Datasheet
LTC4257
20
4257fb
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 1205 REV B • PRINTED IN USA
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
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SENSE
™ Current Mode Flyback, Adjustable Switching Frequency, Programmable Undervoltage
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®
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LTC3803 Current Mode Flyback DC/DC Controller in ThinSOT™ 200kHz Constant Frequency, Adjustable Slope Compensation,
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LTC4257-1 IEEE 802.3af PD Interface Controller 100V, 400mA Internal Switch, Dual Current Limit
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2
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LTC4259A-1 Quad IEEE 802.3af Power over Ethernet Controller AC or DC Disconnect, IEEE-Compliant PD Detection and
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LTC4267 IEEE 802.3af PD Interface Controller with 100V, 400mA Internal Switch, 16-Pin SSOP or 3mm × 5mm
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TYPICAL APPLICATIO
U
1
3
2
RX
–
6
RX
+
3
TX
–
2
TX
+
J1
T1
XFMR
RJ45
1
7
8
5
4
SPARE
–
SPARE
+
6
8
7
TXOUT
+
TXOUT
–
RXOUT
+
RXOUT
–
TO
PHY
R12
75Ω
R11
75Ω
0.01µF
200V
75Ω
C4
0.01µF
200V
C3
0.01µF
200V
C8
0.001µF
2kV
16
14
15
11
9
10
0.01µF
200V
75Ω
BR2
DF01SA
C14
0.1µF
100V
LTC4257
LTC1871
Q3
FDC2512
C1A
4.7µF
100V
Q2
FMMT625
D3
TVS
SMAJ58A
D4
MMBZ5235B
6.8V
R
CLASS
1%
NC
R
CLASS
NC
V
IN
GND
NC
PWRGD
V
OUT
RUN
I
TH
FB
FREQ
MODE/SYNC
SENSE
V
IN
INTV
CC
GATE
GND
~+
~–
BR1
DF01SA
~+
~–
C1B
2.2µF
100V
R10
100k
R
T
80.6k
1%
R14
12.4k
1%
R15
21k 1%
C6
1µF 6.3V
Q1
2N7002
C
C1
1nF
R
C
12k
R17
750Ω
R13
100k
L1
1µH
R16
100Ω
Q4
FMMT2222
D6
1N4148
R9
100k
R18
10k
+
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTOR VALUES ARE 5%
2. SELECT R
CLASS
FOR CLASS 1-4 OPERATION.
REFER TO DATA SHEET APPLICATIONS INFORMATION SECTION
3. CONNECT TO CHASSIS GROUND
C1A: PANASONIC ECEV2AA4R7P
C1B: TDK C5750X7R2A225KT
C8: AVX 1808GC102MAT
C9, C10, C12, C13: TDK C4532X5ROJ107
L1: LQLB2518T1ROM
T1: PULSE H2019
R5
0.1Ω
1%
C5
4.7µF
6.3V
•
4
2
11
9
T2
CTX-02-15242
D5
UPS840
12
4257 TA03
10
••
C9
100µF
X5R
6.3V
C10
100µF
X5R
6.3V
V
OUT
+
3.3V
AT 3A
V
OUT
–
+
+
C12
100µF
X5R
6.3V
C13
100µF
X5R
6.3V
+
+
3
2
Burst Mode is a registered trademark of Linear Technology Corporation. No R
SENSE
and ThinSOT are trademarks of Linear Technology Corporation.