MAX3243CDBR from Texas Instruments, in a SSOP-28. 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	C2+	passive	Positive lead of C2 charge-pump flying capacitor (0.1 µF at Vcc = 3.3 V; 0.33 µF at Vcc = 5 V).
2	C2-	passive	Negative lead of C2 charge-pump flying capacitor.
3	V-	power_out	Negative charge-pump output for storage capacitor only (approximately -5.5 V). Bypass to GND with a 0.1-0.33 µF capacitor.
4	RIN1	input	RS-232 receiver 1 line data input from remote RS-232 system. Input voltage range ±25 V; input resistance 3-7 kΩ.
5	RIN2	input	RS-232 receiver 2 line data input from remote RS-232 system. Feeds both ROUT2 (gated by FORCEOFF) and the always-active ROUT2B (ring-indicator).
6	RIN3	input	RS-232 receiver 3 line data input from remote RS-232 system.
7	RIN4	input	RS-232 receiver 4 line data input from remote RS-232 system.
8	RIN5	input	RS-232 receiver 5 line data input from remote RS-232 system.
9	DOUT1	output	RS-232 line data output 1 (to remote RS-232 system). Typical VOH = 5.4 V, VOL = -5.4 V into RL = 3 kΩ. High-Z when FORCEOFF is low.
10	DOUT2	output	RS-232 line data output 2 (to remote RS-232 system). High-Z when FORCEOFF is low.
11	DOUT3	output	RS-232 line data output 3 (to remote RS-232 system). High-Z when FORCEOFF is low.
12	DIN3	input	Logic-level data input 3 from UART (drives DOUT3). Accepts 3-V logic on Vcc = 3.3 V and 5-V logic on Vcc = 3.3-5.5 V.
13	DIN2	input	Logic-level data input 2 from UART (drives DOUT2).
14	DIN1	input	Logic-level data input 1 from UART (drives DOUT1).
15	ROUT5	output	Logic-level data output 5 to UART (from RIN5). Gated to high-Z by FORCEOFF/auto-powerdown.
16	ROUT4	output	Logic-level data output 4 to UART (from RIN4). Gated to high-Z by FORCEOFF/auto-powerdown.
17	ROUT3	output	Logic-level data output 3 to UART (from RIN3). Gated to high-Z by FORCEOFF/auto-powerdown.
18	ROUT2	output	Logic-level data output 2 to UART (from RIN2). Gated to high-Z by FORCEOFF/auto-powerdown.
19	ROUT1	output	Logic-level data output 1 to UART (from RIN1). Gated to high-Z by FORCEOFF/auto-powerdown.
20	ROUT2B	output	Always-active non-inverting logic output for RIN2, typically used as a ring-indicator that stays live during auto-powerdown so a wake-on-ring can be detected.
21	INVALID	output	Active-low status output; asserts low when all RIN inputs are unpowered/idle (no valid RS-232 signal). Used to trigger auto-powerdown of drivers.
22	FORCEOFF	input	Active-low driver disable. Low forces DOUT1-3 and ROUT1-5 to high-Z per device functional modes. Tie high (or to Vcc) for normal operation.
23	FORCEON	input	Driver force-on control. High forces drivers on unconditionally; low selects automatic power-down mode (driven by INVALID).
24	C1-	passive	Negative lead of C1 charge-pump flying capacitor (0.047 µF at Vcc = 3.3 V; 0.1 µF at Vcc = 5 V).
25	GND	power_in	Device ground reference (0 V).
26	VCC	power_in	Supply voltage input; 3 V to 5.5 V (recommended 3.0-3.6 V at 3.3-V rail or 4.5-5.5 V at 5-V rail). Bypass with 0.1 µF to GND.
27	V+	power_out	Positive charge-pump output for storage capacitor only (approximately +5.5 V). Bypass to GND with 0.1-0.33 µF capacitor.
28	C1+	passive	Positive lead of C1 charge-pump flying capacitor.

Key specifications

Parameter	Value
Manufacturer	Texas Instruments
Package	SSOP-28
Category	Interface
Pins	28

Ordering variants

Same part, different packaging or reel option.

MAX3243CDBRDW
MAX3243CDBRCDW
MAX3243CDBRIDW
MAX3243CDBRCDWR
MAX3243CDBRIDWR
MAX3243CDBR
MAX3243CDBRIDB
MAX3243CDBRIDBR
MAX3243CDBRPW
MAX3243CDBRCPW
MAX3243CDBRIPW
MAX3243CDBRCPWR
MAX3243CDBRIPWR

CAD (KiCad official)

Symbol: MAX3243CDBR
Footprint: Package_SO:SSOP-28_5.3x10.2mm_P0.65mm
3D model: SSOP-28 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`max3243cdbr.step`	362 KB	You want the bare part, or you mark your own boards.
`max3243cdbr-etched.step`	3.4 MB	You want the part with `MAX3243CDBR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 848 faces against 447 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: Texas Instruments datasheet (31 pp, sha256 71f52706280573a4, 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