12
PWM
12.1 Introduction
Pulse width modulation (PWM) is an analog control method that modulates the bias of the transistor base or the
grid of the MOS tube according to the change in the corresponding load. Therefore, the on-time of the transistor
or the MOS tube is changed, and the output of the switch stabilized power supply is changed. This method can
keep the output voltage of the power supply constant when the operating conditions change. It is a very effective
technique for controlling analog circuits using digital signals from microprocessors. It is widely used in many fields
from measurement and communication to power control and conversion.
12.2 Main features
• Supports 5-channel PWM signal generation
• Three clock sources can be selected (bus clock <bclk>, crystal clock <xtal_ck>, slow clock <32k>), with 16-bit
clock divider
• Double threshold setting to increase pulse flexibility
• The maximum operating frequency is 40MHz
12.3 Function description
12.3.1 Clock and divider
There are three options for each PWM counter clock source, the sources are as follows:
A. bclk - Chip bus clock
B. XTAL - External crystal clock
C. f32k - System RTC clock
Each counter has its own 16-bit frequency divider. The selected clock can be divided by APB. The PWM counter will
BL602/604 Reference Manual
157/ 195
@2020 Bouffalo Lab