ATMEL ASK

Features
• Integrated PLL Loop Filter
• ESD Protection also at ANT1/ANT2
(4 kV HBM/200V MM; Except Pin 2: 4 kV HBM/100V MM)
• High Output Power (5.5 dBm) with Low Supply Current (8.5 mA)
• Modulation Scheme ASK/FSK
•
•
•
•
•
•
•
•
– FSK Modulation is Achieved by Connecting an Additional Capacitor Between the
XTAL Load Capacitor and the Open Drain Output of the Modulating Microcontroller
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 2.0V to 4.0V 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 Circuitry
125°C Operation for Tire Pressure Systems
UHF ASK/FSK
Transmitter
T5750
1. Description
The T5750 is a PLL transmitter IC which has been developed for the demands of RF
low-cost transmission systems at data rates up to 32 kBaud. The transmitting
frequency range is 868 MHz to 928 MHz. It can be used in both FSK and ASK
systems.
Figure 1-1.
System Block Diagram
UHF ASK/FSK
Remote control transmitter
UHF ASK/FSK
Remote control receiver
1 Li cell
T5750
T5760/
T5761
1 to 3
Demod
Keys
Encoder
ATARx9x
Control
Microcontroller
PLL
Antenna
XTO
Antenna
VCO
LNA
PLL
LNA
XTO
VCO
4546F–RKE–12/08
2. Pin Configuration
Figure 2-1.
Pinning TSSOP8L
CLK
PA_ENABLE
ANT2
ANT1
Table 2-1.
Pin
1
2
3
4
8
7
6
5
ENABLE
GND
VS
XTAL
Pin Description
Symbol
Function
Configuration
VS
1
CLK
Clock output signal for micro con roller
The clock output frequency is set by the
crystal to fXTAL/4
100Ω
CLK
100Ω
PA_ENABLE
2
PA_ENABLE
50 kΩ
UREF = 1.1V
Switches on power amplifier, used for
ASK modulation
20 µA
ANT1
3
ANT2
Emitter of antenna output stage
4
ANT1
Open collector antenna output
ANT2
2
T5750
4546F–RKE–12/08
T5750
Table 2-1.
Pin
Pin Description (Continued)
Symbol
Function
Configuration
VS
1.5 kΩ
5
XTAL
VS
1.2 kΩ
Connection for crystal
XTAL
182 µA
6
VS
7
GND
8
ENABLE
Supply voltage
See ESD protection circuitry (see Figure 4-5 on page 9)
Ground
See ESD protection circuitry (see Figure 4-5 on page 9)
ENABLE
Figure 2-2.
200 kΩ
Enable input
Block Diagram
T5750
Power up/down
f
CLK
ENABLE
4
1
8
f
64
PA_ENABLE
GND
2
7
PDF
CP
ANT2
VS
6
3
LF
ANT1
4
PA
VCO
XTO
5
XTAL
PLL
3
4546F–RKE–12/08
3. General Description
This fully integrated PLL transmitter allows particularly simple, low-cost RF miniature transmitters to be assembled. The VCO is locked to 64 × fXTAL hence a 13.5672 MHz crystal is needed
for a 868.3 MHz transmitter and a 14.2969 MHz crystal for a 915 MHz transmitter. All other PLL
and VCO peripheral elements are integrated.
The XTO is a series resonance oscillator so that only one capacitor 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 ≥ 4 ms must be used 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 50Ω. A high
power efficiency of η= Pout/(IS,PA × VS) of 24% for the power amplifier at 868.3 MHz results when
an optimized load impedance of ZLoad = (166 + j226)Ω is used at 3V supply voltage.
4. Functional Description
If ENABLE = L and the PA_ENABLE = L, the circuit is in standby mode consuming only a very
small amount of current, so that a lithium cell used as power supply can work for several years.
With ENABLE = H the XTO, PLL and the CLK driver are switched 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 64 times the XTO frequency.
With ENABLE = H and PA_ENABLE = H the PLL, XTO, 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.
4.1
ASK Transmission
The T5750 is activated by ENABLE = H. PA_ENABLE must remain L for t ≥ 4 ms, 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 T5750 is switched back to standby mode with
ENABLE = L.
4.2
FSK Transmission
The T5750 is activated by ENABLE = H. PA_ENABLE must remain L for t ≥ 4 ms, then the CLK
signal can be taken to clock the microcontroller and the power amplifier is switched on with
PA_ENABLE = H. The chip is then ready for FSK modulation. The microcontroller starts to
switch on and off the capacitor between the XTAL load capacitor and GND with an open-drain
output port, thus changing the reference frequency of the PLL. If the switch is closed, the output
frequency is lower than if the switch is open. After transmission PA_ENABLE is switched to L
and the microcontroller switches back to internal clocking. The T5750 is switched back to
standby mode with ENABLE = L.
The accuracy of the frequency deviation with XTAL pulling method is about ±25% when the following tolerances are considered.
4
T5750
4546F–RKE–12/08
T5750
Figure 4-1.
Tolerances of Frequency Modulation
VS
CStray1
CStray2
LM
C4
XTAL
CM
RS
C0
C5
CSwitch
Using C4 = 9.2 pF ±2%, C5 = 6.8 pF ±5%, a switch port with CSwitch = 3 pF ±10%, stray capacitances on each side of the crystal of CStray1 = CStray2 = 1 pF ±10%, a parallel capacitance of the
crystal of C0 = 3.2 pF ±10% and a crystal with CM = 13 fF ±10%, an FSK deviation of ±21.5 kHz
typical with worst case tolerances of ±16.8 kHz to ±28.0 kHz results.
4.3
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.
4.3.1
Clock Pulse Take-over
The clock of the crystal oscillator can be used for clocking the microcontroller. Atmel ® ’s
ATARx9x has the special feature of starting with an integrated RC-oscillator to switch on the
T5750 with ENABLE = H, and after 4 ms to assume the clock signal of the transmission IC, so
that the message can be sent with crystal accuracy.
4.3.2
Output Matching and Power Setting
The output power is set by the load impedance of the antenna. The maximum output power is
achieved with a load impedance of ZLoad,opt = (166 + j226)Ω at 868.3 MHz. There must be a low
resistive path to VS to deliver the DC current.
The delivered current pulse of the power amplifier is 7.7 mA and the maximum output power is
delivered to a resistive load of 475Ω if the 0.53 pF output capacitance of the power amplifier is
compensated by the load impedance.
An optimum load impedance of:
Z Load = 475Ω || j/(2 × p × f × 0.53 pF) = (166 + j226)Ω thus results for the maximum output
power of 5.5 dBm.
The load impedance is defined as the impedance seen from the T5750’s ANT1, ANT2 into the
matching network. Do not confuse this large signal load impedance with a small signal input
impedance delivered as input characteristic of RF amplifiers and measured from the application
into the IC instead of from the IC into the application for a power amplifier.
Less output power is achieved by lowering the real parallel part of 475Ω where the parallel imaginary part should be kept constant.
Output power measurement can be done with the circuit of Figure 4-2 on page 6. Note that the
component values must be changed to compensate the individual board parasitics until the
T5750 has the right load impedance ZLoad,opt = (166 + j226)Ω at 868.3 MHz. Also the damping of
the cable used to measure the output power must be calibrated out.
5
4546F–RKE–12/08
Figure 4-2.
Output Power Measurement
VS
C1
1 nF
L1
C2
ANT1
ZLopt
ANT2
4.4
10 nH
1.5 pF
C3
Z = 50Ω
Power
meter
Rin
2.7 pF
50Ω
Application Circuit
For the supply-voltage blocking capacitor C3 a value of 68 nF/X7R is recommended (see Figure
4-3 on page 7 and Figure 4-4 on page 8). C1 and C2 are used to match the loop antenna to the
power amplifier where C1 typically is 3.9 pF/NP0 and C2 is 1 pF/NP0; for C2 two capacitors in
series should be used to achieve a better tolerance value and to have the possibility to realize
the ZLoad,opt by using standard valued capacitors.
C1 forms together with the pins of T5750 and the PCB board wires a series resonance loop that
suppresses the 1st harmonic, hence the position of C1 on the PCB is important. Normally the
best suppression is achieved when C1 is placed as close as possible to the pins ANT1 and
ANT2.
The loop antenna should not exceed a width of 1.5 mm, otherwise the Q-factor of the loop
antenna is too high.
L1 (≈ 50 nH to 100 nH) can be printed on PCB. C4 should be selected so that the XTO runs on
the load resonance frequency of the crystal. Normally, a value of 12 pF results for a 15 pF
load-capacitance crystal.
6
T5750
4546F–RKE–12/08
T5750
Figure 4-3.
ASK Application Circuit
S1
BPXY
VDD
ATARx9x
VS
1
S2
VSS
BPXY
20
BPXY
BPXY
OSC1
7
T5750
Power up/down
CLK
ENABLE
f
4
1
8
f
64
GND
PA_ENABLE
2
7
PDF
C3
C2
CP
VS
ANT2
3
6
VS
Loop
Antenna
LF
C1
XTAL
ANT1
4
PA
VCO
PLL
L1
XTO
XTAL
5
C4
VS
7
4546F–RKE–12/08
Figure 4-4.
FSK Application Circuit
S1
BPXY
VDD
ATARx9x
VS
1
S2
VSS
BPXY
20
BP42/T2O
BPXY
18
BPXY
OSC1
7
T5750
Power up/down
CLK
ENABLE
f
4
1
8
f
64
PA_ENABLE
GND
2
7
PDF
C3
C2
CP
ANT2
VS
3
Loop
Antenna
6
VS
LF
C1
C5
ANT1
XTAL
4
PA
VCO
PLL
L1
XTO
XTAL
5
C4
VS
8
T5750
4546F–RKE–12/08
T5750
Figure 4-5.
ESD Protection Circuit
VS
ANT1
CLK
PA_ENABLE
ANT2
XTAL
ENABLE
GND
5. Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameters
Maximum
Unit
Supply voltage
Symbol
VS
5
V
Power dissipation
Ptot
100
mW
Tj
150
°C
°C
Junction temperature
Minimum
Storage temperature
Tstg
–55
125
Ambient temperature
Tamb
–55
125
Input voltage
Note:
VmaxPA_ENABLE
°C
(1)
–0.3
(VS + 0.3)
V
1. If VS + 0.3 is higher than 3.7V, the maximum voltage will be reduced to 3.7V.
6. Thermal Resistance
Parameters
Junction ambient
Symbol
Value
Unit
RthJA
170
K/W
7. Electrical Characteristics
VS = 2.0V to 4.0V, Tamb = –40°C to 125°C unless otherwise specified.
Typical values are given at VS = 3.0V and Tamb = 25°C. All parameters are referred to GND (pin 7).
Parameters
Test Conditions
Supply current
Power down,
VENABLE < 0.25V, –40°C to 85°C
VPA_ENABLE < 0.25V, –85°C to +125°C
VPA_ENABLE < 0.25V, 25°C
(100% correlation tested)
Supply current
Output power
Note:
Symbol
Min.
Typ.
IS_Off
Max.
Unit
350
7
nA
µA
nA
<10
Power up, PA off, VS = 3V,
VENABLE > 1.7V, VPA_ENABLE < 0.25V
IS
3.6
4.6
mA
Power up, VS = 3.0,
VENABLE > 1.7V, VPA_ENABLE > 1.7V
IS_Transmit
8.5
11
mA
5.5
8
dBm
VS = 3.0V, Tamb = 25°C,
f = 868.3 MHz, ZLoad = (166 + j226)Ω
PRef
3.5
1. If VS is higher than 3.6V, the maximum voltage will be reduced to 3.6V.
9
4546F–RKE–12/08
7. Electrical Characteristics (Continued)
VS = 2.0V to 4.0V, Tamb = –40°C to 125°C unless otherwise specified.
Typical values are given at VS = 3.0V and Tamb = 25°C. All parameters are referred to GND (pin 7).
Parameters
Test Conditions
Output power variation for the full
temperature range
Tamb = –40°C to +85°C,
VS = 3.0V
VS = 2.0V
Output power variation for the full
temperature range
Tamb = –40°C to +125°C,
VS = 3.0V
VS = 2.0V,
POut = PRef + ΔPRef
Achievable output-power range
Selectable by load impedance
Spurious emission
fCLK = f0/128
Load capacitance at pin CLK = 10 pF
fO ±1 × fCLK
fO ±4 × fCLK
other spurious are lower
Oscillator frequency XTO
(= phase comparator frequency)
fXTO = f0/64
fXTAL = resonant frequency of the XTAL,
CM ≤ 10 fF, load capacitance selected
accordingly
Tamb = –40°C to +85°C,
Tamb = –40°C to +125°C
Symbol
Max.
Unit
ΔPRef
ΔPRef
–1.5
–4.0
dB
dB
ΔPRef
ΔPRef
–2.0
–4.5
dB
dB
+5.5
dBm
POut_typ
Min.
Typ.
–3
–52
–52
dBc
dBc
fXTO
–30
–40
PLL loop bandwidth
fXTAL
+30
+40
250
ppm
ppm
kHz
Phase noise of phase comparator
Referred to fPC = fXT0,
25 kHz distance to carrier
–116
–110
dBc/Hz
In loop phase noise PLL
25 kHz distance to carrier
–80
–74
dBc/Hz
Phase noise VCO
at 1 MHz
at 36 MHz
–89
–120
–86
–117
dBc/Hz
dBc/Hz
928
MHz
Frequency range of VCO
fVCO
868
Clock output frequency (CMOS
microcontroller compatible)
Voltage swing at pin CLK
f0/256
CLoad ≤ 10 pF
Series resonance R of the crystal
V0h
V0l
VS × 0.8
Rs
Capacitive load at pin XT0
MHz
VS × 0.2
V
V
110
Ω
7
pF
FSK modulation frequency rate
Duty cycle of the modulation signal = 50%
0
32
kHz
ASK modulation frequency rate
Duty cycle of the modulation signal = 50%
0
32
kHz
Low level input voltage
High level input voltage
Input current high
0.25
ENABLE input
20
V
V
µA
0.25
VS(1)
5
V
V
µA
PA_ENABLE input
Note:
10
Low level input voltage
High level input voltage
Input current high
VIl
VIh
IIn
VIl
VIh
IIn
1.7
1.7
1. If VS is higher than 3.6V, the maximum voltage will be reduced to 3.6V.
T5750
4546F–RKE–12/08
T5750
8. Ordering Information
Extended Type Number
Package
Remarks
T5750-6AQJ
TSSOP8L
Taped and reeled, Marking: T570, Pb-free
9. Package Information
3±0.1
+0.06
0.31-0.07
0.65 nom.
3.8±0.3
4.9±0.1
+0.0
0.1±0.05
3±0.1
0.15-0.025
0.85±0.05
+0.05
1-0.15
Package: TSSOP 8L
Dimensions in mm
3 x 0.65 = 1.95 nom.
8
5
technical drawings
according to DIN
specifications
Drawing-No.: 6.543-5083.01-4
1
4
Issue: 2; 15.03.04
11
4546F–RKE–12/08
10. Revision History
Please note that the following page numbers referred to in this section refer to the specific revision
mentioned, not to this document.
12
Revision No.
History
4546F-RKE-12/08
• Put datasheet in the newest template
• Section 7 “Electrical Characteristics” on page 10 changed
4546E-RKE-02/07
• Put datasheet in the newest template
• Pb-free logo on page 1 deleted
4546D-RKE-09/05
• Pb-free logo on page 1 added
• Ordering Information on page 11 changed
4546C-RKE-05/05
• Put datasheet in the newest template
• Rename M4xCx9x in ATARx9x
• Table “Absolute Maximum Ratings” on page 9: New heading rows added
4546B-RKE-07/04
• Table “Absolute Maximum Ratings” on page 9: row “Input voltage” added
• Table “Absolute Maximum Ratings” on page 9: table note 1 added
• Table “Electrical Characteristics” on pages 9 to 10: row “PA_ENABLE input”
changed
• Table “Electrical Characteristics” on pages 9 to 10: table note 1 added
• Table “Ordering Informations” on page 11: Remarks changed
T5750
4546F–RKE–12/08
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4546F–RKE–12/08