LMH0036 Datasheet, PDF (12/19 Pages) National Semiconductor (TI) – SD SDI Reclocker with 4:1 Input Multiplexer

LMH0036
SNLS254B – MARCH 2008 – REVISED APRIL 2013
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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 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.
SEL0 and SEL1 have internal pulldowns to select the SDI0 input by default.
The inputs are LVPECL compatible. The LMH0036 has a wide input common mode range and in most cases the
input should be DC coupled. For DC coupling, the inputs must be kept within the common mode range specified
in DC ELECTRICAL CHARACTERISTICS.
Figure 6 shows an example of a DC coupled interface between the LMH0074 cable equalizer and the LMH0036.
The LMH0074 output common mode voltage and voltage swing are within the range of the input common mode
voltage and voltage swing of the LMH0036. All that is required is a 100Ω differential termination as shown. The
resistor should be placed as close as possible to the LMH0036 input. 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 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 LMH0036 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 7 shows an example of a DC coupled interface between the LMH0036 and LMH0001 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 LMH0036 has multiple ground connections, however; the primary ground connection is through the large
exposed DAP. The DAP must be connected to ground for proper operation of the LMH0036.
Coaxial Cable
75:
6.8 nH
LMH0074
SD SDI Cable Equalizer
1.0 PF
SDI SDO
1.0 PF
SDI
SDO
100:
75:
37.4:
SDI0
LMH0036
SDI0
Figure 6. DC Input Interface
+3.3V
75:
LMH0001
SD SDI Cable Driver
75:
5.6 nH
SDO
LMH0036
100:
SDO
SDI
SDO
SDO
SDI
75:
4.7 PF Coaxial Cable
75:
4.7 PF
Coaxial Cable
75:
75:
5.6 nH
12
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Figure 7. DC Output Interface
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