Datasheet

Description STM32F103x4, STM32F103x6
12/90 Doc ID 15060 Rev 6
Figure 2. Clock tree
1. When the HSI is used as a PLL clock input, the maximum system clock frequency that can be achieved is
64 MHz.
2. For the USB function to be available, both HSE and PLL must be enabled, with USBCLK running at 48
MHz.
3. To have an ADC conversion time of 1 µs, APB2 must be at 14 MHz, 28 MHz or 56 MHz.
HSE OSC
4-16 MHz
OSC_IN
OSC_OUT
OSC32_IN
OSC32_OUT
LSE OSC
32.768 kHz
HSI RC
8 MHz
LSI RC
40 kHz
to Independent Watchdog (IWDG)
PLL
x2, x3, x4
PLLMUL
Legend:
MCO
Clock Output
Main
PLLXTPRE
/2
..., x16
AHB
Prescaler
/1, 2..512
/2
PLLCLK
HSI
HSE
APB1
Prescaler
/1, 2, 4, 8, 16
ADC
Prescaler
/2, 4, 6, 8
ADCCLK
PCLK1
HCLK
PLLCLK
to AHB bus, core,
memory and DMA
USBCLK
to USB interface
to TIM2, TIM3
USB
Prescaler
/1, 1.5
to ADC
LSE
LSI
HSI
/128
/2
HSI
HSE
peripherals
to APB1
Peripheral Clock
Enable (13 bits)
Enable (3 bits)
P
eripheral Clock
APB2
Prescaler
/1, 2, 4, 8, 16
PCLK2
to TIM1
peripherals
to APB2
Peripheral Clock
Enable (11 bits)
Enable (1 bit)
Peripheral Clock
48 MHz
72 MHz max
72 MHz
72 MHz max
36 MHz max
to RTC
PLLSRC
SW
MCO
CSS
to Cortex System timer
/8
Clock
Enable (3 bits)
SYSCLK
max
RTCCLK
RTCSEL[1:0]
TIM1CLK
TIMXCLK
IWDGCLK
SYSCLK
FCLK Cortex
free running clock
TIM2, TIM3
If (APB1 prescaler =1) x1
else x2
TIM1 timer
If (APB2 prescaler =1) x1
else x2
HSE = high-speed external clock signal
HSI = high-speed internal clock signal
LSI = low-speed internal clock signal
LSE = low-speed external clock signal
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