KS8721SL Micrel Inc, KS8721SL Datasheet - Page 16

• Manufacturer Part Number: KS8721SL
• Description: TXRX 10/100 3.3V 48-SSOP
• Manufacturer: Micrel Inc
• Type: Transceiverr

Specifications of KS8721SL

• Number Of Drivers/receivers: 1/1
• Protocol: IEEE 802
• Voltage - Supply: 2.375 V ~ 2.625 V
• Mounting Type: Surface Mount
• Package / Case: 48-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With: 576-1010 - BOARD EVAL EXPERIMENT KS8721SL
• Lead Free Status / RoHS Status: Not Compliant, Contains lead / RoHS non-compliant

Micrel, Inc.
Power Management
The KS8721BL/SL offers the following modes for power management:
100BT FX Mode
Please contact your local field application engineer (FAE) for a reference schematic on fiber connection.
100BT FX mode is activated when FXSD/FXEN is higher than 0.6V (this pin has a default pull down). Under this mode,
the auto-negotiation and auto-MDI-X features are disabled.
In fiber operation, the FXSD pin should connect to the signal detect (SD) output of the fiber module. The internal
threshold of FXSD is around 1/2 V
The operation is summarized in the following table:
To ensure proper operation, the swing of fiber module SD should cover the threshold variation. A resistive voltage
divider is recommended to adjust the SD voltage range.
Far End Fault (FEF), repetition of a special pattern which consists of 84-one and 1-zero, is generated under “FX mode
with no signal detected.” The purpose of FEF is to notify the sender of a faulty link. When receiving an FEF, the LINK
will go down to indicate a fault, even with fiber signal detected. The transmitter is not affected by receiving an FEF and
June 2009
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Power-Down Mode: This mode can be achieved by writing to Register 0.11 or pulling pin 30 PD# low.
Power-Saving Mode: This mode can be disabled by writing to Register 1fh.10. The KS8721BL/SL turns off
everything except for the Energy Detect and PLL circuits when the cable is not installed. In other words, the
KS8721BL/SL shuts down most of the internal circuits to save power if there is no link. Power-saving mode is in
the most effective state when auto-negotiation mode is enabled.
FXSD/FXEN
Less than 0.6V
Less than 1.25V,
but greater than 0.6V
Greater than 1.25
10/100 BASE-T
Media Dependent Interface
Modular Connector (RJ45)
(Repeater or Switch)
Transmit Pair
Receive Pair
HUB
DD
±50mV (1.25V ±0.05V). Above this level, the fiber signal is considered detected.
Condition
100TX mode
FX mode
No signal detected
FEF generated
FX mode
Signal detected
Figure 2. Crossover Cable
Table 1. 100BT FX Mode
16
10/100 BASE-T
Media Dependent Interface
Modular Connector (RJ45)
(Repeater or Switch)
Receive Pair
Transmit Pair
HUB
M9999-062509-1.3
KS8721BL/SL