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PDF ATA5749 Data sheet ( Hoja de datos )
| Número de pieza | ATA5749 | |
| Descripción | Fractional-N PLL Transmitter IC | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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Features
• Fully Integrated Fractional-N PLL
• ASK and Closed Loop FSK Modulation
• Output Power Up to +12.5dBm from 300MHz to 450MHz
• Current Consumption is Scaled by Output Power Programming
• Fast Crystal Oscillator Start-up Time of Typically 200µs
• Low Current Consumption of Typically 7.3mA at 5.5dBm
• Only One 13.0000MHz Crystal for 314.1MHz to 329.5MHz and 424.5MHz to 439.9MHz
Operation
• Single Ended RF Power Amplifier Output
• Many Software Programmable Options Using SPI:
– Output Power from –0.5dBm to +12.5dBm
– RF Frequency from 300MHz to 450MHz with Different Crystals
– FSK Deviation with 396Hz Resolution
– CLK Output Frequency 3.25MHz or 1.625MHz
• Data Rate Up to 40kbit/s (Manchester)
• 4KV HBM ESD Protection Including XTO
• Operating Temperature Range of –40°C to +125°C
• Supply Voltage Range of 1.9V to 3.6V
• TSSOP10 Package
Fractional-N
PLL Transmitter
IC
Atmel ATA5749
Benefits
• Robust Crystal Oscillator with Fast Start Up and High Reliability
• Lower Inventory Costs and Reduced Part Number Proliferation
• Longer Battery Lifetime
• Supports Multi-channel Operation
• Wide Tolerance Crystal Possible with PLL Software Compensation
1. Description
The Atmel® ATA5749 is a fractional-N-PLL transmitter IC for 300MHz to 450MHz
operation and is especially targeted for Tire Pressure Sensor Gauges, Remote
Keyless Entry, and Passive Entry and other automotive applications. It operates at
data rates up to 40kbit/s Manchester for ASK and FSK with a typical 5.5dBm output
power at 7.3mA. Transmitter parameters such as output power, output frequency,
FSK deviation, and current consumption can be programmed using the SPI interface.
This fully integrated PLL transmitter IC simplifies RF board design and results in very
low material costs.
9128E–RKE–09/10
Free Datasheet http://www.datasheet4u.com/
1 page  
ATA5749
The PA is enabled when the PLL is locked and the configuration register programming is com-
pleted. Upon enabling PA at FSK-mode, the RF output power will be switched on. At ASK mode,
the input signal must be additionally set high for RF at output pins. The output power is user pro-
grammable from –0.5dBm to +12.5dBm in steps of approximately 1dB. Changing the output
power requirements, you also modify the current consumption. This gives the user the option to
optimize system performance (RF link budget versus battery life). The PA is implemented as a
Class-C amplifier, which uses an open-collector output to deliver a current pulse that is nearly
independent from supply voltage and temperature. The working principle is shown in Figure 3-1.
Figure 3-1.
Class C Power Amplifier Output
VANT1
VS
IANT2
IPulse = (PWR[0:3])
Power Meter
50Ω
VS
VANT1
L1
C2
ANT1
5
ZLOPT
IANT2
ANT2
4
The peak value of this current pulse IPulse is calibrated during Atmel® ATA5749 production to
about ±20%, which corresponds to about 1.5dB variation in output power for a given power set-
ting under typical conditions. The actual value of IPulse can be programmed with the 4-bit value in
PWR. This allows the user to scale both the output power and current consumption to optimal
levels.
ASK modulation is achieved by using the SDIN_TXDIN signal where a HIGH on this pin corre-
sponds to RF carrier “ON” and a LOW corresponds to RF “OFF”. FSK uses the same signal path
but HIGH switch on the upper FSK-frequency.
9128E–RKE–09/10
5
Free Datasheet http://www.datasheet4u.com/
5 Page 
ATA5749
5. Pulling of Frequency due to ASK Modulation (PA Switching)
The switching effect on VCO frequency in ASK Mode is very low if a correct PCB layout and
decoupling is used. Therefore, power ramping is not needed to achieve a clean spectrum (see
Figure 5-1).
Figure 5-1. Typical RF Spectrum of 40kHz ASK Modulation at Pout = 12.5dBm
9128E–RKE–09/10
11
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet ATA5749.PDF ] | |
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