AN31 SILABS [Silicon Laboratories], AN31 Datasheet - Page 5

• Manufacturer Part Number: AN31
• Description: INDUCTOR DESIGN FOR THE Si41XX SYNTHESIZER FAMILY
• Manufacturer: SILABS [Silicon Laboratories]

8. Verifying Margin in Design
Important: Please note that this procedure is only intended
It is possible to determine the frequency tuning margin
on a design implementation. This is accomplished by
reading back from the synthesizer register values which
indicate the tuning range of the VCOs using the
following procedure:
IF synthesizer:
1. Program the IF synthesizer to its highest frequency
2. Write 0x0001DE (hexadecimal) to enable a read of
3. Read 18 bits from the serial interface. (See “Serial
4. The 18-bit value read from the interface is the tuning
5. Program the IF synthesizer to its lowest frequency in
6. Write 0x0001DE (hexadecimal) to enable a read of
7. Read 18 bits from the serial interface. (See “Serial
8. The 18-bit value read from the interface is the tuning
RF1 synthesizer:
1. Program the RF1 synthesizer to be active and at its
2. Write 0x0000DE (hexadecimal) to enable a read of
3. Read 18 bits from the serial interface. (See “Serial
4. The 18-bit value read from the interface is the tuning
5. Program the RF1 synthesizer to be active and at its
6. Write 0x0000DE (hexadecimal) to enable a read of
7. Read 18 bits from the serial interface. (See “Serial
8. The 18-bit value read from the interface is the tuning
in the application.
the IF tuning code.
Read Timing.")
code. This value should be greater than 0x40
(hexadecimal) if the unit has adequate tuning
margin.
the application.
the IF tuning code.
Read Timing.")
code. This value should be less than 0x780
(hexadecimal) if the unit has adequate tuning
margin.
highest frequency in the application.
the RF tuning code.
Read Timing.")
code. This value should be greater than 0x40
(hexadecimal) if the unit has adequate tuning
margin.
lowest frequency in the application.
the RF tuning code.
Read Timing.")
for initial verification of the design of the board and
external VCO tuning inductor.
Rev. 1.3
RF2 synthesizer:
1. Program the RF2 synthesizer to be active and at its
2. Write 0x0000DE (hexadecimal) to enable a read of
3. Read 18 bits from the serial interface. (See “Serial
4. The 18-bit value read from the interface is the tuning
5. Program the RF2 synthesizer to be active and at its
6. Write 0x0000DE (hexadecimal) to enable a read of
7. Read 18 bits from the serial interface. (See “Serial
8. The 18-bit value read from the interface is the tuning
8.1. Serial Read Timing
In addition to the functions described in the data sheet,
the AUXOUT pin can be used to read the contents of
some synthesizer registers. By writing the values of
0x0001DE and 0x0000DE as described above, the
serial interface is configured to read the tuning codes.
During the readback, the function of the AUXOUT pin is
to provide the serial data output from the device. Writing
to any of the registers described in the data sheet will
cause the function of AUXOUT to revert to its previously
programmed function. This is illustrated in Figure 4
below. Refer to Table 3 for timing values.
code. This value should be less than 0x780
(hexadecimal) if the unit has adequate tuning
margin.
highest frequency in the application.
the RF tuning code.
Read Timing.")
code. This value should be greater than 0x40
(hexadecimal) if the unit has adequate tuning
margin.
lowest frequency in the application.
the RF tuning code.
Read Timing.")
code. This value should be less than 0x780
(hexadecimal) if the unit has adequate tuning
margin.
AN31
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