
Page 5
Page 4
PIN ASSIGNMENTS
PDN
LADJ
VCC
LO_V_D
/CLK SE
/CLK
GND
DATA
ANT
GND
1
2
3
4
56
7
8
9
10
Figure 7: ES Series Transmitter Pinout (Top View)
Pin #
Name
Description
1
PDN
Power Down. Pulling this line low will place the transmitter
into a low-current state. The module will not be able to
transmit a signal in this state.
2
LADJ
Level Adjust. This line can be used to adjust the output
power level of the transmitter. Connecting to Vcc will give
the highest output, while placing a resistor to GND will
lower the output level (see Figure 4 on Page 3).
3
VCC
Supply Voltage
4
GND
Analog Ground
5
DATA
Analog or Digital Data Input
6
/CLK
Divided Clock Output
7
/CLK SEL
Clock Frequency Selection. Logic low selects divide by
256, logic high selects divide by 1,024.
8
LO_V_D
Low Voltage Detect. This line goes low when VCC is less
than 2.15V.
9
GND
Analog Ground
10
ANT
50-ohm RF Output
PIN DESCRIPTIONS
MODULE DESCRIPTION
The TXM-***-ES module is a single-channel transmitter designed for the wireless
transfer of digital or analog information over distances of up to 1,000 feet
outdoors and up to 500 feet indoors. It is based on a high-performance
synthesized architecture. FM / FSK modulation is utilized to provide superior
performance and noise immunity over AM-based solutions. The ES Series is
incredibly compact and cost-effective when compared with other FM / FSK
devices. Best of all, it is packed with many useful features and capabilities that
offer a great deal of application flexibility to the designer. Some of these features,
which will be discussed in depth in this data guide, are:
/CLK Output (use for an external micro-controller)
LO_V_DET (low-voltage detection)
LADJ
(adjust the RF output power)
The ES Series is offered in the 902-928MHz band, which is free from the legal
restrictions of the lower 260-470MHz band. This gives the designer much more
freedom in the types of applications that can be designed. The 869.85MHz
version allows for the same freedom of design in European applications.
THEORY OF OPERATION
The ES Series FM / FSK transmitter is capable of generating 1mW of output
power into a 50-ohm load while suppressing harmonics and spurious emissions
to within legal limits. The transmitter is comprised of a VCO and a crystal-
controlled frequency synthesizer. The frequency synthesizer, referenced to a
precision crystal, locks the VCO to achieve a high-Q, low phase-noise oscillator.
The transmitter operates by directly modulating the crystal with the baseband
signal present on the DATA line. Pulling the crystal in this manner achieves the
desired deviation and linearity. If the transmitter’s VCO were modulated, the
frequency synthesizer would track out much of the deviation within the
bandwidth of the loop filter (this is a common limitation of most synthesized FM
transmitters). The carrier is then amplified and filtered before being output on the
50-ohm ANT line.
The frequency of the Divided Clock output is determined by the state of the Clock
Frequeny Selection line. A low on the Select line will generate a signal on the
clock output that is the center frequency divided by 256, a high will be the center
frequency divided by 1,024.
Precision
Crystal
Data In
/CLK SEL
/CLK Output
PLL Frequency
Synthesizer
Frequency Divider
256 / 1,024
LC
Filter
RF Amplifier
Antenna Port
Figure 8: ES Series Transmitter Block Diagram