lmx5080mx National Semiconductor Corporation, lmx5080mx Datasheet - Page 4

• Manufacturer Part Number: lmx5080mx
• Description: Pllatinum? 2.7 Ghz Low Power Dual Modulus Prescaler For Rf Personal Communications
• Manufacturer: National Semiconductor Corporation

www.national.com
Functional Description
The basic phase-lock-loop (PLL) configuration using an ex-
ternal prescaler consists of a high-stability crystal reference
oscillator, a prescaler such as the National Semiconductor
LMX5080, a low frequency synthesizer, a voltage controlled
oscillator (VCO), and a loop filter. The frequency synthesizer
typically includes programmable reference [R] and feedback
[N] frequency dividers, a phase detector, as well as a charge
pump. The MC signal is fed back to the prescaler from either
Block Diagram
4
the low frequency synthesizer, or a controller to set the pres-
caler divide ratio to N or N+2. The prescaler output fre-
quency is established by dividing the VCO signal down via
the prescaler modulus. The RF inputs to the prescalar con-
sist of the Fin and /Fin input pins which are complementary
inputs to a differential pair amplifier. This configuration can
operate to 2 GHz with an input sensitivity of −15 dBm.
DS100940-3