Analog Devices Inc. DC1337A

Overview

LTC2309 from Analog Devices (formerly Linear Technology) is a low-noise, 8-channel, 12-bit successive approximation register (SAR) analog-to-digital converter with I²C interface, internal 2.5V reference, and software-selectable unipolar/bipolar input ranges. It delivers 73.4dB SNR, 14ksps throughput, 1.3µs conversion time, and operates from a single 5V supply across –40°C to 125°C in TSSOP or QFN packages - used in industrial process control and isolated data acquisition systems.

For engineers reviewing the LTC2309 datasheet, LTC2309 pinout, LTC2309 application, or LTC2309 equivalent, this page provides verified technical context, package-specific pin functions, real-world application mappings, and validated alternative parts for system-level design and BOM optimization.

Technical Context

The LTC2309 integrates an internal 2.5V bandgap reference buffered to 4.096V at REFCOMP, a fully differential sample-and-hold circuit, and an 8-channel analog multiplexer supporting both single-ended and differential configurations. Its SAR architecture uses capacitive charge redistribution with factory-trimmed internal clock for deterministic 1.3µs conversion.

It implements a 2-wire I²C slave interface with nine programmable addresses (via AD0/AD1), global synchronization capability, and supports 400kHz SCL frequency. Conversion results are output as 12-bit data + 4 trailing zeros, latched on rising SCL edges, with no latency between completion and read readiness.

Key Specifications

Pinout & Package

Available in two RoHS-compliant packages: 20-pin TSSOP (LTC2309HF#PBF, –40°C to 125°C) and 24-pin 4mm × 4mm QFN (LTC2309IUF#PBF, –40°C to 85°C). Exposed pad (QFN Pin 25) and all GND pins must be soldered to solid ground plane for thermal and noise performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-channel, 12-bit SAR ADC applications.

Compared with LTC2309, ADS7822U demands additional support components and firmware overhead for channel sequencing, while MAX11612EEE+ trades off speed, noise performance, and temperature range for lower unit cost - making LTC2309 optimal for high-integrity industrial sensing where integration, accuracy, and extended temperature operation are mandatory.

Availability

LTC2309 is available at Aetrix Electronics and suitable for industrial process control, motor control, and battery-operated instrumentation requiring stable component supply, long-lifecycle assurance, and traceable sourcing.

Supply support for LTC2309 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017 and maintains its precision analog product lines with full backward compatibility and extended support.

The LTC2309 belongs to Linear's high-accuracy SAR ADC family designed for space-constrained, low-power, multi-channel data acquisition in harsh industrial and automotive environments.

FAQ

What is the maximum operating temperature supported by the LTC2309?

The LTC2309HF#PBF variant in 20-pin TSSOP is rated for –40°C to 125°C operation and is qualified for under-hood automotive and industrial ambient conditions. The QFN variants (e.g., LTC2309IUF#PBF) are specified from –40°C to 85°C. Thermal derating applies above 85°C for non-H-grade parts, and junction temperature must remain ≤150°C.

Does the LTC2309 require external components for basic operation?

Yes - the LTC2309 requires external bypass capacitors: 2.2µF on VREF, 10µF + 0.1µF on REFCOMP, and 10µF + three 0.1µF ceramics on VDD pins. Pull-up resistors on SDA/SCL are also mandatory for I²C communication. No external clock or reference is needed for default operation due to integrated 2.5V reference and internal conversion clock.

How does the LTC2309 handle differential input configurations?

The LTC2309 supports four differential pairs (CH0–CH1, CH2–CH3, CH4–CH5, CH6–CH7) via software-programmed DIN word. Each pair uses fully differential sample-and-hold with 70dB CMRR, rejecting common-mode noise. Input range is ±2.048V in bipolar mode, and COM must be tied to REFCOMP/2 - not ground - for proper common-mode biasing.

Can the LTC2309 be used with an external reference instead of the internal one?

Yes - grounding VREF disables the internal reference buffer, allowing REFCOMP to be driven by an external 4.096V source (e.g., LT1790A-4.096). Alternatively, VREF can be overdriven directly with a precision 2.5V reference. This improves initial accuracy and temperature drift beyond the internal reference's ±25ppm/°C spec.

What is the purpose of the AD0 and AD1 pins on the LTC2309?

AD0 and AD1 are three-state I²C address configuration pins that set the device's 3-bit hardware address. Each pin accepts LOW, HIGH, or floating states, enabling nine unique addresses (0x48–0x4E) plus one global address (0x4F) for synchronized conversions across multiple LTC2309 devices on the same I²C bus.