ZHCSP40B October 2021 – June 2022 LMX2571-EP
PRODUCTION DATA
The LMX2571-EP is a frequency synthesizer with low-noise, high-performance integrated VCOs. The 5-GHz VCO cores, together with the output channel dividers, can produce frequencies from 10 MHz to 1344 MHz. The LMX2571-EP supports two operation modes, synthesizer mode and PLL mode. In synthesizer mode, the entire device is used; in PLL mode the internal VCO is bypassed, and an external VCO is required to implement a complete synthesizer.
The PLL is a fractional-N PLL with programmable Delta Sigma modulator (first order to fourth order). The fractional denominator is of variable length and up to 24-bits long, providing a frequency step with very fine resolution.
The internal VCO can be bypassed, allowing the use of an external VCO. A separate 5-V charge pump is dedicated for the external VCO, eliminating the need for an op-amp to support 5-V VCOs. A new advanced FastLock technique is developed to shorten the lock time to less than 1.5 ms, even there is a very narrow loop bandwidth.
A unique programmable multiplier is incorporated in the R-divider. The multiplier is used to avoid and reduce integer boundary spurs or to increase the phase detector frequency for higher performance.
The LMX2571-EP supports direct digital FSK modulation, thus allowing a change in the output frequency by changing the N-divider value. The N-divider value can be programmed through MICROWIRE interface or through pins. Discrete 2-, 4- and 8-level FSK, as well as arbitrary-level FSK, are supported. Arbitrary-level FSK can be used to construct pulse-shaping FSK or analog-FM modulation.
The output has an integrated T/R switch, and the divided-down internal or external VCO signal can be output to either the TX port or the RX port. The switch can also be configured as a 1:2 fanout buffer, providing the signal on both outputs at the same time. In addition to port switching, the output frequency can be switched between two pre-defined frequencies, F1 and F2, simultaneously. This feature is ideal for use in FDD duplex system where the TX frequency is different from RX (LO) frequency.
The LMX2571-EP requires only a single 3.3-V power supply. Digital logic interface is 1.8-V input compatible. The analog blocks power supplies use integrated LDOs, eliminating the need for high performance external LDOs.
Programming of the device is achieved through the MICROWIRE interface. The device can be powered down through a register programming or toggling the Chip Enable (CE) pin.