MICROCHIP ATA8401C-6AQY-66

The Atmel ATA8401 is a PLL transmitter IC, which has been developed for the demands of RF low-cost transmission systems for industrial applications at data rates up to 50kBaud ASK and 32kBaud FSK modulation scheme. The transmitting frequency range is 300MHz to 350MHz. It can be used in both FSK and ASK systems. This fully integrated PLL transmitter allows particularly simple, low-cost RF miniature transmitters to be assembled. The VCO is locked to 32 f_XTAL, and therefore a 9.8438MHz crystal is needed for a 315MHz transmitter. All other PLL and VCO peripheral elements are integrated. The XTO is a series resonance oscillator so that only one capacitor together with a crystal connected in series to GND are needed as external elements. The crystal oscillator together with the PLL typically needs < 3ms until the PLL is locked and the CLK output is stable. There is a wait time of ≥ 3ms until the CLK is used for the microcontroller and the PA is switched on. The power amplifier is an open-collector output delivering a current pulse, which is nearly independent from the load impedance. The delivered output power is therefore controllable via the connected load impedance. This output configuration enables a simple matching to any kind of antenna or to 50Ω. A high power efficiency of η = P_out/(I_S,PA V_S) of 40% for the power amplifier results when an optimized load impedance of Z_Load = (255 + j192)Ω is used at 3V supply voltage. If ENABLE = L and the PA_ENABLE = L, the circuit is in standby mode, consuming only a very small amount of current, so that a lithium cell used as power supply can work for several years. With ENABLE = H the XTO, PLL, and the CLK driver are switched on. If PA_ENABLE remains L, only the PLL and the XTO are running, and the CLK signal is delivered to the microcontroller. The VCO locks to 32 times the XTO frequency. With ENABLE = H and PA_ENABLE = H the PLL, XTO, CLK driver, and the power amplifier are on. The power amplifier can be switched on and off with PA_ENABLE. This is used to perform the ASK modulation. The Atmel ATA8401 is activated by ENABLE = H. PA_ENABLE must remain L for typically ≥3 ms, then the CLK signal can be taken to clock the microcontroller and the output power can be modulated by means of the PA_ENABLE pin. After transmission, PA_ENABLE is switched to L and the microcontroller switches back to internal clocking. The Atmel ATA8401 is switched back to standby mode with ENABLE = L. The Atmel ATA8401 is activated by ENABLE = H. PA_ENABLE must remain L for typically ≥ 3ms, then the CLK signal can be taken to clock the microcontroller, and the power amplifier is switched on with PA_ENABLE = H. The chip is then ready for FSK modulation. The microcontroller starts to switch on and off the capacitor between the XTAL load capacitor and GND with an open-drain output port, thus changing the reference frequency of the PLL. If the switch is closed, the output frequency is lower than if the switch is open. After transmission, PA_ENABLE is switched to L, and the microcontroller switches back to internal clocking. The Atmel ATA8401 is switched back to standby mode with ENABLE = L. An output CLK signal is provided for a connected microcontroller. The delivered signal is CMOS compatible if the load capacitance is lower than 10pF.

• Integrated PLL loop filter
• ESD protection (3kV HBM/150V MM)
• High output power (8.0dBm) with low supply current (9.0mA)
• Modulation scheme ASK/FSK
• FSK modulation is achieved by connecting an additional capacitor between the XTAL load capacitor and the open drain output of the modulating microcontroller
• Easy to design-in due to excellent isolation of the PLL from the PA and power supply
• Single Li-cell for power supply
• Supply voltage 2.0V to 4.0V in the temperature range of -40°C to +85°C
• Package TSSOP8L
• Single-ended antenna output with high efficient power amplifier
• CLK output for clocking the microcontroller
• One-chip solution with minimum external circuitry

• Industrial/aftermarket remote keyless entry systems
• Alarm, telemetering, and energy metering systems
• Remote control systems for consumer and industrial markets
• Access control systems
• Home automation
• Home entertainment
• Toys