LMH1983SQE/NOPB National Semiconductor, LMH1983SQE/NOPB Datasheet - Page 32

• Manufacturer Part Number: LMH1983SQE/NOPB
• Description: IC VID CLK GEN MULTI RATE 40LLP
• Manufacturer: National Semiconductor
• Type: Clock Generatorr

Specifications of LMH1983SQE/NOPB

• Applications: Video Equipment
• Mounting Type: Surface Mount
• Package / Case: 40-LLP
• Leaded Process Compatible: Yes
• Rohs Compliant: Yes
• Interface Type: I2C
• Supply Voltage (max): 3.3 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Peak Reflow Compatible (260 C): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMH1983SQETR

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between the two is large. Furthermore, if the difference is
large, then the user has the opportunity to tell the device to
achieve alignment either via advancing or retarding the phase
of PLL1 in order to achieve alignment. Note that if the differ-
ence in alignment is large, to achieve alignment via drift lock
may take a very long time (10s of seconds), during which time
the output clock will not be phase locked to the input H
TOF2 and TOF3 Timing
Like with TOF1, each of the second and third channels has a
video format associated with it. The format is determined by
programming this into registers 0x07h and 0x08h respective-
ly. Once the format is programmed, and the TOF outputs are
enabled, a TOF pulse is generated at the appropriate rate for
each of the outputs. There are four different alignment modes
which may be selected for TOF2 and TOF3:
TOF2/TOF3 Alignment
Mode
10ns / div. Top 200mV / div, Bottom 1V / div
4ns / div, Top 200mV / div, Bottom 1V / div
Top Trace CLKout1, Bottom Trace TOF1
Top Trace CLKout3, Bottom Trace TOF3
TOF2/TOF3 Alignment Modes
0
1
2
3
TOF1 Timing
TOF3 Timing
Description
Auto Align when misaligned
One shot manual align
always align
never align
30085160
30085162
IN
.
32
TOF2 and TOF3 are generally aligned with TOF1. The align-
ment status bit will only be set if the frame rates are the same
as one another. Another option for alignment is via software,
where a but is written to the TOFX_INIT bit. For example, the
LSB of register 0x12h is the TOF2_INIT bit. Writing a one to
this bit, while also setting TOF2 alignment mode to anything
other than 3, will cause TOF2 immediately reset its phase.
This bit is a self clearing bit, so reading it will always return a
zero.
TOF4 Alignment Modes
The fourth channel of the LMH1983 is most often used to
generate an audio clock. The default base audio clock rate is
48 kHz, and this sample clock is synchronous in phase with
the video frame only once every 5 frames for 29.97 and 30
Hz frame rate standards, or once every 10 frames for 60 Hz
and 59.94 Hz systems. The LMH1983 can generate a TOF4
pulse which will happen at this rate, allowing audio frames to
be synchronized with the video frames.
TOF4 may be aligned either to TOF1, or to the F
ditionally, there is an external INIT input which can be used
to set the TOF4 alignment.
10ns / div, Top 200mV / div, Bottom 1V / div
4ns / div, Top 200mV / div, Bottom 1V / div
Top Trace CLKout2, Bottom Trace TOF2
Top Trace CLKout4, Bottom Trace TOF4
TOF2 Timing
TOF4 Timing
IN
30085161
30085163
input. Ad-