SI3460 Silicon Laboratories, SI3460 Datasheet - Page 11

• Manufacturer Part Number: SI3460
• Description: IEEE 802.3af PSE INTERFACE AND DC-DC CONTROLLER
• Manufacturer: Silicon Laboratories

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5. Si3460-EVB Functional Description
In combination with low-cost external components, the Si3460 controller provides a complete PSE solution for
embedded PoE applications. Included in the Si3460-EVB reference design is a digital PWM controller-based dc-dc
converter that simplifies overall system design by generating the –48 V PSE supply voltage. An isolated 11 to 16 V
input dc supply is all that is needed to supply the Si3460-EVB reference design. Refer to the Si3460-EVB User’s
Guide and schematics for descriptions in the following sections.
5.1. Reset State
At powerup or if reset is held low, the Si3460 is in an inactive state with the PWM turned off (the switcher FET, M1,
is off) and the pass FET, M2, is off.
5.2. Operating Mode Configuration
At powerup, the Si3460 reads the voltage on the STATUS pin, which is set by a resistor divider from V
ground. The STATUS pin voltage level configures all of the Si3460's operating modes as summarized in Table 8.
(no resistors populated)
(pullup resistor only)
Pin voltage at V
Pin Voltage
STATUS
< 0.25 V
2.75 V
2.25 V
1.75 V
1.25 V
3.0 V
2.5 V
2.0 V
1.5 V
1.0 V
0.5 V
EE
Supported (W)
Power Level
15.4
15.4
15.4
15.4
7.0
4.0
7.0
4.0
4.0
4.0
7.0
7.0
Table 8. Operating Modes
Classes Supported
Preliminary Rev. 0.4
All class levels
All class levels
All class levels
All class levels
Class 1 or 2
Class 1 or 2
Class 1 or 2
Class 1 or 2
Class 1
Class 1
Class 1
Class 1
Operating Mode
Midspan/
Endpoint
Endpoint
Endpoint
Endpoint
Endpoint
Endpoint
Endpoint
Midspan
Midspan
Midspan
Midspan
Midspan
Midspan
Auto restart after 2 s
Auto restart after 2 s
Auto restart after 2 s
Auto restart after 2 s
Auto restart after 2 s
Auto restart after 2 s
Restart Action on
Fault or Overload
Event Condition
Restart on RST
Restart on RST
Restart on RST
Restart on RST
Restart on RST
Restart on RST
Si3460
EE
to chip
11
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