LTC3900
20
3900fb
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2003
LT 0511 REV B • PRINTED IN USA
relaTeD parTs
Typical applicaTion
PART NUMBER DESCRIPTION COMMENTS
LT1952/LT1952-1 Synchronous Forward Converter Controllers Ideal for Medium Power 24V or 48V Input Isolated Applications
LTC3901 Secondary Side Synchronous Driver for Push-Pull and Full
Bridge Converters
Similar to the LTC3900, Used in Full Bridge and Push-Pull
Converters
LT4430 Secondary Side Optocoupler Driver Optocoupler Driver with Precise Reference Voltage
LT1431 Programmable Reference Adjustable Shunt Voltage Regulator with 100mA Sink Capability
LTC3726/LTC3725 Synchronous No Opto Forward Converter Controller Chip Set Ideal for Medium Power 24V or 48V Input Isolated Applications
LTC3723-1/
LTC3723-2
Synchronous Push-Pull Controllers High Efficiency with On-Chip MOSFET Drivers
LTC3721-1/
LTC3721-2
Nonsynchronous Push-Pull Controllers Minimizes External Components, On-Chip MOSFET Drivers
LTC3722/
LTC3722-2
Synchronous Phase Modulated Full Bridge Controllers Ideal for High Power 24V or 48V Input Applications
36V to 72V Input to 12V at 20A “No Optocoupler” Synchronous “Bus Converter”
LTC3900-Based Synchronous “Bus Converter” Efficiency vs Load Current
•
••
••
LTC3900
8V
BIAS
V
U1
V
U1
220pF
8V
BIAS
3
FG
5
CG
V
IN
36V TO 72V
PA0815.002
BAS516
BCX55
V
OUT
12V, ±10%,
20A MAX
10k
10k
10k
C
T
1nF
1µF
R
T
15k
560Ω
L1: PULSE PA1494.242
ALL CAPACITORS ARE TDK, X5R CERAMIC
C
OUT
33µF, 16V
X5R, TDK
×3
0.1µF
2.2µF, 100V
×2
1nF
BAT
760
12V
Si7370
×2
PH4840
×2
18V
Q4470-B
82k
47k
3900 TA07a
L1
2.4µH
SD_V
SEC
OUT
LT1952
7 14
R
OSC
V
IN
3 15
BLANK GND
9 8
SS_MAXDC PGND
5 13
DELAY
12
V
R
= 2.5V OC
6 11
COMP I
SENSE
1 10
FB = 1.23V SOUT
2 16
PH21NQ15
×2
1
GND
6
CS
+
2
V
CC
4
CS
–
7
SYNC
8
TIMER
370k
9mΩ
1µF
470Ω
39k
13.2k
115k
27k
0.47µF
0.1µF
10k59k
LOAD CURRENT (A)
4
EFFICIENCY (%)
96.0
95.5
95.0
94.5
94.0
93.5
93.0
10 12 1486 16 18 20
3900 TA07b
V
IN
= 48V
V
OUT
= 12V
16
12
8
4
POWER LOSS (W)
EFFICIENCY
POWER LOSS
