MAX1091BEEI+T
MAX1091BEEI+T - 10-Bit 250ksps 8-Ch SAR ADC w/ Reference | Maxim
The Maxim Integrated MAX1091BEEI+T is a 250 ksps, +3 V, 8-channel, 10-bit successive-approximation analog-to-digital converter (SAR ADC) with an internal +2.5 V reference and a byte-wide parallel interface, housed in a 28-pin QSOP (EIAJ) package. It combines low power consumption, automatic power-down between conversions, 2 µs wake-up, and a separate VLOGIC pin that lets the digital interface run from +1.8 V to +5.5 V while the analog core stays on a single +3 V supply.
An ADC (analog-to-digital converter) is a mixed-signal integrated circuit that quantizes a continuous analog input voltage into a discrete binary code. Within the broader taxonomy, the MAX1091 belongs to SAR ADCs -> data converters -> data acquisition ICs -> signal chain -> semiconductor. SAR architectures use a binary-search capacitor DAC and a single comparator to resolve N bits in N clock cycles, trading speed for excellent DC accuracy, intrinsic monotonicity, and zero pipeline latency. That makes them the dominant choice for multiplexed multi-channel systems, precision instrumentation, and control loops where a deterministic per-channel conversion time matters more than raw throughput.
Key differentiating features of the MAX1091 include 8 single-ended analog input channels (vs. 4 on the MAX1093), 250 ksps maximum sample rate, true 10-bit linearity with no missing codes, an internal +2.5 V reference (also usable as an external drive), hardware- and software-configurable power-down modes that drop supply current to microamp levels between conversions, and an on-chip 4 MHz SAR oscillator that eliminates the need for an external clock. The wide +1.8 V to +5.5 V VLOGIC range lets the part drop directly onto the bus of 1.8 V DSPs, 2.5 V FPGAs, 3.3 V ASICs or 5 V microcontrollers without level shifters.
Architecturally, the device integrates an 8:1 input mux, a fully differential switched-capacitor DAC, an internal +2.5 V bandgap reference, a comparator, a successive-approximation register, a wide parallel output latch, and the power-down/wake-up sequencer. Automatic power-down between conversions keeps average current extremely low in low-duty-cycle applications; in continuous 250 ksps operation the part draws a few milliamps from AVDD and a fraction of that from DVDD.
Typical applications include 4–20 mA sensor-conditioning front ends, portable data loggers, battery-powered medical instrumentation, multi-channel PLC analog input modules, and touch/position sensing front ends. The +3 V single-supply operation, internal reference and tiny QSOP-28 footprint also make it attractive for space-constrained designs that still need more than 4 channels.
When designing with this part, observe the AVDD/DVDD decoupling guidelines in the Maxim datasheet: place a 0.1 µF ceramic close to each supply pin and a bulk tantalum or ceramic on AVDD, keep analog input traces short and guarded, and bypass REF to AGND with the recommended 4.7 µF capacitor to minimize reference noise. The internal reference has limited drive capability, so treat REF as a low-current bias node, not a system rail.
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