Texas Instruments LMK00101, Руководство пользователя

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Power Supplies
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4 SNLU098A – March 2012 – Revised July 2019
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LMK00101 User’s Guide
4 Power Supplies
By default, Vdd and VddCLKout are supplied by two external power supplies. To modify the EVK with a
different power supply configuration, populate the resistor options as shown in
Table 5 .Then, apply the
appropriate voltage(s) to the EVK power input(s).
Decoupling capacitors and 0 Ω resistor footprints, which can accommodate ferrite beads, can be used to
isolate the EVK power input(s) from the device power pins. Do not disconnect or ground any of the
VddCLKout pins as they are all internally connected inside the device.
Table 5. Power Supply Configuration
DUAL EXTERNAL INPUTS (DEFAULT) SINGLE EXTERNAL INPUT 3.3 V
Vdd input Apply 3.3 V Apply 3.3 V ± 5%
VddCLKout input Apply Voltage ≤ Vdd Not used
R38 0
Ω
DNP
R39 0
Ω
0
Ω
R43 DNP 0 Ω
5 Clock Inputs
The SMA inputs labeled CLKin0 & CLKin0* and CLKin1 & CLKin1* are configured to receive a differential
clock or single ended clock. Best performance is achieved with DC-coupled differential input clock.
5.1 Crystal Oscillator Interface
The LMK00101 has an integrated crystal oscillator interface (OSCin/OSCout) that supports a fundamental
mode, AT-cut crystal. If the crystal input is selected, an optional onboard crystal on either footprint Y1 or
Y2 will start-up and the oscillator clock can be measured on any enabled output.
A crystal with the HC49 footprint can be populated on the bottom side of the PCB. Alternatively, a 3.2 x
2.5 mm crystal can be populated on Y2, located on the top side. Only one crystal footprint should be used
at a time.
The values of C42 and C25(C
EXT
) depend on the load capacitance (C
L
) specified for the crystal. The OSC
input capacitance (C
IN
) of the device is 1 pF differential, and the trace capacitance (C
TRACE
) of OSCin and
OSCout is around 1 pF. If the selected crystal is specified for C
L
of 18 pF, the C
EXT
is calculated as
follows:
C
EXT
= (C
L
–C
IN
–C
TRACE
/2) * 2 (1)
C
EXT
= (18 pF –1 pF –1 pF/2) * 2 (2)
C
EXT
= 33 pF (3)
5.2 Configuring OSCin for a Crystal Mode
To configure the board to use crystal mode remove C26 to disconnect the OSCin Port. Install 0
Ω
resistors
on R33 and R34. Install a crystal in either footprint (Y1 or Y2) and install the proper load capacitors in C24
and C25.
6 Clock Outputs
All clock outputs are LVCMOS. In the case that not all outputs are used, any unused outputs should be
left floating.