LMH0346 Datasheet, PDF (15/23 Pages) Texas Instruments – HD/SD SDI Reclocker with Dual Differential Outputs

LMH0346
www.ti.com
SNLS248J – APRIL 2007 – REVISED APRIL 2013
The LMH0346 outputs are LVPECL compatible. SDO is the primary data output and SCO/SDO2 is a second
output that may be set as the serial clock or a second data output. Both outputs are always active. The LMH0346
output should be DC coupled to the input of the receiving device as long as the common mode ranges of both
devices are compatible. Figure 6 shows an example of a DC coupled interface between the LMH0346 and
LMH0302 cable driver. All that is required is a 100Ω differential termination as shown. The resistor should be
placed as close to the LMH0302 input as possible. If desired, this network may be terminated with two 50Ω
resisters and a center tap capacitor to ground in place of the single 100Ω resistor.
The external loop filter capacitor (between LF1 and LF2) should be 56 nF. This is the only supported value; the
loop filter capacitor should not be changed.
RATE0 and RATE1 have internal pulldowns to select Auto-Rate Detect mode by default. These pins may also be
used to set the device to SD mode or HD/3G mode.
BYPASS/AUTO BYPASS has an internal pulldown to enable Auto Bypass mode by default. This pin may be
pulled high to force the LMH0346 to bypass all data.
OUTPUT MUTE has an internal pullup to enable the outputs by default. This pin may be pulled low to mute the
outputs.
The XTAL IN/EXT CLK and XTAL OUT pins are shown with a 27 MHz crystal and the proper loading. The crystal
should match the parameters described in Table 3. Alternately, a 27MHz LVCMOS compatible clock signal may
be input to XTAL IN/EXT CLK.
The active high LOCK DETECT output provides an indication that proper data is being received and the PLL is
locked.
The SD/HD output may be used to drive the SD/HD pin of an SDI cable driver (such as the LMH0302) in order to
properly set the cable driver’s edge rate for SMPTE compliance. It defaults to HD/3G (low) when the LMH0346 is
not locked.
SCO_EN has an internal pulldown to set the second output (SCO/SDO2) to output data. This pin may be pulled
high to set the second output as a serial clock.
The ground connection for the LMH0346 is through the large exposed DAP. The DAP must be connected to
ground for proper operation of the LMH0346. This is the only ground connection for the LMH0346MH. It is the
primary ground connection, required for good signal integrity, for the LMH0346SQ.
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: LMH0346
Submit Documentation Feedback
15