# FT838NB1-RT

**FMD Fremont Micro Devices** · Power Distribution Switches · SOP-8

FT838NB1-RT from FMD Fremont Micro Devices, in a SOP-8. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | CS | input | Primary current sense input; the cycle-by-cycle current limit threshold Vcs_max is 541-563 mV (552 mV typ), with leading edge blanking of 350-450 ns. |
| 2 | FB | input | Output voltage feedback pin; the feedback voltage threshold Vfb is 2.856-2.944 V (2.9 V typ), and feedback loop open protection triggers at Ifb_open 120-160 uA (140 uA typ). |
| 3 | VCC | power_in | Supply voltage pin; UVLO turn-on is 16.5-18.5 V (17.6 V typ) and turn-off is 6.6 V typ, VCC over-voltage protection is 26-29 V (27.5 V typ), and the absolute maximum VCC to GND is +30 V. |
| 4 | NC | unconnected | No internal connection; leave unconnected. |
| 5 | GND | power_in | Ground reference for the controller; absolute maximum ratings are referenced to GND. |
| 6 | GND | power_in | Ground reference for the controller; absolute maximum ratings are referenced to GND. |
| 7 | C | passive | Collector of the integrated power NPN, connected to the transformer primary; Vcbo is 700 V min at Ic=0.1 mA and the absolute maximum C to GND is +700 V. |
| 8 | C | passive | Collector of the integrated power NPN, connected to the transformer primary; Vcbo is 700 V min at Ic=0.1 mA and the absolute maximum C to GND is +700 V. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | FMD Fremont Micro Devices |
| Package | SOP-8 |
| Category | Power Management (PMIC) |
| Pins | 8 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| FB to GND voltage |  | -0.3 |  | 7 | V |  | 2 |
| CS to GND voltage |  | -0.3 |  | 7 | V |  | 2 |
| VCC to GND voltage |  | -0.3 |  | 30 | V |  | 2 |
| C to GND voltage |  | -0.3 |  | 700 | V |  | 2 |
| Operating Temperature Range |  | -40 |  | 125 | ℃ |  | 2 |
| Junction Temperature |  | -40 |  | 150 | ℃ |  | 2 |
| Storage Temperature Range |  | -60 |  | 150 | ℃ |  | 2 |
| Maximum Current Threshold | Vcs_max | 541 | 552 | 563 | mV |  | 6 |
| Leading Edge Blanking Duration | Tleb | 350 | 400 | 450 | ns |  | 6 |
| Feedback Voltage Threshold | Vfb | 2.856 | 2.9 | 2.944 | V |  | 6 |
| Start Up Threshold Voltage | Vcc_on | 16.5 | 17.6 | 18.5 | V |  | 6 |
| Under Voltage Lockout Voltage | Vcc_off | 6 | 6.6 | 7 | V |  | 6 |
| VCC Start Up Current (FT838NB) | Istart_up |  | 2 | 5 | uA |  | 6 |
| Operating Current | Iop | 0.4 | 0.5 | 0.7 | mA |  | 6 |
| Feedback Loop Open Protection | Ifb_open | 120 | 140 | 160 | uA |  | 6 |
| VCC Over Voltage Protection | Vcc_OVP | 26 | 27.5 | 29 | V |  | 6 |
| Line Compensation | Vline | 30 | 33 | 36 | mV | Ifb=1mA | 6 |
| Cable compensation (Kcab), version 1 (FT838NB1, Cable Comp = 3%) | Kcab |  | 3 |  | % | Cable Comp version 1 per marking/ordering table | 6 |
| Propagation Delay | Tpd |  | 200 |  | ns | OUT=1.0nF to GND | 6 |
| CCM protection Threshold Level | Vcp |  | 100 |  | mV |  | 6 |
| Over Temperature Protection | T_OTP |  | 145 |  | ℃ |  | 6 |
| Collector-Emitter saturation voltage | VCEsat |  | 0.3 | 0.9 | V | IB=0.25A,IC=1A | 6 |
| Base-Emitter saturation voltage | VBEsat |  | 0.9 | 1.2 | V | IB=0.25A,IC=1A | 6 |
| Maximum collector current | Icm |  | 0.4 | 0.45 | A | Vc=2V | 6 |
| Collector-Base breakdown voltage | Vcbo |  | 700 |  | V | Ic=0.1mA | 6 |
| Collector-Emitter breakdown voltage | Vceo |  | 400 |  | V | Ic=1mA | 6 |
| Emitter-Base breakdown voltage | Vebo |  | 9 |  | V | IE=0.1mA | 6 |

## CAD (KiCad official)

- Symbol: `FT838NB1-RT`
- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`
- 3D model: SOP-8 (KiCad packages3D, STEP)
- 3D model files: `ft838nb1-rt-etched.step` / `ft838nb1-rt-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `ft838nb1-rt.step` / `ft838nb1-rt.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [FMD Fremont Micro Devices datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8588884267644018688) (10 pp, sha256 `b63c10317d94c974`, retrieved 2026-10-18, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/ft838nb1-rt-datasheet.pdf)