402-00005-00
DAC and PLL Programming
4–8
Rev 02; February 8, 2002
4.2.8 PLL Register 4 (PLLA4)
0
7
PLL Address 0x4
INTFLT
PDEN
PFD2
PFD1
PFD0
VCO2
VCO1
VCO0
8
15
Reserved
Reserved
Reserved
Reserved
Reserved
1
CLKSEL
INTVCO
PCR_PLLA4_16
This register contains several control bits for the VCO (voltage controlled oscillator) and the phase detector. Bit 10
must always be one. Program the reserved bits to zero.
Bit
Mnemonic
Function
2–0
VCO
VCO Gain
5–3
PFD
Phase Frequency Detector Gain
6
PDEN
Phase Frequency Detector Enable
7
INTFLT
Loop Filter Select
8
INTVCO
VCO Select
9
CLKSEL
Feedback Divider Clock Select
10
Reserved
Must be one
15–11
Reserved
Don’t care
4.2.8.1 VCO Gain (VCO) R/W
These bits control the PLL VCO Gain. The default setting is 4.
VCO
VCO Gain
0
10 MHz / Volt
1
15 MHz / Volt
2
20 MHz / Volt
3
25 MHz / Volt
4
45 MHz / Volt
5
60 MHz / Volt
6
75 MHz / Volt
7
90 MHz / Volt
Use the following formula to calculate the value for VCO Gain:
For both XTAL and PLL mode:
VCO gain = (PDA x LCOUNT x Fdesired) / 3.5Volts
Program VCO(2–0) to the next value greater than the calculated VCO gain. For example, if the calculated value is
12, use 15 MHz (not 10).
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