Texas Instruments TMP421YZDT

Overview

TMP421YZDT from Texas Instruments is a dual-channel digital temperature sensor IC with one local die sensor and one remote junction sensor, delivering ±1°C remote accuracy (max) and ±1.5°C local accuracy (max) over –40°C to +125°C, operating from 2.55V to 5.5V supply, and communicating via SMBus 2-wire interface - used for precision thermal monitoring in FPGA and processor subsystems.

For engineers reviewing the TMP421YZDT datasheet, TMP421YZDT pinout, TMP421YZDT application, or TMP421YZDT equivalent, key selection criteria include its DSBGA-8 (YZD) package, single remote channel architecture, series resistance cancellation up to 3 kΩ, diode fault detection, and support for n-factor correction across multiple transistor types.

Technical Context

The TMP421YZDT implements a dedicated sigma-delta ADC per channel, with programmable conversion rate (0.0625–8 conversions/sec), 12-bit resolution for both local and remote measurements, and automatic series resistance cancellation using dual-current source methodology on the DXP/DXN pins.

It supports SMBus v2.0 commands (Write Byte, Read Byte, Send Byte, Receive Byte), includes built-in diode fault detection logic, and uses an optimized ideality factor (η = 1.008) for accurate remote sensing with NPN/PNP transistors or diodes embedded in microcontrollers, FPGAs, or processors.

Key Specifications

Pinout & Package

Package: DSBGA-8 (YZD), 1.35 mm × 1.35 mm, 0.5 mm pitch, bottom-side ball array.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel remote/local temperature sensing applications.

Compared with TMP421DCNT, TMP421YZDT offers 60% smaller board area and better high-density routing; versus LM95235CIMM/NOPB, it provides SMBus integration and hardware-based series resistance compensation - critical for reliable remote sensing in telecom and computing platforms.

Availability

TMP421YZDT is available at Aetrix Electronics and suitable for processor thermal monitoring, FPGA junction sensing, LCD projector light engines, and central office telecom equipment requiring stable component supply across extended temperature and long-lifecycle deployments.

Supply support for TMP421YZDT 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies, with decades of heritage in precision sensing and power management ICs.

The TMP421YZDT belongs to TI's precision temperature sensor product line, engineered specifically for high-accuracy, low-power, SMBus-compatible thermal monitoring in space-constrained computing, telecom, and projection systems.

FAQ

What is the maximum remote temperature measurement range supported by the TMP421YZDT?

The TMP421YZDT supports a default remote temperature range of –55°C to +150°C. When configured for extended range mode (RANGE bit = 1), it measures from –64°C to +191°C. However, the device is rated for ambient operation only from –40°C to +125°C, and most external diodes are validated within –55°C to +150°C - so full extended range use requires validation of the remote sensor element.

Does the TMP421YZDT require external components for basic SMBus operation?

Yes - the TMP421YZDT requires two external pull-up resistors (typically 4.7 kΩ) on SCL and SDA lines to V+, and a 0.1 μF ceramic bypass capacitor between V+ and GND, placed as close as possible to the V+ pin. No external RC filtering is required for standard operation, though optional series resistors (<1.5 kΩ) may be added on DXP/DXN for noise immunity in electrically noisy environments.

How does the TMP421YZDT handle series resistance in remote sensing lines?

The TMP421YZDT performs automatic series resistance cancellation using dual-current-source measurement on DXP and DXN, correcting for up to 3 kΩ of trace resistance without firmware intervention. This is implemented in analog front-end hardware and does not rely on software algorithms - ensuring consistent ±1°C remote accuracy even with long PCB traces or ribbon cables connecting to remote transistors.

Can the TMP421YZDT monitor more than one remote temperature zone?

No - the TMP421YZDT is a dual-channel sensor with exactly one local and one remote temperature measurement channel. For two remote zones, use TMP422; for three remote zones, use TMP423. All three devices share identical SMBus register maps and configuration methods, enabling firmware reuse across variants while maintaining pin-to-pin compatibility in SOT23-8 packages - but TMP421YZDT itself supports only a single remote junction.

What is the SMBus slave address configuration for the TMP421YZDT?

The TMP421YZDT uses a 7-bit SMBus slave address determined by A1 and A0 pins: base address 10011xx₂, where xx is set by A1 (pin 3) and A0 (pin 4). With both pins grounded, address is 1001100₂ (0x4C); with A1=V+, A0=GND, it becomes 1001101₂ (0x4D). This allows up to four TMP421YZDT devices on the same SMBus segment without address conflict.