LTC4257CDD#PBF Linear Technology, LTC4257CDD#PBF Datasheet - Page 14

• Manufacturer Part Number: LTC4257CDD#PBF
• Description: IC CONTROLLER POE INTERFACE 8DFN
• Manufacturer: Linear Technology
• Type: Power over Ethernet Switch (PoE)r

Specifications of LTC4257CDD#PBF

• Applications: IP Phones, Power over LAN, Network Routers and Switches
• Internal Switch(s): Yes
• Current Limit: 350mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-WFDFN Exposed Pad
• Linear Misc Type: Negative Voltage
• Package Type: DFN EP
• Operating Supply Voltage (max): -57V
• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Product Depth (mm): 3mm
• Product Length (mm): 3mm
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LTC4257
14
RJ45
RJ45
RJ45
U
1
2
3
6
4
5
7
8
1
2
3
6
4
5
7
8
1
2
3
6
4
5
7
8
TX
TX
RX
RX
TX
TX
RX
RX
TX
TX
RX
RX
+
–
+
–
+
–
+
–
+
–
+
–
SPARE
SPARE
SPARE
SPARE
SPARE
SPARE
U
+
–
+
–
+
–
TRANSFORMER
TRANSFORMER
TRANSFORMER
ISOLATED
ISOLATED
ISOLATED
WALL
WALL
WALL
W
T1
T1
T1
OPTION 3: AUXILIARY POWER APPLIED TO LTC4257 AND PD LOAD
OPTION 1: AUXILIARY POWER INSERTED BEFORE LTC4257
OPTION 2: AUXILIARY POWER INSERTED AFTER LTC4257
Figure 9. Auxiliary Power Source for PD
44V TO 57V
+
–
+
–
+
–
44V TO 57V
TO PHY
TO PHY
TO PHY
U
~
~
~
~
~
~
~
~
~
~
~
~
DF01SA
DF01SA
DF01SA
DF01SA
DF01SA
DF01SA
BR1
BR2
BR1
BR2
BR1
BR2
+
–
+
–
+
–
+
–
+
–
+
–
S1B
D8
D3
SMAJ58A
TVS
D3
SMAJ58A
TVS
D3
SMAJ58A
TVS
4
4
4
V
V
V
IN
IN
IN
LTC4257
LTC4257
LTC4257
V
V
V
GND
GND
GND
OUT
OUT
OUT
C14
0.1µF
100V
C14
0.1µF
100V
C14
0.1µF
100V
D10
S1B
8
5
8
5
8
5
42571 F09
MINIMUM
LOAD
S1B
D10
S1B
D9
C1
C1
LOAD
PD
LOAD
PD
C1
LOAD
PD
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