Rev. 4669BRKE10/03

Features

Programmable Driver Current Regulation

Antenna Driver Stage for 1 A Peak Current

LF Baudrates between 1 kbaud to 8 kbaud

Integrated Oscillator for Ceramic Resonators

Two Inputs for Push-button Switches

Bi-directional Single-wire Interface

Diagnosis Function and Overtemperature Protection

Quick Start Control (QSC) for Fast Oscillation Build-up and Decay Timing

Operation Temperature -40

C to +85

Carrier Frequency Range from 100 kHz to 150 kHz

Amplitude Shift Keying (ASK) Modulation

Phase Shift Keying (PSK) Modulation

Power Supply Range 7 V to 16 V Direct Battery Input (6 V and 28 V with Limited
Function Range)

EMI and ESD According to Automotive Requirements

Highly Integrated -- Less External Components Required

Applications

Car Access

Benefits

Dedicated for Decentralized Systems

Constant Magnetic Field Strength

Electrostatic sensitive device.
Observe precautions for handling.

Description

The circuit is an integrated BCDMOS antenna driver IC dedicated as a transmitter for
Passive Entry/Go (PEG) car applications and for other handsfree access control
applications.

It includes the full functionality to generate a magnetic LF field in conjunction with an
antenna coil to transmit data to a receiver in a key fob, card or transponder. The trans-
mission can be controlled via an one wire I/O interface (DIO) by an external control
unit.

Stand-alone
Antenna Driver

ATA5277

Preliminary

ATA5277 [Preliminary]

4669BRKE10/03

Figure 1. Block Diagram

Pin Configuration

Figure 2. Pinning QFN 28

5 V

Regulator

Oscillator

Serial interface

(single wire )

ATA5277

Switch

debounce

and

wake-up

Boost

converter

control

driver

Driver

control

logic

Control and

status

Current and

zero crossing

sensing

TEST

DGND

SCANE SCANI

AGND

VSHUNT

QSC

DRV1

CBOOST

PGND1

PGND2

VDS

VL1 VL2 VL3

VBATT

VDD OSCI OSCO

VSW

SW1

SW2

CLKO

VDIO

DIO

PGND3

CINT

driver

PGND1

PGND2

PGND3

VDS

DRV1

CBOOST

SW1

VDD

OSCI
OSCO

CLKO

TEST

SCANI

VBATT

VSW

HUNT

DGND

8 9 10 11 12 13 14

28 27 26 25 24 23 22

3
4

ATA5277

ATA5277 [Preliminary]

4669BRKE10/03

Pin Description

Pin

Symbol

Function

PGND1

Power supply ground

PGND2

Power supply ground

PGND3

Power supply ground

VDS

Driver voltage supply input

DRV1

Antenna driver stage output

CBOOST

External bootstrap capacitor connection

Not connected

QSC

QSC transistor driver stage output

VSHUNT

Antenna current sensing

AGND

Analog ground (sensoric and antenna driver)

DGND

Digital ground (logic)

CINT

External integrator capacitor connection

VDIO

DIO line interface supply voltage

DIO

One-wire serial interface line

SCANI

For test purposes only

TEST

For test purposes only

CLKO

Clock output

OSCO

Oscillator output (for resonator/crystal connection)

OSCI

Oscillator input (for external source or resonator/crystal)

VDD

5 V supply output (for filter capacitor only)

SW1

Door switch input 1

VSW

Door switch interface supply voltage

SW2

Door switch input 2

VBATT

Battery supply voltage 7 V to 16 V (28 V jump start)

SCANE

For test purposes only

VL1

Coil input of the switch mode power supply

VL2

Coil input of the switch mode power supply

VL3

Coil input of the switch mode power supply

ATA5277 [Preliminary]

4669BRKE10/03

Functional Description

General Description

The IC contains a half-bridge coil driver stage with a special driver voltage regulator and
control logic with diagnosis circuitry. Further it contains a one-wire bi-directional micro-
controller interface for the carrier modulation and the mode selection. An integrated
oscillator for ceramic resonators generates the clock signal for the control logic. Addi-
tionally, the IC contains two connectors for switches to wake-up the IC.

The IC generates an electromagnetic LF field in combination with an LC antenna cir-
cuitry. The carrier frequency for the antenna is generated by the oscillator and prescaler
logic.

The LF field can be modulated to transmit data to a suitable receiver. There are two
modulation modes available, Amplitude Shift Keying (ASK) and 180° Phase Shift Keying
(PSK). A microcontroller or another control unit must be used to control the transmitter
via the bi-directional single-wire interface.

A boost converter power supply is used to supply the driver half-bridge and the antenna
with a high voltage and a regulated current even if the battery voltage is low. The
antenna current is programmable in 16 steps to support a transmission with various field
strengths.

The driver circuitry is Short Circuit (SC) protected and the driver logic contains diagnosis
functions for short circuit and open wire detection at the antenna outputs.

Operation Modes

Three different operation modes are defined:

Standby

Command mode

Modulation mode

After power-on reset, the ATA5277 is in standby mode. To achieve minimum power con-
sumption, only the internal 5-V supply, the DIO-line interface and the door switch inputs
are active. The IC can be activated either by the external control unit via the serial inter-
face or by one of the switch inputs. A low signal at the DIO-line or at the switch inputs
(SW1, SW2) powers up the IC. If this is done at a switch input, a low signal is generated
on th e DIO-lin e w hich can b e used a s a wake -u p sign al f or t he con necte d
microcontroller.

In command mode, the IC can be configured and diagnostics can be run. This mode is
always activated after wake-up from standby mode and after leaving modulation mode.
The communication is based on a one-wire serial interface (DIO-line) with the con-
nected microcontroller being the master and ATA5277 being the slave. In this mode, the
antenna driver stage is disabled, except if the automatic field generation after wake-up
is selected.

In modulation mode, the antenna driver stage is activated (if enabled) and the data
applied to the DIO-line modulates the LF field (in ASK or PSK). This mode is activated
after the command mode and remains active as long as data is applied to the DIO-line
(i.e., until a timeout has occured). After that, the IC falls back to command mode.

Standby and Wake-up

There are two different wake-up modes. In the default mode the antenna driver stage
remains off after wake-up. The second mode can be programmed by a control com-
mand. Here, also the driver output stage is enabled. The IC generates the carrier signal
for the antenna immediately.

ATA5277 [Preliminary]

4669BRKE10/03

Figure 3. Wake-up by External Switch

In Figure 3, the IC is woken up by an external switch (pulled to ground). After a
debouncing time t

deb

, the IC leaves sleep mode and sends a wake-up impulse to a con-

nected microcontroller via the DIO line. Note that this impulse is already the start bit of
the first command. After that, the ATA5277 waits for a control or status command from
the microcontroller. The carrier remains off as the configuration bit M_Wake (see control
command 2) is '0'.

Figure 4. Wake-up by External Switch, Automatic Field Generation

The wake-up event as shown in Figure 4 is the same as in Figure 3, except for the con-
figuration bit M_Wake which is '1'. The driver stage will start operation after the wake-up
command has been confirmed. This behaviour can be used to build up an LF field inde-
pendently of the connected microcontroller.

Figure 5. Wake-up by Connected Microcontroller, Automatic Field Generation

Figure 5 shows a wake-up event triggered by the connected microcontroller, which now
pulls the DIO line to ground. To prevent the ATA5277 from waking up due to noise on
the DIO line, there is also a debouncing time before it will start operation. In this exam-
ple, M_Wake is again '1', so the driver stage starts operation after the wake-up event
has been confirmed.

Ext. switch

DIO line

Carrier state

deb

wake

Ext. switch

DIO line

Carrier state

deb

wake

Ext. switch

DIO line

Carrier state

deb

wake

Part Number ATA5277