2.7V to +5.25V Low-Power 8-Channel Serial 10-Bit ADCs

The MAX148/MAX149 10-bit data-acquisition systems combine an 8-channel multiplexer, high-bandwidth track/hold, and serial interface with high conversion speed and low power consumption. They operate from a single +2.7V to +5.25V supply, and sample to 133ksps. Both devices’ analog inputs are software configurable for unipolar/bipolar and single-ended/differential operation.

The 4-wire serial interface connects directly to SPI/QSPI™ and MICROWIRE™ devices without external logic. A serial-strobe output allows direct connection to TMS320-family digital signal processors. The MAX148/MAX149 use either the internal clock or an external serial-interface clock to perform successive-approximation analog-to-digital conversions.

The MAX149 has an internal 2.5V reference, while the MAX148 requires an external reference. Both parts have a reference-buffer amplifier with a ±1.5% voltage-adjustment range.

These devices provide a hard-wired active-low SHDN pin and a software-selectable power-down, and can be programmed to automatically shut down at the end of a conversion. Accessing the serial interface automatically powers up the MAX148/MAX149, and the quick turn-on time allows them to be shut down between all conversions. This technique can cut supply current to under 60µA at reduced sampling rates.

The MAX148/MAX149 are available in 20-pin PDIP and 20-pin SSOP packages.

For 4-channel versions of these devices, see the MAX1248/MAX1249 data sheet.

Applications

* Battery-Powered Instruments * Data Acquisition * Medical Instruments * Pen Digitizers * Portable Data Logging * Process Control

* 8-Channel Single-Ended or 4-Channel Differential Inputs

* Single-Supply Operation: +2.7V to +5.25V

* Internal 2.5V Reference (MAX149)

* Low Power:

* 1.2mA (133ksps, 3V Supply)

* 54µA (1ksps, 3V Supply)

* 1µA (Power-Down Mode)

* SPI/QSPI/MICROWIRE/TMS320-Compatible 4-Wire Serial Interface

* Software-Configurable Unipolar or Bipolar Inputs

* 20-Pin PDIP/SSOP Packages