Abstract: A voltage ladder is used to generate reference voltages. The voltage ladder is used by multiple digital-to-analog converters (DACs). In particular, the voltage ladder is used by multiple pulse-width modulation (PWM) DACs. Having multiple DACs utilize a common voltage ladder for their reference voltages reduces mismatched output voltages between DACs. Having multiple DACs utilize the common voltage ladder helps ensure that the reference voltages used by different DACs are not affected by process, voltage, and/or temperature variations in the reference voltages that would occur when using different voltage ladders for each DAC.

Abstract: The embodiments herein describe technologies for back-gate biasing of clock trees using a reference generator. A circuit includes a set of clock buffers and a programmable voltage reference generator to apply a voltage to a back gate of a transistor of the set of clock buffers.

Abstract: A voltage ladder is used to generate reference voltages. The voltage ladder is used by multiple digital-to-analog converters (DACs). In particular, the voltage ladder is used by multiple pulse-width modulation (PWM) DACs. Having multiple DACs utilize a common voltage ladder for their reference voltages reduces mismatched output voltages between DACs. Having multiple DACs utilize the common voltage ladder helps ensure that the reference voltages used by different DACs are not affected by process, voltage, and/or temperature variations in the reference voltages that would occur when using different voltage ladders for each DAC.

Abstract: The embodiments herein describe technologies for back-gate biasing of clock trees using a reference generator. A circuit includes a set of clock buffers and a programmable voltage reference generator to apply a voltage to a back gate of a transistor of the set of clock buffers.

Abstract: A voltage ladder is used to generate reference voltages. The voltage ladder is used by multiple digital-to-analog converters (DACs). In particular, the voltage ladder is used by multiple pulse-width modulation (PWM) DACs. Having multiple DACs utilize a common voltage ladder for their reference voltages reduces mismatched output voltages between DACs. Having multiple DACs utilize the common voltage ladder helps ensure that the reference voltages used by different DACs are not affected by process, voltage, and/or temperature variations in the reference voltages that would occur when using different voltage ladders for each DAC.

Abstract: A payment reader includes a tuning circuit that provides a tuned transmission source signal to an antenna for transmission. A sense circuit coupled to the antenna provides a measured transmitted signal to a binary phase detection circuit. The binary phase detection circuit filters and processes the signal to provide an analog phase signal that corresponds to a phase difference between the measured transmitted signal and the transmission source signal. A comparison circuit compares the analog phase signal to a reference signal, and a decision circuit adjusts the operation of the transmission circuitry based on the comparison.

Abstract: A payment reader includes an anti-tamper circuit for comparing a voltage measured from a temperature sensing circuit with a voltage from one or more threshold nodes. A voltage of a measurement node of the temperature sensing circuit and of each threshold node may correspond to a temperature. A temperature comparison circuit may determine whether a pre-determined temperature threshold has been breached on a comparison of a voltage of the measurement node of the temperature sensing circuit with voltages corresponding to the one or more temperature thresholds. A tamper attempt may be detected if the voltage measured from the temperature sensing circuit exceeds a high voltage threshold or falls below a low voltage threshold. The temperature comparison circuit may provide an output to anti-tamper circuit indicating a result of the comparison.

Abstract: A comparator can incorporate a hysteresis circuit to control when the output of the comparator changes between a high voltage signal and a low voltage signal. The comparator can receive a differential signal and can output either the high voltage signal or the low voltage signal. When the differential input signal is above a first threshold voltage, the output of the comparator can transition to the high voltage signal and when the differential input signal is below a second threshold voltage, the output of the comparator can transition to the low voltage signal. The hysteresis circuit of the comparator is used to adjust the first threshold voltage and the second threshold voltage required to transition the output of the comparator based on the present state of the output signal of the comparator.

Abstract: A level shifting circuit can be used to adjust the level of the input signal to a desired output level while maintaining the duty cycle of the input signal. The level shifting circuit can include a capacitor to AC couple the input signal to an inverter that is self-biased at the threshold voltage for the inverter. The AC coupling of the input signal permits the input signal to “ride on” the threshold voltage and transition the inverter between states depending on the value of the input signal. The inverter can be biased at the threshold voltage by connecting the output of the inverter in feedback with the input of the inverter using one or more resistors.

Abstract: A payment reader includes a tuning circuit that provides a tuned transmission source signal to an antenna for transmission. A sense circuit coupled to the antenna provides a measured transmitted signal to a binary phase detection circuit. The binary phase detection circuit filters and processes the signal to provide an analog phase signal that corresponds to a phase difference between the measured transmitted signal and the transmission source signal. A comparison circuit compares the analog phase signal to a reference signal, and a decision circuit adjusts the operation of the transmission circuitry based on the comparison.

Abstract: A brown-out detector and power-on-reset circuit can be used to monitor a supply voltage to determine when brown-out and power-on events occur and provide the appropriate reset signal in response. The circuit can include a comparator to generate the reset signal and a first monitoring circuit that operates in conjunction with a second monitoring circuit to provide an input voltage to the comparator. The first monitoring circuit can incorporate a bandgap circuit and can be used to control the input voltage based on the comparison of the supply voltage and a corresponding supply voltage threshold. The second monitoring circuit can incorporate a diode and can be used when the supply voltage is lower than a threshold voltage for the bandgap circuit. The second monitoring circuit can be used to control the input voltage based on a comparison of the supply voltage and a threshold voltage for the diode.

Abstract: A brown-out detector and power-on-reset circuit can be used to monitor a supply voltage to determine when brown-out and power-on events occur and provide the appropriate reset signal in response. The circuit can include a comparator to generate the reset signal and a first monitoring circuit that operates in conjunction with a second monitoring circuit to provide an input voltage to the comparator. The first monitoring circuit can incorporate a bandgap circuit and can be used to control the input voltage based on the comparison of the supply voltage and a corresponding supply voltage threshold. The second monitoring circuit can incorporate a diode and can be used when the supply voltage is lower than a threshold voltage for the bandgap circuit. The second monitoring circuit can be used to control the input voltage based on a comparison of the supply voltage and a threshold voltage for the diode.

Abstract: A level shifting circuit can be used to adjust the level of the input signal to a desired output level while maintaining the duty cycle of the input signal. The level shifting circuit can include a capacitor to AC couple the input signal to an inverter that is self-biased at the threshold voltage for the inverter. The AC coupling of the input signal permits the input signal to “ride on” the threshold voltage and transition the inverter between states depending on the value of the input signal. The inverter can be biased at the threshold voltage by connecting the output of the inverter in feedback with the input of the inverter using one or more resistors.

Abstract: A payment reader includes an anti-tamper circuit for periodically providing control signals to tamper detection devices for detecting tamper attempts. The anti-tamper circuit includes a battery that drives a clock source. The clock source outputs a periodic signal to an enabling circuit and a pulse generator. The pulse generator provides enabling signal to an enabling circuit when it receives the periodic signal, and the enabling circuit provides an oscillator activation signal to a local oscillator when the enabling circuit receives the enabling signal and the periodic signal. The local oscillator provides an oscillating signal to the pulse generator, which utilizes the oscillating signal to exchange control signals with the tamper detection devices.

Abstract: A transition glitch suppression circuit can be used to remove unwanted glitches occurring within a time delay of the rising edge or falling edge of a signal. The transition glitch suppression circuit has a delay element that can delay the input signal by the time delay to generate a delayed input signal. The transition glitch suppression circuit also has first and second logic circuits that process the input signal and the delayed input signal to generate corresponding outputs. A multiplexer provides the output signal for the suppression circuit by selecting between the output of the first logic circuit and the output of the second logic circuit based on the value of the output signal.