ISM 433/315 MHz FSK/ASK Transmitter – Data Sheet
AS3901
1.7.1 Interface Description
Wake-up sequence:
TX/ASK=H, STDBY=H: Standby. All off low current state.
TX/ASK→ L, STDBY=H; → XTAL oscillator starts up. NRES goes L, resetting (starting)
the µC for tXTON plus 3 clock cycles.
NRES returns to H, µC initializes.
After µC is initialized, it sets STDBY→ L; PLL is turned on, after tPLLon a stable RF carrier
is generated.
TX/ASK→ H, STDBY=L; → TX is turned on, tTXON later the RF signal is available and data
can be transmitted.
To switch the AS3901 „on“a „push button“with series resistance ~10-20 kΩ can be
used to make TX/ASK = „L“. The „push-button“must be pushed long enough (typ. >
3ms) for the µC to reset and sustain the TX/ASK „L“state.
Standby procedure (for sleep-mode ( IDD1 <1µA):
The µC outputs a „H“to TX/ASK and STDBY. After minimal 3 CLK cycles the XTAL
oscillator will be switched off. The pull-up resistors at the AS3901 TX/ASK and STDBY
inputs will sustain the sleep mode.
Note: Multiple „push buttons“for different functions can be used.
Rev. 6, August 2000
Page 7 of 18