component
Si4438-B1C-FMR
Public Made by Adomby adom
SILICON LABS RF Transceiver ICs, QFN-20-EP(4x4). Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.
3D Model
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Symbol & Footprint
Schematic Symbol
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PCB Footprint
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Datasheet
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README
markdownSi4438-B1C-FMR
SILICON LABS · RF Transceiver ICs · QFN-20-EP(4x4)
Si4438-B1C-FMR from SILICON LABS, in a QFN-20-EP(4x4). Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.
Pinout
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | SDN | input | Shutdown input, 0 to VDD V digital; SDN must be 0 in all modes except Shutdown, and when SDN = 1 the chip is fully shut down and register contents are lost. |
| 2 | RXp | input | Differential RF input pin of the LNA, to be matched per the application schematic. |
| 3 | RXn | input | Differential RF input pin of the LNA, to be matched per the application schematic. |
| 4 | TX | output | Transmit output pin; the PA output is an open-drain connection, so the L-C match must supply VDD (+3.3 VDC nominal) to this pin. |
| 5 | NC | unconnected | It is recommended to connect this pin to GND per the reference design schematic; it is not connected internally to any circuitry. |
| 6 | VDD | power_in | Supply voltage input to internal regulators, +1.8 to +3.8 V, with a recommended supply of +3.3 V. |
| 7 | TXRAMP | output | Programmable bias output with ramp capability for an external FET PA, as described in section 5.4. |
| 8 | VDD | power_in | Supply voltage input to internal regulators, +1.8 to +3.8 V, with a recommended supply of +3.3 V. |
| 9 | GPIO0 | bidirectional | General purpose digital I/O that can be configured for functions such as microcontroller clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW and antenna diversity control. |
| 10 | GPIO1 | bidirectional | General purpose digital I/O; the datasheet gives no further description for this pin. |
| 11 | nIRQ | output | General microcontroller interrupt status output that goes low when any enabled interrupt event occurs; no external pull-up is required but one may be desirable when multiple interrupt lines are connected. |
| 12 | SCLK | input | Serial clock input, 0 to VDD V digital; data is clocked into the Si4438 on positive edge transitions. |
| 13 | SDO | output | Serial data output, 0 to VDD V digital, providing serial readback of the internal control registers. |
| 14 | SDI | input | Serial data input, 0 to VDD V digital, providing the serial data stream for the 4-line serial bus. |
| 15 | nSEL | input | Serial interface select input, 0 to VDD V digital, providing the select/enable function for the 4-line serial bus. |
| 16 | XOUT | output | Crystal oscillator output; connect to an external 25 to 32 MHz crystal, or leave floating when driving with an external source on XIN. |
| 17 | XIN | input | Crystal oscillator input; connect to an external 25 to 32 MHz crystal or to an external clock source. |
| 18 | GND | power_in | Ground; when using a XTAL leave floating per the reference design, and when using a TCXO connect to TCXO GND, which should be separate from the board reference ground plane. |
| 19 | GPIO2 | bidirectional | General purpose digital I/O that can be configured for functions such as microcontroller clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW and antenna diversity control. |
| 20 | GPIO3 | bidirectional | General purpose digital I/O; the datasheet notes GPIO2 and GPIO3 are more susceptible to spurious synthesizer emissions than GPIO0 and GPIO1. |
| 21 | EP | passive | Exposed pad (from the footprint; not named in the datasheet pin table). |
Key specifications
| Parameter | Value |
|---|---|
| Manufacturer | SILICON LABS |
| Package | QFN-20-EP(4x4) |
| Category | RF & Radio |
| Pins | 21 |
CAD (KiCad official)
- Symbol:
Si4438-B1C-FMR - Footprint:
Package_DFN_QFN:QFN-20-1EP_4x4mm_P0.5mm_EP2.5x2.5mm - 3D model: QFN-20-EP(4x4) (KiCad packages3D, STEP)
- 3D model files:
si4438-b1c-fmr-etched.step/si4438-b1c-fmr-etched.glbcarry the MPN laser-etched on the die in a toggleableAdom.LaserEtchgroup (Fusion-ready);si4438-b1c-fmr.step/si4438-b1c-fmr.glbare the bare package body.
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: SILICON LABS datasheet (45 pp, sha256
dce8b8eac80fbb6e, retrieved 2026-10-27, tier: lcsc) - Extractor: parts-factory
2.0.0/extract_pins 0.3, primaryclaude-haiku-5-5(text), consensusclaude-sonnet-5-5(agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish. - CAD: KiCad official libraries (CC-BY-SA 4.0).