AT32WB415
Series Reference Manual
2022.04.13
Page 47
Ver 2.00
4
Clock and reset manage (CRM)
4.1 Clock
AT32WB415 series provide different clock sources: HEXT oscillator clock, HICK oscillator clock, PLL
clock, LEXT oscillator and LICK oscillator.
Figure 4-1 AT32WB415 clock tree
USB
Divider
/1,1.5,
2,2.5,
3,3.5,
4
USB48M
To USB interface
/128
LEXT
RTCCLK
To RTC
LICK RC
40 kHz
RTCSEL[1:0]
LICK
To WDT
WDTCLK
Clock Output
CLKOUT
ADC
Divider
/2,4,6,8,12,16
To ADC1 ADCCLK
Max.28 MHz
Peripheral
clock enable
To AHB peripheral/memory
HICK RC
48 MHz
/6
HICK48M
HICKDIV
HEXT_IN
HEXT OSC
4-25 MHz
HEXT
HEXT
PLLRCS
PLLCLK
PLLCLK
LEXT OSC
32.768 kHz
LEXT_IN
LEXT_OUT
LEXT
LICK
HICK_TO_SCLK
SCLKSEL
CFD
HICK8M
HEXT
HICK
SCLK
Max. 150 MHz
12S1/2 CLK
Peripheral
clock enable
AHB
Divider
/1,2...512
HCLK
Max.150MHz
CPU FCLK
/8
CPU SysTick
CLKOUT
Divider
/1,2..512
Peripheral
Clock enable
PCLK1/2
Max.75 MHz
To APB1/2 peripheral
Max.150 MHz
to TMRxCLK
Peripheral
clock enable
x1,x 2
APB1/2
Divider
/1,2,4,8,16
/2
HEXT
Divider
/2
*2,*3,*4
*16,
,*64,
PLL
PLLMULT
PLLHEXTDIV
HICK4M
PCLK2
Max.75 MHz
/2
/4
PLLCLK
PLLCLK
HICK
HEXT
SCLK
USB48M
ADCCLK
LICK
LEXT
CLKOUT_SEL
AHB, APB1 and APB2 all support multiple frequency division. The AHB domain has a maximum of 150
MHz, and both APB1 and APB2 are up to 75 MHz.
4.1.1
Clock sources
High speed external oscillator (HEXT)
An external clock source can be provided by HEXT bypass. Its frequency can be up to 25 MHz. The
external clock signal should be connected to the HEXT_IN pin.
High speed internal clock (HICK)
The HICK oscillator is clocked by a high-speed RC in the microcontroller. The internal frequency of the
HICK clock is 48 MHz. Although it is less accurate, the HICK clock frequency of each device is calibrated
to 1% accuracy (25°C) in factory. The factory calibration value is loaded in the HICKCAL[7: 0] bit of the
clock control register. The RC oscillator speed may be affected by voltage or temperature variations.
Thus the HICK frequency can be trimmed using the HICKTRIM[5: 0] bit in the clock control register.
The HICK clock signal is not released until it becomes stable.
PLL clock
The HICK or HEXT clock can be used as an input clock source of the PLL, and these clocks must be a
range of 2 M and 16 MHz. The input clocks and multiplication factor must be selected before enabling
PLL. The reason is that the configuration parameters cannot be changed once PLL is enabled. The PLL
clock signal is not released before it becomes stable.
Low speed external oscillator (LEXT)
The LEXT oscillator provides two clock sources: LEXT crystal/ceramic resonator and LEXT bypass.
LEXT crystal/ceramic resonator: