LMK01000_14 Datasheet, PDF (13/27 Pages) Texas Instruments – 1.6 GHz High Performance Clock Buffer, Divider, and Distributor

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LMK01000
SNAS437G – FEBRUARY 2008 – REVISED OCTOBER 2009
CLKoutX_DLY[3:0] -- Clock Output Delays
These bits control the delay stages for each clock output. In order for these delays to be active, the respective
CLKoutX_MUX (See Section 2.3.2) bit must be set to either "Delayed" or "Divided and Delayed" mode. By
adding the delay block to the output path a fixed delay of approximately 400 ps is incurred in addition to the
delay shown in the table below.
CLKoutX_DLY[3:0]
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Delay (ps)
0 (default)
150
300
450
600
750
900
1050
1200
1350
1500
1650
1800
1950
2100
2250
CLKoutX_EN bit -- Clock Output Enables
These bits control whether an individual clock output is enabled or not. If the EN_CLKout_Global bit is set to zero
or if GOE pin is held low, all CLKoutX_EN bit states will be ignored and all clock outputs will be disabled.
CLKoutX_EN bit
0
1
Conditions
EN_CLKout_Global bit = 1
GOE pin = High / No Connect 1
CLKoutX State
Disabled (default)
Enabled
REGISTER R9
R9 only needs to be programmed if Vboost is set to 1. Program all other bits in R9 as indicated in register map
(See Section 2.2)
Vboost - Voltage Boost Bit
Enabling this bit sets all clock outputs in voltage boost mode which increases the voltage at these outputs. This
can improve the noise floor performance of the output, but also increases current consumption, and can cause
the outputs to be too high to meet the LVPECL/LVDS specifications.
Vboost bit
0
1
f_CLKoutX < 1300 MHz
Recommended to hit voltage level
specifications for LVPECL/LVDS
Voltage May overdrive LVPECL/LVDS
specifications, but noise floor is about 2-4 dB
better and current consumption is increased
1300 MHz ≤ f_CLKoutX < 1500
MHz
1500 MHz ≤ f_CLKoutX ≤ 1600 MHz
Insufficient voltage level for LVDS/LVPECL specifications, but saves
current
Voltage is sufficient for
LVDS/LEVPECL specifications.
Current consumption is
increased, but noise floor is
about the same.
Insufficient voltage for
LVDS/LVPECL specifications, but
still higher than when Vboost=0.
Increased current consumption.
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