Texas Instruments LMH2191 Evaluation Board LMH2191TMEVAL/NOPB LMH2191TMEVAL/NOPB Datenbogen
Produktcode
LMH2191TMEVAL/NOPB
User's Guide
SNAA071A – July 2010 – Revised May 2013
AN-2028 LMH2191 Evaluation Board
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General Description
The evaluation board (
) is designed to help the evaluation of the LMH2191 Dual Channel 52 MHz
Clock Tree Driver. The LMH2191 is ideal suitable for the distribution of a system clock to peripheral
devices in mobile handsets. It provides a solution to clocking issues such as limited drive capability,
protection of the master clock from varying loads and frequency pulling effects, isolation from noisy
modules, and crosstalk isolation. It has very low phase noise which enables it to drive sensitive modules
such as Wireless LAN and Bluetooth.
devices in mobile handsets. It provides a solution to clocking issues such as limited drive capability,
protection of the master clock from varying loads and frequency pulling effects, isolation from noisy
modules, and crosstalk isolation. It has very low phase noise which enables it to drive sensitive modules
such as Wireless LAN and Bluetooth.
The setup of the evaluation board consist of three segments:
•
The TCXO oscillator that generates the clock signal that is fed to the clock buffer.
•
The circuit around the LMH2191 itself. The DUT needs a stable supply to be able to operate
adequately. Furthermore there is the possibility to switch each CLK output ON and OFF separately
using a CLK request jumper setting or an external connector. Each clock output has several different
capacitive load settings which are selectable by using jumper shorts. Each clock output is also fed to
an SMA connector.
adequately. Furthermore there is the possibility to switch each CLK output ON and OFF separately
using a CLK request jumper setting or an external connector. Each clock output has several different
capacitive load settings which are selectable by using jumper shorts. Each clock output is also fed to
an SMA connector.
•
The output buffer, that makes it possible to monitor both clock outputs or the TCXO voltage one by one
by jumper selection. The output buffer is capable to drive a 50 ohm cable in order to connect the test
board to measuring equipment.
by jumper selection. The output buffer is capable to drive a 50 ohm cable in order to connect the test
board to measuring equipment.
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Detailed Operating Description
The LMH2191 evaluation board is designed to have maximum flexibility in evaluating the LMH2191 in
various configurations. The schematic, Bill of material and board layout can be found at the end of this
application report. In the following sections, a description is given on how the circuit works and how to
setup the measurement bench. For the factory default jumper setting, refer to
various configurations. The schematic, Bill of material and board layout can be found at the end of this
application report. In the following sections, a description is given on how the circuit works and how to
setup the measurement bench. For the factory default jumper setting, refer to
2.1
Power Supply
The board is powered by the use of banana connections, which is mostly a preferable connector type
rather than a multi pole connector. The DUT (LMH2191) uses a single supply called V
rather than a multi pole connector. The DUT (LMH2191) uses a single supply called V
BAT
while the output
buffer, used for monitoring the CLK outputs and the TCXO voltage, is powered by a dual supply (called V+
& V-). The supply for the DUT ranges from 2.5V to 5.5V while the supply for the output buffer (LMH6559)
has a fixed voltage of +5V and –5V. The output voltage of the LDO is 1.8V and can be monitored on an
extra banana connector called V
& V-). The supply for the DUT ranges from 2.5V to 5.5V while the supply for the output buffer (LMH6559)
has a fixed voltage of +5V and –5V. The output voltage of the LDO is 1.8V and can be monitored on an
extra banana connector called V
OUT
.
2.1.1
TCXO Supply
The supply for this on-board oscillator is done by the LMH2191 via the V
OUT
pin. The V
OUT
voltage is
decoupled by C13 and C14 and is connected to jumper J8 pin 2. For normal operation, pin 1 and pin 2 are
shorten and the LDO voltage is connected to the supply pin of the TCXO. If, for any reason, an external
supply is needed, this supply voltage can be connected to J8 at the pins 3 and 4. Pin 3 is the supply of the
TCXO and pin 4 is the ground connection. (NOTE: The jumper short for the pins 1 and 2 must be
removed then).
shorten and the LDO voltage is connected to the supply pin of the TCXO. If, for any reason, an external
supply is needed, this supply voltage can be connected to J8 at the pins 3 and 4. Pin 3 is the supply of the
TCXO and pin 4 is the ground connection. (NOTE: The jumper short for the pins 1 and 2 must be
removed then).
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SNAA071A – July 2010 – Revised May 2013
AN-2028 LMH2191 Evaluation Board
Copyright © 2010–2013, Texas Instruments Incorporated