ATAB5757 Atmel, ATAB5757 Datasheet - Page 4

• Manufacturer Part Number: ATAB5757
• Description: BOARD DEMO RF TRANSMITTER 433MHZ
• Manufacturer: Atmel
• Series: Smart RFr
• Type: Transmitterr

Specifications of ATAB5757

• Frequency: 433MHz
• Wireless Frequency: 433 MHz
• Modulation: ASK, FSK
• For Use With/related Products: ATA5757 @ 433MHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

3. General Description
4
ATA5756/ATA5757
Figure 2-2.
This fully integrated PLL transmitter allows the design of simple, low-cost RF miniature transmit-
ters for TPM and RKE applications. The VCO is locked to 24 × f
ATA 5 7 5 6 / ATA 5 7 5 7 . T h u s , a 1 3 . 1 2 5 M H z / 1 3 . 5 6 M H z c r y s t a l i s n e e d e d f o r 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 con-
nected 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 transmission can start. This results in a signifi-
cantly 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.
Block Diagram
ANT2
ANT1
FSK
ASK
CLK
2
1
3
4
5
ATA5756 /
ATA5757
OR
f
8
PA
EN
EN
PLL
VCO
f
Power up/down
PFD
CP
LF
32
24/
XTO
Ampl. OK
10
7
ENABLE
GND
9
VS
8
6
XTO1
XTO2
X T A L
/32 × f
4702J–RKE–09/08
X T A L
for