مدار مجتمع (آی سی) آی‌سی جمع‌آوری داده مبدل دیجیتال به آنالوگ (دی‌ای‌سی)

Product Attributes

Introduction

SD24A421 is a complete loop-powered 4–20mA DAC that converts digital data to current, designed specifically for smart transmitter manufacturers in industrial control applications. It provides a highly integrated, high-precision, low-cost solution for implementing high-resolution 4–20mA smart transmitters.

This DAC employs a Σ-Δ architecture, guaranteeing 16-bit resolution, monotonicity, and ±0.01% integral nonlinearity. The output ranges from 4mA zero-scale current (error ±0.02%FS) to 20mA full-scale current (error ±0.1%FS). Full-scale ±0.1% settling time does not exceed 8ms.

The SD24A421 integrates a selectable-output voltage regulator to supply power to itself and other devices in the transmitter system. The regulated output can be selected via pin configuration as 3V, 3.3V, or 5V. In addition, the on-chip precision voltage reference provides 2.5V and 1.25V references for other devices in the system. Therefore, the SD24A421 requires no external standalone regulator or voltage reference — only a few external components and one pass transistor are needed. The pass transistor is primarily used to extend the loop voltage range, enabling the SD24A421 to operate within a range from a minimum of VCC + 2V up to the breakdown voltage of the pass transistor.

The SD24A421 can be used in conjunction with standard HART or similar FSK protocol communication circuits without affecting its rated performance. The high-speed serial interface operates at up to 3Mbps and connects simply to common microprocessors and microcontrollers via a standard 3-wire serial interface.

The SD24A421 features a programmable alarm current function, allowing the transmitter to indicate sensor faults by sending an over-range current.

Short-circuit protection is provided between COM and LOOPRTN, and overcurrent protection is provided between BOOST and LOOPRTN, ensuring that both the device itself and the external discrete pass transistor are protected from damage.

The SD24A421 is a 16-bit current DAC for use in loop-powered 4–20mA smart transmitters. As a remote instrument, a smart transmitter draws power from the 4–20mA loop and controls the loop's current signal output. The SD24A421 provides the following key functions within a smart transmitter: DAC functionality for converting digital data to analog format, a current amplifier for setting the loop current magnitude, and stable operating voltage. In addition, the device provides two precision voltage references, an integrated clock oscillator, and a high-speed serial interface.

Features

• 4–20mA current output
• 16-bit resolution and monotonicity
• ±0.01% integral nonlinearity
• 3V/3.3V/5V regulator output
• 2.5V and 1.25V precision reference voltage output
• Maximum quiescent current 520uA
• HART protocol compatible
• Flexible noise-immune serial interface
• Programmable alarm current output capability
• Overcurrent and short-circuit protection
• 16-pin SOIC package
• -40°C to +85°C industrial operating temperature range

Applications

• Smart transmitter