Low-Power, 8-Channel, Serial 12-Bit ADCs 

General Description

The MAX186/MAX188 are 12-bit data-acquisition systems that combine an 8-channel multiplexer, high-bandwidth track/hold, and serial interface together with high conversion speed and ultra-low power consumption. The devices operate with a single +5V supply or dual ±5V supplies. The analog inputs are software configurable for unipolar/bipolar and single-ended/differential operation. The 4-wire serial interface directly connects to SPI™, QSPI™ and Microwire™ devices without external logic. A serial strobe output allows direct connection to TMS320 family digital signal processors. The MAX186/MAX188 use either the internal clock or an external serial-interface clock to perform successive-approximation A/D conversions. The serial interface can operate beyond 4MHz when the internal clock is used. The MAX186 has an internal 4.096V reference while the MAX188 requires an external reference. Both parts have a reference-buffer amplifier that simplifies gain trim . The MAX186/MAX188 provide a hard-wired SHDN pin and two software-selectable power-down modes. Accessing the serial interface automatically powers up the devices, and the quick turn-on time allows the MAX186/MAX188 to be shut down between every conversion. Using this technique of powering down between conversions, supply current can be cut to under 10µA at reduced sampling rates. The MAX186/MAX188 are available in 20-pin DIP and SO packages, and in a shrink small-outline package (SSOP), that occupies 30% less area than an 8-pin DIP. For applications that call for a parallel interface, see the MAX180/MAX181 data sheet. For anti-aliasing filters, consult the MAX274/MAX275 data sheet.

ABSOLUTE MAXIMUM RATINGS

VDD to AGND............................................................-0.3V to +6V

VSS to AGND ............................................................+0.3V to -6V VDD to VSS..............................................................-0.3V to +12V

AGND to DGND.....................................................-0.3V to +0.3V

CH0–CH7 to AGND, DGND.............(VSS - 0.3V) to (VDD + 0.3V)

CH0–CH7 Total Input Current ..........................................±20mA

VREF to AGND ...........................................-0.3V to (VDD + 0.3V)

REFADJ to AGND.......................................-0.3V to (VDD + 0.3V)

Digital Inputs to DGND...............................-0.3V to (VDD + 0.3V)

Digital Outputs to DGND............................-0.3V to (VDD + 0.3V)

Digital Output Sink Current .................................................25mA

Continuous Power Dissipation (TA = +70°C)

Plastic DIP (derate 11.11mW/°C above +70°C) ...........889mW

SO (derate 10.00mW/°C above +70°C)........................800mW

SSOP (derate 8.00mW/°C above +70°C) .....................640mW

CERDIP (derate 11.11mW/°C above +70°C)................889mW

Operating Temperature Ranges:

MAX186_C/MAX188_C ........................................0°C to +70°C MAX186_E/MAX188_E......................................-40°C to +85°C

MAX186_M/MAX188_M ..................................-55°C to +125°C

Storage Temperature Range .............................-60°C to +150°C

Lead Temperature (soldering, 10sec) .............................+300°C

Detailed Description

The MAX186/MAX188 use a successive-approximation conversion technique and input track/hold (T/H) circuitry to convert an analog signal to a 12-bit digital output. A flexible serial interface provides easy interface to microprocessors. No external hold capacitors are required. Figure 3 shows the block diagram for the MAX186/MAX188.