Rainbow Electronics T5754 User Manual
Features
• Integrated PLL Loop Filter
• ESD Protection (4 kV HBM/ 200 V MM; Except Pin 2: 4 kV HBM/ 100 V MM) also at
ANT1/ANT2
• High Output Power (7.5 dBm) with Low Supply Current (9.0 mA)
• Modulation Scheme ASK/ FSK
– FSK Modulation is Achieved by Connecting an Additional Capacitor Between the
XT AL Load Capacito r and the Open Drain Out put of the Modul ating Micr oco ntro ller
• Easy to Design-in Due to Excellent Isolation of the PLL from the PA and Power Supply
• Single Li-cell for Power Supply
• Supply Voltage 2.0 V to 4.0 V in the Temperature Range of -40°C to 85°C/125°C
• Package TSSOP8L
• Single-ended Antenna Output with High Efficient Power Amplifier
• CLK Output for Clocking the Microcontroller
• One-chip Solution with Minimum External Cir cuit ry
• 125°C Operation for Tire Pressure Systems
UHF ASK/FSK
Transmitter
T5754
Description
The T5754 is a PLL t ransmitte r IC whic h has been developed for the demands of R F
low-cost transmission systems at data rates up to 32 kBaud. The transmitting
frequency range is 429 MHz to 439 MHz. It can be used in both FSK and ASK
systems.
Figure 1. System Block Diagram
1 Li cell
Keys
Encoder
M44Cx9x
UHF ASK/FSK
Remote control transmitter
T5754
PLL
XTO
VCO
Power
amp.
Antenna Antenna
U3741B/
U3745B/
T5743/
T5744
LNA VCO
UHF ASK/FSK
Remote control receiver
Demod.
IF Amp
PLL XTO
Control
1...3
µC
Preliminary
Rev. 4511D–RKE–08/02
1
Pin Configuration
Figure 2. Pinning TSSOP8L
CLK
PA_ENABLE
ANT2
ANT1
1
2
T5754
3
4
8
7
6
5
ENABLE
GND
VS
XTAL
Pin Description
Pin Symbol Function Configuration
1 CLK Clock output signal for microconroller
The clock output fre quency is set by the
crystal to f
XTAL
/ 4
2 PA_ENABLE Switches on power amplifier, used for
ASK modulation
PA_ENABLE
VS
100
100
50k
CLK
Uref=1.1V
20 mA
3
4
5 XTAL Connection for crystal
ANT2
ANT1
Emitter of antenna output stage
Open collector antenna output
XTAL
182 mA
1.5k
ANT1
ANT2
VS
1.2k
6 VS Supply voltage See ESD protection circuitry (see Figure 8)
7 GND Ground See ESD protection circuitry (see Figure 8)
8 ENABLE Enable input
ENABLE
200k
VS
2
T5754
4511D–RKE–08/02
Figure 3. Block Diagram
CLK
1
T5754
T5754
Power up / down
f
4
f
32
ENABLE
8
PA_ENABLE
ANT2
ANT1
2
3
4 5
PA
PLL
PFD
CP
LF
VCO
XTO
GND
7
VS
6
XTAL
General Desc ription This fully integr ated PLL tran smitter allows particu larly simp le, low-cos t RF miniature
transmitters to be assembled. The VCO is locked to 32 f
is needed for a 433.92 MHz transmitter. All other PLL and VCO peripheral elements are
integrated.
hence a 13.56 MHz crysta l
XTAL
4511D–RKE–08/02
The XTO is a series res onance oscillator so that only one capac itor together with a
crystal connected in series to GND are needed as external elements.
The crystal oscillator together with the PLL needs typically <1 ms until the PLL is locked
and the CLK output is stable. There is a wait time of ³ 1 ms until the CLK is used for the
microcontroller and the PA is switched on.
The power amplifier is an open-collector output delivering a current pulse which is nearly
independent from the load impedance. The delivered output power is hence controllable
via the connected load impedance.
This output configuration enables a simple matching to any kind of antenna or to 50 W. A
high power effici ency of h =P
an optimized load impedance of Z
out
/(I
S,PA VS
Load
) of 36% for the power amplifier results when
= (166 + j223) W is used at 3 V supply voltage.
3
Functional
Description
If ENABLE = L and the PA _EN AB LE = L, the circuit is i n s tand by mo de c on su min g o nly
a very small amount of current so that a lithium c ell used as pow er supply can work for
several years.
With ENABLE = H the XTO, PLL and the CLK driver ar e switche d on. If PA _ENABLE
remains L only the PLL and the XTO is running and the CLK signal is delivered to the
microcontroller. The VCO locks to 32 times the XTO frequency.
With ENABLE = H and PA_ENABLE = H the PLL, XT O, CLK driver and the power
amplifier are on. With PA_ENABLE the power amplifier can be switched on and off,
which is used to perform the ASK modulation.
ASK Transmission The T5754 is activated by ENABLE= H. PA_ENABLE must remain L for t ³1ms, then
the CLK signal can be taken to clock the microcontroller and the output power can be
modulated by means of Pin PA_ENABLE. After transmission PA_ENABLE is switched
to L and the microcontroller switches back to internal clocking. The T5754 is switched
back to standby mode with ENABLE = L.
FSK Transmission The T5754 is activated by ENABLE = H. PA_ENABLE must remain L for t ³1ms, then
the CLK signal can be taken to clo ck the microcontroll er and the power amplifie r is
switched on with PA_ENABLE = H. The chip is then ready for FSK modulation. The
microcontroller sta rts to switch on and off the capacit or between the XT AL load cap acitor and GND with an open-drain output port, thus changing the reference frequency of
the PLL. If the switc h is closed , the ou tput frequ ency is lower than if the switc h is ope n.
After transmission PA_ENABLE is switched to L and the microcontroller switches back
to internal clocking. The T5754 is switched back to standby mode with ENABLE = L.
The accuracy of the freq uency dev ia tio n with XT A L pulli ng me tho d is abo ut ±25% when
the following tolerances are considered.
Figure 4. Tolerances of Frequency Modulation
~
V
S
C
Stray1
CMLMR
Crystal equivalent circuit
C
0
Using C
XTAL
~
=9.2pF ±2%, C5=6.8pF ±5%, a switch port with CS
4
capacitances on each side of the crystal of C
capacitance of the crystal of C
=3.2pF ±10% and a crystal with CM=13fF ±10%, an
0
S
Stray1=CStray2
C
Stray2
C
4
C
5
C
Switch
=3pF ±10%, stray
witch
=1pF ±10%, a parallel
FSK deviatio n of ±21 kHz typical with worst case tolerances of ±16.3 kHz to ±28.8 kHz
results.
CLK Output An output CLK signal is provided for a connected microcontroller, the delivered signal is
CMOS compatible if the load capacitance is lower than 10 pF.
Clock Pulse Take-over The clock of the crystal oscillator can be used for clocking the microcontroller. Atmel’s
M4xCx9x has the special feature of starting with an integrated RC-oscillator to switch on
the T5754 with ENABLE = H, and after 1 ms to assume the clock signal of the transmission IC, so that the message can be sent with crystal accuracy.
4
T5754
4511D–RKE–08/02
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