LMH2190 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – Quad Channel 27 MHz Clock Tree Driver with I2C Interface

LMH2190
October 7, 2009
Quad Channel 27 MHz Clock Tree Driver with I²C Interface
General Description
The LMH2190 is a quad channel configurable clock tree driver
which supplies a digital system clock to peripherals in mobile
handsets or other applications. It provides a solution to clock-
ing issues such as limited drive capability for fanout or longer
traces, protection of the master clock from varying loads and
frequency pulling effects, isolation buffering from noisy mod-
ules, and crosstalk isolation. It has very low phase noise
which enables it to drive sensitive modules such as Wireless
LAN and Bluetooth.
The LMH2190 can be clocked up to 27 MHz, and has an in-
dependent clock request pin for each clock output which
allows the peripheral to control the clock. It features an inte-
grated LDO which provides an ultra low noise voltage supply
with 10 mA external load current which can be used to supply
the TCXO or other clock source.
The I²C serial interface can be used to override the default
configuration of the device to optimize the LMH2190 for the
application. Some of these programmable features include
setting the polarity of both the clock and the clock request
inputs. In addition, the clock outputs have programmable out-
put drive current to optimize for the connected load. EMI
switching noise can be controlled by configuring output drive
and skew settings.
The LMH2190 quad clock distributor is offered in a tiny
1.615mm x 1.615mm 16 bump microSMD package. Its small
size and low supply current make it ideal for portable appli-
cations.
Features
■ ^{1 input clock, 4 output clocks}
■ ^{Supports both square or sine wave input}
■ ^{1.8V square wave clock outputs}
■ ^{Skewed clock outputs}
■ ^{Independent clock request}
■ ^{High isolation of supply noise to clock input}
■ ^{High output to output Isolation}
■ ^{Output Drive up to 50 pF}
■ ^{EMI controlled output edges and EMI filtering}
■ ^{Integrated 1.8V Low-Dropout Regulator}
— Low Output Noise Voltage
— 10 mA load current
■ ^{I2C Configurable up to 400 kHz (Fast Mode)}
■ ^{Ultra low standby current}
■ ^V_BAT ^{range = 2.5V to 5.5V}
Applications
■ ^{Mobile handsets}
■ ^PDAs
■ ^{Portable Equipment}
Typical Application
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