RTL8153B-VB-CG from Realtek Semicon, in a QFN-40-EP(5x5). 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	MDIP0	bidirectional	Ethernet MDI pair 0 positive. In MDI mode, BI_DA+ (first pair) in 1000Base-T; TX+ in 10/100Base-T. Route as controlled-Z differential to magnetics.
2	MDIN0	bidirectional	Ethernet MDI pair 0 negative. BI_DA- in 1000Base-T; TX- in 10/100Base-T. In MDI-X crossover mode acts as BI_DB- (RX-).
3	AVDD10	power_in	Analog 1.0V power supply (PHY analog rail). Decouple locally; supplied from internal or external 1.0V regulator.
4	MDIP1	bidirectional	Ethernet MDI pair 1 positive. In MDI mode, BI_DB+ (second pair, RX+ in 10/100Base-T). In MDI-X acts as BI_DA+ (TX+).
5	MDIN1	bidirectional	Ethernet MDI pair 1 negative. BI_DB- in MDI (RX- in 10/100Base-T); BI_DA- in MDI-X.
6	MDIP2	bidirectional	Ethernet MDI pair 2 positive. BI_DC+ (third pair in 1000Base-T). Unused in 10/100Base-T.
7	MDIN2	bidirectional	Ethernet MDI pair 2 negative. BI_DC- (BI_DD- in MDI-X crossover).
8	AVDD10	power_in	Analog 1.0V power supply (PHY analog rail). Second AVDD10 pin - decouple locally.
9	MDIP3	bidirectional	Ethernet MDI pair 3 positive. BI_DD+ (fourth pair in 1000Base-T).
10	MDIN3	bidirectional	Ethernet MDI pair 3 negative. BI_DD- (BI_DC- in MDI-X crossover).
11	AVDD33	power_in	Analog 3.3V power supply. Bulk + local decoupling; internal LDO on AVDD33 rail feeds analog blocks.
12	U3SSTXN	output	USB 3.0 SuperSpeed transmit differential pair, negative. AC-couple with 75-200nF caps to the USB connector; route as 90Ω differential.
13	U3SSTXP	output	USB 3.0 SuperSpeed transmit differential pair, positive. AC-coupled; 90Ω differential.
14	U3VDD10	power_in	USB 3.0 (SuperSpeed) 1.0V power supply. Decouple locally to GND.
15	U3SSRXN	input	USB 3.0 SuperSpeed receive differential pair, negative. 90Ω differential from connector; host end AC-couples.
16	U3SSRXP	input	USB 3.0 SuperSpeed receive differential pair, positive. 90Ω differential.
17	U2DM	bidirectional	USB 2.0/1.1 D- data line. 90Ω differential with U2DP; series ESD/EMI protection recommended at the connector.
18	U2DP	bidirectional	USB 2.0/1.1 D+ data line. 90Ω differential with U2DM.
19	U2VDD10	power_in	USB 2.0/1.1 1.0V power supply. Decouple locally.
20	AVDD33	power_in	Analog 3.3V power supply / internal LDO 3.3V output node. Datasheet: 'embedded LDO is for RTL8153B-VB internal use only; do not power other devices.'
21	VDD5	power_in	Analog 5.0V power supply. Sourced from USB VBUS (typ 5V).
22	DVDD10_UPS	power_out	Digital 1.0V uninterruptible power supply / LDO 1.0V output. Feeds always-on digital domain for wake logic. Do not use to power other devices.
23	DVDD33	power_in	Digital 3.3V power supply. Bulk + local decoupling.
24	EEDO/LED2/SPISDO/LANWAKEB/GPIO	bidirectional	Shared multi-function pin: EEPROM data-in (EEDO, from EEPROM SDO), LED2 output, SPI flash SDO input, LANWAKEB power-management event (open-drain, active low), or general-purpose I/O. Mode chosen by autoload (eFUSE).
25	EEDI/SPISDI/ENSWREG	bidirectional	Shared pin: EEPROM data-out to EEPROM SDI (EEDI), SPI flash serial-data-input driver (SPISDI), and power-on latch ENSWREG (3.3V=enable switching regulator, 0V=LDO or external 1.0V). Latch sampled at power-on.
26	VDDREG33	power_in	Digital 3.3V supply for the internal switching/LDO regulator.
27	VDDREG5	power_in	Digital 5V supply for the internal switching/LDO regulator (from USB VBUS).
28	REGOUT	power_out	Switching/LDO regulator 1.0V output. Feeds internal 1.0V rails via external inductor/cap network. Internal-use only per datasheet.
29	GND	power_in	Switching/LDO regulator ground return.
30	EESK/LED1/SPISCK	output	Shared pin: EEPROM serial clock (93C46/56/66), LED1 output (default), or SPI flash serial clock. Mode chosen by autoload.
31	EECS	output	EEPROM chip select (93C46/56/66). Active only when EEPROM mode is selected by autoload.
32	LED0/SPICSB	output	Shared pin: LED0 output (default) or SPI flash chip select (active low). Mode chosen by autoload.
33	DVDD33	power_in	Digital 3.3V power supply. Second DVDD33 pin - decouple locally.
34	DVDD10	power_in	Digital 1.0V power supply (core). Fed from REGOUT or external 1.0V source.
35	CKXTAL1	input	Clock reference input. Connect to 25MHz crystal (Y1) with load caps; connect to GND if an external clock source drives CKXTAL2 instead.
36	CKXTAL2	bidirectional	Clock reference output when using a crystal, or external clock input (25MHz/48MHz oscillator).
37	AVDD10	power_in	Analog 1.0V power supply. Third AVDD10 pin - decouple locally.
38	RSET	input	External bias resistor reference. Connect a precision resistor to GND to set the internal current bias for the PHY.
39	AVDD33	power_in	Analog 3.3V power supply. Decouple locally.
40	AVDD33	power_in	Analog 3.3V power supply. Decouple locally.
41	GND	power_in	Ground - exposed thermal pad on QFN underside. Must be soldered to a solid GND copper pour with thermal vias for both electrical return and heat sinking.

Key specifications

Parameter	Value
Manufacturer	Realtek Semicon
Package	QFN-40-EP(5x5)
Category	Interface
Pins	41

Ordering variants

Same part, different packaging or reel option.

RTL8153B-VB-CG

CAD (KiCad official)

Symbol: RTL8153B-VB-CG
Footprint: Package_DFN_QFN:QFN-40-1EP_5x5mm_P0.4mm_EP3.6x3.6mm
3D model: QFN-40-EP(5x5) (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`rtl8153b-vb-cg.step`	435 KB	You want the bare part, or you mark your own boards.
`rtl8153b-vb-cg-etched.step`	3.1 MB	You want the part with `RTL8153B-VB-CG` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 775 faces against 254 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

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

Datasheet: Realtek Semicon datasheet (34 pp, sha256 c598af5b177c86c1, 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