KSZ8081RNACA-TR from Microchip, in a QFN-24-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	VDD_1.2	power_in	1.2V core VDD supplied by the on-chip regulator. Decouple with 2.2 uF and 0.1 uF capacitors to ground.
2	VDDA_3.3	power_in	3.3V analog VDD supply.
3	RXM	bidirectional	Physical Receive or Transmit Signal (negative differential). Media-side MDI/MDI-X pair, on-chip terminated.
4	RXP	bidirectional	Physical Receive or Transmit Signal (positive differential). Media-side MDI/MDI-X pair, on-chip terminated.
5	TXM	bidirectional	Physical Transmit or Receive Signal (negative differential). Media-side MDI/MDI-X pair, on-chip terminated.
6	TXP	bidirectional	Physical Transmit or Receive Signal (positive differential). Media-side MDI/MDI-X pair, on-chip terminated.
7	XO	output	Crystal feedback for 25 MHz crystal. Leave as a no-connect if an oscillator or external clock source is used on XI.
8	XI	input	25 MHz +/-50 ppm crystal/oscillator/external clock input (RMII 25 MHz mode). KSZ8081RNA power-up default: 25 MHz crystal on this pin. Programmable to 50 MHz mode via PHY Register 1Fh bit [7].
9	REXT	input	PHY transmit output current setting. Connect a 6.49 kOhm 1% resistor from this pin to ground.
10	MDIO	bidirectional	Management Interface (MII) data I/O. Open-drain with weak internal pull-up; requires an external 1.0 kOhm pull-up resistor.
11	MDC	input	Management Interface (MII) clock input, synchronous to MDIO. Weak internal pull-up.
12	RXD1	output	RMII Receive Data Output[1]. Synchronous to the 50 MHz RMII reference clock; two bits sent per clock while CRS_DV is asserted. Internal pull-down active at reset.
13	RXD0	output	RMII Receive Data Output[0]. Synchronous to the 50 MHz RMII reference clock; two bits sent per clock while CRS_DV is asserted. Internal pull-up active at reset.
14	VDDIO	power_in	Digital I/O supply. Selectable 3.3V, 2.5V, or 1.8V.
15	CRS_DV/PHYAD[1:0]	bidirectional	RMII mode: Carrier Sense / Receive Data Valid output to the MAC. Config mode: the pull-up/pull-down value on this pin is latched as PHYAD[1:0] at de-assertion of reset (pull-up = 0x3, pull-down default = 0x0).
16	REF_CLK	bidirectional	RMII 25 MHz mode (RNA default): outputs the 50 MHz RMII reference clock to the MAC. RMII 50 MHz mode: no-connect. Latched pull-down active at reset.
17	RXER	output	RMII Receive Error output. Needs a latched pull-down at de-assertion of reset for normal operation; add an external pull-down if the MAC drives this pin high.
18	INTRP	output	Programmable interrupt output. Open-drain with weak internal pull-up; requires an external 1.0 kOhm pull-up resistor.
19	TXEN	input	RMII Transmit Enable input from the MAC.
20	TXD0	input	RMII Transmit Data Input[0] from the MAC. Synchronous to the 50 MHz RMII reference clock while TXEN is asserted.
21	TXD1	bidirectional	RMII Transmit Data Input[1] from the MAC. NAND Tree mode: acts as the NAND tree output pin.
22	GND	power_in	Ground.
23	LED0/ANEN_SPEED	bidirectional	Programmable LED0 output (Link/Activity by default; modes selected via Register 1Fh bits [5:4]). Config mode: latched at de-assertion of reset as auto-negotiation enable (pull-up default = enabled) and speed select (pull-up = 100 Mbps, pull-down = 10 Mbps).
24	RST#	input	Chip reset, active-low. Weak internal pull-up.
25	PADDLE_GND	power_in	Exposed paddle on the bottom of the QFN package. Must be soldered to the board ground plane.

Key specifications

Parameter	Value
Manufacturer	Microchip
Package	QFN-24-EP(4x4)
Category	Interface
Pins	25

Ordering variants

KSZ8081RNACA-TR
KSZ8081RNACA-TRKSZ8081RNDCA-TR

CAD (KiCad official)

Symbol: KSZ8081RNACA-TR
Footprint: Package_DFN_QFN:QFN-24-1EP_4x4mm_P0.5mm_EP2.7x2.7mm
3D model: QFN-24-EP(4x4) (KiCad packages3D, STEP)

Provenance

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

Datasheet: Microchip datasheet (52 pp, sha256 6d02bb0e0b96569f, retrieved 2026-08-17, tier: manufacturer)
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