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PDF LT8309 Data sheet ( Hoja de datos )
| Número de pieza | LT8309 | |
| Descripción | Secondary-Side Synchronous Rectifier Driver | |
| Fabricantes | Linear | |
| Logotipo |  |
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LT8309
Secondary-Side
Synchronous Rectifier Driver
Features
n Works with DCM and BCM/CrCM Conduction Mode
Flyback Topologies
n VCC: 4.5V to 40V
n Supports Up to 150V MOSFETs
n 26ns Turn-Off Propagation Delay
n Accurate Minimum On and Off Timers for Reliable
Operation
n Adjustable and Accurate Trip Point: +5mV to –30mV
n 1Ω Gate Driver Pull-Down
n SOT-23 5-Lead Package
Applications
n High Output Current Flybacks
n High Efficiency Flybacks
Description
The LT®8309 is a secondary-side synchronous rectifier
driver that replaces the output rectifier diode in a flyback
topology. By replacing the diode with a N-channel MOSFET,
applications are no longer restricted by the heat constraints
of the output diode. The IC replicates the behavior of a
diode by sensing the drain-to-source voltage to determine
when the current becomes negative. The LT8309's low
minimum on- and off-times help improve noise immunity.
The fast propagation delay of 26ns allows applications to
operate in discontinuous conduction mode (DCM) and
critical conduction mode (CrCM). The gate driver features
a 0.8Ω pull-down device for fast turn-offs. The 40V VCC
rating allows the part to be driven from the output volt-
age or the rectified drain voltage of the MOSFET. A low
quiescent current of 400µA maximizes efficiency at low
output currents.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Application
40W, 5V Isolated Telecom Supply
VIN
36V TO
72V
10µF
15.4k
412k
EN/UVLO
VIN
LT3748
RFB
RREF
5.33:1
60Ω •
100pF •
147k
6.04k
10Ω
1µF
2.2k
30.9k
0.1µF
TC GATE
SS SENSE
VC GND INTVCC
12.1k
15nF
4.7µF
12mΩ
400µF
LT8309
VCC
DRAIN
GATE INTVCC
GND
4.7µF
VOUT +
5V, 8A
6.2V
VOUT–
8309 TA01a
Efficiency vs Load Current
100
95
90 VIN = 48V WITH LT8309
85
80 VIN = 48V WITH PDS760 DIODE
75
70
65
012345678
LOAD CURRENT (A)
8309 TA01b
For more information www.linear.com/LT8309
8309fa
1
1 page  
Typical Performance Characteristics
DRAIN Pin Current
vs Temperature
14
12
10
8
6
4
2
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8309 G10
Latch Reset Threshold
vs Temperature
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8309 G13
Comparator Turn-On Threshold
vs Temperature
–40
–45
–50
–55
–60
–65
–70
–75
–80
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8309 G11
GATE Rise and Fall Time vs Charge
200
150
RISE TIME
100
50
0
0
FALL TIME
30 60 90 120 150
CHARGE (nC)
8309 G14
LT8309
Comparator Turn-Off Threshold
vs Temperature
40
35
30
25
20
15
10
5
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8309 G12
GATE Current vs Charge
4.0
3.5
3.0 GATE SINK CURRENT
2.5
2.0
1.5 GATE SOURCE CURRENT
1.0
0.5
0
0 30 60 90 120 150
CHARGE (nC)
8309 G15
For more information www.linear.com/LT8309
8309fa
5
5 Page 
Typical Applications
40W, 5V Isolated Telecom Supply
LT8309
VIN
36V TO
72V
5.33:1 PULSE: PA1735NL
10µF
412k
VIN
EN/UVLO
15.4k
LT3748
RRRFEBF
60Ω
100pF •
•
147k
6.04k
30.9k
TC
GATE
INFINEON:
SS SENSE BSC320N20NS3
VC GND INTVCC
12mΩ
12.1k
0.1µF
4.7µF
15nF
400µF
10Ω
VCC
1µF LT8309
2.15k
INFINEON:
BSC028N06LS
DRAIN
GATE
INTVCC
GND
4.7µF
VOUT+
5V, 8A
6.2V
CENTRAL SEMI:
CMZ5920B
VOUT–
8309 TA03
For more information www.linear.com/LT8309
8309fa
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet LT8309.PDF ] | |
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