The SP8858 is a single chip synthesiser intended for PLL signal synthesis applications up to 1.5GHz and includes a dual modulus prescaler (4N/N11), programmable A, M and R dividers, digital phase detector, charge pump and lock detect circuits.

The SP8858 is a development of the SP8853 synthesiser with low residual phase noise, increased dynamic range above 1GHz and an improved high gain phase detector design that eliminates the dead-band.

The low prescaler modulus, programmable to either 16/17 or 8/9, together with the 15-bit M counter and 13-bit reference counter make this device ideal for a diverse range of high performance applications.

The nominal phase detector gain is set by a reference current into pin 24 and the gain can be varied over a 4:1 range when the device is programmed. The dividers, the phase detector sense, the prescaler modulus and the data buffer control logic are also programmable using the three wire serial interface. An alternative 22-bit control word for the A and M dividers and phase detector gain can be stored so allowing fast frequency hopping and bandwidth switching by simply toggling the logic level on pin 13 (F1/F2). In addition, the A counter of the ‘a(chǎn)ctive’ buffer can be programmed with only 6 bits, allowing fast hopping to adjacent channels.

A simple exclusive - or lock detect circuit is also provided, the sensitivity of which is determined by an external capacitor.

FEATURES

■ Low Residual Phase Noise (see Reference 1)

■ Operation to 1·5GHz over Full Temperature Range

■ High Input Sensitivity

■ Improved Linear Digital Phase Detector

■ Programmable Charge Pump Current: 10μA to 2 mA

■ On-chip 416/17 or 48/9 Dual Modulus Prescaler

■ Three-wire Serial Data Interface

■ 13-bit Reference Counter

■ 15-bit M Counter

■ Stores an Alternative Programming Word

■ Facility to Program A counter Only

■ Power Saving Standby Mode