This application note describes how to configure the STMicroelectronics STOTG04 USB OTG transceiver for low power mode. This mode can reduce the transceiver's power consumption to 1 μA, and can disable its functionality when not needed.
The document describes the STOTG04, a low-speed/full-speed USB OTG transceiver that integrates a charge pump and ID line detector. It focuses on reducing current draw by configuring internal registers for power-down operation.
Key topics include the conditions required to enter power-down mode (suspend bit and pin), specific register settings to minimize consumption (such as disabling UART mode or pull-up resistors), and warnings regarding driver biasing control in receive mode that may cause USB compliance test failures.
Power-down mode is entered when both the suspend bit in control register 1 and the suspend pin are set.
UART mode is enabled by setting bit 6 (uart_en) in control register 1.
Failures occur if data is sent too early after the output enable signal goes low, causing a longer first bit that misaligns with reference points.