SI4133-BT - 1.8 GHz Dual-Band RF Synthesizer | Silicon Labs
MPN: SI4133-BT ✗ End of Life| Qty | Unit Price | Extended |
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| 1 | $0 | $0.00 |
| 10 | $0 | $0.00 |
| 100 | $0 | $0.00 |
| 500 | $0 | $0.00 |
| 1,000 | $0 | $0.00 |
SI4133-BT Overview
A frequency synthesizer is a clock-and-timing or RF integrated circuit that locks an output oscillator to a stable reference frequency. By dividing the reference, comparing phases, and driving a voltage-controlled oscillator through an integrated loop filter, the SI4133 generates programmable wireless-communications carrier frequencies. This synthesis function places it within the hierarchy PLL frequency synthesizer, clock and timing IC, RF signal generator, and semiconductor.
The SI4133-BT requires only two external components according to the verified datasheet excerpt because its VCOs, loop filters, varactors, and resonators are integrated. It offers low phase noise, programmable power-down modes, and a self-tuning algorithm that compensates for tank-inductance variation after startup or a programmed frequency change. Those features simplify RF design while preserving the sensitivity expected in wireless links.
Silicon Labs specifies that package inductance must be considered because total VCO tank inductance is in the low-nanohenry range. The 24-TSSOP outline is only 0.173 inch, or 4.40 mm, wide, and surface mounting makes it practical for compact radio designs. The verified operating-temperature listing spans -40 C to +85 C, while the provided evidence does not establish the complete set of frequency bands for this exact orderable MPN.
Typical uses include RF local-oscillator generation, dual-band wireless receivers and transmitters, intermediate-frequency synthesis, and compact RF communications modules. In these systems, the synthesizer converts a reference oscillator into a programmable RF carrier used by mixers, modulators, or demodulators. Low phase noise supports signal integrity, while power-down current helps preserve battery life between active periods.
The primary design consideration is reference and power-layout discipline. Keep the reference path short, use recommended decoupling at the supply pins, and follow the manufacturer's external-inductor and grounding guidance. PCB parasitics can alter the low-inductance VCO tank, so placement and trace geometry should be treated as part of the RF network rather than as purely electrical interconnect.
This page consolidates the verified distributor specifications, a manufacturer-hosted datasheet link, family architecture, and engineering-focused usage guidance. Pricing remains quote-dependent because the supplied web results advertise live distributor purchasing without numeric prices, and it does not present five verified drop-in replacements.
Drop-in alternatives for SI4133-BT — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with SI4133-BT (same form factor and footprint) — differing in Mounting Type, Package, Product Type, Standby Current, Integrated VCO Count.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
SI4133-BMR
✅ Drop-In📋 Reference alternative (not in catalog)
SI4133-BM
✅ Drop-In📋 Reference alternative (not in catalog)
SI4133-D-GM
✅ Drop-In✓ In Stock
$3.3339 / Unit
View Datasheet →SI4133-D-GT
✅ Drop-In✓ In Stock
Contact for price
View Datasheet →SI4133-BT-T
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
SI4133-BT Specifications
| Product Type | Frequency synthesizer IC |
| Maximum Frequency | 1.8 GHz |
| Operating Supply Voltage | 2.7 V to 3.6 V |
| Typical Supply Current | 18 mA |
| Standby Current | 1 uA |
| Number of Circuits | 1 |
| Integrated VCO Count | 3 |
| Synthesis Architecture | Dual-band RF and IF synthesis |
| PLL | Yes |
| Reference Input | Crystal |
| Output | Clock |
| External Components Required | 2 components minimum |
| Operating Temperature Range | -40 C to +85 C |
| Package | 24-TSSOP, 0.173 inch / 4.40 mm wide |
| Mounting Type | SMD |
| Power-Down Modes | Programmable |
| VCO Tuning | Self-tuning algorithm |
| RoHS Details | N |
| Number of Pins | 24 pins |
SI4133-BT 24-tssop, 0.173 inch / 4.40 mm wide Pin Configuration Guide
Pin configuration for SI4133-BT (24-tssop, 0.173 inch / 4.40 mm wide 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 SI4133-BT.
Refer to the datasheet for full pin configuration.
Typical Applications
SI4133-BT is suitable for 6 applications: Dual-Band Wireless Receiver, Wireless Transmitter Local Oscillator, Intermediate-Frequency Synthesizer, Battery-Powered Wireless Module, RF Test and Measurement Source, RF Power and Frequency Control.
Dual-Band Wireless Receiver
The SI4133-BT fits a receiver that requires programmable IF or RF synthesis because it integrates three VCOs, loop filters, phase detectors, and programmable dividers in one 24-TSSOP device. Its verified maximum frequency is 1.8 GHz, while the 2.7 V to 3.6 V operating range fits a 3.3 V-class RF signal chain. The synthesizer can generate a local oscillator for mixers that translate received channels into a lower-frequency processing band. Low phase noise is valuable, but the exact RF and IF output ranges must be checked against the programming tables before schematic release.
Recommended
Wireless Transmitter Local Oscillator
The SI4133-BT can generate a programmable RF carrier for a compact wireless transmitter when the requested frequency falls within the exact SI4133-BT output plan. Its integrated VCOs and loop filters reduce the number of external components to two minimum, while the 1 uA standby current supports power-managed equipment. In the transmit path, the synthesized carrier may feed a mixer or modulator after appropriate filtering and gain. Engineers must verify output drive, spur performance, tuning resolution, and regulatory harmonics from the manufacturer datasheet before release.
Recommended
Intermediate-Frequency Synthesizer
The SI4133-BT is designed to perform IF synthesis as well as dual-band RF synthesis, making it suitable for radios that derive multiple intermediate frequencies from one reference. Its phase detectors, dividers, loop filters, and three integrated VCOs support closed-loop frequency generation without building separate analog synthesizer blocks around discrete components. The 18 mA typical current is acceptable for many compact systems, but phase-noise and integrated phase-deviation requirements should be evaluated at the IF frequency used by the receiver or transmitter.
Recommended
Battery-Powered Wireless Module
The SI4133-BT's programmable power-down modes and 1 uA standby current make it relevant to battery-operated wireless modules that spend substantial time between RF bursts. During active operation, its typical supply current is 18 mA, so total system energy depends on activity ratio, supply efficiency, and RF-path load. The 24-TSSOP package limits board area, and the minimum two-external-component architecture can simplify assembly. Firmware must use the documented power-down and wake-up sequence to achieve the intended current reduction.
Recommended
RF Test and Measurement Source
The SI4133-BT can provide a programmable RF or IF source for compact instrumentation when the required output lies within its verified 1.8 GHz maximum. Integrating VCOs, loop filters, dividers, and phase detectors provides a compact synthesizer suitable for repeatable bench and embedded measurement setups. For metrology-grade use, engineers should evaluate phase noise, tuning accuracy, spur performance, warm-up time, and calibration stability; these figures are not quantified in the supplied snippets. A shielded, well-grounded PCB is important because external tank inductance and package parasitics affect behavior.
Recommended
RF Power and Frequency Control
The SI4133-BT may serve as the frequency-control element in RF systems requiring a stable, programmable carrier for power and signal-path coordination. Its integrated PLL blocks remove the need for a separate reference divider, phase detector, and loop filter for each synthesized output. A self-tuning algorithm compensates for tank-inductance variation after startup or a frequency change, improving repeatability when PCB and component tolerances vary. Nevertheless, loop bandwidth and filtering must be selected correctly; otherwise, phase noise or settling performance can be inadequate for demanding RF power-control loops.
Recommended
Recommended Products Summary
Engineering reference data for SI4133-BT — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SI4133-BMR | SI4133-BM | SI4133-D-GM | SI4133-D-GT |
|---|---|---|---|---|---|
| Brand | Silicon Labs | Silicon Labs | Silicon Labs | Silicon Labs | Silicon Labs |
| Package | 24-TSSOP | 24-TSSOP | 24-TSSOP | 24-TSSOP | 24-TSSOP |
Key Differentiators
- Integration level (vs SI4133-D-GM)
- Frequency capability (vs SI4133-D-GM)
- External-component reduction (vs SI4133-BM)
- Power-management capability (vs SI4133-D-GT)
Design Notes
Treat the VCO tank as an RF structure. The manufacturer datasheet states that package inductance matters because total tank inductance is in the low-nanohenry range. Place the external inductor and associated RF loop exactly as recommended, minimize return-path discontinuity, and avoid copper or test-point geometries that unexpectedly raise capacitance. Review the final stack-up and enclosure because nearby metal can alter tank behavior even when the schematic values are unchanged.
Provide local supply decoupling at the SI4133-BT and route the return current continuously under the device and RF network. The verified operating range is 2.7 V to 3.6 V, with 18 mA typical active current and 1 uA standby current. Measure ripple at the IC under maximum synthesizer activity rather than at a quiet point on the rail. Validate wake-up timing and programmed frequency settling before relying on the advertised standby reduction.
Keep the reference oscillator path controlled and inspect its amplitude, edge quality, and return path because PLL performance depends on a clean reference in addition to the RF divider settings. Route RF outputs away from noisy digital programming lines and use the shortest practical connection from the synthesizer to the next RF stage. Confirm phase noise, spurs, settling time, and output isolation against the manufacturer's plots for the intended channel plan.
Do not assume that a similarly named SI4133 orderable code is automatically software- and pin-compatible. Verify register addresses, power-on defaults, serial interface levels, RF output assignments, divider ranges, and package pins against the exact datasheet. The verified cross-reference search names SI4133-BMR and SI4133-BM but does not establish zero-difference pin compatibility, so substitute approval should include schematic review and firmware regression testing.
Compliance Information
The supplied comparison explicitly lists RoHS Details as N. No verified REACH, AEC-Q100, lead-free, halogen-free, or conflict-minerals statement was provided, so those fields remain unknown or not applicable.
