Seagate ST3400755SS 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 12 for the output characteristics of the LED drive signals.

Table 12:	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

9.5.2Differential signals

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

Table 13 defines the general interface characteristics.

Table 13: General interface characteristics

Characteristic	Units	1.5 Gbps	3.0 Gbps
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

9.5.2.1Eye masks

9.5.2.1.1Eye masks overview

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

time limits on the signal at the compliance of the jitter population. The random content

56 Cheetah NS SAS Product Manual, Rev. B