NXP Semiconductors TDA8024T-T

Overview

TDA8024T-T from NXP Semiconductors is a complete analog smart card interface IC designed to sit between ISO 7816-compliant cards and host microcontrollers. It delivers regulated 3 V or 5 V card supply (VCC), integrates a 26 MHz crystal oscillator, provides three protected bidirectional I/O lines (C4/C7/C8), and implements automatic hardware-controlled activation/deactivation sequences with thermal and short-circuit protection.

For engineers reviewing the TDA8024T-T datasheet, TDA8024T-T pinout, TDA8024T-T application, or TDA8024T-T equivalent, key selection criteria include its dual-voltage card supply capability (3 V/5 V), integrated DC-to-DC converter with 4–6.5 V VDDP input, 28-pin SO package, ISO 7816/GSM11.11/EMV compliance, and support for synchronous clock division (÷1/2/4/8) up to 20 MHz.

Technical Context

The TDA8024T-T integrates a voltage-doubler/follower DC-to-DC converter whose mode depends on VDDP and selected VCC (3 V or 5 V), enabling efficient card power generation from a single 4–6.5 V supply. Its clock circuitry accepts either a 26 MHz crystal (XTAL1/XTAL2) or external clock, then divides by 1, 2, 4, or 8 via CLKDIV1/CLKDIV2 inputs with synchronous transitions and guaranteed 45–55% duty cycle.

Three half-duplex transceivers (I/O, AUX1, AUX2) feature active pull-up (11 kΩ to VCC), 15 mA current limiting, and anti-latch arbitration to prevent bus contention. Fault detection includes card removal, VDD dropout, overcurrent (~120 mA threshold), and thermal shutdown - all triggering automatic deactivation without host intervention.

Key Specifications

Pinout & Package

Package: SO28 - plastic small outline package, 28 leads, body width 7.5 mm (SOT136-1).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar smart card interface applications.

Compared with TDA8024T-T, the TDA8024AT removes PORADJ flexibility but reduces cost, while the TDA8024TT offers miniaturization at the expense of higher thermal resistance - both retain identical smart card interface functionality, pin compatibility, and ISO/EMV compliance.

Availability

TDA8024T-T is available at Aetrix Electronics and suitable for banking card readers, electronic payment terminals, secure identification systems, and Pay TV conditional access modules requiring stable component supply and long-term industrial availability.

Supply support for TDA8024T-T 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

NXP Semiconductors is a global semiconductor leader specializing in secure connectivity solutions for automotive, industrial, and consumer applications, with deep expertise in smart card and secure element technologies.

The TDA8024 series belongs to NXP's dedicated smart card interface product line, engineered specifically to simplify ISO 7816-3 compliance in payment, identification, and access control systems while minimizing external component count and firmware burden.

FAQ

What is the primary function of the TDA8024T-T in a smart card system?

The TDA8024T-T serves as a complete analog interface between a host microcontroller and ISO 7816-compliant smart cards. It generates regulated 3 V or 5 V card supply (VCC), provides three protected bidirectional I/O lines (C4/C7/C8), delivers synchronized clock (CLK) up to 20 MHz, manages reset (RST), and executes automatic hardware-based activation/deactivation sequences - all with integrated protection and supervision logic. The TDA8024T-T eliminates the need for discrete regulators, level shifters, and protection components in smart card reader designs.

How does the TDA8024T-T handle card presence detection and debounce?

The TDA8024T-T features dual card presence inputs (PRES active-LOW and PRES active-HIGH) that independently detect physical card insertion or removal. Either signal asserting "present" triggers an internal 8 ms debounce timer, ensuring stable OFF output and preventing false activation due to mechanical switch bounce. During card extraction, the first true/false transition on either PRES input initiates immediate emergency deactivation. This hardware-based debounce eliminates software polling overhead and guarantees robust operation across mechanical connector variations.

Can the TDA8024T-T support both 3 V and 5 V smart cards in the same design?

Yes, the TDA8024T-T supports both 3 V and 5 V smart cards through the 5V/3V pin (Pin 3). Driving this pin HIGH configures the internal DC-to-DC converter for 5 V VCC output (4.75–5.25 V), while driving it LOW selects 3 V output (2.85–3.15 V). The device automatically adapts its VCC regulation, current limits (65 mA max at 3 V, 80 mA at 5 V), and DC-to-DC operating mode (voltage follower or doubler) based on this setting - enabling single-hardware designs compatible with legacy and modern smart cards.

What clock sources and frequencies does the TDA8024T-T support for smart card communication?

The TDA8024T-T accepts either a 26 MHz crystal connected between XTAL1 and XTAL2 or an external clock signal applied to XTAL1. Its integrated clock circuitry divides this source by 1, 2, 4, or 8 via CLKDIV1/CLKDIV2 inputs to generate card clock (CLK) frequencies up to 20 MHz. Frequency changes are synchronous - ensuring no pulse distortion during transitions - and maintain 45–55% duty cycle. The TDA8024T-T meets ISO 7816-3 timing requirements for all supported frequencies and guarantees glitch-free switching essential for reliable ATR exchange and protocol compliance.

How does the TDA8024T-T respond to fault conditions such as short circuits or card removal?

Upon detecting faults - including VCC short-circuit, card removal during transaction, VDD dropout, overheating, or DC-to-DC converter failure - the TDA8024T-T asserts OFF (Pin 23) LOW and initiates an automatic emergency deactivation sequence. This sequence disables CLK, pulls RST LOW, forces I/O/AUX lines LOW, and ramps down VCC to zero within defined timing windows (tde ≤ 100 µs). The OFF signal remains LOW until the host sets CMDVCC HIGH and completes full deactivation, allowing firmware to distinguish hardware faults from intentional card removal based on OFF state persistence.