Demonstration circuit 726 is for the evaluation of Linear Technology's programmable oscillator ICs, the LTC6903 and LTC6904. The DC726A-A features the LTC6903 IC in an 8-lead MSOP package. The LTC6903 is a 1kHz to 68MHz oscillator programmable thru a 3-wire digital interface compatible with the SPI serial protocol. The DC726A-B features the LTC6904 IC in an 8-lead MSOP package. The LTC6904 is a 1kHz to 68MHz oscillator programmable thru a 3-wire digital interface compatible with the I2C serial protocol (a Philips Corp. trademark). The LTC6903 and LTC6904 require no external components and operate over a single power supply range from 2.7V to 5.5V. The maximum frequency error is 1.1% or 1.6% when operating with a single 3V or 5V power supply respectively. Demonstration circuit 726 is operated in one of two modes: 1. A Local Mode using DC726 as stand-alone demonstration board with external power supplies. 2. A QuickEval mode for interfacing to a USB port of a PC using Linear Technology?s DC590 Serial Controller Board and a QuickEval program for Windows 98 or later downloaded from www.linear.com/software. In Local Mode, a 16-bit serial code is entered in HEX with push-button switches to a 4-digit LED display. The HEX code is read by PIC (Peripheral Interface Controller) that updates the control word of the LTC6903/LTC6904. In QuickEval Mode, the DC726 PIC shuts down when it is connected to a DC590A. Control of the LTC6903/LTC6904 is thru a PC with a QuickEval program which uses either a frequency or a HEX code input. The frequency or HEX code input entered on the computer display, is sent as a 16-bit serial word to the DC726A-A/B.