46.875-1682.5MHz Fractional-N PLL with integrated VCO and FM/FSK modulator

  • Inquiry
  • Data Sheet


Two-way Radio ICs
The AK1574 is a fractional-N PLL synthesizer with a VCO (Voltage Controlled Oscillator) that has frequency modulation function. It integrates an output divider for VCO signal that operates by 3365MHz frequency at maximum realizing wide range output frequency from 46.875MHz to 1682.5MHz. The AK1574 reduces the power consumption while realizing low normalized phase noise of -221dBc/Hz. It achieves 90mW(3V/Single output) operation when outputting -6dBm. It is capable of replacing VCOs, that use to consist of variable capacitance diode and etc., in various wireless applications especially suitable for hand portable wireless devices. The fast lock-up, that completes in only less than 1ms, suites for intermittent operation of PLL/VCO. It contributes to reducing the system power consumption.

Two set of mode settings that include frequency setting and On/Off settings of RF output pins are available.
 Output Mode A: Frequency setting fRx, RFOUT_A On, RFOUT_B Off (Single output)
 Output Mode B: Frequency setting fTx, RFOUT_A Off, RFOUT_B On (Single output)
By setting as above, the RFOUT_A pin can be used as receiving output and the RFOUT_B pin can be used as transmitting output.
 Output Mode A: Frequency fRx, RFOUT_A On, RFOUT_B On (Differential Output)
By setting as above, two lines of common-frequency can be output. It is able to use for diversity receivers. When both RFOUT_A and B are On, the signal is output as differential signal so that it is capable of being used as single differential output.

Data input format for frequency modulation corresponds to both analog and digital data inputs. Digital I/F data format can be selected from I2S (Inter-IC Sound), Left-justified and SPI. The AK1574 has a frequency shift compensation function for TCXO that is used when shipping user’s product. Therefore, it is able to use TCXO instead of VCTCXO.

Key Features

● Easy to Modulate the Frequency of an Analog Voice Signal Input

By integrating a dedicated A/D converter, (ADC), frequency modulation of analog voice signal inputs are accomplished. 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).

● Low Phase Noise and Low Power Consumption

The AK1574 is optimized for narrow band radio below 1 GHz. While achieving low normalized phase noise of -221 dBc/Hz, it operates with power consumption of 90 mW, (3V/single output), at -6 dBm output.
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. The intermittent operation the PLL and VCO can reduce the power consumption of the system.

Main Specifications

PLL Synthesizer with VCO support from 46.875 to 1682.5MHz
Product Name
AK1573/B/C (3 Chip Options)
MethodFractional NInteger N
Operating Frequency46.875MHz to 1682.5MHz30MHz to 3000MHz
Consumption Current30mA at 3V, 520.1MHz,
-6dBm Output (Single Output)
33mA at 3V, 1600MHz,
-5dBm Output
Power Supply
/Temperature Range
2.7 to 3.45V (IOVDD: 1.7V Operation)
/ -40 to +85ºC
2.7 to 3.3V
/ -40 to +85ºC
Normalized Phase Noise-221dBc/Hz (Fractional N in operation)-223dBc/Hz
In-band Phase Noise-125dBc/Hz at 12.5kHz Offset,
420MHz Output, PFD Frequency =50.4MHz
Not availabe
Modulation Function·Support analog voice signal inputs
(integrated ADC)
·Various Digital I/F: I2S, Left justified, SPI
Not availabe
23-bit ΔΣ Modulator10Hz or less frequency resolution
Not availabe
Variable Output Buffer of Output Current-12 to +6dBm Output (Single Output)-12 to +6dBm Output
Reference Clock Multiplying/Dividing CircuitReduce Integer Boundary Spurious(IBS)Not availabe
Reference Clock Divider Output FunctionCommon System ClockNot availabe
REFCKIN Frequency10MHz to 60MHz10MHz to 300MHz
Package36-pin QFN
(5mm×5mm×0.75mm0.4mm pitch)
24-pin QFN
(4mm×4mm×0.75mm0.5mm pitch)

>> Read more

Block Diagram

Block Diagram

Page Top