ATA8741-PXQW【PDF 8/238 页】MCU W/TRANSMITTER ASK/FSK 24QFN

收藏本站

您好，
买卖IC网欢迎您。
请登录
免费注册

买卖IC网

Sheet目录52

4页 5页 6页 7页 [8页]9页 10页 11页 12页

9140CINDCO02/10

ATA8741

3.1

Description of RF Transmitter

The integrated PLL transmitter is particularly suitable for simple, low-cost RF applications. The

VCO is locked to 32 f

XTAL

hence a 9.8438 MHz crystal is needed for a 315 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 con-

nected in series to GND are needed as external elements.

The crystal oscillator together with the PLL typically need < 3 ms until the PLL is locked and the

CLK output is stable. There is a wait time of e 3 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 inde-

pendent from the load impedance. Thus, the delivered output power is controllable via the

connected load impedance.

This output configuration enables simple matching to any kind of antenna or to 50 ? This results

in a high power efficiency of ? P

out

/(I

S,PA

) of 40% for the power amplifier when an optimized

load impedance of Z

Load

= (255 + j192) ?is used at 3 V supply voltage.

3.2

ASK Transmission

The RF TX block is activated by ENABLE = H. PA_ENABLE must remain L for typically e 3 ms,

then the CLK signal is taken to clock the AVR 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 RF TX is switched back to standby mode with

ENABLE = L.

3.3

FSK Transmission

The RF TX is activated by ENABLE = H. PA_ENABLE must remain L for typically e 3 ms, then

the CLK signal is taken to clock the AVR and the power amplifier is switched on with

PA_ENABLE = H. The chip is then ready for FSK modulation. The AVR 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. When the switch is closed, the output frequency is

lower than when the switch is open. After transmission, PA_ENABLE is switched to L and the

microcontroller switches back to internal clocking. The RF TX is switched back to standby mode

with ENABLE = L.

The accuracy of the frequency deviation with XTAL pulling method is about ?5% when the fol-

lowing tolerances are considered.

Figure 3-1. Tolerances of Frequency Modulation

TAL

Crystal equivalent circuit

wi h

Stray1

Stray2

发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

*型号	*数量	厂商	批号	封装

添加更多采购

采购需求

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

我的联系方式