Datasheet

KSZ8041TL/FTL/MLL
DS00002436B-page 32  2017 Microchip Technology Inc.
3.22 100BASE-FX Fiber Operation (KSZ8041FTL Only)
100BASE-FX fiber operation is similar to 100BASE-TX copper operation with the differences being that the scrambler/
de-scrambler and MLT3 encoder/decoder are bypassed on transmission and reception. In addition, auto-negotiation is
bypassed, auto MDI/MDI-X is disabled, and speed is set to 100 Mbps. The duplex can be set to either half or full. Usu-
ally, it is set to full-duplex.
3.22.1 FIBER SIGNAL DETECT
In 100BASE-FX operation, FXSD (fiber signal detect), input pin 48, is usually connected to the fiber transceiver SD (sig-
nal detect) output pin. 100BASE-FX mode is activated when the FXSD input pin is greater than 1V. When FXSD is
between 1V and 1.8V, no fiber signal is detected and a Far-End Fault is generated. When FXSD is over 2.2V, the fiber
signal is detected.
100BASE-FX mode and signal detection is summarized in the following table:
FIGURE 3-9: KSZ8041TL/FTL/MLL POWER AND GROUND CONNECTIONS
TABLE 3-10: KSZ8041TL/FTL/MLL POWER PIN DESCRIPTION
Power Pin Pin Number Pin Type Description
V1.8_OUT 6 Output 1.8V supply output from KSZ8041TL/FTL/MLL
Decouple with 1 µF and 0.1 µF capacitors to ground.
VDD_1.8 31 Input Connect to V1.8_OUT (pin 6) through ferrite bead.
Decouple with 0.1 µF capacitor to ground.
VDDA_1.8 4, 5 Input Connect to V1.8_OUT (pin 6) through ferrite bead.
Decouple with 0.1 µF capacitor on each pin to ground.
VDDIO_3.3 25, 26 Input Connect to board’s 3.3V supply.
Decouple with 22 µF and 0.1 µF capacitors to ground.
VDDA_3.3 7, 8 Input Connect to board’s 3.3V supply through ferrite bead.
Decouple with 22 µF and 0.1 µF capacitors to ground.
Ferrite
Bead
7
8
3.3V
22μF 0.1μF
25
26
22μF 0.1μF
V
IN
VDDA_3.3
VDDIO_3.3
KSZ8041TL/FTL/MLL
1.8V Low Noise
Regulator
(integrated)
GND
VDDA_1.8
VDD_1.8
V1.8_OUT
V
OUT
123173037
4
5
0.1μF
0.1μF
0.1μF
Ferrite
Bead
Ferrite
Bead
0.1μF1μF
31
6