FM4057S52 from Shenzhen Fuman, in a SOT-23-5. 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	CHRG	output	Open-drain charge status indicator. Drives an external LED (to VIN through a series resistor): pulled low (LED on) while charging, high-impedance (LED off) when charge terminates.
2	GND	power_in	Device ground / analog return. Connect directly to the system ground plane.
3	BAT	power_out	Battery connection and charger output. Sources the constant-current / constant-voltage charge current to the single-cell Li-ion pack. Regulated to 4.2V (S52), with battery-OVP at ~104% of VBAT_FULL and recharge threshold ~4.05V. Bypass with a 10µF ceramic capacitor to GND.
4	VIN	power_in	Charger power input. Recommended 4.2-6.5V operating range, absolute-max 32V (the part's headline 32V input tolerance). VIN UVLO rising ~4.6V / falling ~4.2V; VIN OVP ~6.5V. A 1µF ceramic bypass to GND is recommended (may be omitted per app circuit).
5	ISET	input	Charge-current programming pin. A resistor from ISET to GND sets the constant-current charge level: RISET ≈ 3kΩ → 1.0A, 5kΩ → 0.6A, 6kΩ → 0.5A. Precharge current is ~60mA and termination current is ~60mA at RISET=5kΩ.

Key specifications

Parameter	Value
Manufacturer	Shenzhen Fuman
Package	SOT-23-5
Category	PMIC
Pins	5

Ordering variants

Same part, different packaging or reel option.

FM4057S52
FM4057S52BS52
FM4057S52S53
FM4057S52S54
FM4057S52S42
FM4057S52S43
FM4057S52S44
FM4057S52E42
FM4057S52BE42
FM4057S52E43
FM4057S52E44
FM4057S52D42
FM4057S52D43
FM4057S52D44

CAD (KiCad official)

Symbol: FM4057S52
Footprint: Package_TO_SOT_SMD:SOT-23-5
3D model: SOT-23-5 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`fm4057s52.step`	85 KB	You want the bare part, or you mark your own boards.
`fm4057s52-etched.step`	1.8 MB	You want the part with `FM4057S52` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 437 faces against 102 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: Shenzhen Fuman datasheet (14 pp, sha256 bfc23830eabbc3b5, 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