AD7156BCPZ-REEL

Overview

The AD7156BCPZ-REEL is a dual-channel capacitance-to-digital converter (CDC) from Analog Devices, housed in a 10-lead LFCSP package measuring 3 mm × 3 mm. It operates on a single supply voltage ranging from 1.8 V to 3.6 V with a typical operating current of 70 μA and a power-down current of 2 μA. The device features two capacitive input channels (CIN1/CIN2) and two excitation outputs (EXC1/EXC2), supporting sensor capacitances up to 13 pF. It utilizes a Sigma-Delta architecture with an internal reference and provides a 2-wire I²C-compatible serial interface for configuration and data retrieval.

Feature Summary

• Ultralow power consumption: 70 μA typical operation, 2 μA typical power-down.
• Dual-channel capacitance sensing with adaptive environmental compensation for humidity and temperature variations.
• Fast response time: 10 ms conversion per channel and 300 μs wake-up time from serial interface.
• Integrated CAPDAC allows offset capacitance compensation up to 10 pF, extending the measurable range.

Applications

• Buttons and switches
• Proximity sensing
• Contactless switching
• Position detection
• Level detection

Procurement Notes

Verify the specific ordering suffix REEL against the manufacturer's current documentation to confirm tape-and-reel packaging quantities and handling requirements. Ensure the component meets RoHS compliance standards as specified in the official datasheet before integration into regulated assemblies.

Selection Notes

Select this component when designing systems requiring low-power capacitive touch or proximity detection. It supports both standalone fixed-threshold operation and microcontroller-configurable adaptive modes. Ensure the application environment stays within the -40°C to +85°C operating temperature range and that the supply voltage remains between 1.8 V and 3.6 V.

Part Context

This part belongs to the AD7156 series of specialized data acquisition ADCs designed for capacitive sensors. It integrates a complete signal processing solution including excitation sources, comparators, and digital filters. The device is distinct from linear regulators like the ADP7156, focusing solely on capacitance measurement rather than power management.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Verify compatibility with existing PCB footprints and firmware drivers if considering alternative CDC devices from other manufacturers.

FAQ

How does the AD7156 handle environmental drift?

It uses an integrated adaptive threshold algorithm that dynamically adjusts thresholds to compensate for slow changes in sensor capacitance caused by factors like humidity, temperature, or dielectric material aging.

What is the maximum sensor capacitance supported?

The device supports sensor capacitances (C_SENS) from 0 pF up to 13 pF. The internal CAPDAC can compensate for offset capacitance up to 10 pF, allowing the effective input range to be shifted.

Can the AD7156 operate without a microcontroller?

Yes, it offers a standalone mode using fixed power-up settings where detection is indicated directly on two digital output flags (OUT1 and OUT2) without requiring serial interface communication.