Datasheet LTC1291 (Analog Devices) - 10

LTC1291
O U U W U APPLICATI S I FOR ATIO Output Code
The LTC1291 performs a unipolar conversion. The follow-
Unipolar Transfer Curve
ing shows the output code and transfer curve:
Unipolar Output Code
1 1 1 1 1 1 1 1 1 1 1 1
INPUT VOLTAGE
1 1 1 1 1 1 1 1 1 1 1 0
OUTPUT CODE INPUT VOLTAGE (VREF = 5V)
• 1 1 1 1 1 1 1 1 1 1 1 1 VREF – 1LSB 4.9988V • 1 1 1 1 1 1 1 1 1 1 1 0 VREF – 2LSB 4.9976V • • • • • • • • • • 0 0 0 0 0 0 0 0 0 0 0 1 VIN 0 0 0 0 0 0 0 0 0 0 0 1 1LSB 0.0012V 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0V 0V 0V 1LSB V V V REF REF REF 1291 AI05a –2LSB –1LSB 1291 AI05b
Microprocessor Interfaces Table 1. Microprocessor with Hardware Serial Interfaces
The LTC1291 can interface directly (without external hard-
Compatible with the LTC1291**
ware) to most popular microprocessors’s (MPU) synchro-
PART NUMBER TYPE OF INTERFACE
nous serial formats (see Table 1). If an MPU without a
Motorola
dedicated serial port is used, then three of the MPU’s MC6805S2, S3 SPI MC68HC11 SPI parallel port lines can be programmed to form the serial MC68HC05 SPI link to the LTC1291. Included here are one serial interface
RCA
example and one example showing a parallel port pro- CDP68HC05 SPI grammed to form the serial interface.
Hitachi
HD6305 SCI Synchronous HD6301 SCI Synchronous
Motorola SPI (MC68HC11)
HD63701 SCI Synchronous The MC68HC11 has been chosen as an example of an MPU HD6303 SCI Synchronous HD64180 SCI Synchronous with a dedicated serial port. This MPU transfers data MSB
National Semiconductor
-first and in 8-bit increments. The DIN word sent to the data COP400 Family MICROWIRE† register starts the SPI process. With three 8-bit transfers, COP800 Family MCROWIRE/PLUS† NS8050U MICROWIRE/PLUS the A/D result is read into the MPU. The second 8-bit HPC16000 Family MICROWIRE/PLUS transfer clocks B11 through B8 of the A/D conversion
Texas Instruments
result into the processor. The third 8-bit transfer clocks the TMS7002 Serial Port TMS7042 Serial Port remaining bits, B7 through B0, into the MPU. The data is TMS70C02 Serial Port right justified in the two memory locations. ANDing the TMS70C42 Serial Port TMS32011* Serial Port second byte with 0DHEX clears the four most significant TMS32020* Serial Port bits. This operation was not included in the code. It can be TMS370C050 SPI inserted in the data gathering loop or outside the loop * Requires external hardware when the data is processed. ** Contact LTC marketing for interface information for processors not on this list † MICROWIRE and MICROWIRE/PLUS are trademarks of National Semiconductor Corporation. 1291fa 10