AS1152 Просмотр технического описания (PDF) - austriamicrosystems AG

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AS1152

Quad LVDS Driver

austriamicrosystems AG 

AS1152

Data Sheet

austriamicrosystems

LVDS Interface

8 Detailed Description

LVDS Interface

The LVDS interface standard is a signaling method intended for point-to-point communication over a controlled-imped-

ance medium as defined by the ANSI/TIA/EIA-644 and IEEE 1596.3 standards. The LVDS standard uses a lower volt-

age swing than other common communication standards, achieving higher data rates with reduced power

consumption while reducing EMI emissions and system susceptibility to noise.

The AS1152 is an 500Mbps quad differential LVDS driver that is designed for high-speed, point-to-point, low-power

applications. This device accepts LVTTL/LVCMOS input levels and translates them to LVDS output signals.

The AS1152 generates a 2.5mA to 4.5mA output current using a current-steering configuration. This current steering

approach induces less ground bounce and no shoot-through current, enhancing noise margin and system speed per-

formance. The driver outputs are short-circuit current limited, and enter a high-impedance state when the device is not

powered or is disabled.

The current-steering architecture of the AS1152 requires a resistive load to terminate the signal and complete the

transmission loop. Because the device switches current and not voltage, the actual output voltage swing is determined

by the value of the termination resistor at the input of an LVDS receiver (AS1150, AS1151). Logic states are deter-

mined by the direction of current flow through the termination resistor.

With a typical 3.7mA output current, the AS1152 produces an output voltage of 370mV when driving a 100Ω load.

Note: The AS1152 is conform to the ANSI TIA/EIA 644 LVDS Standards when operating ≤150MHz. Paired with the

AS1150 the datarate can be increased to 500Mbps. While operating faster then 150MHz, the rise and fall time,

as well as the setup and hold time are not conform to the ANSI TIA/EIA 644 LVDS Standards.

Termination

Because the AS1152 is a current-steering device, no output voltage will be generated without a termination resistor.

The termination resistors should match the differential impedance of the transmission line. Output voltage levels

depend upon the value of the termination resistor.

The AS1152 is optimized for point-to-point interface with 100Ω termination resistors at the receiver inputs. Termination

resistance values may range between 90 and132Ω, depending on the characteristic impedance of the transmission

medium.

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