LTC4269CDKD-2#PBF Linear Technology, LTC4269CDKD-2#PBF Datasheet - Page 15
LTC4269CDKD-2#PBF
Manufacturer Part Number
LTC4269CDKD-2#PBF
Description
IC PD/SYNC FORWARD CTRLR 32-DFN
Manufacturer
Linear Technology
Type
Power Over Ethernet (PoE)r
Datasheet
1.LTC4269CDKD-2PBF.pdf
(34 pages)
Specifications of LTC4269CDKD-2#PBF
Applications
Power Interface Switch for Power Over Ethernet (PoE) Devices
Voltage - Supply
14 V ~ 16 V
Operating Temperature
0°C ~ 70°C
Mounting Type
Surface Mount
Package / Case
32-DFN
Current - Supply
1.35mA
Interface
IEEE 802.3af
Controller Type
Powered Device Interface Controller (PD)
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
applicaTions inForMaTion
also ceases operation for classification and turns off the
internal Hot Swap FET. If this feature is not used, connect
SHDN to V
CLASSIFICATION
Classification provides a method for more efficient power
allocation by allowing the PSE to identify a PD power clas-
sification. Class 0 is included in the IEEE specification for
PDs that don’t support classification. Class 1-3 partitions
PDs into three distinct power ranges. Class 4 includes the
new power range under IEEE 802.3at (see Table 2).
During classification probing, the PSE presents a fixed
voltage between 15.5V and 20.5V to the PD (Figure 1).
The LTC4269-2 asserts a load current representing the
PD power classification. The classification load current
is programmed with a resistor R
from Table 2.
Table 2. Summary of Power Classifications and LTC4269-2
R
2-EVENT CLASSIFICATION AND THE T2P PIN
A Type 2 PSE may declare the availability of high power by
performing a 2-event classification (Layer 1) or by com-
municating over the high speed data line (Layer 2). A Type
2 PD must recognize both layers of communication. Since
CLASS
CLASS
0
1
2
3
4
PSE
TO
Resistor Selection
USAGE
Figure 3. 25k Signature Resistor with Disable
Type 1
Type 1
Type 1
Type 1
Type 2
PORTN
SHDN
V
LTC4269-2
PORTN
POWER LEVELS
AT INPUT OF PD
.
0.44 to 12.95
6.49 to 12.95
12.95 to 25.5
0.44 to 3.84
3.84 to 6.49
MAXIMUM
(W)
14k
CLASSIFICATION
LOAD CURRENT
SIGNATURE DISABLE
NOMINAL
25k SIGNATURE
RESISTOR
(mA)
CLASS
<0.4
10.5
18.5
28
40
V
PORTP
that is chosen
42692 F03
LTC4269-2
RESISTOR
(Ω, 1%)
R
Open
69.8
45.3
30.9
CLASS
124
Layer 2 communications takes place directly between the
PSE and the PD, the LTC4269-2 concerns itself only with
recognizing 2-event classification.
In 2-event classification, a Type 2 PSE probes for power
classification twice. Figure 4 presents an example of a
2-event classification. The 1st classification event occurs
DETECTION V1
PSE
DETECTION I
DETECTION V2
DETECTION I
Figure 4. V
Result of 2-Event Classification
40mA
INRUSH = 100mA R
I
LOAD
–10
–20
–30
–40
–50
R
50
40
30
20
10
50
40
30
20
10
CLASS
I
IN
=
1
1ST CLASS
2
V
R
1ST CLASS
PORTP
LOAD
NEG
2ND CLASS
2ND CLASS
R
V
dV
dt
CLASS
PORTN
INRUSH
, T2P and PD Current as a
UVLO
LTC4269-2
=
CLASS
INRUSH
1ST MARK
2ND MARK
2ND MARK
1ST MARK
C1
V
PORTP
V
= 30.9Ω
T2P
NEG
ON
ON
LTC4269-2
UVLO
= R
TRACKS
V
UVLO
R
PORTN
LOAD, I
LOAD
42692 F04
LOAD
TIME
TIME
TIME
C1
C1
LOAD
42692fb