Seagate ST3450802SS LED drive signal, Differential signals, General interface characteristics

The Ready LED Out signal is designed to pull down the cathode of an LED. The anode is attached to the proper +3.3 volt supply through an appropriate current limiting resistor. The LED and the current limiting resis- tor are external to the drive. See Table 23 for the output characteristics of the LED drive signals.

Table 23:	LED drive signal
State		Test condition	Output voltage
LED off, high		0 V ≤ VOH ≤ 3.6 V	-100 μA < IOH < 100 μA
LED on, low		IOL = 15 mA	0 ≤ VOL ≤ 0.225 V

10.5.2Differential signals

The drive SAS differential signals comply with the intra-enclosure (internal connector) requirements of the SAS standard.

Table 24 defines the general interface characteristics.

Table 24:	General interface characteristics
Characteristic		Units	1.5Gb/s	3.0Gb/s
Bit rate (nominal)		Mbaud	1,500	3,000
Unit interval (UI)(nominal)		ps	666.6	333.3
Impedance (nominal, differential )		ohm	100	100
Transmitter transients, maximum		V	± 1.2	± 1.2
Receiver transients, maximum		V	± 1.2	± 1.2
10.5.2.1	Eye masks
10.5.2.1.1	Eye masks overview

The eye masks are graphical representations of the voltage and time limits on the signal at the compliance point. The time values between X1 and (1 - X1) cover all but 10-12of the jitter population. The random content of the total jitter population has a range of ± 7 standard deviations.

54 Cheetah NS 10K.2 SAS Product Manual, Rev. F