Patent ID: 8547271

Claim:
An analog-to-digital converter, comprising M Analog-to-Digital Converters (ADCs) ADC j , j=1, 2, . . . , M, M being an integer and greater than 1, and an ADC j , j=1, 2, . . . , M, comprising n j cells each of which comprises: a first switch comprising a first end and a second end, the first end being operatively coupled to an input signal of the ADC j , j=1, 2, . . . , M; a second switch comprising a first end and a second end, the second end being operatively coupled to the second end of the first switch; a current sink operatively coupled to the second end of the first switch, the current sink being supplied by a current source; and an inverter comprising an input terminal and an output terminal, the input terminal being operatively coupled to the second end of the first switch and the second end of the second switch; wherein an ADC j , j=2, 3, . . . , M, is enabled to perform analog-to-digital conversion on a residual current of ADC j-1 after ADC j-1 has completed its analog-to-digital conversion and has been disabled, the residual current of ADC j-1 being represented by I R(j-1) =I R(j-2) −i n(j-1) *n c(j-1) , where I R0 is the current associated with the input signal of ADC 1 , n c(j-1) is the number of cells in ADC j-1 that are switched on, and i n(j-1) is the current carried by the current source in a single cell in ADC j-1 ; wherein when an ADC j , j=1, 2, 3, . . . , M, is enabled, the first switch of a first cell is closed, the first switches of a 2 nd to n j th cells are open, and the second switches of the n j cells are closed; and the inverter of a k th cell, k=1, 2, 3, . . . , n j , in ADC j changes state if the current associated with the input signal of ADC j is higher than a threshold determined by the current associated with the k current sinks of the 1 st to k th cells, the second switch of the k th cell is open in response to the changing state of the inverter of the k th cell, and the first switch of a (k+1) th cell is closed in response to the changing state of the inverter of the k th cell if k is less than n j .