PCF7936AS/3851/C,1 - HITAG2 256-Bit Security Transponder | NXP
MPN： PCF7936AS-3851-C1 ✓ 啟用中PCF7936AS-3851-C1 概覽
A security transponder is a passive contactless memory device that powers itself from the inductive coupling of an external reader's 125 kHz magnetic field. The HITAG2 family from NXP is widely used in automotive immobilizer systems, building access control, and industrial asset tracking, where robust mutual-authentication and replay-attack resistance are required. The transponder category sits hierarchically inside NFC/RFID tags → RFID transponders → security/authentication ICs → wired/wireless identification semiconductors.
Key features include HITAG2 protocol operation, a 39 ms typical read/write transaction time, 32-byte user EEPROM with bit-level access granularity, and an operating temperature range of -40 °C to +85 °C suitable for automotive under-hood and outdoor industrial deployments. The device is supplied in tape-and-reel packaging to support high-volume injection molding of transponder keys.
Internally, the IC uses a tuned LC resonant front-end, a low-power analog front-end for demodulation/load modulation, a deterministic HITAG2 cryptographic state machine, and a serial EEPROM array. The protocol includes rolling-code mutual authentication, making it suitable for systems where a static UID alone would be insufficient to defeat unauthorized cloning.
Typical applications include automotive vehicle immobilizers, RFID key fobs, building access control tokens, and industrial equipment authentication modules. The 256-bit memory and HITAG2 cipher make it appropriate where cloned-readers and replay attacks are realistic threat models. Compared with 1-Wire or 13.56 MHz ISO14443 credentials, 125 kHz HITAG2 offers longer read range in metal-rich environments and lower reader BOM cost.
When designing with this device, ensure the transponder coil inductance and matching capacitor are tuned for 125 kHz resonance (typical Q > 10) to achieve the rated 39 ms transaction time at the target read distance. Pair the transponder with an HITAG2-compatible reader IC such as the NXP HTRC110 or derivative, and verify EMC compliance of the complete reader system to EN 300 330 or local equivalents.
This page synthesizes distributor pricing, same-family NXP alternatives, and practical HITAG2 integration notes not found in the manufacturer datasheet. Cross-reference data is sourced from Mouser, NXP datasheet portals, and authorized NXP distributor listings as of 2026-10-05.
直接替換替代品，適用於 PCF7936AS-3851-C1 — 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。
PCF7936AS/3851/C,1-CT
✅ 直接替換📋 參考替代品（不在目錄中）
PCF7937AS
✅ 直接替換📋 參考替代品（不在目錄中）
PCF7935AS
✅ 直接替換📋 參考替代品（不在目錄中）
PCF7936AS/3851
✅ 直接替換📋 參考替代品（不在目錄中）
PCF7936AS-3851-C1 規格（製造商公布）
| Product Type | HITAG2 Security Transponder (RFID/NFC Tag) |
| Manufacturer | NXP Semiconductors |
| Carrier Frequency | 125 kHz |
| 記憶體容量 | 256 bit (32 byte × 8 bit) EEPROM |
| Protocol | HITAG2 (mutual authentication) |
| Read/Write Time (typical) | 39 ms |
| 工作溫度範圍 | -40 °C to +85 °C |
| 封裝 | SOT-385-1 (transponder module) |
| 安裝類型 | Embedded in transponder housing |
| Power Source | Passive (inductively coupled from reader field) |
| Authentication | Mutual authentication with rolling code |
| Tape and Reel Packaging | Yes |
| Application Domain | Automotive immobilizer / access control |
PCF7936AS-3851-C1 腳位配置
| 腳位 1 | ANT1 — Antenna coil terminal 1 (125 kHz LC resonant input) |
| 腳位 2 | ANT2 — Antenna coil terminal 2 (125 kHz LC resonant input) |
功率與熱特性
| 操作溫度 | -40 °C to +85 °C |
PCF7936AS-3851-C1 由製造商公布的功率輸入與熱參數。
典型應用
PCF7936AS-3851-C1 適用於 6 應用s: Automotive Vehicle Immobilizer, RFID Key Fob / Credential, Building Access Control Token, Industrial Equipment Authentication, Fleet Management / Asset Tracking, Replacement Key / Aftermarket Immobilizer.
Automotive Vehicle Immobilizer
The PCF7936AS/3851/C,1 is embedded in vehicle ignition keys to provide HITAG2 mutual authentication with the engine ECU's reader basestation. At 125 kHz carrier and 39 ms typical transaction, it reliably authenticates within the short window between key insertion and crank, while the rolling-code cipher prevents replay and cloning attacks. The -40 °C to +85 °C range covers under-hood and exterior-mounted key-slot environments.
推薦
RFID Key Fob / Credential
Used inside plastic key fobs for residential and commercial access, the PCF7936AS/3851/C,1 powers itself from the reader's 125 kHz field, eliminating battery maintenance. Its 256-bit EEPROM stores site codes and user identifiers, while HITAG2 mutual authentication prevents card cloning. Long LF read range makes it tolerant of metal-rich wallets and key rings that would shield higher-frequency credentials.
推薦
Building Access Control Token
The PCF7936AS/3851/C,1 serves as a passive contactless credential for door readers in medium-security office and apartment buildings. HITAG2 mutual authentication with 256-bit storage supports per-user keys, audit logs, and revocable access lists. Its SOT-385-1 module is small enough to embed in ISO card or token form factors without affecting reader read range.
推薦
Industrial Equipment Authentication
For industrial machinery requiring operator-presence authentication (e.g., forklift, lift, or tool authorization), the PCF7936AS/3851/C,1 is embedded in operator badges. HITAG2 authentication prevents unauthorized equipment use, and the rugged -40 °C to +85 °C operating range tolerates factory and outdoor environments. The SOT-385-1 package withstands injection molding encapsulation used in industrial-grade credentials.
推薦
Fleet Management / Asset Tracking
Mounted in trailers, containers, or high-value mobile assets, the PCF7936AS/3851/C,1 enables HF/LF RFID reader portals to authenticate asset identity without line-of-sight. Its passive operation means zero maintenance over the asset's service life, and HITAG2 security prevents tag spoofing by unauthorized readers. Long LF read range is advantageous for portal-reader installations.
推薦
Replacement Key / Aftermarket Immobilizer
The PCF7936AS/3851/C,1 is widely stocked by automotive locksmiths and aftermarket key-programming services to replace lost or damaged immobilizer keys for European vehicles. Its 256-bit EEPROM accommodates transponder-specific codes, and HITAG2 compatibility with major OEM reader basestations (VW, BMW, Mercedes, PSA generations) makes it a generic fit. Tape-and-reel packaging supports custom key blank assembly.
推薦
推薦產品摘要
工程參考資料，適用於 PCF7936AS-3851-C1 — 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 | PCF7936AS/3851/C,1-CT | PCF7937AS | PCF7935AS | PCF7936AS/3851 |
|---|---|---|---|---|---|
| Package | SOT-385-1 | SOT-385-1 - same | SOT-385-1 - same | SOT-385-1 - same | SOT-385-1 - same |
| Brand | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors |
| Carrier Frequency | 125 kHz | 125 kHz | 125 kHz | 125 kHz | 125 kHz |
| Protocol | HITAG2 | HITAG2 | HITAG2 extended | HITAG2 | HITAG2 |
| Read/Write Time | 39 ms (typical) | 39 ms | 39 ms | 39 ms | 39 ms |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C |
| Authentication | Mutual + rolling code | Mutual + rolling code | Mutual + rolling code (extended) | Mutual + rolling code | Mutual + rolling code |
| Package Suffix Variant | Reel (C1 customer code) | Cut Tape (C1-CT) | Standard reel | Standard reel | Reel (no C1 suffix) |
主要差異化特點
- Mutual-authentication HITAG2 cipher (對比PCF7935AS)
- Extended HITAG2 command set upgrade path (對比PCF7937AS)
- Customer-specific C1 suffix code (對比PCF7936AS/3851)
設計說明
The PCF7936AS/3851/C,1 is supplied as a SOT-385-1 transponder module, not a discrete IC, and is typically molded into a key-head or fob housing rather than soldered onto a PCB. Design the external antenna coil with inductance tuned to resonate at 125 kHz with the IC's internal capacitor, targeting a Q > 10 for the rated 39 ms transaction at the desired read distance (typically 5-10 cm). Place a matching capacitor within 1% tolerance across the coil terminals.
Do not substitute the PCF7936AS/3851/C,1 with non-HITAG2 LF transponders (e.g., EM4100, TIRIS) - the reader basestation implements HITAG2 mutual authentication and will reject incompatible tags. When sourcing replacements, verify the HITAG2 protocol support and rolling-code cipher compatibility on the reader side before considering cross-brand parts. Cross-brand LF substitutes require firmware changes and are not drop-in.
Inside the fob housing, keep the antenna coil at least 5 mm from any ferrous or aluminum components (springs, battery contacts) to avoid Q-factor degradation and read-range loss. Orient the coil axis to align with the reader basestation's magnetic field during typical use orientation (e.g., key inserted vertically). Avoid routing the transponder module near high-frequency digital traces that could couple noise into the LC tank.
合規資訊
RoHS, REACH, AEC-Q100, lead-free, halogen-free, and conflict-mineral status for PCF7936AS/3851/C,1 were not present in the verified web data; marked [DATA_NEEDED] in specs. NXP HITAG2 family typically supports EN 300 330 EMC compliance of the complete reader system.
