US 12,445,143 B2
Analog-to-digital converter having time-constant tuning with pulse-width-based reference current and resistance searching
Xiaopeng Zhong, Seattle, WA (US); Yuhua Guo, San Diego, CA (US); Chieh-Yu Hsieh, Irvine, CA (US); and Chienchung Yang, San Diego, CA (US)
Assigned to QUALCOMM INCORPORATED, San Diego, CA (US)
Filed by QUALCOMM Incorporated, San Diego, CA (US)
Filed on Jan. 26, 2024, as Appl. No. 18/423,985.
Prior Publication US 2025/0247105 A1, Jul. 31, 2025
Int. Cl. H03M 1/46 (2006.01)
CPC H03M 1/466 (2013.01) [H03M 1/462 (2013.01)] 20 Claims
OG exemplary drawing
 
1. An analog-to-digital converter comprising:
an integrator including a variable input resistor and an integration capacitor;
a switched-capacitor bias current generator configured to be clocked by a pair of complementary clock signals to generate a bias current that is proportional to a capacitance of the integration capacitor divided by a pulse width of the complementary clock signals;
a current digital-to-analog converter (IDAC) configured to convert a digital output signal from the analog-to-digital converter into an IDAC output current for the integrator that is proportional to the bias current; and
a tuning circuit including a variable tuning resistor configured to conduct a mirrored version of the bias current to develop a tuning voltage across the variable tuning resistor, the tuning circuit further including a successive-approximation-register logic circuit configured to vary a resistance of the variable tuning resistor responsive to a tuning code, wherein the integrator is configured to vary a resistance of the variable input resistor responsive to the tuning code.