PCF7936AS - HITAG 2 Security Transponder | NXP Semiconductors
N.º da peça: PCF7936AS ✓ Ativo| Qtd. | Preço unitário | Total |
|---|---|---|
| 1 | $2.85 | $2,85 |
| 10 | $2.55 | $25,50 |
| 100 | $2.18 | $218,00 |
| 500 | $1.92 | $960,00 |
| 1.000 | $1.65 | $1.650,00 |
| 3.000 | $1.42 | $4.260,00 |
PCF7936AS Visão geral
What is a security transponder? A security transponder (also called an RFID tag or contactless transponder) is a passive semiconductor device that harvests its operating energy from the magnetic field emitted by a basestation reader, then modulates that field to transmit a unique identification code back to the reader. Within the broader product taxonomy, a security transponder belongs to: RFID transponder -> contactless IC -> NFC/RFID tag -> semiconductor. The HITAG 2 family specifically targets automotive immobilizer and access-control markets where mutual authentication prevents relay attacks and code duplication.
Key features of the PCF7936AS include HITAG 2 protocol support with mutual authentication, a 32x8 user-programmable memory array providing 256 bits of storage, and an extended read/write transaction time of 39 ms that supports robust cryptographic handshakes. The transponder derives its supply voltage entirely from the LF magnetic field established by the basestation coil, eliminating any on-board battery. The encapsulated SOT-385-1 glass package withstands the mechanical and thermal stresses of injection-molded key-head assembly.
The PCF7936AS implements the HITAG 2 cryptographic protocol using a hardware finite-state machine rather than a software stack, which minimizes gate count and dynamic power consumption. Because the device is fully passive, all energy for both computation and LF backscatter modulation comes from the reader's H-field; this drives both the read range and the maximum allowed transaction latency of 39 ms. The mutual-authentication sequence uses a rolling-code challenge-response mechanism that defeats static-code replay attacks common to earlier fixed-code immobilizer systems.
Typical applications include automotive remote keyless entry (RKE) and immobilizer systems, vehicle ignition keys, building access control, fleet management transponders, and asset tracking tags. The 39 ms transaction time makes it compatible with legacy HITAG 2 basestations deployed across major European OEM vehicle platforms from the late 1990s onward.
When designing the antenna coil, ensure the LC tank Q is high enough to deliver adequate H-field at the desired read distance (typically 2-5 cm). The 39 ms transaction time imposes a minimum field-on duration in the basestation firmware; do not poll faster than the protocol allows or the authentication handshake will time out.
This page synthesizes distributor inventory, drop-in alternatives, and practical design notes not found in the manufacturer datasheet, helping sourcing engineers and immobilizer system integrators evaluate the PCF7936AS against current alternatives.
Alternativas drop-in para PCF7936AS — mesmo encapsulamento, compatível pino a pino. Peças de encapsulamento diferente que exigem retrabalho na PCB são excluídas.
Variantes desta série
Modelos da mesma série compatíveis como drop-in com PCF7936AS (mesmo formato e footprint) — diferindo em Operating Temperature, Product Type.
Ferramenta de comparação rápida — selecione peças alternativas para comparação lado a lado:
PCF7936AS/3851,122
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
PCF7936AS/3851/C,1
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
PCF7937AS
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
PCF7935AS
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
PCF7945P
✅ Drop-In📋 Alternativa de referência (fora do catálogo)
PCF7936AS Especificações (publicadas pelo fabricante)
| Product Type | Security Transponder (HITAG 2) |
| Carrier Frequency | 125 kHz |
| Protocol | HITAG 2 with mutual authentication |
| User Memory | 256 bits (32 x 8 bits) |
| Transaction Time | 39 ms (typical) |
| Power Supply | Derived from LF magnetic field (passive, no battery) |
| Package Type | SOT-385-1 (glass-encapsulated transponder) |
| Mounting Form | Embedded in key head / plastic overmold |
| Authentication Type | Mutual (challenge-response, rolling code) |
| Read/Write | Read/Write |
| Temperatura de operação | -40C to +85C (industrial / automotive) |
| Encryption Algorithm | HITAG 2 proprietary stream cipher |
| Target Application | Automotive immobilizer, RKE, access control |
| Status RoHS | Compliant |
| REACH Status | Compliant |
Configuração de pinos do PCF7936AS
| Pino 1 | LA — Antenna coil terminal A (LF 125 kHz inductive link) |
| Pino 2 | LB — Antenna coil terminal B (LF 125 kHz inductive link) |
Características de potência e térmicas
| Temperatura de Funcionamento | -40C to +85C (industrial / automotive) |
Parâmetros de entrada de potência e térmicos para PCF7936AS, conforme publicados pelo fabricante.
Aplicações típicas
PCF7936AS é adequado para 7 aplicaçãos: Automotive Immobilizer Systems, Remote Keyless Entry (RKE) Keys, Building Access Control, Fleet Management Transponders, Motorcycle and Scooter Immobilizers, Industrial Equipment Authentication, Pet and Livestock Identification.
Automotive Immobilizer Systems
The PCF7936AS is purpose-built for automotive immobilizer applications where the basestation (typically integrated into the steering column or ignition switch) must verify that the inserted key contains an authorized transponder before enabling engine start. The 39 ms mutual-authentication transaction time aligns with the typical 50-100 ms user tolerance for ignition-on to crank engagement, while the HITAG 2 rolling-code challenge-response defeats the static-code relay attacks that plagued earlier fixed-code immobilizer generations. The passive LF-powered design eliminates battery replacement across the 10+ year vehicle service life, and the SOT-385-1 glass package withstands the injection-molding process used to embed the transponder into the key head alongside the remote-entry transmitter PCB.
Recomendado
Remote Keyless Entry (RKE) Keys
In RKE keys the PCF7936AS handles the passive-immobilizer half of the dual-function key fob while a separate UHF transmitter (typically 315 MHz or 433 MHz) handles the active remote-lock/unlock buttons. The 125 kHz LF transponder is interrogated by a basestation coil wound around the ignition barrel, providing the cryptographic proof-of-presence required to release the steering column lock. The 39 ms transaction completes well within the user's key-insertion-to-crank window, and the SOT-385-1 glass pill can be co-molded alongside the UHF PCB antenna inside a single key head without RF interference.
Recomendado
Building Access Control
The PCF7936AS is deployed in commercial building access-control readers where HITAG 2 basestations are already installed and need replacement credential cards or key fobs. The 256-bit user memory stores facility codes, personal identification numbers, and time-stamped access logs that the access-control panel reads during the 39 ms handshake. The passive LF operation means credential cards have an unlimited shelf life and require no battery maintenance, which is critical for large enterprise deployments where managing thousands of battery-powered credentials would be operationally prohibitive.
Recomendado
Fleet Management Transponders
Fleet operators attach PCF7936AS-equipped transponder tags to vehicles, trailers, and high-value cargo so that HITAG 2 basestations installed at depot gates, fuel islands, and weigh stations can automatically identify and log each asset. The 256-bit user memory stores the asset ID, depot routing codes, and last-service timestamps, while the 39 ms read time allows vehicles to pass through a gate reader at normal depot speeds without requiring a complete stop. The passive LF design eliminates the maintenance burden of replacing batteries across thousands of in-service fleet assets operating in harsh outdoor environments.
Recomendado
Motorcycle and Scooter Immobilizers
The PCF7936AS is widely used in motorcycle and scooter anti-theft systems where the compact ignition key form factor benefits from the small SOT-385-1 glass pill and the passive LF operation eliminates battery service in the vibration- and weather-exposed key environment. The 39 ms authentication latency is well within the rider's ignition-to-start expectation, and the HITAG 2 mutual-authentication protocol provides theft protection comparable to automotive-grade immobilizers at a cost point acceptable for two-wheeled vehicles.
Recomendado
Industrial Equipment Authentication
Construction equipment, agricultural machinery, and rental-tool fleets use PCF7936AS transponders embedded in operator keys to enforce authorized-use policies and prevent theft of high-value mobile assets. The 125 kHz LF basestation installed near the equipment ignition verifies the operator key during the 39 ms handshake before enabling the starter or hydraulic systems, and the 256-bit memory stores operator ID, shift codes, and hour-meter data that the equipment's telematics unit can read for fleet-management reporting.
Recomendado
Pet and Livestock Identification
Vets and livestock operators use PCF7936AS-style glass-pill transponders (injection-implanted under the animal's skin) for unique animal identification. The passive LF design ensures lifetime identification without battery service, and the 125 kHz LF basestation hand-held readers can read the 256-bit ID at ranges of 5-15 cm through the animal's hide. The SOT-385-1 glass encapsulation is biocompatible and withstands the implantation process, providing reliable 20+ year operational life in the animal.
Recomendado
Resumo dos produtos recomendados
Dados de referência de engenharia para PCF7936AS — comparação, orientação de projeto e informações de conformidade.
Guia de seleção
Comparação com alternativas
| Parâmetro | Este produto | PCF7936AS/3851,122 | PCF7936AS/3851/C,1 | PCF7937AS | PCF7935AS | PCF7945P |
|---|---|---|---|---|---|---|
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Package | SOT-385-1 (glass pill) | SOT-385-1 (glass pill) | SOT-385-1 (glass pill) | SOT-385-1 (glass pill) | SOT-385-1 (glass pill) | SOT-385-1 (glass pill) |
| Carrier Frequency | 125 kHz | 125 kHz | 125 kHz | 125 kHz | 125 kHz | 125 kHz |
| Protocol | HITAG 2 | HITAG 2 | HITAG 2 | HITAG 2 (enhanced memory) | HITAG 1 (legacy) | HITAG AES (AES-128) |
| User Memory | 256 bits (32x8) | 256 bits | 256 bits | Larger (~768 bits) | 128 bits | Larger (AES-128) |
| Mutual Authentication | Yes | Yes | Yes | Yes | No (HITAG 1 fixed code) | Yes (AES-128) |
| Power Supply | Passive (LF field) | Passive (LF field) | Passive (LF field) | Passive (LF field) | Passive (LF field) | Passive (LF field) |
| Distributor Stock (2026-10-05) | Active | Active | Active | Active | Active (legacy) | Active |
Principais diferenciais
- Industry-standard HITAG 2 reference part for automotive immobilizers (vs PCF7945P (HITAG AES))
- Mutual authentication with rolling-code challenge-response (vs PCF7935AS (HITAG 1))
- Compact 256-bit user memory in standard SOT-385-1 glass pill (vs PCF7937AS (extended memory))
Notas de projeto
The PCF7936AS derives all operating power from the basestation's 125 kHz magnetic field, so the key-head antenna coil inductance (typically 4.7 mH to 7.5 mH) and Q-factor (>15) directly determine read range and reliability. Use Litz wire for the key-head coil to mitigate skin-effect losses at 125 kHz, and keep the coil at least 3 mm away from any ferrous components in the key housing that would shunt the H-field. Estimated: read range scales approximately linearly with coil diameter and Q-factor in the 2-5 cm operating envelope.
The SOT-385-1 glass encapsulation must survive the injection-molding process when the transponder is embedded into a plastic key head. Peak plastic-melt temperatures of 220-260 C and injection pressures of 800-1200 bar are typical; verify with NXP's key-head molding application note that the glass pill orientation and surrounding wall thickness provide adequate mechanical standoff. Post-mold, allow the key to cool below 60 C before any battery or PCB subassembly is installed to avoid thermal-shock cracking of the glass.
Do not poll the basestation faster than the 39 ms transaction time, or the HITAG 2 mutual-authentication handshake will time out before completion and the immobilizer will not release the engine. In firmware, implement a minimum 50 ms field-on window per interrogation cycle. Also, do not substitute HITAG 1 (PCF7935AS) parts in a HITAG 2 basestation expecting backward compatibility - HITAG 1 lacks the mutual-authentication handshake and will be rejected by the newer basestation firmware.
When the PCF7936AS is co-located in a key head with a UHF remote-entry transmitter (315/433 MHz), maintain at least 10 mm of physical separation between the LF transponder coil and the UHF PCB antenna to prevent UHF harmonic interference from degrading the 125 kHz signal-to-noise ratio. Use a ferrite bead on the UHF feed line if the physical separation cannot be achieved, and verify with a near-field probe that 125 kHz noise from the UHF section is below -80 dBm at the transponder coil terminals.
For basestation reader designs, use a class-D or class-E LF driver with a tuned LC tank matched to a 4.7 mH to 7.5 mH antenna coil. Add a series resistor to set Q to 12-15 (avoid overly high Q which slows the envelope recovery between bits). Place the receiver preamplifier within 10 mm of the antenna coil to minimize stray capacitance that detunes the tank, and use a differential input configuration to reject common-mode noise from the reader's own LF driver.
Informações de conformidade
RoHS and REACH compliance confirmed from NXP product page. AEC-Q100 not formally listed (transponder is not a safety-critical automotive IC), though the part is widely deployed in automotive immobilizer applications. Halogen-free status not explicitly stated in the verified data.
