Basic Operation
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2
Basic Operation
The LMH2190 evaluation board is designed such that it gives maximum flexibility in evaluating the
LMH2190 in various configurations. The schematic, Bill of material and board layout can be found at the
end of this document. In the following sections a description will be given on how to setup the
measurement bench. For the factory default jumper setting, refer to
Section 3
.
2.1
Supply
The common ground of the evaluation board is connected via Connector CON3. The LMH2190 is
powered via V
BAT
(CON2). The typical supply voltage for V
BAT
is 3.5V, but it may range from 2.5V to 5.5V.
In the factory default configuration the ENABLE voltage is supplied externally via connector CON7 and
should be 1.8V. Three on-board buffers are separately powered through Connector CON18 (+5V) and
CON 19 (-5V). If they are not used for evaluation they can be left un-powered when jumper locations J7,
J16 and J17 are open.
2.2
Applying Clock
In factory default configuration the clock to the LMH2190 is supplied by the on-board TCXO. Alternatively
the clock can be applied externally either in DC mode via CON12 or in AC mode via CON10. The clock
source can be selected by J13. Note that for DC mode, the I
2
C registers also need to be changed.
The LMH2190 distributes the clock to a maximum of 4 outputs, CLK1 to CLK4, that are accessible via
CON1, CON5, CON6 and CON8. An additional capacitive load can be connected between CLK to GND to
simulate the load in the actual application via J1, J2, J14 and J15.
There is also a possibility to measure the clocks as well as the TCXO clock via a buffer. This buffer can
drive 50 ohm making them excellent for connecting to measurement equipment, like a Signal Source
Analyzer. This analyzer can for instance measure the Phase noise and Jitter. The three buffers can be
connected to the clock's by J7, J16 and J17. When the buffers are not used it is recommended to
disconnect them, since they increase the capacitive load on the clocks slightly.
2.3
Clock Request
The CLK's can be enabled by their appropriate CLK_REQ's. The CLK_REQ pin can be connected to a
logic Low or High level via J6, J8, J10 and J12. The level of the Logic High can be selected by J5, either
V
OUT
, V
BAT
or V
ENABLE
. Instead of via the jumpers, the CLK_REQ's can also be controlled via CON9,
CON11, CON13 and CON14. Make sure that the jumpers are removed in this case. In factory default
configuration only CLK1 is enabled. The other clocks can simply be enabled by placing the jumper on J8,
J10 and J12 in the other position.
2.4
I
2
C Interface
The LMH2190 can be controlled by an I
2
C host device that can be connected via J4. It can configure the
registers inside the LMH2190 to change the default configuration. According to the I
2
C specification one
set of pull-up resistors needs to be present on the I
2
C bus. If they are not present elsewhere in the system
they can be connected on the evaluation board via J19. The evaluation board can be used without I
2
C
host device connected. It will then work in its default configuration.
3
Configuration
The LMH2190 evaluation board can be configured via jumper settings. An overview of the various jumper
positions on the board is given in
Figure 2
. The settings of these jumpers and their functions are listed in
Table 1
.
2
AN-1966 LMH2190 Evaluation Board
SNAA068B – July 2009 – Revised May 2013
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