Rev. 4702HRKE09/04
Features
·
PLL Transmitter IC with Single-ended Output
·
High Output Power (6 dBm) at 8.1 mA (315 MHz) and 8.5 mA (433 MHz) Typical Values
·
Divide by 24 (
ATA5756)
and 32 (
ATA5757
) Blocks for 13 MHz Crystal Frequencies and
for Low XTO Start-up Times
·
Modulation Scheme ASK/FSK with Internal FSK Switch
·
Up to 20 kBaud Manchester Coding, Up to 40 kBaud NRZ Coding
·
Power-down Idle and Power-up Modes to Adjust Corresponding Current Consumption
through ASK/FSK/Enable Input Pins
·
ENABLE Input for Parallel Usage of Controlling Pins in a 3-wire Bus System
·
CLK Output Switches ON if the Crystal Current Amplitude has Reached 35% to 80% of
its Final Value
·
Crystal Oscillator Time Until CLK Output is Activated, Typically 0.6 ms
·
Supply Voltage 2.0 V to 3.6 V in Operation Temperature Range of -40
° C to 125° C
·
ESD Protection at all Pins (4 kV HBM)
·
Small Package MSOP10
Benefits
·
Low Parasitic FSK Switch Integrated
·
Very Short and Reproducible Time to Transmit Typically < 0.85 ms
·
13.125 MHz/13.56 MHz Crystals Give Opportunity for Small Package Sizes
Description
The ATA5756/ATA5757 is a PLL transmitter IC which has been developed for the
demands of RF low-cost transmission systems at data rates up to 20 kBaud Manches-
ter coding and 40 kBaud NRZ coding. The transmitting frequency range is 313 MHz to
317 MHz (ATA5756) and 432 MHz to 448 MHz (ATA5757), respectively. It can be used
in both FSK and ASK systems. Due to its shorten crystal oscillator settling time it is
well suited for Tire Pressure Monitoring (TPM) and for Passive Entry Go applications.
Figure 1. System Block Diagram
Demod.
IF Amp
LNA
VCO
PLL
XTO
Control
U3741B/
U3745B/
T5743/
T5744/
1...3
µC
Power
amp.
XTO
VCO
PLL
ATA5756/
ATA5757
Antenna Antenna
UHF ASK/FSK
TPM and Remote control
transmitter
UHF ASK/FSK
Remote control receiver
Encoder
ATARx9x
1 Li cell
Keys
UHF ASK/FSK
Transmitter
ATA5756
ATA5757
2
ATA5756/ATA5757
4702HRKE09/04
Pin Configuration
Figure 2. Pinning MSOP10
1
2
3
4
10
9
8
7
CLK
ASK
FSK
ANT2
ENABLE
GND
VS
XTO1
ATA5756
ATA5757
5
ANT1
6
XTO2
Pin Description
Pin
Symbol
Function
Configuration
1
CLK
Clock output signal for the
microcontroller.
The clock output frequency is set by the
crystal to f
XTAL
/8.
The CLK output stays Low in power-
down mode and after enabling of the
PLL.
The CLK output switches on if the
oscillation amplitude of the crystal has
reached a certain level.
2
ASK
Switches on the power amplifier for
ASK modulation and enables the PLL
and XTO if the ENABLE pin is open
3
FSK
Switches off the FSK switch (switch has
high Z if signal at pin FSK is High) and
enables the PLL and the XTO if the
ENABLE pin is open
CLK
VS
100
100
200k
ASK
50k
V
Ref
= 1.1V
20 µA
200k
FSK
200k
V
Ref
= 1.1V
5 µA
200k
3
ATA5756/ATA5757
4702HRKE09/04
4
ANT2
Emitter of antenna output stage
5
ANT1
Open collector antenna output
6
XTO2
Diode switch, used for FSK modulation
7
XTO1
Connection for crystal
8
VS
Supply voltage
See ESD protection circuitry (see Figure 12)
9
GND
Ground
See ESD protection circuitry (see Figure 12)
10
ENABLE
ENABLE input
If ENABLE is connected to GND and
the ASK or FSK pin is High, the device
stays in idle mode.
In normal operation ENABLE is left
open and ASK or FSK is used to enable
the device.
Pin Description
Pin
Symbol
Function
Configuration
ANT1
ANT2
XTO2
210 µA
(FSK < 0.25V)
AND
(ENABLE > 1.7V)
XTO1
1.2k
VS
1.5k
VS
182 µA
ENABLE
150k
30 µA
(FSK >1.7 V ) OR
(ASK > 1.7 V)
250k
VS
4
ATA5756/ATA5757
4702HRKE09/04
Figure 3. Block Diagram
General Description
This fully integrated PLL transmitter allows the design of simple, low-cost RF miniature
transmitters for TPM and RKE applications. The VCO is locked to 24
× f
XTAL
/32
× f
XTAL
for ATA5756/ATA5757. Thus, a 13.125 MHz/13.56 MHz crystal is needed for a
315 MHz/433.92 MHz transmitter. All other PLL and VCO peripheral elements are
integrated.
The XTO is a series resonance (current mode) oscillator. Only one capacitor and a
crystal connected in series to GND are needed as external elements in an ASK system.
The internal FSK switch, together with a second capacitor, can be used for FSK
modulation.
The crystal oscillator needs typically 0.6 ms until the CLK output is activated if a crystal
as defined in the electrical characteristics is used (e.g., TPM crystal). For most crystals
used in RKE systems, a shorter time will result.
The CLK output is switched on if the amplitude of the current flowing through the crystal
has reached 35% to 80% of its final value. This is synchronized with the 1.64/1.69 MHz
CLK output. As a result, the first period of the CLK output is always a full period. The
PLL is then locked <250 µs after CLK output activation. This means an additional wait
time of
250 µs is necessary before the PA can be switched on and the data transmis-
sion can start. This results in a significantly lower time of about 0.85 ms between
enabling the ATA5756/ATA5757 and the beginning of the data transmission which saves
battery power especially in tire pressure monitoring systems.
CLK
FSK
ANT2
ANT1
ENABLE
GND
VS
XTO2
1
3
4
5
6
8
9
10
VCO
LF
CP
f
24/
XTO
PLL
PA
f
8
Power up/down
ATA5756 /
ATA5757
PFD
ASK
2
XTO1
7
EN
OR
EN
Ampl. OK
32
5
ATA5756/ATA5757
4702HRKE09/04
The power amplifier is an open-collector output delivering a current pulse which is nearly
independent from the load impedance and can therefore be controlled via the connected
load impedance.
This output configuration enables a simple matching to any kind of antenna or to 50
. A
high power efficiency for the power amplifier results if an optimized load impedance of
Z
Load, opt
= 380
+ j340 (ATA5756) at 315 MHz and Z
Load, opt
= 280
+ j310
(ATA5757) at 433.92 MHz is used at the 3-V supply voltage.
Functional
Description
If ASK = Low, FSK = Low and ENABLE = open or Low, the circuit is in power-down
mode consuming only a very small amount of current so that a lithium cell used as
power supply can work for many years.
If the ENABLE pin is left open, ENABLE is the logical OR operation of the ASK and FSK
input pins. This means, the IC can be switched on by either the FSK of the ASK input.
If the ENABLE pin is Low and ASK or FSK are High, the IC is in idle mode where the
PLL, XTO and power amplifier are off and the microcontroller ports controlling the ASK
and FSK inputs can be used to control other devices. This can help to save ports on the
microcontroller in systems where other devices with 3-wire interface are used.
With FSK = High and ASK = Low and ENABLE = open or High, the PLL and the XTO
are switched on and the power amplifier is off. When the amplitude of the current
through the crystal has reached 35% to 80% of its final amplitude, the CLK driver is
automatically activated. The CLK output stays Low until the CLK driver has been acti-
vated. The driver is activated synchronously with the CLK output frequency, hence, the
first pulse on the CLK output is a complete period. The PLL is then locked within
<250 µs after the CLK driver has been activated, and the transmitter is then ready for
data transmission.
With ASK = High the power amplifier is switched on. This is used to perform the ASK
modulation. During ASK modulation the IC is enabled with the FSK or the ENABLE pin.
With FSK = Low the switch at pin XTO2 is closed, with FSK = High the switch is open.
To achieve a faster start-up of the crystal oscillator, the FSK pin should be High during
start-up of the XTO because the series resistance of the resonator seen from pin XTO1
is lower if the switch is off.
The different modes of the ATA5756/ATA5757 are listed in Table 1, the corresponding
current consumption values can be found in the table "Electrical Characteristics" on
page 15.
Table 1. ATA5756/ATA5757 Modes
ASK Pin
FSK Pin
ENABLE Pin
Mode
Low
Low
Low/open
Power-down mode, FSK switch High Z
Low
Low
High
Power-up, PA off, FSK switch Low Z
Low
High
High/open
Power-up, PA off, FSK switch High Z
High
Low
High/open
Power-up, PA on, FSK switch Low Z
High
High
High/open
Power-up, PA on, FSK switch High Z
Low/High
High
Low
Idle mode, FSK switch High Z
High
Low/High
Low
Idle mode, FSK switch High Z
PDF 
ZIP