In battery-powered devices and low-voltage sensor systems, operational amplifiers must not only accommodate limited supply voltages but also minimize their own power consumption while providing sufficient headroom for both input and output signals. The CDV321 is a single-channel, low-power, rail-to-rail input/output operational amplifier designed for sensor signal conditioning, low-frequency active filtering, and general analog signal processing in portable devices.

1、CDV321 Product Overview

The CDV321 from ChisynV Micro is a single-channel, low-power, rail-to-rail input/output operational amplifier in this series, operating within a supply voltage range of 2.5 V to 5.5 V and a temperature range of −40°C to +125°C. The device is available in SOT23-5, MSOP-8, and SOIC-8 package options, making it suitable for sensor signal conditioning, low-frequency active filtering, and single-channel analog signal processing in portable devices. When designing, the appropriate package can be selected based on PCB space constraints, assembly requirements, and circuit specifications.

2、Performance Characteristics and Specifications

Low-voltage power supply, compatible with common analog systems

CDV321 supports a supply voltage range from 2.5 V to 5.5 V, making it suitable for a variety of low-voltage analog circuits. This wide low-voltage supply range provides flexibility for power supply design and analog front-end integration.

In single-power-supply systems, the input signal often approaches ground potential. The common-mode input range of the CDV321 is from −0.1 V to +5.6 V at Vs = 5.5 V, which facilitates the handling of input signals close to the power supply rail. In practical design, it is still necessary to verify that the input voltage complies with the device's rated specifications and to incorporate an appropriate margin for signal variations.

Rail-to-rail input and output capabilities, enhancing signal utilization in low-voltage systems.

The available voltage headroom between power rails in a low-voltage system is limited. Rail-to-rail input/output characteristics help expand the input signal range and improve the utilization of the output dynamic range.

The actual output swing varies with the load. For the CDV321, the output swing from the power rail is approximately 8 mV under a 10 kΩ load, and approximately 26 mV under a 2 kΩ load. Therefore, when operating under heavier loads or in applications where the output needs to approach the power rail, the output range should be recalculated based on the actual load, and a margin should be reserved for signal peak values.

Low quiescent current, making it ideal for designs where power consumption is a critical consideration.

The typical quiescent current of CDV321 is approximately 60 μA per amplifier. For battery-powered devices, sensor nodes, and continuously operating analog front-ends, a lower quiescent current helps reduce the power consumption of the operational amplifier itself.

The actual power consumption of the system may also be affected by the supply voltage, the output load, and the peripheral circuits. The basic model of the CDV321 does not include a shutdown function; if the design requires shutdown capability under logical control, a model featuring this functionality should be selected.

Determine the signal processing range based on bandwidth and slew rate.

The gain-bandwidth product of CDV321 is 1.1 MHz (typical), and its slew rate is 0.5 V/μs (typical). Both the gain-bandwidth product and the slew rate jointly determine the operational amplifier's capability to process signals of varying frequencies and amplitudes. The available bandwidth in a practical circuit may vary depending on the closed-loop gain, signal amplitude, and load conditions. For signals at higher frequencies or with larger amplitudes, it is recommended to evaluate the bandwidth and distortion performance in conjunction with the specific circuit design.

Input characteristics optimized for high-impedance signal source applications

The typical input bias current of CDV321 is 1 pA, with a maximum value of 10 pA. A lower input bias current facilitates connection to high-impedance signal sources and reduces errors caused by the bias current flowing through the signal source impedance.

The typical input offset voltage is 0.8 mV, with a maximum value of 4.5 mV. In circuits with high closed-loop gain or precision DC measurement applications, input offset may affect the system's zero-point error and should therefore be included in the error budget. Actual accuracy also depends on the feedback network, temperature variations, and the inherent errors of the sensor itself.

A lower input bias current is a design advantage; however, whether an additional buffer is required should still be determined based on the sensor's output impedance, target bandwidth, noise level, and circuit topology.

CDV321 Key Specifications at a Glance

3、Compatible with a variety of analog front-ends

1. Sensor signal conditioning: This can be used for buffering, amplifying, or filtering sensor signals. During design, the circuit gain should be determined based on the sensor's output range and source impedance, and the input common-mode range as well as the output headroom should be verified.

2. Optoelectronic signal front-end: The low input bias current makes the CDV321 a suitable candidate for evaluation as an optoelectronic detection circuit. When employing a transimpedance amplifier topology, the design should integrate feedback resistors and capacitors, target bandwidth, and stability considerations.

3. Low-frequency active filtering: A gain-bandwidth product of 1.1 MHz can support active filtering applications within a certain range. The filter order, closed-loop gain, and cutoff frequency all affect the bandwidth requirements of the operational amplifier; therefore, sufficient margin should be reserved during the design phase.

4. Signal buffering and pre-amplification for ADCs: The CDV321 can be used for general voltage buffering or pre-amplification schemes prior to an ADC. For ADCs featuring sampling capacitors, additional considerations should be made regarding sampling transients, signal source impedance, and rise time, with verification performed based on the actual circuit design.

4、Extended model selection within the same family

When the channel requirements of a project change, or when a sleep/turn-off functionality is required to reduce standby power consumption, a derivative model from the same family may be directly selected. The electrical characteristics of the core are identical to those of the CDV321; the only differences lie in the number of channels, the turn-off functionality, and the package type, meaning that there is no need to re-evaluate the operational core parameters of the op-amp.

Note: CDV324 does not support an S-version with shutdown capability; the dual-channel configuration of CDV358S features independent enablement, allowing each channel to be individually enabled or disabled.

Selection Summary: For single-channel amplification without hibernation requirements, prioritize the CDV321; if hibernation is required, select the CDV321S; for dual-channel signals, choose either the CDV358 or the CDV358S with independent shutdown capability; for four-channel parallel acquisition, select the CDV324.

epilogue

The CDV321 integrates low-voltage power supply, low quiescent current, and rail-to-rail input/output capabilities into a single-channel operational amplifier, making it ideal for single-channel signal amplification in portable battery-powered and industrial data acquisition systems. It features comprehensive specifications, a wide range of packaging options, and supports the domestic substitution of imported devices (PintoPin). If the project later requires an upgrade to multi-channel acquisition or intermittent sleep modes, users can directly switch to other devices within the same family, thereby reducing the workload associated with re-evaluating component selection, simplifying BOM management, and mitigating supply chain risks.