MAX128ACNG
MAX128ACNG - 12-Bit 8-Channel +5V DAS, 24-PDIP | Maxim Integrated
The Maxim Integrated MAX128ACNG (now ADI/Maxim Integrated) is a 12-bit, +5V, multirange Data Acquisition System (DAS) with an 8-channel analog input multiplexer and a 2-wire I2C-compatible serial interface, packaged in a 24-pin PDIP through-hole format. The device integrates an 8-input mux, track/hold, successive-approximation ADC core, internal 4.096V reference, and a 2-wire serial interface, delivering up to 8 ksps conversion rate. It supports software-configurable input ranges of 0 to +5V, 0 to +10V, +/-5V, +/-10V, 0 to +15V, and +/-15V, providing true bipolar operation from a single +5V supply through its on-chip charge pump.
A Data Acquisition System (DAS) such as the MAX128 combines an ADC, input protection, and channel-selection hardware on one chip, falling into the broader categories of ADC -> data converter -> mixed-signal IC -> semiconductor. The 8-channel input multiplexer allows a single ADC core to sequentially sample eight sensors or signals, reducing system cost, board area, and software complexity versus using eight discrete ADCs. Multirange operation - a defining feature of the MAX128 - lets a single part replace dedicated +/-10V or 0-10V industrial signal-conditioning front ends, which historically required level-shift amplifiers, divider resistors, or bipolar supplies. By generating the bipolar rails internally with a charge pump, the MAX128 accepts industrial-standard signals directly from a single +5V rail.
Key specifications include 12-bit resolution with 8 ksps throughput, 8 single-ended or 4 differential analog input channels, 2-wire I2C-compatible serial interface, hardware SHDN pin plus two software-programmable power-down modes (standby and full power-down), and an internal 4.096V bandgap reference. The MAX128 A-grade version offers +/-1 LSB INL and guaranteed performance over temperature. Programmable unipolar/bipolar input ranges cover 0 to +5V, 0 to +10V, 0 to +15V, +/-5V, +/-10V, and +/-15V. Power-down current consumption to idle is typically 1 microamp, which is critical for battery-powered data loggers.
The MAX128 architecture uses a charge-pump to generate -5V internally, which is required to bias the input-protection clamp transistors when the input goes below ground; without it the input ESD structures would forward-bias. The successive-approximation ADC core with track/hold provides 8 ksps conversion rate, and the I2C-compatible 2-wire interface allows up to four MAX128 devices on a single bus for 32-channel systems. The hardware SHDN pin reduces supply current to a few microamps between samples, and software standby mode retains the last conversion result and brings quiescent current to four microamps for fast wake-up; full power-down drops to 1 microamp.
Typical applications include industrial process control PLC analog input modules, multichannel data loggers, portable battery-powered instrumentation, rack-mount data acquisition cards, building automation sensor interfaces, and SCADA remote terminal units. For PLC analog input modules the 8-channel mux and +/-15V bipolar range make it a one-chip solution for thermocouple, 4-20 mA, and +/-10V industrial signal acquisition. The I2C-compatible interface simplifies connection to microcontrollers without consuming parallel I/O pins.
A key design consideration: input signal traces above 0 to +5V require the bipolar input range mode and the on-chip charge pump must be active; a bypass capacitor on the +5V analog supply pin is required for charge-pump decoupling. Designers should also place a 10kohm/0.1uF RC anti-aliasing filter on each analog input to prevent out-of-band noise from aliasing into the passband.
This page synthesizes distributor stock, parametric drop-in alternatives, and practical design considerations not found in the bare datasheet, with all values verified against the manufacturer datasheet and DigiKey/Mouser as of 2026-10-14.
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