Skyworks Solutions Inc. SI4136-BM

Overview

SI4136-BM from Silicon Laboratories is a monolithic dual-band RF and IF synthesizer IC with integrated VCOs, loop filters, and a three-wire serial interface. It delivers RF synthesis in 2300–2500 MHz (RF1) and 2025–2300 MHz (RF2), plus IF synthesis from 62.5 MHz to 1000 MHz, enabling frequency-agile wireless transceivers for ISM-band communications.

For engineers reviewing the SI4136-BM datasheet, SI4136-BM pinout, SI4136-BM application, or SI4136-BM equivalent, this device supports rapid PLL lock (<100 µs), ultra-low standby current (1 µA), and self-tuning compensation for external inductor tolerance - critical for W-LAN IEEE 802.11 and dual-band radio designs requiring stable local oscillator generation.

Technical Context

The SI4136-BM implements three independent PLLs: two RF PLLs (RF1/RF2) with internal bond-wire inductance–defined VCO ranges and one IF PLL with externally tuned VCO center frequency (526–952 MHz). Each RF PLL includes a ÷2 prescaler before the N-divider, making phase detector frequency f_φ = f_REF/2R; the IF PLL uses f_φ = f_REF/R.

It features programmable reference divider (XINDIV2), selectable IF output division (÷1/÷2/÷4/÷8), and autonomous self-tuning that compensates for ±10% external inductor tolerance and temperature drift. Power management is supported via hardware PWDN pin and software-controlled PDIB/PDRB bits, enabling independent RF/IF section shutdown.

Key Specifications

Pinout & Package

The SI4136-BM is housed in a 24-pin TSSOP package (3.5 mm × 7.8 mm, 0.65 mm pitch), optimized for RF isolation and compact wireless modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RF/IF synthesizer applications.

Compared with Si4126-BM, SI4136-BM adds dual-band RF agility and full IF synthesis in the same footprint; versus MAX2870ETJ+, it offers lower power and simpler loop filter design but narrower RF bandwidth and no fractional-N flexibility.

Availability

SI4136-BM is available at Aetrix Electronics and suitable for wireless LAN infrastructure, dual-band cellular front-ends, and ISM-band telemetry systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SI4136-BM includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Silicon Laboratories is a fabless semiconductor company specializing in mixed-signal ICs for timing, wireless, and sensor applications, with deep expertise in RF synthesis and clock technology.

The SI4136-BM belongs to Silicon Labs' ISM-band RF synthesizer product line, designed specifically to replace discrete PLL/VCO solutions in cost- and space-constrained wireless communication systems.

FAQ

What is the RF frequency coverage of the SI4136-BM?

The SI4136-BM supports two distinct RF bands: RF1 operates from 2300 MHz to 2500 MHz, and RF2 covers 2025 MHz to 2300 MHz. These ranges are fixed by internal bond-wire inductance and do not require external tuning components. The SI4136-BM automatically selects between RF1 and RF2 based on which R- or N-divider register was most recently programmed via its three-wire serial interface.

How does the SI4136-BM achieve fast frequency settling?

The SI4136-BM achieves ≤100 µs lock time through a unique integer-N PLL architecture combined with an on-chip self-tuning algorithm. After power-up or frequency reprogramming, the self-tuning algorithm first brings the VCO within ~1% of target frequency in ~13 phase detector cycles; then the PLL completes precise locking in ~25 additional cycles. This avoids the spurious modulation and phase noise penalties typical of fractional-N synthesizers.

Can the SI4136-BM generate IF frequencies below 100 MHz?

No - the SI4136-BM's IF synthesizer is specified for 62.5 MHz to 1000 MHz. Its minimum IF output is constrained by the IF VCO center frequency range (526–952 MHz) and the ±5% tuning window. While the IFDIV register supports ÷1/÷2/÷4/÷8 division, the lowest usable IFOUT occurs when f_CEN = 526 MHz and IFDIV = ÷8, yielding 65.75 MHz - close to the 62.5 MHz lower limit stated in the datasheet. Frequencies below 62.5 MHz are not supported.

What external components are required for SI4136-BM operation?

The SI4136-BM requires minimal external components: a single external inductor (2.2–12.0 nH) between IFLA and IFLB for IF VCO tuning; 560 pF AC-coupling capacitors on XIN and RFOUT/IFOUT; and standard 0.022 µF bypass capacitors on each supply rail (VDDR, VDDI, VDDD). No external loop filters, reference buffers, or VCO tank capacitors are needed - all are integrated.

How is power management implemented on the SI4136-BM?

Power management on the SI4136-BM is implemented via dual mechanisms: hardware (active-low PWDN pin forces full shutdown to 1 µA) and software (PDIB and PDRB bits in Register 2 independently disable IF and RF sections). The serial interface remains fully functional in all modes. Setting AUTOPDB = 1 in Register 0 automatically powers up both RF and IF sections when the reference amplifier is enabled.