LMK00304_16 Datasheet, PDF (21/39 Pages) Texas Instruments – 3-GHz 4-Output Ultra-Low Additive Jitter Differential Clock Buffer/Level Translator

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LMK00304
SNAS577F – FEBRUARY 2012 – REVISED MARCH 2016
9.3.3 Clock Outputs
The differential output buffer type for both Bank A and B outputs are configured using the CLKout_TYPE[1:0] as
shown in Table 4. For applications where all differential outputs are not needed, any unused output pin should be
left floating with a minimum copper length (see note below) to minimize capacitance and potential coupling and
reduce power consumption. If all differential outputs are not used, it is recommended to disable (Hi-Z) the banks
to reduce power. Refer to Termination and Use of Clock Drivers for more information on output interface and
termination techniques.
NOTE
For best soldering practices, the minimum trace length for any unused pin should extend
to include the pin solder mask. This way during reflow, the solder has the same copper
area as connected pins. This allows for good, uniform fillet solder joints helping to keep
the IC level during reflow.
CLKout_
TYPE1
0
0
1
1
Table 4. Differential Output Buffer Type Selection
CLKout_
TYPE0
0
1
0
1
CLKoutX BUFFER TYPE
(BANK A and B)
LVPECL
LVDS
HCSL
Disabled (Hi-Z)
9.3.3.1 Reference Output
The reference output (REFout) provides a LVCMOS copy of the selected input clock. The LVCMOS output high
level is referenced to the Vcco voltage. REFout can be enabled or disabled using the enable input pin,
REFout_EN, as shown in Table 5.
REFout_EN
0
1
Table 5. Reference Output Enable
REFout STATE
Disabled (Hi-Z)
Enabled
The REFout_EN input is internally synchronized with the selected input clock by the SYNC block. This
synchronizing function prevents glitches and runt pulses from occurring on the REFout clock when enabled or
disabled. REFout will be enabled within 3 cycles (t_EN) of the input clock after REFout_EN is toggled high. REFout
will be disabled within 3 cycles (t_DIS) of the input clock after REFout_EN is toggled low.
When REFout is disabled, the use of a resistive loading can be used to set the output to a predetermined level.
For example, if REFout is configured with a 1 kΩ load to ground, then the output will be pulled to low when
disabled.
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