MICROCHIP ATA5756C-6DQY-66

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 20kBaud Manchester coding and 40kBaud NRZ coding. The transmitting frequency range is 313MHz to 317MHz (ATA5756) and 432MHz to 448MHz (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. 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 13.125MHz/13.56MHz crystal is needed for a 315MHz/433.92MHz 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 1.64/1.69MHz CLK output. As a result, the first period of the CLK output is always a full period. The PLL is then locked <250μs after CLK output activation. This means an additional wait time of ≥250μs is necessary before the PA can be switched on and the data transmission can start. This results in a significantly lower time of about 0.85ms between enabling the ATA5756/ATA5757 and the beginning of the data transmission which saves battery power especially in tire pressure monitoring systems. 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 50Ω. A high power efficiency for the power amplifier results if an optimized load impedance of z_Load,opt = 380Ω+j340Ω (ATA5756) at 315MHz and z_Load,opt = 280Ω+j310Ω (ATA5757) at 433.92MHz is used at the 3-V supply voltage.

• PLL transmitter IC with single-ended output
• High output power (6dBm) at 8.1mA (315MHz) and 8.5mA (433MHz) typical values
• Divide by 24 (ATA5756) and 32 (ATA5757) blocks for 13MHz crystal frequencies and for Low XTO start-up times
• Modulation scheme ASK/FSK with internal FSK switch
• Up to 20kBaud manchester coding, up to 40kBaud 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 0.6ms
• Supply voltage 2.0V to 3.6V in operation temperature range of -40°C to +125°C
• ESD protection at all pins (4kV HBM)
• Small package TSSOP10