571BCB000107DG Silicon Labs, 571BCB000107DG Datasheet - Page 16

• Manufacturer Part Number: 571BCB000107DG
• Description: VCXO Oscillators PRGRMMBL VCXO 8 PIN 0.5PS RS JTR
• Manufacturer: Silicon Labs

Specifications of 571BCB000107DG

• Product Category: VCXO Oscillators
• Rohs: yes
• Frequency: 10 MHz
• Frequency Stability: 50 PPM
• Supply Voltage: 3.3 V
• Termination Style: SMD/SMT
• Dimensions: 5 mm W x 7 mm L x 1.65 mm H
• Mounting Style: SMD/SMT
• Product: VCXO

Si570/Si571
3.1.2.1. Writing the New Frequency Configuration
Once the new values for RFREQ, HSDIV, and N1 are
determined, they can be written directly into the device
from the serial port using the following procedure:
1. Freeze the DCO (bit 4 of Register 137)
2. Write the new frequency configuration (RFREQ,
3. Unfreeze the DCO and assert the NewFreq bit (bit 6
The process of freezing and unfreezing the DCO will
cause the output clock to momentarily stop and start at
any arbitrary point during a clock cycle. This process
can take up to 10 ms. Circuitry that is sensitive to
glitches or runt pulses may have to be reset after the
new frequency configuration is written.
Example:
An Si570 generating 156.25 MHz must be re-configured
to generate a 161.1328125 MHz clock (156.25 MHz x
66/64). This frequency change is greater than
±3500 ppm.
f
Read the current values for RFREQ, HS_DIV, N1:
RFREQ
16
out
HSDIV, and N1) to addresses 7–12 for all Si571
devices and Si570 devices with 20 ppm and 50 ppm
temperature stability; or addresses 13–18 for Si570
devices with 7 ppm temperature stability.
of Register 135) within the maximum Unfreeze to
NewFreq Timeout specified in Table 12,
“Programming Constraints and Timing,” on page 13.
= 156.25 MHz
current
= 0x2BC011EB8h = 11744124600d,
Convert integer portion to a 10-bit binary number
Figure 4. Example of RFREQ Decimal to Hexadecimal Conversion
46 = 00 0010 1110b
00 0010 1110 0000 1011 0000 0100 1100 1110 0000b
Concatenate the two results
02E0B04CE0h
46.043042064
Convert to Hex
Rev. 1.3
Convert to a 28-bit binary number (pad 0s on the left)
11744124600d x 2
HS_DIV = 4
N1 = 8
Calculate f
Given
dividers that will keep f
5.67 GHz. In this case, keeping the same output
dividers will still keep f
Calculate the new value of RFREQ given the new DCO
frequency:
0000 1011 0000 0100 1100 1110 0000
f
f
DCO_current
DCO_new
Multiply the fractional portion by 2
=
.043042064 x 2
Truncate the remaining fractional portion
161.1328125 MHz 4
f
out_new
RFREQ
=
f
XTAL
XTAL
0x2D1E127AD
=
=
, f
f
=
out_new
= 161.1328125 MHz,
f
new
DCO_current
28
out
-------------------------------------- -
RFREQ
= 11554016
28
= 11554016.077
f
DCO_current

=
= 43.7502734363d
HSDV
DCO

f
---------------------- -
DCO_new
DCO
HSDV

f
current
XTAL
within its range limits:


within the range of 4.85 to
8
N1
new
28
=
=
=
5.156250000 GHz
=

114.285 MHz
45.11746948
N1
5.000000000 GHz
new
choose
output