Jumpers to power onboard TCXO:
The onboard TCXO can be powered in
three manners:
1. Direct 3.3-V supply provided to VIN3.
Tie pins 5-6 (adjacent to JP4 designator).
2. 3.3-V supply provided from output of
LDO3 (U9). Tie pins 3-4.
3. 3.3-V supply provided from output of
DCDC1 (U500). Tie pins 1-2 (opposite to
JP4 designator).
Remove jumper from JP4 when
providing external XO input.
External XO Input
Onboard 48 MHz
TCXO
Figure 3-9. XO Input
3.5.1 48-MHz TCXO (Default)
By default, the EVM is populated with a 48-MHz, 3.3-V LVCMOS, low-jitter TCXO, designated as Y1 (3.2 mm
x 2.5 mm), which drives the XO input of the LMK5B33216 with the onboard termination and AC coupling. See
. All LMK5B33216 EVMs have a TXC 7N48071001 48-MHz TCXO populated on Y1. Y1 can be used
to evaluate various frequency configurations.
3.5.2 External Clock Input
Another option is to feed an external clock to the SMA port (J8) to drive the XO input. See
. This path
can be connected to the XO input pins. Y1 should be powered down when using the external XO input path. To
power down Y1 and use an external XO input, the jumper on JP4 must be removed. Suggested XO frequencies
for best device performance are frequencies of 38.88 and 48 MHz.
3.5.3 Additional XO Input Options
For flexibility, the EVM provides additional XO input options (use one at a time). C70 allows an external
reference to be provided at SMA connector XO (J8). C71 allows one of the onboard XO/TCXO/OCXO footprints
to be used.
By default, Y1 is populated with a 48-MHz TCXO and selected with the populated R43 and R206. R43 provides
the output clock of Y1 to the XO pin of the LMK5B33414 and R206 provides power to Y1.
Additional PCB footprints are available to install alternate components for performance evaluation of specific
oscillators. These additional footprints are Y2 (2.5 x 2.0 mm), Y3 (3.2 mm x 2.5 mm), Y4 (9.7 mm x 7.5 mm), Y5
(25 mm x 22 mm), and U4 (2.5 mm x 2 mm).
When using Y2, Y3, Y4, Y5, or U4, R43 and R206 must be removed to power down and isolate the output of
Y1. When populating Y2, R46 must be populated to provide Y2's output to the XO pin. When populating Y3,
R47 must be populated to provide Y3's output to the XO pin. When populating Y4, R48 must be populated to
provide Y4's output to the XO pin. When populating Y5, R49 must be populated to provide Y5's output to the XO
pin. When populating U4, R50 must be populated to provide U4's output to the XO pin.
shows the
components described above.
Take care if more than one device is installed to remove resistors to power down unused oscillators and isolate
their outputs as described above.
EVM Configuration
12
LMK5B33216EVM User's Guide
SNAU263A – FEBRUARY 2022 – REVISED JULY 2022
Copyright © 2022 Texas Instruments Incorporated
