The AK1574 integrates an output divider for the VCO signal that operates with a maximum frequency of 3365MHz, effectively allowing for a wide range of output frequencies from 46.875MHz to 1682.5MHz. It reduces the power consumption - 90mW (3V/Single output) operation, at -6 dBm output - while achieving low normalized phase noise of -221dBc/Hz.
The new device is capable of replacing VCOs that use to consist of variable capacitance diode configurations in various wireless applications, and is especially suitable for handheld and portable wireless devices. Lock-up time, which takes several ms to several tens of ms for a VCO with a general variable capacitance diode and winding coil configuration, is completed in less than 1 ms on the AK1574. This makes it extremely suitable for intermittent operation of PLL/VCO, and contributes to reducing the system power consumption.
Mode settings for the AK1574 include frequency setting and On/Off settings of RF output pins for single output and differential output, supporting diversity receivers.
Data input format for frequency modulation corresponds to both analog and digital data inputs. Digital I/F data format can be selected from I2S, left-justified and SPI. The AK1574 has a frequency shift compensation function for TCXO that is configured when shipping, allowing to use TCXO instead of VCTCXO.
By integrating a dedicated A/D converter, the AK1574 accomplishes frequency modulation of the analog signal inputs. This makes it easy to replace a VCO built-in PLL without changing the design considerably from the conventional architecture, (inputting the analog voice signal directly to the VCO without transmitting via a quadrature modulator).
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