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SI4438-C2A-GMR

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by Ray

SKYWORKS SILICON LABS RF Transceiver ICs, QFN-20-EP(4x4). Datasheet-verified pinout, KiCad symbol/footprint/3D.

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Contents

README

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SI4438-C2A-GMR

SKYWORKS SILICON LABS · RF Transceiver ICs · QFN-20-EP(4x4)

SI4438-C2A-GMR from SKYWORKS SILICON LABS, in a QFN-20-EP(4x4). Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin Name Type Function
1 SDN input Shutdown input pin. 0-VDD V digital input. SDN must be 0 in all modes except Shutdown. When SDN=1, the chip is completely shut down and register contents are lost.
2 RXp input Differential RF input pin of the LNA (positive). See application schematic for example matching network.
3 RXn input Differential RF input pin of the LNA (negative). See application schematic for example matching network.
4 TX output Transmit output pin. The PA output is open-drain; the L-C match must supply VDD (+3.3 VDC nominal) to this pin.
5 NC unconnected Not connected internally to any circuitry. Recommended to connect this pin to GND per the reference design schematic.
6 VDD power_in +1.8 to +3.8 V supply voltage input to internal regulators. Recommended VDD is +3.3 V.
7 TXRAMP output Programmable bias output with ramp capability for driving an external FET PA. See section 5.4 Transmitter (TX).
8 VDD power_in +1.8 to +3.8 V supply voltage input to internal regulators. Recommended VDD is +3.3 V.
9 GPIO0 bidirectional General purpose digital I/O. Configurable via registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW, antenna diversity control, etc.
10 GPIO1 bidirectional General purpose digital I/O. Configurable via registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW, antenna diversity control, etc.
11 nIRQ output Active-low general microcontroller interrupt status output. Driven low when any enabled interrupt event occurs; MCU reads the interrupt status registers to determine the source. External pull-up not required but useful for wire-OR configurations.
12 SCLK input Serial clock input for the 4-line SPI bus. 0-VDD V digital input; data is clocked into the Si4438 on positive edge transitions.
13 SDO output SPI serial data output (0-VDD V digital output). Provides serial readback of the internal control registers.
14 SDI input SPI serial data input. 0-VDD V digital input carrying the serial data stream for the 4-line SPI bus.
15 nSEL input Active-low SPI chip-select / enable input for the 4-line SPI bus. 0-VDD V digital input.
16 XOUT output Crystal oscillator output. Connect to an external 25-32 MHz crystal, or leave floating when driving with an external source on XIN.
17 XIN input Crystal oscillator input. Connect to an external 25-32 MHz crystal, or drive from an external clock source.
18 GND power_in Ground. When using a crystal, leave floating per the reference design schematic. When using a TCXO, connect to the TCXO GND which should be separate from the board reference ground plane.
19 GPIO2 bidirectional General purpose digital I/O. Configurable via registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW, antenna diversity control, etc.
20 GPIO3 bidirectional General purpose digital I/O. Configurable via registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW, antenna diversity control, etc.
PAD PADDLE_GND power_in Exposed metal paddle on the bottom of the package supplying RF and circuit ground for the entire chip. Must be well-soldered to the PCB ground plane underneath the device.

Key specifications

Parameter Value
Manufacturer SKYWORKS SILICON LABS
Package QFN-20-EP(4x4)
Category RF And Wireless
Pins 21

Ordering variants

Same part, different packaging or reel option.

  • SI4438-C2A-GMR

CAD (KiCad official)

  • Symbol: SI4438-C2A-GMR
  • Footprint: Package_DFN_QFN:QFN-20-1EP_4x4mm_P0.5mm_EP2.5x2.5mm
  • 3D model: QFN-20-EP(4x4) (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: SKYWORKS SILICON LABS datasheet (44 pp, sha256 341e03e736615be5, retrieved 2026-08-17, tier: lcsc)
  • Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF