Compaq manual Overview, 1. M-LVDS Devices Supported by the EVM

Overview

1.1 Overview

The EVM comes with all the production devices in Table 1−1. The SN65MLVD201 and SN65MLVD207 are installed on the circuit board, and can easily be replaced with the other devices supplied. The M-LVDS devices evaluated with this EVM are in the SN75ALS180 and SN75176 footprint. Use of these industry standard footprints allows the designer to easily configure the parts into a simplex or half-duplex data bus. These are all TIA/EIA−899 M-LVDS standard compliant devices. While initially intended for half-duplex or multipoint applications, M-LVDS devices are not precluded from being used in a point-to-point or multidrop configuration. In these configurations there can be a distinct advantage to the additional current drive provided by an M-LVDS driver.

The M-LVDS devices shown in Table 1−1 all include output slew-rate limited drivers, thus the need for different nominal signaling rates. The M-LVDS standard recommends the transition time not exceed 0.5 of the unit interval (UI). The definition of transition time (tr and tf) in M-LVDS is the 10% to 90% levels shown in Figure 1−1. Using the maximum transition time for each of the drivers and the 0.5(tUI) rule results in the signaling rates shown in Table 1−1. This slew-rate control differentiates M-LVDS devices from LVDS (TIA/EIA−644A) compliant devices. The slower transition times available with M-LVDS help to reduce higher frequency components in the transmitted signal. This reduces EMI and allows longer stubs on the main transmission line. For this reason it is generally better to select a driver with a specified signaling rate no greater than is required in the system.

Figure 1−1. M-LVDS Unit Interval Definition

tr

tf

90%

50%

10%

UI

Table 1−1. M-LVDS Devices Supported by the EVM

Nominal		Receiver	Part
Signaling Rate	Footprints			Status
		Type	Number
(Mbps)
100	SN75176	Type-1	SN65MLVD200AD	Production
200	SN75176	Type-1	SN65MLVD201D	Production
100	SN75ALS180	Type-1	SN65MLVD202AD	Production
200	SN75ALS180	Type-1	SN65MLVD203D	Production
100	SN75176	Type-2	SN65MLVD204AD	Production
100	SN75ALS180	Type-2	SN65MLVD205AD	Production
200	SN75176	Type-2	SN65MLVD206D	Production
200	SN75ALS180	Type-2	SN65MLVD207D	Production

1-2 The M-LVDS Evaluation Module