LTC2410 24-Bit No Latency ∆ΣTM ADC with Differential Input and ...

LTC2410TYPICAL APPLICATIO SUSample Driver for LTC2410 SPI InterfaceThe LTC2410 has a very simple serial interface that makesinterfacing to microprocessors and microcontrollers veryeasy.The listing in Figure 56 is a simple assembler routine forthe 68HC11 microcontroller. It uses PORT D, configuringit for SPI data transfer between the controller and theLTC2410. Figure 55 shows the simple 3-wire SPIconnection.The code begins by declaring variables and allocating fourmemory locations to store the 32-bit conversion result.This is followed by initializing PORT D’s SPI configuration.The program then enters the main sequence. It activatesthe LTC2410’s serial interface by setting the SS outputlow, sending a logic low to CS. It next waits in a loop fora logic low on the data line, signifying end-of-conversion.After the loop is satisfied, four SPI transfers are completed,retrieving the conversion. The main sequence endsby setting SS high. This places the LTC2410’s serialinterface in a high impedance state and initiates anotherconversion.The performance of the LTC2410 can be verified using thedemonstration board DC291A, see Figure 57 for theschematic. This circuit uses the computer’s serial port togenerate power and the SPI digital signals necessary forstarting a conversion and reading the result. It includes aLabview application software program (see Figure 58)which graphically captures the conversion results. It canbe used to determine noise performance, stability andwith an external source, linearity. As exemplified in theschematic, the LTC2410 is extremely easy to use. Thisdemonstration board and associated software is availableby contacting Linear Technology.LTC2410SCKSDOCS13121168HC11SCK (PD4)MISO (PD2)SS (PD5)2410 F55Figure 55. Connecting the LTC2410 to a 68HC11 MCU Using the SPI Serial Interface43