LTC4268-1 Datasheet, PDF (24/48 Pages) Linear Technology – High Power PD with Synchronous NoOpto Flyback Controller

LTC4268-1
APPLICATIONS INFORMATION
OPTION 1: AUXILIARY POWER INSERTED BEFORE LTC4268-1
RJ45 _TX+
1
TX^–
2 _RX+
3
T1
~+
TO PHY BR1
D3
SMAJ58A
TVS
C14
0.1μF
100V
RX^–
6
SPARE⁺
4
5
7
SPARE^–
8
+
ISOLATED
WALL
V_WW
TRANSFORMER _–
~–
~+
BR2
~–
D8
S1B
V_PORTP
LTC4268-1
V_PORTN V_NEG
C1
V_IN
• 42V ≤ V_WW ≤ 57V
• NO POWER PRIORITY ISSUES
• LTC4268-1 CURRENT LIMITS FOR BOTH PoE AND V_WW
OPTION 2: AUXILIARY POWER INSERTED AFTER LTC4268-1 WITH SIGNATURE DISABLED
RJ45 _TX+
1
TX^–
2 _RX+
3
RX^–
6
T1
~+
TO PHY _BR1
~–
SPARE⁺
4
5
7
SPARE^–
8
+
ISOLATED
WALL
V_WW
TRANSFORMER _–
~+
BR2
~–
D3
SMAJ58A
TVS
C14
0.1μF
100V
4.7k
V_PORTP
BSS63 _LTC4268-1
100k
SHDN
D9
S1B
V_PORTN V_NEG
D10
S1B
C1
V_IN
• V_WW ANY VOLTAGE BASED ON PD LOAD
• REQUIRES EXTRA DIODE
• SEE APPS REGARDING POWER PRIORITY
OPTION 3: AUXILIARY POWER APPLIED TO LTC4268-1 AND PD LOAD
RJ45 _TX+
1
TX^–
2 _RX+
3
RX^–
6
T1
~+
TO PHY _BR1
~–
SPARE⁺
4
5
7
SPARE^–
8
+
ISOLATED
WALL
V_WW
TRANSFORMER _–
~+
BR2
~–
D3
SMAJ58A
TVS
C14
0.1μF
100V
V_PORTP
LTC4268-1
V_PORTN V_NEG
D10
S1B
C1
V_IN
• 42V ≤ V_WW ≤ 57V
• NO POWER PRIORITY ISSUES
• NO LTC4268-1 CURRENT LIMITS FOR V_WW
OPTION 4: AUXILIARY POWER APPLIED TO ISOLATED LOAD
RJ45 _TX+
1
TX^–
2 _RX+
3
RX^–
6
T1
~+
TO PHY _BR1
~–
SPARE⁺
4
5
7
SPARE^–
8
+
ISOLATED
WALL
V_WW
TRANSFORMER _–
~+
BR2
~–
D3
SMAJ58A
TVS
C14
0.1μF
100V
V_PORTP
PG
LTC4268-1
SHDN GND
V_PORTN V_NEG
C1
ISOLATED DC/DC CONVERTER
DRIVE
LOAD
• V_WW ANY VOLTAGE BASED ON PD LOAD
• SEE APPS REGARDING POWER PRIORITY
• BEST ISOLATION
Figure 10. Interfacing Auxiliary Power Source to the PD
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