si5338b Silicon Laboratories, si5338b Datasheet - Page 18

• Manufacturer Part Number: si5338b
• Description: I2c-programmable Any-rate , Any-output Quad Clock Generator
• Manufacturer: Silicon Laboratories

Si5338
Registers
CLK0,1,2,3 respectively. Each single write of 01 to the
CLKnPHASESTEPCTRL[1:0] will cause the phase to
be incremented. Likewise a write of 10 will decrement
the phase.
2.9. Output Clock Frequency
The Si5338 has a digitally controlled frequency
increment/decrement feature that allows the user to
transition from one frequency to another either by pin
control or I
increment and decrement is from 0.1 kHz to 10 MHz.
Each channel output can be independently set for the
size of the frequency step and whether or not the
channel responds to pin control of frequency. Pin control
of frequency is available on Si5338G/H/J. All Si5338
devices allow I
decrement.
glitchless. The new output frequency after a frequency
step may have an error of up to 1 ppb more than the
frequency error that existed at the previous output
frequency. Because the MultiSynth fractional divider has
a resolution of nine decimal places, in nearly all cases,
the frequency error at the initial frequency is going to be
zero.
18
Increment/Decrement
CLKnFRQSTEPCTRL[1:0] REGISTERS
2
52,63,74,85
C writes. The step size for the frequency
CLKnPHASESTEPCTRL[1:0]
The
Registers 52,63,74,85[1:0]
2
C control of frequency increment/
52,63,74,85[6:5]
frequency
control
00
01
10
11
00
01
10
11
Table 14. Output Clock Frequency Control
transition
Table 13. Output Clock Phase Control
the
clock
is
outputs
always
Rev. 0.3
Disable all phase increment/decrement and reset phase
to the initial phase offset value.
Enable pin control of phase inc/dec
Phase is incremented
Phase is decremented
Disable all frequency increment/decrement and reset
frequency to the initial value.
Enable pin control of frequency inc/dec
Frequency is incremented
Frequency is decremented
The maximum clock output frequency in this mode of
operation is fVCO/8 where fVCO is the frequency of the
device's internal Voltage Controlled Oscillator for the
configured frequency plan. If the output frequency is
below 5 Mhz, the special considerations in section 2.10
need to be understood. The Si5338 programmer
software should be used to set the parameters of the
frequency increment/decrement function. When pin
control is desired, pins 1 and 2 must be used for the
input clock (crystal) so that IN3 and IN4 pins are
available to implement the FINC and FDEC functions.
Pin control of frequency requires a positive pulse that is
greater than 100 ns followed by at least 100ns of low
level. The NVM can be programmed at the factory to set
all of the frequency change parameters.
control, the frequency change can occur as fast as
1 MHz. The magnitude of the change must be set using
the Si5338 programmer.
Since the Si5338A,B,C,D,E,F devices do not provide
pin control of frequency, these devices must use the I
interface for this function. Table 14 lists the registers
that control the activation of frequency increment and
decrement.
Output Frequency
Output Phase
Using pin
2
C