SX1223 데이터 시트보기 (PDF) - Semtech Corporation

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SX1223

425 – 475 MHz / 850 – 950 MHz Integrated UHF Transmitter

Semtech Corporation 

SX1223

Add Bits MOD_I Comments

3 7-3 1..31 The deviation frequency is linearly dependent of MOD_I

Table 23: Modulator current setting for frequency deviation

Add Bits

3 2-0

MOD_A

0..4

Comments

Frequency deviation attenuator (or range selector). The attenuations are

(values 0 through 4, respectively)

1

1

,

12 ,

1

4

,

1

8

,

and

1

16

.

Table 24: Modulator attenuator setting for frequency deviation

Add Bits

4 5-3

BRn

0..5

Comments

The bit rate clock is set by dividing the crystal oscillator frequency by

RefClk_K*2^(3+BRn)

Table 25: Bit Rate setting

Add Bits

4 2-0

MOD_F

0..3

Comments

Programmable smoothing filter after attenuator. This can be programmed in

four steps, and will produce reasonable results for the highest bit rates.

Table 26: Modulator filter setting

Add Bits RefClk_K Comments

5 5-0

1..63

The crystal oscillator is divided by this number to produce modulator clock and

it is divided further down by 2^(3+BRn) to produce the bit rate clock.

Table 27: Modulator and Bit Rate clock setting

Add Bit Prescal_s State

16 4

0

(default)

1

Prescaler enabled

Comments

Reserved.

f RF

=

M

f XCO

(16 ⋅ N

⋅ (2 − FreqBand)

+

A)

Table 28: Prescaler enable bit

“1” should be written in Prescal_s register to operate SX1223 PLL dividers.

5.2.3 Optional and Test Parameters

In most applications, the user has only to be concerned with the parameters given in sections 5.2.1 and 5.2.2.

However some options and test modes are available for special purposes. They are described in the tables below.

Add Bits

16 7-5

VCO_IB2

1

1

0

0

VCO_IB1

1

0

1

0

VCO_IB0 Comments - default = [0 0 1]

1

Bias setting for 850 MHz

1

Bias setting for 868 MHz

1

Bias setting for 915 MHz

0

Bias setting for 950 MHz

Table 29: VCO bias

The two VCO_freq bits have to be programmed by the user according to the selected frequency band, whereas the

three VCO_IB bits can be either forced by the user or set automatically by the circuit which will select the

combination having the best phase noise. This automatic setting can be enabled by setting the three VCO_IB bits to

‘0’.

© Semtech 2007

www.semtech.com

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