LTC2309CF - 8-Ch 12-Bit SAR ADC I2C 20-TSSOP | Analog Devices
MPN： LTC2309CF ✓ 啟用中LTC2309CF 概覽
A SAR ADC (successive-approximation-register analog-to-digital converter) is a class of ADC that performs a binary search through successive bit trials to converge on the input voltage, combining the compact form factor and low power of a sigma-delta with the speed and deterministic latency of a flash converter. SAR ADCs sit within the broader hierarchy of data converters (ADC -> data converter -> signal chain IC -> semiconductor), and are preferred when applications demand accurate, single-shot conversions of multi-channel analog inputs at moderate sample rates.
Key features of the LTC2309CF include 73 dB SINAD and 73 dB common-mode rejection at the analog inputs, an I2C-compatible 2-wire serial interface with hardware-address pins that allow up to nine devices on one bus, an automatic channel sequencer, and a power-down mode that drops supply current to under 1 microampere between conversions. Internal calibration circuitry and an integrated 2.5V reference with low 10ppm/C drift ensure stable conversion accuracy across temperature. The 20-pin TSSOP package measures 6.5 mm x 4.4 mm x 1.0 mm, making it suitable for space-constrained industrial and instrumentation boards. The part carries the CF suffix, which denotes the 20-pin TSSOP package (the alternate LTC2309CUF denotes a 24-pin QFN package).
Typical applications include industrial process control and multi-channel data acquisition, portable and battery-powered instrumentation, programmable logic controller (PLC) analog input modules, and medical instrumentation such as patient monitoring front-ends. The integrated sequencer and I2C interface keep microcontroller pin count and firmware overhead minimal.
When designing with the LTC2309CF, ensure the input signal does not exceed the supply rails and add an external anti-aliasing RC filter on each analog input to limit out-of-band noise. The I2C address pins allow multi-slave addressing on a shared bus, and the power-down mode should be invoked during idle intervals to maximize battery life in portable designs.
直接替換替代品，適用於 LTC2309CF — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： LTC2309CF （相同外形與佔位） — 差異在於 Architecture, Conversion Time, Input Type, Internal Reference, Number of Channels.
LTC2309CF#PBF
✅ 直接替換📋 參考替代品（不在目錄中）
LTC2309IF#PBF
✅ 直接替換📋 參考替代品（不在目錄中）
LTC2309CF 最大額定值與電氣特性
| 解析度 | 12 bits |
| Number of Channels | 8 single-ended / 4 differential |
| Architecture | SAR (Successive Approximation Register) |
| Conversion Time | 1.3 us (typical) |
| 介面 | I2C-compatible 2-wire serial |
| Input Type | Single-ended or differential |
| Internal Reference | 2.5 V (10 ppm/C drift) |
| External Reference Input | Yes |
| 供應電壓 | 5 V (single supply) |
| Analog Input Range | 0 V to VREF (unipolar) |
| SINAD | 73 dB |
| Power-Down Current | < 1 uA |
| 工作溫度 | 0C to +70C (C grade) |
| 封裝 | 20-pin TSSOP (CF) |
| 安裝類型 | Surface Mount |
| MSL 等級 | 1 |
| Lead-Free | Yes (#PBF suffix) |
LTC2309CF 腳位配置
| 腳位 1 | CH0 — Analog input channel 0 |
| 腳位 2 | CH1 — Analog input channel 1 |
| 腳位 3 | CH2 — Analog input channel 2 |
| 腳位 4 | CH3 — Analog input channel 3 |
| 腳位 5 | CH4 — Analog input channel 4 |
| 腳位 6 | CH5 — Analog input channel 5 |
| 腳位 7 | CH6 — Analog input channel 6 |
| 腳位 8 | CH7 — Analog input channel 7 |
| 腳位 9 | GND — Ground |
| 腳位 10 | REF — Reference input / output (2.5V internal) |
| 腳位 11 | REFCOMP — Reference bypass capacitor |
| 腳位 12 | AD0 — I2C address select bit 0 |
| 腳位 13 | AD1 — I2C address select bit 1 |
| 腳位 14 | SDA — I2C serial data |
| 腳位 15 | SCL — I2C serial clock |
| 腳位 16 | NC — Not connected |
| 腳位 17 | NC — Not connected |
| 腳位 18 | NC — Not connected |
| 腳位 19 | VCC — +5V supply |
| 腳位 20 | GND — Ground |
典型應用
LTC2309CF 適用於 6 應用s: Industrial Process Control / PLC Analog Input Modules, Portable / Battery-Powered Multi-Channel Instrumentation, Medical Instrumentation and Patient Monitoring Front-Ends, Data Acquisition Systems and DAQ Cards, Automotive Sensor Interface Modules, Test & Measurement Equipment and Bench Instruments.
Industrial Process Control / PLC Analog Input Modules
The LTC2309CF fits industrial process control and PLC analog input modules because it provides 8 single-ended or 4 differential 12-bit SAR conversion channels on a single I2C bus, eliminating per-channel signal chains. Its integrated 2.5V reference and 73 dB SINAD ensure accurate digitization of 0-10V or 4-20 mA-derived signals through scaling resistors. Placed on the PLC backplane I2C bus, it shares wiring with other Analog Devices slaves via hardware address pins AD0/AD1. The 1.3 us conversion time supports polling rates above 10 ksps per channel aggregate, while the <1 uA power-down current aids thermally-constrained control cabinets. Compared with discrete ADCs per input, the LTC2309CF reduces BOM count and PCB area by roughly 60 percent.
推薦
Portable / Battery-Powered Multi-Channel Instrumentation
The LTC2309CF suits portable, battery-powered multi-channel instrumentation due to its 1.3 us SAR conversion, integrated 2.5V reference, and <1 uA power-down current. It draws only milliamps during conversion and idles at less than 1 microampere between samples, extending battery life by 5-10x compared to discrete ADCs in handheld multimeters, environmental loggers, and field data recorders. Its I2C interface allows direct connection to low-power microcontrollers such as the MAX32660 or STM32L0 with no additional glue. The TSSOP-20 footprint is hand-solderable for low-volume prototypes. The integrated sequencer removes firmware overhead, enabling deterministic multi-channel scans at sub-millisecond intervals for vibration, strain gauge, or thermocouple arrays.
推薦
Medical Instrumentation and Patient Monitoring Front-Ends
The LTC2309CF suits medical instrumentation front-ends where 12-bit resolution across multiple biopotential or sensor channels is required. Its 73 dB SINAD preserves ECG, EEG, or pulse-oximetry signal fidelity, while the integrated 2.5V reference ensures calibration stability across patient sessions. The I2C bus enables a compact interface to medical-grade microcontrollers, while its <1 uA power-down current prolongs battery runtime in ambulatory devices. The differential sample-and-hold rejects 50/60 Hz mains common-mode interference when paired with right-leg-drive circuits. According to the LTC2309 datasheet, the part is not formally medical-qualified; system-level IEC 60601-1 compliance must be validated at the board level.
推薦
Data Acquisition Systems and DAQ Cards
The LTC2309CF fits general-purpose data acquisition (DAQ) cards and modules, particularly PC-based or embedded DAQ systems with multiple analog input channels. Its I2C interface allows simple USB-to-I2C bridge connectivity, while 8 channels of 12-bit resolution cover most general-purpose measurement tasks. The 1.3 us conversion time supports aggregate sample rates above 100 ksps across all channels when sequenced. The integrated sequencer and address pins allow multiple LTC2309CF devices on one bus, scaling to 16, 24, or more channels without firmware changes. The TSSOP-20 package is convenient for stackable DAQ daughterboards.
推薦
Automotive Sensor Interface Modules
The LTC2309CF fits non-safety automotive sensor interface modules such as body controllers, HVAC sensors, and battery management telemetry, where 12-bit resolution across 8 channels is sufficient. Its I2C interface reduces wiring harness complexity compared with SPI or analog point-to-point links. The integrated 2.5V reference and differential inputs handle 0-5V ratiometric and bridge sensor signals directly. For AEC-Q100-qualified automotive deployments, the I-grade (-40C to +85C) variant LTC2309IF#PBF in the same TSSOP-20 footprint is preferred. The <1 uA quiescent current aids always-on battery-powered modules such as remote keyless entry receivers.
推薦
Test & Measurement Equipment and Bench Instruments
The LTC2309CF fits bench-top test and measurement equipment where moderate-speed multi-channel data acquisition is needed. Its 1.3 us SAR conversion and 73 dB SINAD deliver adequate accuracy for bench DMMs, signal loggers, and educational lab instrumentation. The I2C interface simplifies connection to ARM Cortex-M or FPGA-based controllers, while the integrated reference eliminates a separate reference IC. Multiple LTC2309CF devices on one I2C bus allow scalable channel counts for bench automation systems. The TSSOP-20 hand-solderable package suits prototype bench builds and small production runs of test fixtures.
推薦
推薦產品摘要
工程參考資料，適用於 LTC2309CF — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | LTC2309CF#PBF | LTC2309CUF#PBF | LTC2309IF#PBF | LTC2309IUF#PBF | ADS7828E/250 |
|---|---|---|---|---|---|---|
| Package | TSSOP-20 (CF) | TSSOP-20 (CF) - same | QFN-24 (UF) - different | TSSOP-20 (IF) - same | QFN-24 (IUF) - different | TSSOP-16 - different (16 pins vs 20) |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Texas Instruments |
| Resolution | 12 bits | 12 bits | 12 bits | 12 bits | 12 bits | 12 bits |
| Channels | 8 SE / 4 DIFF | 8 SE / 4 DIFF | 8 SE / 4 DIFF | 8 SE / 4 DIFF | 8 SE / 4 DIFF | 8 SE / 4 DIFF |
| Conversion Time | 1.3 us | 1.3 us | 1.3 us | 1.3 us | 1.3 us | 20 us (max) |
| Interface | I2C | I2C | I2C | I2C | I2C | I2C |
| Internal Reference | 2.5 V | 2.5 V | 2.5 V | 2.5 V | 2.5 V | External only |
| Temperature Grade | 0C to +70C (C) | 0C to +70C (C) | 0C to +70C (C) | -40C to +85C (I) | -40C to +85C (I) | -40C to +85C |
主要差異化特點
- Integrated 2.5V reference with 10 ppm/C drift (對比ADS7828E/250)
- Fast 1.3 microsecond conversion time (對比ADS7828E/250)
- Hardware I2C address pins for multi-slave operation (對比MCP3208)
設計說明
Place a 100 nF ceramic bypass capacitor as close as possible to the VCC pin (pin 19) of the LTC2309CF, with a 10 uF tantalum or ceramic bulk capacitor on the same supply trace. Add a 10 uF capacitor on the REF/REFCOMP pin to filter internal reference noise. For multi-channel boards, separate analog (CHx, REF) and digital (SDA, SCL, AD0, AD1) ground returns and join them at a single star point near pin 9/20 ground pins. Estimated: a clean ground layout typically improves SINAD by 3-5 dB versus a noisy layout.
Do not leave the unused analog input channels floating; tie them to mid-supply (VCC/2) or ground through 10 kohm resistors to avoid crosstalk and ADC noise pickup on adjacent channels. When using differential mode, ensure both inputs are within the common-mode range (0 to VREF). Driving an analog input above VCC or below GND will cause input clamping currents; insert 100 ohm series resistors if the source may exceed the supply rails. Always include a TVS diode array (e.g., SP3010) on analog inputs exposed to external connectors for ESD protection up to +/-15 kV HBM.
Route the I2C SDA and SCL traces as a differential pair with 4.2 mm spacing or per I2C specification; add 4.7 kohm pull-up resistors to VCC for reliable operation at 100 kHz or 400 kHz bus speeds. Keep digital traces at least 4 mm away from analog input traces to avoid digital switching noise coupling into the ADC. Use a 4-layer PCB with a dedicated ground plane for best noise performance; for 2-layer boards, flood the bottom layer with ground and stitch analog/digital returns with multiple vias. Estimated: proper 4-layer layout typically improves effective resolution by 0.5-1 LSB.
合規資訊
RoHS and REACH compliant per #PBF suffix. AEC-Q100 not applicable for C-grade commercial temperature; I-grade variant available for industrial applications. Lead-free and halogen-free per Analog Devices LTC2309 datasheet family specifications.
