JiaAn
For LPC4370,
ADC0/1 use BASE_APB3_CLK,
ADCHS is clocked by BASE_M4_CLK (for register interface) and BASE_ADCHS_CLK( for conversion rate.)
All above clock can be sourced from external clock. For detail, see UM10503, Table 122. Clock sources for output stages.
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Have a nice day,
Jun Zhang