GS1675 datasheet(12/37 Pages) SEMTECH

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GS1675 SD/HD SDI Reclocker

Data Sheet

54174 - 1

June 2011

12 of 37

Active circuitry associated with the input buffers and trace EQ can only be turned on for

the selected input. Inputs which are not selected have their input buffers and trace EQs

turned OFF to save power. Unused inputs can be either left floating, or tied to VCC.

3.4 Crystal Buffer

The GS1675 features a crystal buffer supporting a Gennum recommended external

27MHz crystal. The GS1675 requires an external 27MHz reference clock for correct

operation. This reference clock is generated by connecting a crystal to the XTAL- and

XTAL+ pins of the device.

Alternately, a 27MHz external clock source can be connected to the XTAL- pin of the

device, while the XTAL+ pin should be left floating.

3.5 LOS (Loss Of Signal) Detection

The LOS (Loss Of Signal) status pin is an active-high output that indicates when the serial

digital input signal selected at the 2:1 input mux is invalid. In order for this output to be

asserted, transitions must not be present for a period of tLA = 5 - 10μs. After this output

has been asserted, LOS will de-assert within tLD = 0 - 5μs after the appearance of a

transition at the DDIx input. See Figure 3-1.

This signal is HIGH (signal lost), when the number of data edges within a window is

below a defined threshold. The output is automatically muted when LOS is detected.

This signal is LOW (signal valid), when the number of data edges within a window is

above a defined threshold. See Table 3-2.

The LOS function is operational for all operating modes of the device.

Figure 3-1: LOS Signal Timing

Table 3-2: LOS Operation

LOS

Signal

HIGHInvalid

LOW

Valid

DATA

LOS

GS1675 Datasheet(PDF) 12 Page - Semtech Corporation