Abstract: A digital pulse width modulation (DPWM) controlling system for controlling a load of an application circuit with a DPWM unit is provided, which comprises a comparator and a micro-control unit, the comparator receiving a sense signal detected from the load and a reference signal and comparing the sense signal and the reference signal to output an analog comparison signal, and the micro-control unit generating a trigger signal having a minimum pulse width and receiving the analog comparison signal to output a DPWM signal, wherein the micro-control unit adjusts the minimum pulse width of the trigger signal to obtain a pulse width of the DPWM signal in response to the analog comparison signal whenever the sense signal is within a stable duration so as to output the DPWM signal to the application circuit to control the load.

Abstract: A programmable precise frequency divider cooperating with a low frequency crystal and an oscillating circuit is disclosed. The divider includes a low frequency oscillating circuit, a preset code memory, a programmable preset code loader, an adder, and a register. The programmable preset code loader loads and latches a preset code either from the preset code memory or a preset code input line coupled to an external data source. The latched preset code and the current value of the register are commonly supplied to the adder. The adder is used to sum up the latched preset code from the programmable preset code loader and the current value from the register and thereby supply a resultant value to the register. The register accumulates the resultant value from the adder to the oscillating signal from the oscillating circuit and then supplies a output clock signal with a required divided frequency.

Abstract: A method and an interface circuit for scanning keys and external resistors of a keypad are disclosed.

Abstract: A compound type keyboard detector is disclosed. It comprises a time-sequencing generator, a keyboard scanner, a column input port and a row input port, a column lock and a row lock, a keyboard-synchronization detector, a keyboard detector and a keyboard decoder. With the unique design of the keyboard detector in conjunction with the various circuits that are associated therewith, a given number of pins can be used for a relatively greater number of input keys, or a smaller number of pins can be used for relatively complicated input keyw. This type of keyboard detector is good for small IC products, and can reduce the manufacturing cost thereof.