# Isolated DC High\-Side Switch

## Description

Galvanically isolated 11–20 V DC high\-side load switch controlled by an external 3\.3 V STM32F7 GPIO, using a PC817 optocoupler and protected IRF4905 P\-channel MOSFET gate drive\. Intended for static or low\-rate ON/OFF; load current and thermal sizing remain TBD\.

## Project Details

- **Owner:** aldifaber
- **Created:** 9/17/2026
- **Last Updated:** 9/21/2026
- **Visibility:** Public

## Key Components

### D1 — [1N4744A](https://flux.ai/jecstronic/1n4744a~o3l.md)

- Role Details: 15 V gate\-source clamp; cathode to VIN/source and anode to gate
- Functional Group: Gate Driver
- Part Type: Diode
- Power Rating: 1W
- Breakdown Voltage: 15V
- Role: Clamping
- Manufacturer Part Number: 1N4744A
- Datasheet URL: https://rocelec\.widen\.net/view/pdf/7qfz7dzkx8/ONSM\-S\-A0003585147\-1\.pdf?t\.download=true&u=5oefqw
- Manufacturer Name: onsemi
- License: https://creativecommons\.org/licenses/by/4\.0/

**Pins:**
- A [pin 2]
- K [pin 1]

### J1 — [1715031](https://flux.ai/adrian95/1715031~9og.md)

- Role Details: External isolated control header: CTRL\_3V3, CTRL\_SIGNAL, CTRL\_GND
- Manufacturer Name: Phoenix Contact
- Manufacturer Part Number: 1715031
- Part Type: Connector
- Role: Isolation
- License: https://creativecommons\.org/licenses/by/4\.0/
- Datasheet URL: https://mm\.digikey\.com/Volume0/opasdata/d220001/medias/docus/649/1715031\.pdf
- Functional Group: Control Interface

**Pins:**
- 1 [pin 1]
- 2 [pin 2]
- 3 [pin 3]

### J2 — [KF128\-5\.08\-2P\-AA](https://flux.ai/lcsc/kf128-5p08-2p-aa~0pbi.md)

- Connector Pitch: 5\.08mm
- JLCPCB Part Class: Extended Part
- Connector Type: Screw terminal
- Manufacturer Name: KEFA\(科发\)
- Functional Group: Power Input
- LCSC Part Number: C474952
- Manufacturer Part Number: KF128\-5\.08\-2P\-AA
- Operating Temperature: \-40℃\~\+105℃
- Connector Gender: Female
- Connector Rows: 1
- Package or Case Code: CONN\-TH\_P5\.08\_KF128\-5\.08\-2P
- Current Rating: 24A
- Connector Positions: 2
- Role: Switching
- Product Info Url: https://lcsc\.com/product\-detail/New\-Quadratic\-Unclassified\-Data\_Cixi\-Kefa\-Elec\-KF128\-5\-08\-2P\_C474952\.html
- Datasheet URL: https://storage\.googleapis\.com/graviton\-electric\-symbols/document\_assets/lcsc/2408211511\_Cixi\-Kefa\-Elec\-KF128\-5\-08\-2P\-AA\_C474952\.pdf
- Part Type: Screw terminal
- Role Details: 11–20 V DC input and power return; usable current TBD by load/inrush

**Pins:**
- 1 [pin 1]
- 2 [pin 2]

### J3 — [KF128\-5\.08\-2P\-AA](https://flux.ai/lcsc/kf128-5p08-2p-aa~0pbi.md)

- Connector Pitch: 5\.08mm
- JLCPCB Part Class: Extended Part
- Role Details: Switched V\_OUT and power GND load return; usable current TBD by load/inrush
- Connector Type: Screw terminal
- Manufacturer Name: KEFA\(科发\)
- LCSC Part Number: C474952
- Manufacturer Part Number: KF128\-5\.08\-2P\-AA
- Operating Temperature: \-40℃\~\+105℃
- Connector Gender: Female
- Connector Rows: 1
- Package or Case Code: CONN\-TH\_P5\.08\_KF128\-5\.08\-2P
- Current Rating: 24A
- Role: Switching
- Functional Group: Power Output
- Connector Positions: 2
- Product Info Url: https://lcsc\.com/product\-detail/New\-Quadratic\-Unclassified\-Data\_Cixi\-Kefa\-Elec\-KF128\-5\-08\-2P\_C474952\.html
- Datasheet URL: https://storage\.googleapis\.com/graviton\-electric\-symbols/document\_assets/lcsc/2408211511\_Cixi\-Kefa\-Elec\-KF128\-5\-08\-2P\-AA\_C474952\.pdf
- Part Type: Screw terminal

**Pins:**
- 1 [pin 1]
- 2 [pin 2]

### LED1 — [WP7113SGC](https://flux.ai/jecstronic/wp7113sgc~285.md)

- Datasheet URL: https://www\.kingbrightusa\.com/images/catalog/SPEC/WP7113SGC\.pdf
- License: https://creativecommons\.org/licenses/by/4\.0/
- Functional Group: Power Indicator
- Manufacturer Name: Kingbright
- Role: Switching
- Manufacturer Part Number: WP7113SGC
- Role Details: Green VIN\-present indicator driven through 3\.3 kΩ series resistor
- Part Type: LED
- Forward Voltage: 2\.2V

**Pins:**
- A [pin 2]
- K [pin 1]

### Q1 — [IRF4905PBF](https://flux.ai/adrian95/irf4905pbf~z8h.md)

- Datasheet URL: https://www\.infineon\.com/dgdl/irf4905pbf\.pdf?fileId=5546d462533600a4015355e329b1197e
- Manufacturer Name: Infineon Technologies
- Role: Switching
- Part Type: Transistor
- Functional Group: Power Switch
- Manufacturer Part Number: IRF4905PBF
- License: https://creativecommons\.org/licenses/by/4\.0/
- Role Details: P\-channel high\-side switch; source VIN, drain V\_OUT; current and thermal rating TBD by load

**Pins:**
- D [pin 2]
- G [pin 1]
- S [pin 3]

### U1 — [PC817](https://flux.ai/kicad-part-library/pc817~0c.md)

- Functional Group: Isolation Barrier
- Datasheet URL: http://www\.soselectronic\.cz/a\_info/resource/d/pc817\.pdf
- Role Details: Galvanic isolation between external STM32F7 GPIO and power switch domain
- Role: Isolation
- Package or Case Code: DIP\-4\_W7\.62mm
- Manufacturer Part Number: PC817

**Pins:**
- \~ [pin 1]
- \~ [pin 3]
- \~ [pin 2]
- \~ [pin 4]

*The full schematic, PCB layout, bill of materials, and interactive design are available at [https://flux\.ai/aldifaber/isolated\-dc\-high\-side\-switch\~4l](https://flux.ai/aldifaber/isolated-dc-high-side-switch~4l).*

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*Generated from [https://flux\.ai/aldifaber/isolated\-dc\-high\-side\-switch\~4l](https://flux.ai/aldifaber/isolated-dc-high-side-switch~4l)*