User guide

12
4958AS–AUTO–09/06
ATA6285/ATA6286 [Preliminary]
With ASK = High the power amplifier is switched on. This is used to perform the ASK modula-
tion. 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 ATA6285/ATA6286 are listed in Table 4-1.
4.5.1 Transmission with ENABLE = Open
4.5.1.1 ASK Mode
The ATA6285/ATA6286 is activated by ENABLE = open, FSK = High, ASK = Low. The micro-
controller is then switched to external clocking. After typically 0.6 ms, the CLK driver is activated
automatically (i.e., the microcontroller waits until the XTO and CLK are ready). After another
time period of ≤ 250 µs, the PLL is locked and ready to transmit. The output power can then be
modulated by means of pin ASK. After transmission, ASK is switched to Low and the microcon-
troller returns back to internal clocking. Then, the ATA6285/ATA6286 is switched to power-down
mode with FSK = Low.
Figure 4-2. Timing ASK Mode with ENABLE Open
Table 4-1. Transmitter Part
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
Power-downPower-down Power-up,
PA off
Power-up,
PA on
(High)
Power-up,
PA off
(Low)
FSK
ASK
CLK
∆T
XTO
> 250 µs