DEMO MANUAL DC1684A-A/DC1684A-B LTC2758/LTC2752 Dual SPI I OUT 18-Bit/16-Bit DACs Description Demonstration circuit 1684A-A features the LTC 2758A facilitate trimming of residual DC errors without impacting 18-bit SoftSpan I DAC. DC1684A-B features the the excellent temperature stability of this device. OUT pin-compatible 16-bit LTC2752A. The digital interface is The DC1684A-B uses LT 1468 amplifiers recommended a simple, 4-wire Serial Peripheral Interface (SPI), aug- for 16-bit applications. The DC1684A-A uses low noise, mented with separate CLEAR and LDAC pins that reset low offset LT1012A amplifiers for reference inversion, and the output to zero and load the DAC code, respectively. a composite amplifier for I-V conversion that provides These devices feature six output ranges: 0V to 5V, 0V to 18-bit accuracy and fast settling. Amplifier selection is 10V, 5V, 10V, 2.5V, and 2.5V to 7.5V. These ranges detailed in the LTC2758 and LTC2752 data sheets. are programmable through the SPI interface or through Design files for this circuit board are available at separate span control pins if SoftSpan operation is not DEMO MANUAL DC1684A-A/DC1684A-B Quick s tart p D Connect a low noise 15V power supply to the AMPV+, cording to the entries in the control panel. A square wave GND, and AMPV turret posts on the DC1684A board. option is available to test the settling time. The MSPAN jumper should be set to 0 if software span control is de- Connect J1 to a DC590 USB serial controller using the sired. Setting MSPAN high (1) causes the S2, S1 and S0 supplied 14-conductor ribbon cable. Connect DC590 to a pins to set the span according to the table printed on the host PC with a standard USB A/B cable. Run the evaluation board. The corresponding span should be selected in the software supplied with the DC590, or download it from software to ensure that the calculated DAC code is correct. www.linear.com/software. The correct control panel will be loaded automatically (shown in Figure 2). The software Additional software documentation may be available from automatically sets the LTC2758A / LTC2752A outputs ac- the Help menu item, as features may be added periodically. Figure 2. Software Screenshot dc1684aabfb 2 ure roce