SX1211 View Datasheet(PDF) - Semtech Corporation
Part Name
Description
Manufacturer
SX1211 Datasheet PDF : 92 Pages
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ADVANCED COMMUNICATIONS & SENSING
Vbat
1ųF
Y5V
VDD – Pin 26
2.1 – 3.6V
External Supply
SX1211
Reg_top
1.4 V
Biasing :
-SPI
-Config. Registers
-POR
Reg_ana
1.0 V
Biasing analog
blocks
Reg_dig
1.0 V
Biasing digital
blocks
Reg_VCO
0.85 V
Biasing :
-VCO circuit
-Ext. VCO
tank
Reg_PA
1.80 V
Biasing :
-PA Driver
-PA choke
(ext)
VR_1V
Pin 27
VR_DIG
Pin 28
VR_VCO
Pin 3
VR_PA
Pin 29
1ųF
220nF
100nF
47nF
Y5V
X7R
X7R
X7R
Figure 4: Power Supply Breakdown
To ensure correct operation of the regulator circuit, the decoupling capacitor connection shown in Figure 4 is
required. These decoupling components are recommended for any design.
3.2. Frequency Synthesis Description
The frequency synthesizer of the SX1211 is a fully integrated integer-N type PLL. The PLL circuit requires only five
external components for the PLL loop filter and the VCO tank circuit.
3.2.1. Reference Oscillator
The SX1211 embeds a crystal oscillator, which provides the reference frequency for the PLL. The recommended
crystal specification is given in section 7.1.
3.2.2. CLKOUT Output
The reference frequency, or a sub-multiple of it, can be provided on CLKOUT (pin 19) by activating the bit
OSCParam_Clkout_on. The division ratio is programmed through bits OSCParam_Clkout_freq. The two
applications of the CLKOUT output are:
To provide a clock output for a companion uC, thus saving the cost of an additional oscillator. CLKOUT can be
made available in any operation mode, except Sleep mode, and is automatically enabled at power-up.
To provide an oscillator reference output. Measurement of the CLKOUT signal enables simple software
trimming of the initial crystal tolerance.
Note: To minimize the current consumption of the SX1211, ensure that the CLKOUT signal is disabled when
unused.
Rev 7 – Sept 2nd, 2008
Page 13 of 92
www.semtech.com
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