Intel 21143 manual LED Status Signals, 5.1.1 3.3 V Power Supply, LED Time-Stretcher Circuit

Intel® 21143 PCI/CardBus 10/100Mb/s Ethernet LAN Controller

Intel also recommends that the connector’s shield of the adapter should be connected to the PC chassis.

5.1.13.3 V Power Supply

The 21143 operates with a power supply of 3.3 V. At least eight decoupling capacitors are recommended and should contain the following values:

•Three each at 0.1 µF

•Three each at 0.01 µF

•One each at 10 µF (tantalum)

•One each at 47 µF (tantalum)

5.2LED Status Signals

The LED connection requires a serial resistor that is connected to ground. This resistor value should be calculated according to the type of LED used. A typical 2 mA LED requires a 750 Ω resistor. For implementations using the boot ROM, the LED current should not exceed 2 mA. For LED indication and programming information, refer to the CSR15 definition in the 21143 PCI /CardBus 10/100 Mb/s Ethernet LAN Controller Hardware Reference Manual.

The 21143 requires LED time-stretching logic for a visible indication of the activity signal. Figure 11 shows how to implement this circuit.

Figure 11. LED Time-Stretcher Circuit

		+5 V
	100 k Ω
Active Low	1N14B	750 Ω
		74
		HCT132
		22 nF
	1N14B	+5 V
Active High		750 Ω
		74
		HCT132
	100 k Ω	22 nF
		LJ-04061.AI4

22 Design Guide