HUSB238 can negotiate fixed output voltages from a variety of USB power protocols, including USB PD.
Its unique feature is an I2C interface, which is unusual in these entry-level triggering chips.
This is why HUSB238 cannot only be found in USB trigger boards but also boards that expose I2C and can be controlled dynamically by microcontrollers.
HUSB238 supports USB PD3.0, but no PPS, so it can trigger the typical pre-defined voltage steps (5V, 9V, 12V, 15V, 20V) at a maximum of 100W. It cannot trigger freely adjustable voltages, though.
| Feature | HUSB238 |
|---|---|
| PD Version | USB PD3.0, Type-C v1.4 |
| Max Power | 100W (20V/5A) |
| Legacy Protocols | Apple Divider 3, BC1.2 (SDP, CDP, DCP) |
| Configuration | Resistor (VSET/ISET) or I2C |
| I2C Monitoring/Control | Yes |
| Protection | OVP, UVP, OTP |
| Integrated Gate Driver | Yes (PMOS) |
| Dead Battery Support | Yes |
| e-Marker Simulation | No |
| Package | DFN-10L, SOT33-6L |
Overview
HUSB238 is typically found in square DFN-10 packages.
The 10-pin CH224K is typically used for USB trigger boards.
Voltage Selection
The trigger voltage can be set in two ways:
- Pin
VSET:
Connect a resistor between pinVSETandGNDto set a fixed voltage. When no resistor is connected, the default voltage is 20V.
Resistance Configuration
In this mode, a resistor is connected to VSET and GND to set the trigger voltage:
Resistance on VSET to GND |
Request-voltage |
|---|---|
| 0KΩ | 5V |
| 6.04KΩ | 9V |
| 10KΩ | 12V |
| 14KΩ | 15V |
| 17.8KΩ | 18V |
| NC | 20V |
Current Setting
Likewise, a resistor can be connected to ISET and GND to indicate the required current in 250mA increments. If no resistor is connected, the full 3.25A are available:
Resistance on ISET to GND |
Request-current |
|---|---|
| 0KΩ | 1.25A |
| 4.53KΩ | 1.5A |
| 7.5KΩ | 1.75A |
| 10.5KΩ | 2A |
| 13.7KΩ | 2.25A |
| 16.5KΩ | 2.5A |
| 19.6KΩ | 2.75A |
| 22.6KΩ | 3A |
| NC | 3.25A |
I2C Mode
HUSB238 can communicate with external microcontrollers via its I2C interface at address 0x08.
| Address | Register Name | Description |
|---|---|---|
| 0x00 | PD_STATUS0 | Negotiated voltage/current status |
| 0x01 | PD_STATUS1 | Additional status info |
| 0x02 | SRC_PDO_5V | 5V PDO info from source |
| 0x03 | SRC_PDO_9V | 9V PDO info from source |
| 0x04 | SRC_PDO_12V | 12V PDO info from source |
| 0x05 | SRC_PDO_15V | 15V PDO info from source |
| 0x06 | SRC_PDO_18V | 18V PDO info from source |
| 0x07 | SRC_PDO_20V | 20V PDO info from source |
| 0x08 | SRC_PDO | Select which PDO to request |
| 0x09 | GO_COMMAND | Command register (e.g., switch) |
Register Map
For details, see the I2C Register Map.
Libraries
There are several libraries available for HUSB238 and Arduino/ESP32:
- Basic #1: great for figuring out how I2C control works, or to embed quick code chunks without the need to link an entire external library
- Basic #2: same, essential functionality with least code
- Adafruit: production-ready and well documented external library
I2C always has priority over the resistor configuration. The resistors set the baseline default. Once different settings are chosen via I2C, these override the resistor settings.
Selecting USB Power Supply Setting
It is important to understand how trigger boards actually select a given voltage setting. This depends on the actual capabilities of the USB power source.
- HUSB238 initially queries all the power profiles supported by the power source.
- It then tries to find the best matching profile for the requested voltage and current:
- Highest source voltage available that is equal or lower than the requested voltage
- Current is equal or higher than the requested current
That’s why the real output voltage may fall back to a lower voltage than anticipated.
For example, 12V is not an official USB PD base voltage, but it is supported by most chargers and power banks.
If you come across a USB power source that works strictly by USB PD specification, there may be no power profile for 12V, just for 9V and 15V. In this case, HUSB238 will always select a voltage that is lower than the requested voltage, so you may end up with 9V output voltage.
Materials
HUSB238 Datasheet
HUSB238 I2C Register Map
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(content created Jun 29, 2025)