SI3461-KIT Silicon Laboratories Inc, SI3461-KIT Datasheet - Page 10

• Manufacturer Part Number: SI3461-KIT
• Description: BOARD EVAL FOR SI3461
• Manufacturer: Silicon Laboratories Inc
• Type: Controllers & Processorsr

Specifications of SI3461-KIT

• Main Purpose: Special Purpose DC/DC, Power Over Ethernet
• Board Type: Fully Populated
• Utilized Ic / Part: Si3461
• Ethernet Connection Type: 10/100 Base-T, IEEE 802.3
• Interface Type: Ethernet
• Operating Voltage: 12 V to 15 V
• Operating Current: 10 mA
• Product: Modules
• For Use With/related Products: Si3460
• Lead Free Status / RoHS Status: Lead free / RoHS non-compliant
• Current - Output: -
• Voltage - Output: -
• Voltage - Input: -
• Power - Output: -
• Frequency - Switching: -
• Outputs And Type: -
• Regulator Topology: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1843

Si3461-EVB
6.5. Disconnect (Power Removal)
The Si3461 supports a robust disconnect algorithm. If the output current drops below 7.5 mA, a timer is started to
count towards a time-out of 350 ms. If the output current again exceeds the 7.5 mA threshold, the timer is
decremented at 10 times the increment rate towards zero. Power is removed from the output if the timer reaches
the 350 ms limit, but the Si3461 will continue to provide power if the output current is above the 7.5 mA limit for at
least a fraction of the 350 ms timeout (unless an overload condition is sensed). The only other way to force the
Si3461 to disconnect power is by doing a reset.
6.6. Current Limit Control
The Si3461's overcurrent trip point, I
, is determined by the output power set during the classification stage
CUT
power granting process and the actual output voltage. If the output current exceeds the threshold, a timer counts
up towards a timeout of 60 ms. If the current drops below the set threshold, the timer counts down towards zero at
1/16th the rate. If the timer reaches the set timeout, an overcurrent fault is declared, and the channel is shut down
by turning off the pass FET. Additionally, for Class 4 devices, if the output current reaches the ILIM level, the output
is shut down after 15 ms to protect the pass FET. After an overcurrent fault event, the LED will flash rapidly. As set
by the initial voltage on the STATUS pin at powerup, the Si3461 then automatically resumes the detection process
for "automatic restart configuration" unless the Si3461 is configured in a "restart after a disconnect condition"
mode.
For the automatic restart configuration, the LED will flash rapidly after an overcurrent event for 2.2 seconds, and a
new detection cycle will be initiated. The LED will then flash at a 1.5 Hz rate to show that the detection is in
progress.
In the restart on disconnect configuration, the LED will flash rapidly until an open-circuit condition is detected
before a new detection cycle will start. Normally, an open-circuit condition can be created by removing the Ethernet
cable from the Si3461-EVB's RJ-45 jack labelled "PoE". Power will not be provided until an open-circuit condition is
detected. Once the Si3461-EVB detects an open-circuit condition, the detection process begins. The status LED
blinks at a rate of 1.5 Hz, and the Si3461 is then allowed to go into classification and powerup mode if a valid PD
signature resistance is detected.
6.7. UVLO/OVLO
The Si3461-EVB reference design is optimized for 50 V nominal input voltages (44 V minimum to 57 V maximum).
If the input voltage drops below 42 V, a UVLO condition is declared, or, if it exceeds 60 V, an over-voltage condition
is declared, and the output is shut down in both cases. An undervoltage or an overvoltage event is a fault condition
reported through the status LED as a rapid blinking of 10 flashes per second. The UVLO and OVLO conditions are
continuously monitored in all operating states.
6.8. Status LED Function
During the normal detection sequence, the STATUS LED flashes approximately 1.5 times per second as the
detection process continues. After successful powerup, the LED glows continuously. If there is an error condition
(i.e., class level is beyond the programmed value or a fault or overcurrent condition has been detected), the LED
flashes rapidly at 10 times per second. This occurs for two seconds for normal error delay, and the detection
process automatically starts again after 2.2 s unless a "restart after disconnect condition" was set during the initial
configuration. Power will not be provided until an open-circuit condition is detected. Once the Si3461-EVB detects
an open-circuit condition, the LED blinks at 1.5 times per second.
If the PD is disconnected so that a disconnect event occurs, the LED starts flashing at 1.5 times per second once
the detect process resumes.
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