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°C
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
Stand-alone
Antenna Driver
ATA5277
Preliminary
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.
Rev. 4669B–RKE–10/03
Figure 1.
Block Diagram
VL1 VL2 VL3
CINT
VBATT
VDD OSCI OSCO
VSW
PGND1
PGND2
PGND3
VDS
CBOOST
DRV1
Boost
converter
control
5V
Regulator
Switch
Oscillator
debounce
and
wake-up
SW1
ATA5277
HS
driver
LS
driver
Driver
control
logic
Control and
status
register
SW2
CLKO
VDIO
QSC
Current and
zero crossing
sensing
Serial interface
(single wire )
DIO
VSHUNT
AGND
DGND
TEST
SCANE SCANI
Pin Configuration
Figure 2.
Pinning QFN 28
PGND1
PGND2
PGND3
VDS
DRV1
CBOOST
NC
28 27 26 25 24 23 22
21
1
20
2
19
3
ATA5277
18
4
17
5
16
6
15
7
8 9 10 11 12 13 14
QSC
VSHUNT
AGND
DGND
CINT
VDIO
DIO
VL3
VL2
VL1
SCANE
VBATT
SW2
VSW
SW1
VDD
OSCI
OSCO
CLKO
TEST
SCANI
2
ATA5277 [Preliminary]
4669B–RKE–10/03
ATA5277 [Preliminary]
Pin Description
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Symbol
PGND1
PGND2
PGND3
VDS
DRV1
CBOOST
NC
QSC
VSHUNT
AGND
DGND
CINT
VDIO
DIO
SCANI
TEST
CLKO
OSCO
OSCI
VDD
SW1
VSW
SW2
VBATT
SCANE
VL1
VL2
VL3
Function
Power supply ground
Power supply ground
Power supply ground
Driver voltage supply input
Antenna driver stage output
External bootstrap capacitor connection
Not connected
QSC transistor driver stage output
Antenna current sensing
Analog ground (sensoric and antenna driver)
Digital ground (logic)
External integrator capacitor connection
DIO line interface supply voltage
One-wire serial interface line
For test purposes only
For test purposes only
Clock output
Oscillator output (for resonator/crystal connection)
Oscillator input (for external source or resonator/crystal)
5 V supply output (for filter capacitor only)
Door switch input 1
Door switch interface supply voltage
Door switch input 2
Battery supply voltage 7 V to 16 V (28 V jump start)
For test purposes only
Coil input of the switch mode power supply
Coil input of the switch mode power supply
Coil input of the switch mode power supply
3
4669B–RKE–10/03
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 the DIO-line which can be used as a wake-up signal for the connected
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.
4
ATA5277 [Preliminary]
4669B–RKE–10/03
ATA5277 [Preliminary]
Figure 3.
Wake-up by External Switch
Ext. switch
DIO line
Carrier state
t
deb
t
wake
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
Ext. switch
DIO line
Carrier state
t
deb
t
wake
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
Ext. switch
DIO line
Carrier state
t
deb
t
wake
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.
5
4669B–RKE–10/03
