Abstract: A pulse width modulation (PWM) device, system and method for high resolution fan control are disclosed. In one embodiment, the method comprises determining a target duty cycle of a PWM signal, determining the number of PWM cycles in the period of the PWM signal, pseudo-randomly selecting a duty cycle for each PWM cycle using one or more look-up tables and generating the PWM signal based on the duty cycle.

Abstract: A circuit for temperature sensing provides a bias current to a PN junction, and the PN junction provides a PN junction voltage in response to the bias current. Also, a parasitic resistance may be coupled in series with the PN junction. The circuit for temperature sensing is configured to determine the temperature of the PN junction based on the PN junction voltage. Further, the circuit includes registers which store ?trim, which is based on the difference between the non-ideality of the PN junction used from a reference PN junction; ?I, which is based on the difference between a reference bias current and the bias current for the part; Rtrim, which is based the parasitic resistance; and Ntrim, which includes other offsets. The registers may be set during trimming and/or calibration to provide accurate temperature sensing for the parameters employed.

Abstract: An analog front-end (AFE) circuit may include a correlated double sampler (CDS) with a ping-pong architecture, and a ping-pong mismatch correction circuit. The CDS employs a ping data path during ping phases, and employs a pong data path during pong phases. The ping-pong mismatch correction circuit is arranged to correct a mismatch between a gain that is associated with the ping data path and a gain that is associated with the pong data path. Further, the ping-pong mismatch correction circuit is arranged to correct a mismatch between an offset that is associated with the ping data path and an offset that is associated with the pong data path.

Abstract: A method and apparatus improves the accuracy of temperature measurements by sampling measurements from a remote sensor, where currents of different current densities are applied to the remote sensor in a time-interleaved fashion. The remote sensor includes at least one PN junction that produces a voltage corresponding to the applied current at each instance of time, and related to the temperature of the remote sensor. By applying time-interleaved current densities to the remote sensor, adverse effects from temperature variations during the measurement are minimized. Sequences of current biases having differing current densities in a forward order are applied to the remote sensor, followed by the same sequence being applied to the remote sensor in a reverse order. Similarly, a random or pseudo-random sequence may be employed in a forward and reverse order. The application of forward and reverse sequences is utilized to minimize errors in the temperature measurement.

Abstract: A circuit is arranged to pulse-width modulate the duty cycle of a power supply signal that is used to control the rotational speed of a fan in a temperature-controlled system. The control system includes an edge detector for monitoring a tachometer signal that is provided by the fan. The tachometer signal is monitored at a rate (e.g., one Hertz) that is substantially lower than the rotational speed of the fan. The control system also includes a timer for recording time intervals between selected edges of a monitored tachometer signal. The fan speed is determined from the recorded time intervals. The control system extends the duty cycle of the pulse-width modulated signal to ensure that the fan power remains stable over the period in which the tachometer signal is to be monitored. Maintaining fan power ensures the validity of the tachometer signal during the period that the fan power is maintained.

Abstract: The present invention enables an IC to have a fast PWM while maintaining the low frequency clock requirement of the temperature measurement. Methods are presented to increase the resolution of the control using a relatively low input clock. According to one method, the numerator and denominator of the PWM duty cycle equation are adjusted to achieve a desired resolution. According to another method, a determined number of PWM cycles are used to set the PWM duty cycle. For example, an averaging of 1024 duty cycles may be used to achieve an increased resolution of the duty cycle as compared to using only one duty cycle. According to yet another method, an error integrating loop is used to determine the level of the next cycle. The number of cycles used to reach the target PWM duty cycle depends on the desired resolution.