Power supply requirement
The ripple/noise on the supply rail should be below 10mVp-p to avoid problems. If the quality of the supply
is in doubt, it is recommended that a 10µF low-ESR tantalum or similar capacitor be added between the
module supply pin (Vcc) and ground, together with a 10Ω series feed resistor between the Vcc pin and the
supply rail.
The TX2S incorporates a low voltage shutoff circuit, which prevents any possibility of erratic operation by
disabling the RF output if the supply voltage drops below 2.2V (±5%). This feature is self-resetting, i.e.
restoring the supply to greater than 2.2V will immediately restore full RF output from the module.
TX2S modulation requirements
The module will produce the specified FM deviation with a TXD input to pin 4 of 2 to 4V amplitude, i.e. 0V
"low", 4V "high. Where standard 2-level digital data is employed with a logic "low" level of 0V ±0.2V, the
logic "high" level applied to TXD may be any value between +2V and +4V for correct operation.
Module mounting considerations
Good RF layout practice should be observed – in particular, any ground return required by the antenna or
feed should be connected directly to the RF GND pin at the antenna end of the module, and not to the 0V
pin which is intended as a DC ground only. All connecting tracks should be kept as short as possible to
avoid any problems with stray RF pickup.
If the connection between module and antenna does not form part of the antenna itself, it should be made
using 50Ω microstrip line or coax or a combination of both. It is desirable (but not essential) to fill all
unused PCB area around the module with ground plane.
Warning: DO NOT wash the module. It is not hermetically sealed.
Radiometrix Ltd, TX2S/TX3S Data Sheet
page 4
RADIOMETRIX [ RADIOMETRIX LTD ]
