Si3460-EVB
Rev. 1.2
5
Not Recom
m
en
ded
for N
ew D
esigns.
Please Co
ns
id
er Si3462 for
N
ew
D
esigns.
5. The Si3460 PSE Controller
In addition to providing a complete dc-dc controller to generate the PSE output supply, the Si3460 is a fully IEEE
compliant PSE power management controller. The Si3460 is specifically designed and configured to work with an
applications circuit (Si3460-EVB) that together implement a single port PSE solution for either midspans or
endpoints.
Referring to the detailed evaluation board schematics in Section “8. Si3460-EVB Schematics and PCB Layout”, the
overall functionality is described for each operating state of the Si3460 as follows:
5.1. Initialization and Operating Mode Configuration
The Si3460 is initialized at power up, or whenever pin 8 (RST) is held low and then allowed to transition high. Upon
reset (RST asserted), the voltage at the STATUS pin (as determined by resistors R28 and R30) is sensed to
determine the operating mode of the Si3460. The detection process begins immediately after initialization.
Any combination of the following three operating modes can be set by the R28 and R30 resistor pair, as indicated
below:
Classification level: sets what maximum power level the Si3460 will support.
Endpoint or midspan mode: controls the backoff timing per the IEEE specifications.
Restart action on fault or overload: determines whether or not the Si3460 will automatically restart after 2 s
when a fault or overload condition (e.g., input UVLO, output short-circuit event, classification power level
exceeded) is detected, or wait to restart until the RST pin is asserted.
Table 2. Operating Modes
Nominal Status Pin
Voltage
Operating Mode
R28, R30
Power Level
Supported (W)
Classes
Supported
Endpoint/
Midspan
Restart Action on
Fault or Overload
Event
Pin voltage at VEE
2 k
, NP
15.4
All class levels
Endpoint
Auto restart after 2 s
3.0 V
2.21 k
, 22.1 k
7.0
Class 1 or 2
2.75 V
2.37 k
, 11.8 k
4.0
Class 1
2.5 V
2.61 k
, 8.06 k
15.4
All class levels
Restart on RST low
or when open circuit
detected
2.25 V
2.94 k
, 6.19 k
7.0
Class 1 or 2
2.0 V
3.32 k
, 4.99 k
4.0
Class 1
1.75 V
3.83 k
, 4.22 k
4.0
Class 1
Midspan
Restart on RST low
or when open circuit
detected
1.5 V
4.42 k
, 3.57 k
7.0
Class 1 or 2
1.25 V
5.36 k
, 3.16 k
15.4
All class levels
1.0 V
6.81 k
, 2.80 k
4.0
Class 1
Auto restart after 2 s
0.5 V
14 k
, 2.26 k
7.0
Class 1 or 2
< 0.25 V
NP, 2 k
15.4
All class levels
