ADF4108BCPZ - 8 GHz Integer-N PLL Synthesizer | Analog Devices
MPN: ADF4108BCPZ ✓ ActiveADF4108BCPZ Overview
A phase-locked loop, or PLL, is a feedback-controlled timing system that locks an output oscillator to a stable reference frequency. In the broader semiconductor hierarchy, the ADF4108 is a clock-and-timing IC, a frequency synthesizer, and ultimately a programmable RF signal-generation component. Its integer-N architecture allows a reference frequency to be multiplied through programmable counters and a dual-modulus prescaler to create a local oscillator for RF transmitters and receivers.
Key features include an 8 GHz maximum RF input frequency, programmable A and B counters, a programmable reference divider, and a dual-modulus prescaler. The 20-lead WFQFN package with an exposed pad supports compact surface-mount layouts while providing a thermal path for the charge-pump and PLL circuitry. The digital programming interface allows the divider values, prescaler mode, counter settings, and operating mode to be configured by an embedded controller.
The internal architecture separates the phase-frequency detector from the charge pump so the loop can compare the divided output signal with the divided reference. In operation, the charge pump drives the loop-filter error current, while the VCO and feedback divider complete the closed loop. Designers must select the reference, N-divider, loop bandwidth, charge-pump current, and filter components together to achieve adequate phase noise, lock time, and spur performance.
Typical applications include wireless receiver and transmitter local oscillators, up-conversion and down-conversion stages, instrumentation, and test-and-measurement equipment. The device is particularly relevant where a programmable integer division ratio is required for RF channel selection or coherent signal generation.
A key design consideration is the need for a clean reference source and a correctly sized loop filter. Keep the reference and feedback paths short, provide stable decoupling, and use the manufacturer’s recommended PCB stack-up and exposed-pad soldering pattern to preserve RF behavior and thermal performance.
This page combines manufacturer-level operating details with application guidance, pin-package guidance, and practical PLL design notes to support faster component selection and PCB implementation.
Drop-in alternatives for ADF4108BCPZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
ADF4106BCPZ
✅ Drop-In ⚠️ Specs UnverifiedContact for price
View Datasheet →ADF4107BCPZ
✅ Drop-InContact for price
View Datasheet →ADF4110BCPZ
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
ADF4108BCPZ Specifications
| Product Type | Integer-N PLL frequency synthesizer |
| Maximum RF Input Frequency | 8 GHz |
| Channel Count | 1 channel |
| Architecture | Integer-N with dual-modulus prescaler |
| A Counter Resolution | 6 bit |
| B Counter Resolution | 13 bit |
| Prescaler Configuration | Programmable P/P+1 dual-modulus |
| Reference Divider | Programmable |
| Phase-Frequency Detector | Low-noise digital PFD |
| Charge Pump | Precision charge pump |
| Package | 20-lead WFQFN with exposed pad |
| Mounting Type | Surface mount |
ADF4108BCPZ 20-lead wfqfn with exposed pad Pin Configuration Guide
Pin configuration for ADF4108BCPZ (20-lead wfqfn with exposed pad package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for ADF4108BCPZ.
Refer to the datasheet for full pin configuration.
Typical Applications
ADF4108BCPZ is suitable for 6 applications: Wireless Receiver Local Oscillator, Wireless Transmitter Frequency Synthesis, RF Up-Conversion and Down-Conversion, Instrumentation and Test Equipment, Coherent RF Signal Generation, RF Channel-Selection Loops.
Wireless Receiver Local Oscillator
The ADF4108BCPZ fits a wireless receiver local oscillator because its 8 GHz RF input range covers upper-microwave and microwave receiver channels while the integer-N divider supports programmable frequency selection. The 6-bit A counter, 13-bit B counter, programmable reference divider, and P/P+1 dual-modulus prescaler allow the synthesizer ratio to be tuned under serial control. In a receiver, the synthesized local oscillator feeds the mixer's up-conversion or down-conversion stage. The principal design tradeoff is loop performance: reference phase noise, charge-pump current, loop filter, and VCO phase noise directly determine the receiver's noise and spur behavior.
Recommended
Wireless Transmitter Frequency Synthesis
The ADF4108BCPZ can generate a programmable transmitter local oscillator for wireless equipment operating through an 8 GHz RF input range. Its dual-modulus prescaler and independent A and B counters provide flexible integer-N division ratios, while the serial interface permits channel changes from a host controller. The device is placed between the PLL reference and a VCO, with the charge pump driving an external loop filter and the VCO feeding the prescaler through a feedback divider. Designers should optimize lock time and spur suppression for the required channel mask, and should use the same reference frequency presented to both the reference divider and feedback path.
Recommended
RF Up-Conversion and Down-Conversion
The ADF4108BCPZ is appropriate for RF mixers that require an adjustable local-oscillator signal during up-conversion or down-conversion. Its maximum RF input frequency of 8 GHz provides coverage for many microwave and millimeter-wave transceiver front ends, while the integer-N architecture simplifies channel planning by relating the output frequency to a stable reference. The synthesized signal drives the appropriate mixer port, and the resulting intermediate-frequency choice affects image rejection and filtering requirements. A careful frequency-plan review must ensure that the prescaler mode, loop-divider values, charge-pump settings, and loop bandwidth provide reliable locking at every required channel.
Recommended
Instrumentation and Test Equipment
The ADF4108BCPZ can serve as the programmable frequency synthesizer in RF instrumentation where multiple output frequencies must be selected accurately from a common reference. Its register-programmable dividers allow the output ratio to change without replacing hardware, and the 8 GHz maximum RF input range supports microwave test systems. The device can drive the feedback input of a suitable VCO while the charge-pump output controls the external loop filter. For laboratory equipment, phase noise and reference purity are often the decisive specifications. Measure lock behavior across temperature and supply conditions, and allow sufficient settling time before capturing frequency-dependent measurements.
Recommended
Coherent RF Signal Generation
The ADF4108BCPZ supports coherent RF signal generation when a stable reference and a phase-locked VCO are both available. The programmable reference divider, 6-bit A counter, 13-bit B counter, and dual-modulus prescaler create an integer relationship between the reference and synthesized output, which simplifies frequency reconciliation across channels or instruments. Because the PLL responds to phase and frequency error through the detector and charge pump, loop bandwidth determines how quickly the system settles and how much reference noise appears at the output. Use a clean reference source, controlled supply rails, and a stable loop filter, and verify phase-noise degradation across the full tuning range.
Recommended
RF Channel-Selection Loops
The ADF4108BCPZ is useful in RF systems that need programmable channel selection without changing the reference oscillator or synthesizer hardware. A host controller writes the reference-divider, A-counter, B-counter, and prescaler settings to change the VCO's locked frequency. The same architecture can support synthesized local oscillators for multichannel receivers, monitoring equipment, and compact RF modules. Designers must confirm that each requested ratio uses a valid prescaler mode and that the loop settles within the system's channel-switching interval. Adequate supply decoupling, a controlled reference input, and thermal management of the exposed pad help maintain consistent behavior across repeated tuning cycles.
Recommended
Recommended Products Summary
Engineering reference data for ADF4108BCPZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ADF4106BCPZ | ADF4107BCPZ | ADF4110BCPZ |
|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 20-lead WFQFN with exposed pad | 20-lead WFQFN with exposed pad | 20-lead WFQFN with exposed pad | 20-lead WFQFN with exposed pad |
| Maximum RF Input Frequency | 8 GHz | 6 GHz | 7 GHz | 11 GHz |
| Channel Count | 1 channel | 1 channel | 1 channel | 1 channel |
| A Counter Resolution | 6 bit | 6 bit | 6 bit | 6 bit |
| B Counter Resolution | 13 bit | 13 bit | 13 bit | 13 bit |
| Prescaler Architecture | Programmable P/P+1 dual-modulus | Programmable P/P+1 dual-modulus | Programmable P/P+1 dual-modulus | Programmable P/P+1 dual-modulus |
| Reference Divider | Programmable | Programmable | Programmable | Programmable |
| Charge Pump | Precision charge pump | Precision charge pump | Precision charge pump | Precision charge pump |
Key Differentiators
- Higher RF frequency capability than the ADF4107BCPZ (vs ADF4107BCPZ)
- Broader RF input range than the ADF4106BCPZ (vs ADF4106BCPZ)
- More directly matched divider architecture than the higher-frequency ADF4110BCPZ (vs ADF4110BCPZ)
Design Notes
Follow the manufacturer land pattern for the 20-lead WFQFN exposed-pad package, including its thermal and electrical land geometry. Place input, output, reference, and decoupling connections according to the datasheet pin-description table rather than relying only on general guidance. Keep the charge-pump and loop-filter region away from noisy switching nodes, and minimize loop area around sensitive feedback connections.
Place the recommended local bypass capacitors directly beside their associated supply pins, with short ground returns. The reference input is a timing signal and should be isolated from digital return currents and switching-node paths. A stable reference amplitude and clean supply rails reduce unwanted phase noise and improve repeatability across channel changes.
Do not select divider and prescaler settings independently of the required output frequency. First verify that the target ratio can be represented by the reference divider, A counter, B counter, and valid P/P+1 prescaler mode. Then calculate whether the phase-detector frequency remains within the device limits and whether the loop filter can meet the required lock time.
The exposed pad provides the principal thermal path, but it must be soldered according to the manufacturer land pattern and connected to an adequate copper area. Validate the final PCB under worst-case operating temperature, supply voltage, and tuning state. Temperature drift can affect VCO behavior and therefore alter PLL lock time, phase noise, and spur performance even when the synthesizer itself remains within its electrical ratings.
Compliance Information
No specific RoHS, REACH, lead-free, halogen-free, or conflict-minerals statement is identified for the ADF4108BCPZ. AEC-Q100 is not applicable to this general-purpose clock-and-timing IC.
