TDA5101A Datasheet, PDF (14/21 Pages) Infineon Technologies AG – ASK Transmitter 315 MHz

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TDA 5101A
Preliminary
Functional Description
An external pull up resistor (RL) is to connect between this pin and the supply
voltage. The value of RL is dependent on the clock frequency and the load
capacitance CLD (PCB board plus input capacitance of the microcontroller).
RL can be calculated to :
R_L = -2----_×-----f--_C----_L---_K----_O-1--_U----_T----_×-----C----_L----_D- = _{2----0----×}-----1---0--1-₆----_×-----C----_L---_D--
Remark: Because to the reason of a low current consumption an a low
spurious radiation the largest possible RL should be choosen.
3. Power Amplifier
In ASK transmission the power amplifier can be switched on with pin 5 (DTA).
In this case the same pin is used as the data input.
The PAOUT pin is an open collector output and requires an external pull up
coil to provide bias. The coil is part of the tuning and matching LC cuircit to get
best performance with the external loop antenna. To achieve the best power
amplifier efficiency the high frequency voltage swing at the PAOUT pin should
be two times the supply voltage.
The power amplifier has its own ground pin (PAGND) in order to reduce the
amount of coupling to the other circuit blocks.
4. Low Power Detect
The supply voltage is sensed by a low power detector. If the supply voltage
drops below 2.15 V, the LPD pin (pin10) switches to low. The minimum sink
current is 1 mA. To spare at most cases the external pull up resistor, an internal
pull up current of 30µA is implemented.
A simple application of this feature is the switching off of the power amplifier
via pin 5.
5. Power Modes
The IC provides three power modes, the POWER DOWN MODE, the PLL
ENABLE MODE and the TRANSMIT MODE. How to get in this modes is
described in the table below.
Table 3-2
PDWN
L
H
H
DTA
L
L
H
POWER DOWN MODE
PLL ENABLE MODE
TRANSMIT MODE
Semiconductor Group
3-6
Specification, May 1999