.1µF, SHDN = V
IN
, BLANK = 0V, I
SENSE
= 0V, V
IN2
= 15V, GATE = 1nF, BOOST = open, V
IN
= 15V, V
SEC
= 0V, unless otherwise
specified.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
TOP VIEW
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
COMP
FB
R
OSC
SYNC
SLOPE
V
REF
SHDN
GND
V
SEC
V
IN
BOOST
PGND
GATE
V
IN2
I
SENSE
BLANK
PARAMETER CONDITIONS MIN TYP MAX UNITS
PWM Controller
Operating Input Voltage I
VREF
= 0µA ● 3.0 25 V
Minimum Start-Up Voltage I
VREF
= 0µA ● 2.6 3.0 V
V
IN
Quiescent Current I
VREF
= 0µA, FB = 1V, I
SENSE
= 0.2V 2.3 3.0 mA
V
IN
Shutdown Current SHDN = 0V 5 20 µA
Shutdown Threshold 3V < V
IN
< 25V ● 1.261 1.32 1.379 V
Shutdown Pin Current SHDN = 70mV Above Threshold –7 –10 –13 µA
Shutdown Pin Current Hysteresis SHDN = 100mV Below Threshold 4 7 10 µA
V
IN2
Quiescent Current I(V
REF
) = 0µA, FB = 1V, I
SENSE
= 0.2V 1.7 2.5 mA
V
IN2
Shutdown Current SHDN = 0V, V
IN2
= 2.7V (Boost Diode from V
IN
= 3V) 500 700 µA
V
REF
(External Output)
Output Voltage I
VREF
= 0µA ● 2.425 2.500 2.575 V
Line Regulation I
VREF
= 0µA, 3V < V
IN
< 25V 1 5 mV
Load Regulation 0µA < I
VREF
< 2.5mA 1 5 mV
Oscillator
Frequency: f
OSC
R
OSC
= 249k, FB = 1V ● 170 200 230 kHz
Minimum Programmable f
OSC
R
OSC
= 499k 85 100 115 kHz
Maximum Programmable f
OSC
R
OSC
= 90.9k 440 500 560 kHz
SYNC Input Resistance 20 kΩ
SYNC Switching Threshold 1.5 2.2 V
SYNC Frequency/f
OSC
(R
OSC
= 249k, f
OSC
=200kHz), FB = 1V (Note 7) 1.25 1.5
f
OSC
Line Reg 3V < V
IN
< 25V 0.05 0.15 %/V
9.5V < V
IN2
< 25V 0.05 0.25 %/V
V
ROSC
1V
BOOST ....................................................... –0.3V to 35V
V
IN
, V
IN2
, SHDN ......................................... –0.3V to 25V
FB, SYNC, V
SEC
........................................... –0.3V to 6V
COMP, BLANK .......................................... –0.3V to 3.5V
SLOPE ...................................................... –0.3V to 2.5V
I
SENSE
......................................................... –0.3V to 1V
R
OSC
.................................................................... –50µA
V
REF
.................................................................... –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
LT1950
3
1950fa
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. COMP = open, FB = 1.4V, R
OSC
= 249k, SYNC = 0V, SLOPE = open, V
REF
= 0.1µF, SHDN = V
IN
, BLANK = 0V, I
SENSE
= 0V, V
IN2
= 15V, GATE = 1nF, BOOST = open, V
IN
= 15V, V
SEC
= 0V, unless otherwise
specified.
Error Amplifier
FB Reference Voltage 3V < V
IN
< 25V, V
OL
+ 0.2V < COMP < V
OH
– 0.2 ● 1.205 1.230 1.254 V
FB Input Bias Current FB = FB Reference Voltage –75 –200 nA
Open Loop Voltage Gain V
OL
+ 0.2V < COMP < V
OH
– 0.2 65 85 dB
Unity Gain Bandwidth (Note 6) 3 MHz
COMP Source Current FB = 1V, COMP = 1.6V ● –0.3 –1.1 –1.8 mA
COMP Sink Current FB = 1.4V, COMP = 1.6V 8 13 mA
COMP High Level: V
OH
FB = 1V, I
COMP
= – 250µA 2.5 V
COMP Active Threshold Start of GATE Switching (Duty Cycle > 0%) 1.0 V
COMP Low Level: V
OL
FB = 1.4V, I
COMP
= 250µA 0.15 V
Current Sense
I
SENSE
Maximum Threshold Duty Cycle < 10%, COMP = V
OH
90 100 110 mV
I
SENSE
Input Bias Current COMP = 2.5V, I
SENSE
= I
SENSE
Max Threshold –125 –170 –250 µA
Default Blanking Time FB = 1V, COMP = 2V, I
SENSE
= 75mV 110 ns
Adjustable Blanking Time FB = 1V, COMP = 2V, I
SENSE
= 75mV 290 ns
BLANK = 75k to Ground
Blanking Override Voltage– BLANK = Open, COMP = 2.5V (Note 4) 15 25 40 mV
I
SENSE
Maximum Threshold
Turn-Off Delay to Gate COMP = 2V 60 ns
Slope Compensation (Note 4) I
SENSE
Max Threshold (DC < 10%) – (DC = 80%) (Note 4)
Default, R
SLOPE
= ∞ 14 mV
2x Default, R
SLOPE
= 8k 28 mV
3x Default, R
SLOPE
= 3.3k 42 mV
Internal Switcher
Boost Switch I
LIMIT
V
IN2
= 8V, 3V < V
IN
< 10V 70 125 180 mA
Boost Switch Off Time V
IN2
= 8V, 3V < V
IN
< 10V 250 500 1000 ns
V
IN2
: Boost Disable 3V < V
IN
< 10V ● 9.5 11.0 11.75 V
V
IN2
: Boost Disable Hysteresis 3V < V
IN
< 10V –1.0 V
V
IN2
: Gate Enable 3V < V
IN
< 10V, FB = 1V (Note 4) ● 7.0 8.2 9.27 V
V
IN2
: Gate Enable Hysteresis 3V < V
IN
< 10V, FB = 1V (Note 4) –0.6 V
GATE Driver Output
GATE Rise Time FB = 1V, V
IN2
= 12V, C
L
= 1nF (Notes 3, 6) 50 ns
GATE Fall Time FB = 1V, V
IN2
= 12V, C
L
= 1nF (Notes 3, 6) 30 ns
GATE Clamp Voltage I
GATE
= 0µA, COMP = 2.5V, FB = 6V 11.5 13 14.5 V
GATE Low Level I
GATE
= 20mA 0.25 0.4 V
I
GATE
= 200mA 1.2 1.75 V
GATE High Level I
GATE
= –20mA, V
IN2
= 12V, COMP = 2.5V, FB = 6V 10 V
I
GATE
= –200mA, V
IN2
= 12V, COMP = 2.5V, FB = 6V 9.75 V
Maximum Duty Cycle FB = 1V, f
OSC
= 200kHz 90 95 97 %
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LT1950IGN#TRPBF

Mfr. #:
Buy LT1950IGN#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 1x Switch PWM Cntr w/ Auxiliary Boost Co
Lifecycle:
New from this manufacturer.
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