我使用库例程，时钟使用HSI，72MHz，APB2不分频；ADC_PRESCARE设置为12；
设置采样通道2个，通道采样时间在55.5周期以上，符合数据手册。但如果采样时间设置为13.5周期，却达不到111ksps，任何低于55.5周期的设置，都只能达到65ksps左右；或者ADC_PRESCARE设置为11及以下，提高ADC时钟，也都只能达到65ksps左右；请问瓶颈在哪儿？下面是ADC配置和时钟配置

//ADC配置，2个采样通道
void ADCMultiChannelInit(){
        GPIO_Config_AIN(GPIOA, GPIO_Pin_1);
  GPIO_Config_AIN(GPIOA, GPIO_Pin_3);
       
    ADC_InitTypeDef  ADC_InitStructure;
    ADC_StructInit(&ADC_InitStructure);

    //Initialize PA1 to analog input mode
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);                         //Enable ADC clock

    ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
    ADC_InitStructure.ADC_PRESCARE = ADC_PCLK2_PRESCARE_12;                     //ADC prescale factor
    ADC_InitStructure.ADC_Mode = ADC_Mode_Continuous_Scan;                      //Set ADC mode to continuous conversion mode
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;                      //AD data right-justified
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
    ADC_Init(ADC1, &ADC_InitStructure);

    ADC_RegularChannelConfig(ADC, ADC_Channel_DisableAll, 0, ADC_SampleTime_13_5Cycles);//Block all channels
    ADC_RegularChannelConfig(ADC1, ADCch1, 0, ADC_SampleTime_13_5Cycles);//Enable the channel
    ADC_RegularChannelConfig(ADC1, ADCch2, 0, ADC_SampleTime_13_5Cycles);//Enable the channel

#ifdef ADC_USE_DMA               
    ADC_DMACmd(ADC1, ENABLE);                                                    //Enable ADCDMA
#else
    ADC_ITConfig(ADC1, ADC_IT_EOC, ENABLE);                              //DMA interrupt initialization
    NVIC_InitTypeDef NVIC_InitStruct;
    NVIC_InitStruct.NVIC_IRQChannel = ADC_COMP_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);
#endif               
    ADC_Cmd(ADC1, ENABLE);                                                       //Enable AD conversion
}

//DMA配置
void ADC_DMAInit(void)
{
    DMA_InitTypeDef DMA_InitStructure;
    NVIC_InitTypeDef NVIC_InitStruct;

    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
    DMA_DeInit(DMA1_Channel1);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32) & (ADC1->ADDATA);           //DMA transfer peripheral address
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)&ADCValue;                      //DMA transfer memory address
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;                          //DMA transfer direction from peripheral to memory
    DMA_InitStructure.DMA_BufferSize = 2;                            //DMA cache size
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;            //After receiving the data, the peripheral address is forbidden to move backward
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;                     //After receiving the data, the memory address is shifted backward
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord; //Define the peripheral data width to 16 bits
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;         //Define the memory data width to 16 bits
    DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;                             //Cycle conversion mode
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;                         //DMA priority is high
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;                                //M2M mode is disabled
    DMA_Init(DMA1_Channel1, &DMA_InitStructure);
    DMA_Cmd(DMA1_Channel1, ENABLE);

    DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);                              //DMA interrupt initialization
    NVIC_InitStruct.NVIC_IRQChannel = DMA1_Channel1_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);
               
                ADCTrigFilterflag = 0;
}


//ADCDMA中断处理
u32 measCount;
void DMA1_Channel1_IRQHandler(void)
{
//        ADC_SoftwareStartConvCmd(ADC1, DISABLE);                                     //Stop Conversion
        DMA_ClearITPendingBit(DMA1_IT_TC1);                                          //Clear interrupt flag
        u16 chan = 0;
        measCount++;
//                ADC_SoftwareStartConvCmd(ADC1, ENABLE);
//    ADCflag = 1;                                                                //Erected transmission complete flag

}



//72M时钟配置
void SetSysClockTo72_HSI(void)
{
    unsigned char temp = 0;
    unsigned int temp1 = 0;
    RCC->CR |= RCC_CR_HSION;
    while (!(RCC->CR & RCC_CR_HSIRDY))
        ;

    RCC->CR |= (1 << 20);

    RCC->CR &= ~(1 << 2);

    RCC->CFGR = RCC_CFGR_PPRE1_2;

    FLASH->ACR = FLASH_ACR_LATENCY_2 | FLASH_ACR_PRFTBE;
    RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;

    /* PCLK2 = HCLK PRE2 divide*/
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;

    /* PCLK1 = HCLK PRE1 divide */
    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV1;
    RCC->CFGR &= ~RCC_CFGR_SW;

    temp1 = *(u16 *)0x1FFFF7FA;
    if ((temp1 & 0xff) == 0xff) {
        temp1 &= 0xff00;
    } else {
        temp1 &= 0xff;
        temp1 <<= 8;
    }
    temp1 |= (RCC->CR & 0xFFFF00ff) | 0xf8;
    RCC->CR = temp1;
    RCC->CFGR |= RCC_CFGR_SW_HSI;

    while (1) {
        temp = RCC->CFGR;
        temp = temp >> 2;
        temp &= RCC_CFGR_SW;
        if(temp == RCC_CFGR_SW_HSI)
            break;
    }
}