LT1952EGN-1#PBF Linear Technology, LT1952EGN-1#PBF Datasheet - Page 22

• Manufacturer Part Number: LT1952EGN-1#PBF
• Description: IC CTLR PWM SGL SWITCH 16-SSOP
• Manufacturer: Linear Technology

Specifications of LT1952EGN-1#PBF

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 560kHz
• Duty Cycle: 90%
• Voltage - Supply: 6.82 V ~ 25 V
• Buck: No
• Boost: No
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 16-SSOP
• Frequency-max: 560kHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LT1952/LT1952-1
36V to 72V Input, 3.3V 40A Converter
An LT1952-based synchronous forward converter provides
the ideal solution for power supplies requiring high effi ciency
at low output voltages and high load currents. The 3.3V 40A
solution in Figure 18 achieves peak effi ciencies of 92.5%
(Figure 17) by minimizing power loss due to rectifi cation
at the output. Synchronous rectifi er control output SOUT,
with programmable delay, optimizes timing control for a
secondary side synchronous MOSFET controller (LTC3900)
which results in high effi ciency synchronous rectifi cation.
The LT1952/LT1952-1 use a precision current limit threshold
at the OC pin combined with a soft-start hiccup mode to
provide low stress output short-circuit protection. The
maximum output current will vary only 10% over the full V
range. During short-circuit the average power dissipation
of the circuit will be lower than 15% of maximum rated
power thanks to a soft-start controlled hiccup mode.
22
0.22μF
0.1μF
115k
2.2k
59k
13.2k
27k
22k
10k
33k
370k
L1: PA0713, PULSE ENGINEERING
ALL CAPACITORS X7R, CERAMIC, TDK
T2: COILCRAFT
7
3
9
5
6
1
2
SD_V
R
BLANK
SS_MAXDC
V
COMP
FB = 1.23V
R
OSC
= 2.5V
36V TO 72V
SEC
LT1952
+V
IN
Figure 18. 36V to 72V, 3.3V at 40A Synchronous Forward Converter
DELAY
I
PGND
SENSE
SOUT
GND
OUT
V
47k
82k
OC
IN
14
15
8
13
12
11
10
16
V
U1
18V
BAT760
470Ω
39k
BCX55
12V
V
U1
1μF
220pF
IN
BAS516
2.2mF
Si7846
0.1μF
10mΩ
This allows a signifi cant reduction in power component
sizing using the LT1952-based converter.
PA0912.002
Figure 17. LT1952-Based Synchronous Forward Converter
Effi ciency vs Load Current (For Circuit in Figure 18)
•
•
•
V
U1
1nF
Q4470-B
1mF
• •
T2
BIAS
8V
PS2801
Q2
PH3230
2x
94
93
92
91
90
89
88
87
86
0
560Ω
5
6
4
8
FG
GND
V
SYNC
CC
270Ω
LTC3900
BIAS
8V
10
PH3230
TIMER
OUTPUT CURRENT (A)
CS
CS
Q3
2x
LT1797
CG
+
–
15k
2.2nF
20
1
3
1
2
7
BIAS
8V
5
2
249k
18k
30
1nF
–
+
L1
4
3
10k
10k
10k
V
V
f
OSC
IN
OUT
80.6k
1μF
10k
= 48V
40
= 300kHz
= 3.3V
LT1009
8
4
C
100μF
3x
1952 F17
OUT
10k
50
0.1μF
1952 F18
V
3.3V, 40A
OUT
19521fd