Philips Semiconductors

Product Profile

PCF7946AT

June 1999

Security Transponder plus Remote Keyless Entry, HITAG2

PLUS

Features

• Compatible with Security Transponder, PCF7936AS.

• Rolling Code Generator for keyless entry

• 14-pin SO package

Transponder

• 64/32 bit mutual authentication

• 32 bit unique device identification number

• Fast authentication, 39ms

• 48 bit Secret Key

• 128 bit user memory (EEPROM)

• EEPROM read/write in cipher mode

• EEPROM read/write protection capability

• Excellent sensitivity in read and write mode

Code Hopping Generator

• Four user buttons (15 + 1 commands)

• LED acknowledgment of transmission

• 42 bit unidirectional code hopping

• 48 bit Remote Secret Key

• 114 bit message with run-in, device identification,

function code, terminator and parity bits

• Automatic code synchronisation via transponder

• Programmable data rate and frame repetition rate

• Clock input to support external data rate reference

• Manchester encoding

• Battery low indication

• Single cell operation (2.0V to 3.6V)

• Low power consumption

(ACTIVE: 0.3 mA, POWER DOWN: 300 nA)

General Description

The HITAG2

Security Transponder and Remote Keyless Entry Chip

ideally suited for car immobiliser applications that

incorporate keyless entry functions.

The HITAG2

with the Security Transponder PCF7936AS to support

mixed systems using a HITAG2

Security Transponder, PCF7936AS at the same time.

The Transponder circuitry meets the security and

performance requirements of modern car immobiliser

applications. Excellent device sensitivity (large

distance) and short authentication time ensure easy

application and outstanding system performance. The

Transponder circuitry does not require any battery

supply and full operation is granted in a Keyless Entry

battery low condition.

The Remote Control circuitry features a low power

consumption to ensure long battery lifetime. The device

supports up to four user buttons and a LED for

transmission acknowledgment. Code hopping upon

each button press is provided. The device features

automatic re-synchronisation of the rolling code via the

transponder interface.

The Transponder and rolling code algorithm employ the

same security algorithm for easy system integration on

the receiver side. Separate Secret Keys are provided to

ensure independent code characteristics.

Data rate, modulation and repetition rates of the remote

transmission frame are configurable by the on-chip

EEPROM.

The HITAG2

data rate reference for use with common PLL

transmitter devices.

Typical Application

Command

Buttons

DOUT

XON

Transmitter

IR

or

UHF (PLL)

VBAT

LED

PCF7946

Security Transponder

EEPROM

384 Bit

Calculation

Unit

Control

Logic

Power Management

Remote Control

Modulator

Control

Logic

RC

Oscillator

XCLK

VSS

Li

3V

IN1

IN2

TOUT

optional