Low power touch solution supporting sleep and wake-up

我芯永恒

Low power touch solution supporting sleep and wake-up [Copy link]

Most of the WCH series MCUs have integrated touch key function modules on-chip, and the CH58X series Bluetooth MCUs not only integrate the latest generation of touch key modules of Qinheng, but also have built-in 2.4GHz RF transceiver, baseband and link control, support BLE V5.3, and have excellent low power consumption performance. These features make the CH58X series Bluetooth MCUs one of the best choices for low-power intelligent electronic products with touch keys.

Taking the CH582 touch key evaluation board as an example, this paper describes how the CH582 can achieve low-power touch wake-up. The following figure shows the schematic diagram of the CH582 touch key evaluation board connected to a mobile phone via Bluetooth. The evaluation board leads to four-channel touch pads, four LED lamp beads, a 4-digit digital tube and an onboard Bluetooth antenna. In order to accurately measure the power consumption of the touch keys, the Bluetooth function is turned off and the digital tube is disconnected during the power consumption test. Only when a touch is detected, the corresponding LED lamp bead is lit.

The implementation method is as follows: first, register a task in the Bluetooth tmos that wakes up and executes every 0.5 seconds. In this task, first set the touch button related IO to a floating state, then load the settings saved before sleep, and perform a simple scan. If there is no suspected key, it will enter sleep again and wait for the next wake-up. If there is a suspected key, formally scan the suspected key interface and perform subsequent processing based on the scan results. The flowchart of this task is shown in the figure below.

On the CH582 touch key evaluation board, the average power consumption is about 33.7A at a simple scan interval of 0.5s (when no key is scanned) when the DCDC function is not turned on. If the on-chip DCDC function is turned on, the power consumption can be reduced to less than 20A (theoretical value), and the power consumption can be reduced to a lower level by lengthening the scan interval. After waking up, a formal scan is performed every 25ms, and the average power consumption is about 578A. The power consumption test is shown in the figure below.

Sleep Simple Scan Power Consumption

Wake up 25ms interval scanning power consumption