SP339EER1-L from MaxLinear, in a QFN-40-EP(6x6). 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	L1/R1_OUT	output	Mode-dependent: RS-232 R1 receiver output (MODE=00/01) or logic '1' output (MODE=10/11). Named L1 as CMOS/TTL logic-side signal.
2	L2/R2_OUT/R1_OUT	output	Mode-dependent: RS-232 R2 receiver output in mode 00/01, RS-485/422 R1 receiver output in mode 10/11.
3	L3/T1_IN	input	Mode-dependent T1 (driver 1) CMOS/TTL logic input in all active modes.
4	L4/T2_IN	input	RS-232 T2 driver logic input in mode 00/01; unused in RS-485/422 modes.
5	L6/R3_OUT	output	RS-232 R3 receiver output in mode 00/01; logic '1' in RS-485/422 modes.
6	L7/T3_IN	input	RS-232 T3 driver logic input in mode 00/01; unused in RS-485/422 modes.
7	L8/R4_OUT	output	RS-232 R4 receiver output in mode 00/01; logic '1' in RS-485/422 modes.
8	L9/R5_OUT	output	RS-232 R5 receiver output in mode 00/01; logic '1' in RS-485/422 modes.
9	VCC	power_in	Positive supply input, 3.3V or 5V single-supply operation.
10	GND	power_in	Ground return.
11	SLEW	input	Slew-rate select. SLEW=VCC enables 250 kbps slew-rate limiting on all drivers to reduce EMI.
12	DIR1	input	Direction control for RS-485/422 driver/receiver 1. High enables T1 (and disables R1 in half-duplex mode 10).
13	NC	unconnected	Not connected internally; leave floating or tie as convenient for layout.
14	MODE0	input	Protocol select bit 0. Combined with MODE1 selects RS-232 loopback (00), RS-232 (01), RS-485/422 half-duplex (10), or RS-485/422 full-duplex (11).
15	MODE1	input	Protocol select bit 1. See MODE0 for combined mode encoding.
16	NC	unconnected	Not connected internally.
17	TERM	input	Termination enable. In RS-485/422 modes, high enables the internal 120Ω-class receiver termination network across the bus inputs.
18	NC	unconnected	Not connected internally.
19	ENABLE	input	Device enable. ENABLE=VCC for normal operation; ENABLE=0V puts the device into low-power shutdown (<10 µA).
20	VCC	power_in	Positive supply input, 3.3V or 5V.
21	R9/R5_IN	input	RS-232 R5 receiver bus input in mode 00/01; unused in RS-485/422 modes. ±18V tolerant.
22	R8/R4_IN	input	RS-232 R4 receiver bus input in mode 00/01; unused in RS-485/422 modes. ±18V tolerant.
23	GND	power_in	Ground return.
24	R7/T3_OUT	output	RS-232 T3 driver bus output in mode 00/01; unused in RS-485/422 modes. ±18V tolerant.
25	R6/R3_IN	input	RS-232 R3 receiver bus input in mode 00/01; unused in RS-485/422 modes.
26	GND	power_in	Ground return.
27	R4/T2_OUT/R1_IN_B	bidirectional	Mode-dependent bus pin: RS-232 T2 driver output in mode 01; RS-485/422 R1 receiver input B in mode 11 (full duplex).
28	R3/T1_OUT/R1_IN_A	bidirectional	Mode-dependent bus pin: RS-232 T1 driver output in mode 01; RS-485/422 R1 receiver input A in mode 11 (full duplex).
29	GND	power_in	Ground return.
30	R2/R2_IN/R1_IN_A_T1_OUT_A/T1_OUT_A	bidirectional	Mode-dependent bus pin: RS-232 R2 receiver input (mode 01); RS-485/422 half-duplex R1 input A / T1 output A (mode 10); full-duplex T1 output A (mode 11).
31	R1/R1_IN/R1_IN_B_T1_OUT_B/T1_OUT_B	bidirectional	Mode-dependent bus pin: RS-232 R1 receiver input (mode 01); RS-485/422 half-duplex R1 input B / T1 output B (mode 10); full-duplex T1 output B (mode 11).
32	VCC	power_in	Positive supply, 3.3V or 5V. Bypass with 1.0 µF to ground for supply decoupling.
33	VSS	power_out	Charge-pump negative supply rail (internally generated). Bypass with 0.1 µF to ground.
34	C2-	passive	Charge-pump capacitor 2 negative lead. Connect external 0.1 µF flying cap between C2+ and C2-.
35	C1-	passive	Charge-pump capacitor 1 negative lead. Connect external 0.1 µF flying cap between C1+ and C1-.
36	GND	power_in	Ground return.
37	C1+	passive	Charge-pump capacitor 1 positive lead. 0.1 µF flying capacitor to C1-.
38	VCC	power_in	Positive supply, 3.3V or 5V.
39	C2+	passive	Charge-pump capacitor 2 positive lead. 0.1 µF flying capacitor to C2-.
40	VDD	power_out	Charge-pump positive supply rail (internally generated). Bypass with 0.1 µF to ground.

Key specifications

Parameter	Value
Manufacturer	MaxLinear
Package	QFN-40-EP(6x6)
Category	Interface
Pins	40

Ordering variants

Same part, different packaging or reel option.

SP339EER1-L
SP339EER1-L/TR

CAD (KiCad official)

Symbol: SP339EER1-L
Footprint: Package_DFN_QFN:QFN-40-1EP_6x6mm_P0.5mm_EP4.6x4.6mm
3D model: QFN-40-EP(6x6) (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`sp339eer1-l.step`	538 KB	You want the bare part, or you mark your own boards.
`sp339eer1-l-etched.step`	2.9 MB	You want the part with `SP339EER1-L` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 740 faces against 314 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: MaxLinear datasheet (24 pp, sha256 a608a7bf488833bc, 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