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FEATURES
s
Low supply Current
s
Power down feature
s
Adjustable output power level
s
Low external part count
s
Fully integrated VCO, PLL and Power Amplifier
Figure.2 block diagram
ORDERING INFORMATION
KESTX01/IG/MPAD (Tape and Reel)
KESTX01/IG/MPAS (Tubes)
The KESTX01 is a single chip ASK (Amplitude Shift Key)
transmitter IC. It is designed to operate in a variety of low
power radio applications including keyless entry, general
domestic and industrial remote control, RF tagging and local
paging systems.
The transmitter offers a high level of integration and per-
formance, which enables the harmonic rejection and funda-
mental power requirements of the ESTI 300 220, and
other governing bodies, to be met.
The basic architecture utilises a crystal reference oscilla-
tor, an integrated frequency multiplying PLL and a power
output stage. The design is centred around the popular
433.92MHz operating frequency and particular emphasis has
been placed on low current drain, including a powerdown
feature which greatly increases battery life.
ABSOLUTE MAXIMUM RATINGS
Junction temperature
-55 to +150
C
Storage temperature
-55 to +150
C
Supply voltage
V
EE
-0.5 to +8.0V
Voltage on any pin
V
EE
-0.5 to V
CC
+0.5V
Notes:
1. The voltage on pin OUT and OUTB (open collector outputs)
can support a higher voltage than this (+14V)
MP14
Figure.1 Pin connections - top view
TXEN
XTAL
OSCILLATOR
XTAL1 XTAL2
LF
VCC
PLL POWER SUPPLY
1
64
PHASE
DETECTOR
VCO
VCC
PWRC
DATA
OUT
OUT B
VEE
VEE
2
1
LF1
VCOTST
VCCPA
KESTX01
400MHz - 460MHz ASK Transmitter
Preliminary Information
Supersedes September 1996 version, DS4548 - 2.0
DS3969 - 3.8 August 1998
XTAL2
PWRC
DATA
OUTB
OUT
VCCPA
VEE2
1
1
4
KESTX01
8
7
XTAL1
VCOTST
VEE1
LF
LF1
TXEN
VCC
.
KESTX01
2
KESTX01
ELECTRICAL CHARACTERISTICS Operating conditions
T amb = 40
C to + 85
C, V
CC
= 3.5V to 6.5V. These characteristics are guaranteed by either production test or design.
They apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
Parameter
Symbol
Value
Units
Conditions
Min
Typ
Max
Power supply voltage
V
CC
3.5
6.5
V
Ambient temperature
Ta
40
+85
C
Electro static discharge 2kV all pins human body model
ELECTRICAL CHARACTERISTICS D.C.
T amb = 40
C to + 85
C, V
CC
= 3.5V to 6.5V. These characteristics are guaranteed by either production test or design.
They apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
Parameter
Symbol
Value
Units
Condition
Min
Typ
Max
Supply current
I
CC
1
0.7
A
V
TXEN
=0V; V
DATA
=0V;Ta=25
C
stand by mode
V
CC
= 7V
Supply current
I
CC
2
1.6
2.8
4
mA
I
mod
=0
A; V
CC
=V
TXEN
3.5V
PLL enable/transmit space
V
DATA
=LOW; 434MHz
Supply current
I
CC
3
6.4
8.5
10.1
mA
I
mod
=150
A; V
CC
=V
TXEN
=3.5V
PLL enable/transmit mark
V
DATA
=HIGH; 434MHz
Supply current
I
CC
4
1.6
3.17
5.0
mA
I
mod
=0
A; V
CC
=V
TXEN
=6.5V
PLL enable/transmit space
V
DATA
=LOW; 434MHz
Supply current
I
CC
5
6.4
9.8
12.5
mA
I
mod
=150
A; V
CC
=V
T
XEN
=6.5V
PLL enable/transmit mark
V
DATA
=HIGH; 434MHz
see note 1
TXEN transmit enable
Ven
3.5
V
CC
+0.2
V
TXEN transmit
V
dis
V
EE
0.2
0.5
V
disable/stand by
Input bias current TXEN
I
txen
150
A
TXEN = V
CC
transmit enable
Bias voltage pin PWRC
1.0
1.20
1.5
V
I
mod
=150 A V
CC
= 3.5V
Data pin input logic high
V
ih
0.7V
CC
V
CC
+0.5
V
Data pin input logic low
V
il
V
EE
0.5
0.3V
CC
V
Data pin input current
I
inl
100
A
V
CC
= 7V
logic low
V
DATA
= 2.1V
Data pin input current
I
inh
+100
A
V
CC
= 7V
logic high
V
DATA
= 4.9V
Notes: 1. The maximum supply current is directly related to Imod and hence the output power level. (Figure 4)
3
KESTX01
ELECTRICAL CHARACTERISTICS A.C.
T amb = 40
C to + 85
C, V
CC
= 3.5V to 6.5V. These characteristics are guaranteed by either production test, characterisation
or design. They apply within the specified ambient temperature and supply voltage ranges unless otherwise stated.
Parameter
Symbol
Value
Units
Conditions
Min
Typ
Max
Output current at
IF75
1.4
2.1
2.8
pkpk
I
mod
=75
A, F
o
=434MHz
fundamental, V
CC
=3.5V
mA
Output current at
IF150
2.4
3.8
4.9
pk-pk
I
mod
=150
A, F
o
=434MHz
Fundamental, V
CC
= 3.5V
mA
Output current
IF150(6V5)
3.0
4.6
5.6
pkpk
I
mod
=150
A, F
o
=434MHz
fundamental V
CC
= 6.5V
mA
Output level at 2 x
32
dBc
I
mod
=150
A, F
o
=434MHz
fundamental see note 1
(1)
Output level at 3 x
11
dBc
I
mod
=150
A, F
o
=434MHz (1)
fundamental and all other
spurii see note 1
Phase detector gain
PDG
4.7
8
9.5
A/rad
V
CC
= 3.5V
Extinction ratio
ER
40
dB
see note 2
VCO gain
G
VCO
110
MHz/V
TXEN settling time
Txe
5.0
ms
see note 3
Output sidebands due to
SB
40
dBc
I
mod
=150
A, F
o
=434MHz
reference frequency
see note 4
(1, 4)
30dB rise timeRF envelope
T30R
380
ns
of Data pulse
30dB fall timeRF envelope
T30F
430
ns
of Data pulse
VCO operating frequency
400
434
460
MHz
V
CC
= 3.5
Notes:
1. The spurii are specified relative to the fundamental, measured in a 300KHz resolution bandwidth.
2. Extinction ratio is defined as the ratio of the output power SPACE to output power MARK measured at the output
operating fequency.
3. Regulatory issues demand that transmission does not take place until the PLL has acquired lock and the VCO is
operating at its final output frequency. This requirement demands that pin TXEN is set high at least Txe ms prior to the
transmission of any data. This value is dependent on the PLL loop bandwidth and hence on the value of the external
loop filter component values. The specification value above is for the loop filter components shown in the applications
diagram (Figure. 6)
4. Sidebands on the output due to the PLL reference are a function of the PLL loop bandwidth and the application.
Reducing the closed loop bandwidth of the PLL loop will aid in reducing the level of the PLL reference spurii.
4
KESTX01
PIN LISTING
Signal
Description
XTAL1
Crystal oscillator
XTAL2
Crystal oscillator
DATA
Input data
TXEN
Transmit enable/stand by
OUT
Power amplifier output/antenna interface
OUTB
Power amplifier output/antenna interface
(complementary output)
LF
Phase detector output
FUNCTION
When the IC is enabled (TXEN high) a phase locked loop
locks the output of the VCO to a multiple of a crystal defined
reference input. The output of the VCO operates at the final
output frequency and is the input to a power amplifier stage.
The power amplifier directly drives the antenna.
Signal
Description
LF1
VCO control input
PWRC
Output power control
VCCPA
Power amplifier positive supply
VEE2
Power amplifier ground
VEE1
PLL ground
VCC
Positive supply
VCOTST
VCO test control input
Phase locked loop
Dividers
A divide by 64 prescaler is present in the PLL feedback
loop. The final output frequency is then Fo = 64xFref.
Phase detector
The phase detector used is a phase frequency detector
(PFD) with a current (charge pump) output. This phase
detector has a triangular characteristic for an input phase error
in the range 2
<
e < 2
. The charge pump provides an
output current in the range
50
A and hence gives a phase
detector gain of (50/2
)
A/rad
(
8
A/rad).
The advantage of the PFD over a pure phase detector is
that it is also a frequency discriminator and will always lock the
loop irrespective of the initial frequency offset. The PLL loop
characteristics such as lockup time, capture range, loop
bandwidth and VCO reference sideband suppression are
controlled by the external loop filter.
For certain applications spurious sidebands at the
reference frequency must be adequately suppressed and a
3rd order loop is recommended.
VCO
To minimize external component cost,s the VCO is fully
integrated. The frequency of the VCO is controlled by the
voltage on pin LF.
Reference crystal oscillator
A single transistor Collpits crystal oscillator provides a
reference clock for the PLL. The oscillator is configured for
parallel resonant operation in the fundamental mode (typical
operating frequency of 37MHz). The crystal is connected
between pins XTAL2 and VEE1 with external components as
shown in Figure 6.
Alternatively, a reference clock can be provided by an
external source connected to pin XTAL2 Figure 7.
Output stage (PA)
The input signal at pin DATA produces amplitude shift key
(ASK) modulation of the VCO output. This is achieved by
onoff keying of the bias current in the output power amplifier
stage. The output of the PA is a balanced output (pin OUT and
OUTB) and is current source driven (open collector outputs).
The outputs of which should be D.C. referenced to a positive
supply voltage (anticipated to be V
CC
in most applications).
The current source outputs can drive a PCB antenna directly
(Figure 6) or if a higher output power is required on limited
supply headroom via a simple impedance transforming net-
work. A balanced output stage is used as it automatically
suppresses the even order harmonics of the fundamental. In
order to obtain the benefits of this output stage it is essential
to use a balanced antenna.
Power up
In the intended application, it is expected that the
transmitter will spend a large proportion of time in ``stand by"
not transmitting data. To maximise battery life it is important
that very little quiescent current is taken in this mode.
The ``stand by mode" is selected by setting pin TXEN low
and similarly the transmitter is enabled by setting TXEN high.
To minimize standby current TXEN is used to bias an on
chip npn transistor connected in a common collector
configuration (Figure 3 below). This transistor is used to
provide the supply to large portions of the IC. Collapsing the
supply when TXEN is set low results in a very low stand by
current. The voltage on TXEN should not exceed V
CC
by more
than 0.2Volts.
From an application standpoint the TXEN pin must be able
to source the bias current for the input transistor and should
also be decoupled if possible to prevent high frequency noise
directly coupling into the IC power supply. The value of the
decoupling capacitors and the drive capability of the TXEN
source will affect power up delay. Since TXEN enables the
PLL it is therefore essential that it is set high prior to any data
transmission and that it remains high during the
transmission.Therefore three different power drain modes are
possible
(i) Stand by (TXEN low, DATA low)
(ii) PLL Mode/Transmit SPACE (TXEN high, DATA low)
(iii) Transmit MARK (TXEN high, DATA high)
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