| 摘要 |
A single chip integrated circuit is partitioned to support a microprocessor chip for providing the logic interface between a keyboard peripherally connected to a host computer. The support circuit includes in a single integrated chip a voltage regulator, a serial to parallel converter, a multiple output current source, an oscillator, a DC to DC converter, an audio driver and LED drivers. The voltage regulator produces a plurality of regulated output voltages utilized to operate the microprocessor and the internal circuitry of the support circuit and is comprised of a band gap regulator and output of which is coupled to an external resistor for providing a reference current. The current source is coupled to the voltage regulator and provides a plurality of output currents ratioed with respect to the reference current. The serial to parallel converter converts serial digital data supplied from the microprocessor into parallel data for controlling the operation of the audio and LED driver circuits. The LED driver circuit converts currents supplied thereto from the current source to a higher magnitude sufficient for driving individual LEDs. The audio driver circuit provides a logarithmic output current thereat as controlled by said data.
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