ADF4002 PLL IC Pin Diagram, Circuit and Applications

The ADF4002 is a high-performance phase-locked loop IC designed for integer-N frequency synthesis applications requiring low phase noise and excellent frequency stability. It is widely used in wireless communication equipment, instrumentation, local oscillators, and RF transceivers. This article explains its pin diagram, working principle, circuit, features, and applications.

Key features of ADF4002 PLL

• Bandwidth: 400 MHz
• Power Supply: 2.7 V to 3.3 V
• Extended Tuning Voltage: A separate charge pump supply (Vp) allows for an extended tuning voltage in 3 V systems (up to 5.5 V).
• Programmability: Features programmable charge pump currents and a 14 bit reference counter (R counter) and 13-bit N counter.
• Interface: 3-wire serial interface (SPI compatible) supporting up to 20 MHz clock rates.
• Lock Detect: Supports both analog and digital lock detect.
• Power Management: Includes both hardware and software power down modes.
• Phase Detector: 104 MHz phase detector frequency with a very low normalized phase noise floor (–222 dBc/Hz).

ADF4002 PLL Pin Diagram

Here’s a look at the ADF4002 PLL pin diagram:

Pin No.	Pin Name	Type	Function
1	RSET	Analog	Connect an external precision resistor (typically 5.1 kΩ) to CPGND to set the maximum charge pump output current.
2	CP	Analog Output	Charge pump output. Connects to the external PLL loop filter, which drives the VCO tuning voltage.
3	CPGND	Ground	Ground return for the charge pump circuitry.
4	AGND	Ground	Analog ground for the RF input and analog circuitry.
5	RFINB	RF Input	Complementary RF input to the phase-frequency detector. Normally AC-coupled and paired with RFINA for differential operation.
6	RFINA	RF Input	Primary RF input from the external VCO or divider. Accepts the feedback signal for PLL operation.
7	AVDD	Power	Analog supply voltage (2.7 V to 3.3 V). Decouple close to the pin.
8	REFIN	Input	Reference clock input. Accepts CMOS, TTL, or AC-coupled sine-wave reference signals.
9	DGND	Ground	Digital ground reference.
10	CE	Digital Input	Chip Enable. Logic Low powers down the synthesizer and places the charge pump in high-impedance mode. Logic High enables normal operation.
11	CLK	Digital Input	Serial clock input for the 3-wire SPI-compatible programming interface.
12	DATA	Digital Input	Serial data input (MSB first) used to program the internal registers.
13	LE	Digital Input	Load Enable. Transfers the serial data from the shift register into the selected control register.
14	MUXOUT	Digital Output	Multiplexed output. Can be programmed to provide digital lock detect, analog lock detect, R-counter output, N-counter output, or other diagnostic signals.
15	DVDD	Power	Digital supply voltage (2.7 V to 3.3 V). Should be the same voltage as AVDD.
16	VP	Power	Charge pump supply voltage. Can be higher than DVDD (up to 5.5 V) to support VCOs requiring a wider tuning voltage range.

Example Use Case : ADF4002 as Standalone Phase Frequency Detector (PFD)

Because the ADF4002 allows both the R and N counters to be programmed to exactly 1, the device can effectively bypass the division and act as a standalone PFD and charge pump.

Setup: The reference frequency is fed directly into the PFD (R=1). The charge pump output integrates into a control voltage for a VCXO, which is then divided down to the desired frequency using an external prescaler/divider.

Result: This is particularly useful in “clock cleaning” applications or for creating a high performance LO, taking advantage of the device’s extremely low in-band phase noise floor.

Applications of ADF4002

• Clock conditioning
• Clock generation
• IF LO (Intermediate Frequency Local Oscillator) generation
• Upconversion and downconversion sections of wireless receivers and transmitters.

Summary

The ADF4002 offers reliable frequency synthesis with low phase noise and high stability. It is suitable for RF communication and instrumentation systems.