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LT1952EGN-1#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
LT1952/LT1952-1
1
19521fe
TYPICAL APPLICATION
DESCRIPTION
Single Switch Synchronous
Forward Controller
The LT
®
1952/LT1952-1 are current mode PWM controllers
optimized to control the forward converter topology, using
one primary MOSFET. The LT1952/LT1952-1 provide
synchronous rectifier control, resulting in extremely
high efficiency. A programmable Volt-Second clamp
provides a safeguard for transformer reset that prevents
saturation. This allows a single MOSFET on the primary
side to reliably run at greater than 50% duty cycle for high
MOSFET, transformer and rectifier utilization. The devices
include soft-start for controlled exit from shutdown and
undervoltage lockout. A precision 107mV current limit
threshold, independent of duty cycle, combines with soft-
start to provide hiccup short-circuit protection. The LT1952
is optimized for micropower bootstrap start-up from high
input voltages. The LT1952-1 allows start-up from lower
input voltages. Programmable slope compensation and
leading edge blanking allow optimization of loop bandwidth
with a wide range of inductors and MOSFETs. Each device
can be programmed over a 100kHz to 500kHz frequency
range and the part can be synchronized to an external
clock. The error amplifier is a true op amp, allowing a wide
range of compensation networks. The LT1952/LT1952-1
are available in a small 16-pin SSOP package.
36V to 72V Input, 12V at 20A Semi-Regulated Bus Converter
FEATURES
APPLICATIONS
n
Synchronous Rectifier Control for High Efficiency
n
Programmable Volt-Second Clamp
n
Output Power Levels from 25W to 500W
n
Low Current Start-Up
(LT1952: 460µA; V
IN
On/Off = 14.25V/8.75V)
(LT1952-1: 400µA; V
IN
On/Off = 7.75V/6.5V)
n
True PWM Soft-Start
n
Low Stress Short-Circuit Protection
n
Precision 107mV Current Limit Threshold
n
Adjustable Delay for Synchronous Timing
n
Accurate Shutdown Threshold with Programmable
Hysteresis
n
Programmable Slope Compensation
n
Programmable Leading Edge Blanking
n
Programmable Frequency (100kHz to 500kHz)
n
SynchronizabletoanExternalClockupto1.5•f
OSC
n
Internal 1.23V Reference
n
2.5V External Reference
n
Current Mode Control
n
Small 16-Pin SSOP Package
n
Telecommunications Power Supplies
n
Industrial and Distributed Power
n
Isolated and Non Isolated DC/DC Converters
V
IN
V
IN
T1
PA0905
SUPPLY FROM BIAS
WINDING OF T1
Si7370
×2
PH4840
×2
L1
PA1494.242
47µF
16V
X5R
×2
V
OUT
12V
20A
220pF
560Ω
T2
1952 TA01
V
REF
COMP
SS_MAXDC
SD_V
SEC
FB
SYNC
GND
V
IN
OUT
OC
I
SENSE
SOUT
LT1952/
LT1952-1
BLANK DELAY
R
OSC
0.1µF
40k
16V
340k
13k
52.3k
40k 40k
PGND
178k
100k
Si7450
0.005Ω
SYNC
FG
CG
LTC3900
10µF
0.1µF
12V Bus Converter
V
OUT
vs V
IN
V
IN
(V)
36
8
V
OUT
(V)
10
16
48
60
66
1952 TA01b
14
12
42
54
72
L, LT, LTC and LTM are registered trademarks and ThinSOT is a trademark of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
LT1952/LT1952-1
2
19521fe
PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS
V
IN
(Note 8) ...............................................–0.3V to 25V
SYNC, SS_MAXDC, SD_V
SEC
, I
SENSE
, OC ....–0.3V to 6V
COMP, BLANK, DELAY
...............................–0.3V to 3.5V
FB ................................................................–0.3V to 3V
R
OSC
..................................................................... –50µA
V
REF
....................................................................–10mA
Operating Junction Temperature Range (Notes 2, 5)
E-, I-Grades .......................................–40°C to 125°C
MP-Grade .......................................... –55°C to 125°C
Storage Temperature Range
...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
.................. 300°C
(Note 1)
GN PACKAGE
16-LEAD PLASTIC SSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
COMP
FB
R
OSC
SYNC
SS_MAXDC
V
REF
SD_V
SEC
GND
SOUT
V
IN
OUT
PGND
DELAY
OC
I
SENSE
BLANK
T
JMAX
= 125°C, q
JA
= 110°C/W, q
JC
= 40°C/W
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1952EGN#PBF LT1952EGN#TRPBF 1952 16-Lead Plastic SSOP –40°C to 125°C
LT1952IGN#PBF LT1952IGN#TRPBF 1952I 16-Lead Plastic SSOP –40°C to 125°C
LT1952MPGN#PBF LT1952MPGN#TRPBF 1952 16-Lead Plastic SSOP –55°C to 125°C
LT1952EGN-1#PBF LT1952EGN-1#TRPBF 19521 16-Lead Plastic SSOP –40°C to 125°C
LT1952IGN-1#PBF LT1952IGN-1#TRPBF 1952I1 16-Lead Plastic SSOP –40°C to 125°C
LT1952MPGN-1#PBF LT1952MPGN-1#TRPBF 19521 16-Lead Plastic SSOP –55°C to 125°C
LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1952EGN LT1952EGN#TR 1952 16-Lead Plastic SSOP –40°C to 125°C
LT1952IGN LT1952IGN#TR 1952I 16-Lead Plastic SSOP –40°C to 125°C
LT1952MPGN LT1952MPGN#TR 1952 16-Lead Plastic SSOP –55°C to 125°C
LT1952EGN-1 LT1952EGN-1#TR 19521 16-Lead Plastic SSOP –40°C to 125°C
LT1952IGN-1 LT1952IGN-1#TR 1952I1 16-Lead Plastic SSOP –40°C to 125°C
LT1952MPGN-1 LT1952MPGN-1#TR 19521 16-Lead Plastic SSOP –55°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
LT1952/LT1952-1
3
19521fe
PARAMETER CONDITIONS MIN TYP MAX UNITS
PWM CONTROLLER
Operational Input Voltage I(V
REF
) = 0µA
l
V
IN
OFF 25 V
V
IN
Quiescent Current I(V
REF
) = 0µA, I
SENSE
= OC = Open 5.2 6.5 mA
V
IN
Start-up Current (LT1952) FB = 0V, SS_MAXDC = 0V (Notes 4, 9)
l
460 700 µA
V
IN
Start-up Current (LT1952-1) FB = 0V, SS_MAXDC = 0V (Notes 4, 9)
l
400 575 µA
V
IN
Shutdown Current SD_V
SEC
= 0V 240 350 µA
SD_V
SEC
Threshold 10V < V
IN
< 25V
l
1.261 1.32 1.379 V
SD_V
SEC (ON)
Current SD_V
SEC
= SD_V
SEC
Threshold + 100mV 0 µA
SD_V
SEC (OFF)
Current SD_V
SEC
= SD_V
SEC
Threshold – 100mV 8.3 10 11.7 µA
V
IN ON
(LT1952)
l
14.25 15.75 V
V
IN OFF
(LT1952)
l
8.75 9.25 V
V
IN HYSTERESIS
(LT1952)
l
3.75 5.5 6.75 V
V
IN ON
(LT1952-1) E-, I-Grades
MP-Grade
l
l
7.75
7.75
8.13
8.3
V
V
V
IN OFF
(LT1952-1)
l
6.5 6.82 V
V
IN HYSTERESIS
(LT1952-1)
l
0.95 1.25 V
V
REF
Output Voltage I(V
REF
) = 0µA
l
2.425 2.5 2.575 V
Line Regulation I(V
REF
) = 0µA, 10V < V
IN
< 25V 1 10 mV
Load Regulation 0µA < I(V
REF
) < 2.5mA 1 10 mV
OSCILLATOR
Frequency: f
OSC
R
OSC
= 178k, FB = 1V, SS_MAXDC = 1.84V
l
165 200 240 kHz
Minimum Programmable f
OSC
Maximum Programmable f
OSC
R
OSC
= 365k, FB = 1V
R
OSC
= 64.9k, COMP = 2.5V, SD_V
SEC
= 2.64V
80
440
100
500
120
560
kHz
kHz
SYNC Input Resistance 18 kΩ
SYNC Switching Threshold FB = 1V 1.5 2.2 V
SYNC Frequency/f
OSC
FB = 1V (Note 7) 1.25 1.5
f
OSC
Line Reg FB = 1V, R
OSC
= 178k; 10V < V
IN
< 25V,
SS_MAXDC = 1.84V
0.05 0.33 %/V
V
ROSC
R
OSC
Pin voltage 1 V
ERROR AMPLIFIER
FB Reference Voltage 10V < V
IN
< 25V, V
OL
+ 0.2V < COMP < V
OH
– 0.2
l
1.201 1.226 1.250 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 –4 –9 mA
COMP Sink Current COMP = 1.6V 4 10 mA
COMP Current (Disabled) FB = V
REF
, COMP = 1.6V 18 23 28 µA
COMP High Level: V
OH
FB = 1V, I
(COMP)
= –250µA 2.7 3.2 V
COMP Active Threshold FB = 1V, SOUT Duty Cycle > 0 % 0.7 0.8 V
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). COMP = open, FB = 1.4V, R
OSC
= 178k, SYNC = 0V,
SS_MAXDC = V
REF
, V
REF
= 0.1µF, SD_V
SEC
= 2V, BLANK = 121k, DELAY = 121k, I
SENSE
= 0V, OC = 0V, OUT = 1nF, V
IN
= 15V, SOUT = open,
unless otherwise specified.
ELECTRICAL CHARACTERISTICS
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LT1952EGN-1#TRPBF

Mfr. #:
Buy LT1952EGN-1#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 1x Switch Sync For Cntr
Lifecycle:
New from this manufacturer.
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