+ + + DEMO MANUAL DC742B LTC2449 8-/16-channel, High Speed 24-Bit Delta Sigma ADC DESCRIPTION Demonstration circuit 742B features the LTC 2449, an DC742B is a member of Linear Technologys QuikEval 8-/16-channel, high speed, 24-bit ADC with ten select- family of demonstration boards. It is designed to allow easy able speed/resolution modes from 6.9Hz/200nV to evaluation of the LTC2449 and may be connected directly RMS 3.5kHz/23V (4kHz with external oscillator). Key DC to the target applications analog signals while using the RMS specifications include 5ppm INL, 5V offset, 10ppm full- DC590 USB Serial Controller board and supplied software scale error and 20nV/C offset drift. In the 6.9Hz/200nV to measure performance. The exposed ground planes allow RMS mode, input normal mode rejection of 50Hz and 60Hz proper grounding to prototype circuitry. After evaluating noise is better than 87dB. The accuracy (offset, full-scale, with LTCs software, the digital signals can be connected linearity, drift) and power dissipation are independent of to the applications processor/controller for development the speed selected. The LTC2449 performs auto-zeroing of the serial interface. of the ADC by reversing the inputs through the multiplexer Design files for this circuit board are available at output/ADC input connections. This allows an external DEMO MANUAL DC742B QUICK START PROCEDURE Connect DC742B to a DC590 USB Serial Controller using chart display to change the oversample ratio (OSR) which the supplied 14-conductor ribbon cable. Connect DC590 will in turn change the data output rate. to host PC with a standard USB A/B cable. Run the evalu- Tools are available for logging data, changing reference ation software supplied with DC590 or downloaded from voltage, changing the number of points in the strip chart www.linear.com. The correct program will be loaded au- and histogram, and changing the number of points aver- tomatically. Click the COLLECT button to start reading the aged for the DVM display. input voltage. Click the slider at the bottom of the strip HARDWARE SETUP JUMPERS cannot be terminated once started, this signal can only be used to slow down the conversion rate. JP1, JP2: Select the positive and negative supply voltages for the onboard amplifier. Supplies can be ground and V CC CONNECTION TO DC590 SERIAL CONTROLLER or supplied externally. J2 is the power and digital interface connector. Connect JP3, JP5: Select the source for REF+ and REF, respec- to DC590 serial controller with supplied 14-conductor tively. REF+ can be 5V from the onboard LT1236 reference ribbon cable. (default) or supplied externally. REF can be ground (0V, default) or supplied externally. ANALOG CONNECTIONS JP4: Select source for analog COM input, either tied to ground or supplied externally to the COM turret post. Analog signal connections are made via the row of turret posts along the edge of the board. Also, if you are connect- JP6: Trigger mode, either normal (default) or externally ing the board to an existing circuit, the exposed ground triggered. planes along the edges of the board may be used to form JP7: Trigger input signal. Pin 1 is a 5V logic input, pin2 is a solid connection between grounds. ground. When triggered mode is selected on JP6, a rising GND: Ground turrets are connected directly to the internal edge starts a new conversion. Note that since a conversion analog ground plane. dc742bfb 2