TH72016KLD-CAA-000-TU Datasheet TH72016KLD-CAA-000-SP, TH72016KLD-CAA-000-TU, TH72016KLD-CAA-000-RE | P4-P6

TH72016

433MHz

FSK/ASK Transmitter

39010 72016 Page 4 of 15 Data Sheet

Rev. 009 Jan/12

min

max

eff

XTAL

CLCX1 CRO

CX1+CRO

(CX1+CX2) CRO

CX1+CX2+CRO

2.2 FSK Modulation

FSK modulation can be achieved by pulling the

crystal oscillator frequency. A CMOS-

compatible data stream applied at the pin

FSKDTA digitally modulates the XOSC via an

integrated NMOS switch. Two external pulling

capacitors CX1 and CX2 allow the FSK devia-

tion ∆f and the center frequency f

to be ad-

justed independently. At FSKDTA = 0, CX2 is

connected in parallel to CX1 leading to the low-

frequency component of the FSK spectrum

min

); while at FSKDTA = 1, CX2 is deactivated

and the XOSC is set to its high frequency f

max

An external reference signal can be directly AC-

coupled to the reference oscillator input pin

ROI. Then the transmitter is used without a

crystal. Now the reference signal sets the car-

rier frequency and may also contain the FSK (or

FM) modulation.

Fig. 2: Crystal pulling circuitry

FSKDTA Description

min

= f

- ∆f (FSK switch is closed)

max

= f

+ ∆f (FSK switch is open)

2.3 Crystal Pulling

A crystal is tuned by the manufacturer to the

required oscillation frequency f

at a given load

capacitance CL and within the specified calibra-

tion tolerance. The only way to pull the oscilla-

tion frequency is to vary the effective load ca-

pacitance CL

eff

seen by the crystal.

Figure 3 shows the oscillation frequency of a

crystal as a function of the effective load ca-

pacitance. This capacitance changes in accor-

dance with the logic level of FSKDTA around

the specified load capacitance. The figure illus-

trates the relationship between the external

pulling capacitors and the frequency deviation.

It can also be seen that the pulling sensitivity

increases with the reduction of CL. Therefore,

applications with a high frequency deviation

require a low load capacitance. For narrow

band FSK applications, a higher load capaci-

tance could be chosen in order to reduce the

frequency drift caused by the tolerances of the

chip and the external pulling capacitors.

Fig. 3: Crystal pulling characteristic

For ASK applications CX2 can be omitted. Then CX1 has to be adjusted for center frequency.

CX2

VCC

XTAL

CX1

ROI

FSKSW

VEE

TH72016

433MHz

FSK/ASK Transmitter

39010 72016 Page 5 of 15 Data Sheet

Rev. 009 Jan/12

2.4 ASK Modulation

The TH72016 can be ASK-modulated by applying data directly at pin PSEL. This turns the PA on and off

which leads to an ASK signal at the output.

2.5 Output Power Selection

The transmitter is provided with an output power selection feature. There are four predefined output power

steps and one off-step accessible via the power selection pin PSEL. A digital power step adjustment was

chosen because of its high accuracy and stability. The number of steps and the step sizes as well as the

corresponding power levels are selected to cover a wide spectrum of different applications.

The implementation of the output power control

logic is shown in figure 4. There are two

matched current sources with an amount of

about 8 µA. One current source is directly ap-

plied to the PSEL pin. The other current source

is used for the generation of reference voltages

with a resistor ladder. These reference voltages

are defining the thresholds between the power

steps. The four comparators deliver thermome-

ter-coded control signals depending on the

voltage level at the pin PSEL. In order to have a

certain amount of ripple tolerance in a noisy

environment the comparators are provided with

a little hysteresis of about 20 mV. With these

control signals, weighted current sources of the

power amplifier are switched on or off to set the

desired output power level (Digitally Controlled

Current Source). The LOCK signal and the

output of the low voltage detector are gating

this current source.

Fig. 4: Block diagram of output power control circuitry

There are two ways to select the desired output power step. First by applying a DC voltage at the pin PSEL,

then this voltage directly selects the desired output power step. This kind of power selection can be used if

the transmission power must be changed during operation. For a fixed-power application a resistor can be

used which is connected from the PSEL pin to ground. The voltage drop across this resistor selects the de-

sired output power level. For fixed-power applications at the highest power step this resistor can be omitted.

The pin PSEL is in a high impedance state during the “TX standby” mode.

2.6 Lock Detection

The lock detection circuitry turns on the power amplifier only after PLL lock. This prevents from unwanted

emission of the transmitter if the PLL is unlocked.

2.7 Low Voltage Detection

The supply voltage is sensed by a low voltage detect circuitry. The power amplifier is turned off if the supply

voltage drops below a value of about 1.85 V. This is done in order to prevent unwanted emission of the

transmitter if the supply voltage is too low.

PSEL

RPS

OUT

TH72016

433MHz

FSK/ASK Transmitter

39010 72016 Page 6 of 15 Data Sheet

Rev. 009 Jan/12

2.8 Mode Control Logic

The mode control logic allows two different

modes of operation as listed in the following

table. The mode control pin EN is pulled-down

internally. This guarantees that the whole circuit

is shut down if this pin is left floating.

EN Mode Description

0 TX standby TX disabled

TX active

CKOUT active

TX / CKOUT

enabled

2.9 Clock Output

The clock output CKOUT is CMOS-compatible and can be used to drive a microcontroller. The frequency of

the clock can be changed by the clock divider control signal CKDIV, that can be selected according to the

following table. A capacitor at pin CKOUT can be used to control the clock voltage swing and the spurious

emission.

CKDIV Clock divider ratio Clock frequency / fc=433.92MHz

0 4 3.39MHz

1 16 848kHz

2.10 Timing Diagrams

After enabling the transmitter by the EN signal, the power amplifier remains inactive for the time t

, the

transmitter start-up time. The crystal oscillator starts oscillation and the PLL locks to the desired output fre-

quency within the time duration t

. After successful PLL lock, the LOCK signal turns on the power amplifier,

and then the RF carrier can be FSK or ASK modulated.

Fig. 5: Timing diagrams for FSK and ASK modulation

RF carrier

low

high

LOCK

FSKDTA

low

high

low

high

LOCK

PSEL

low

high

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15

TH72016KLD-CAA-000-TU

Mfr. #:

Buy TH72016KLD-CAA-000-TU

Manufacturer:

Melexis

Description:

RF Transmitter 433MHz FSK/ASK Transmitter w/ clock O/P

Lifecycle:

New from this manufacturer.

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TH72016KLD-CAA-000-TU

TH72016KLD-CAA-000-TU

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