UMA1021M

Features:

· Low phase noise
· Low current from 3 V supply
· Fully programmable main divider
· 3-line serial interface bus
· Independent fully programmable reference divider,driven from external crystal oscillator
· Dual charge pump outputs
· Hard and soft power-down control.


Application

· 900 MHz and 2 GHz mobile telephones
· Portable battery-powered radio equipment.


Pinout




Description

The device UMA1021M is designed to operate from 3 NiCd cells, in pocket phones, with low current and nominal 3 V supplies. The synthesizer operates at RF input frequencies up to 2.2 GHz, with a fully programmable reference divider. All divider ratios are supplied via a 3-wire serial programming bus. Separate power and ground pins are provided to the analog (charge-pump) and digital circuits.

The UMA1021M ground leads should be externally short-circuited to prevent large currents flowing across the die and thus causing damage. VDD1 and VDD2 must also be at the same potential (VDD). VCC must be equal to or greater than VDD (e.g. VDD = 3 V and VCC = 5 V for wider VCO control voltage range).

The UMA1021M phase detector has two charge-pump outputs, CP and CPF, the latter of which is enabled directly at pin FAST. This permits the design of adaptive loops. The charge pump currents (phase detector gain) are fixed by an external resistance at pin ISET and via the serial interface. Only a passive loop filter is necessary; the charge pumps function within a wide voltage compliance range to improve the overall system performance.