Microchip Technology MA330016 Data Sheet
© 2007-2011 Microchip Technology Inc.
DS70290J-page 99
dsPIC33FJ32GP202/204 and dsPIC33FJ16GP304
For a primary oscillator or FRC oscillator, output ‘F
IN
’,
The PLL output ‘F
OSC
’ is given by:
EQUATION 8-2:
F
OSC
CALCULATION
For example, suppose a 10 MHz crystal is being used,
with “XT with PLL” being the selected oscillator mode.
• If PLLPRE<4:0> = 0, then N1 = 2. This yields a
with “XT with PLL” being the selected oscillator mode.
• If PLLPRE<4:0> = 0, then N1 = 2. This yields a
VCO input of 10/2 = 5 MHz, which is within the
acceptable range of 0.8-8 MHz.
acceptable range of 0.8-8 MHz.
• If PLLDIV<8:0> = 0x1E, then M = 32. This yields a
VCO output of 5 x 32 = 160 MHz, which is within
the 100-200 MHz ranged needed.
the 100-200 MHz ranged needed.
• If PLLPOST<1:0> = 0, then N2 = 2. This provides
a Fosc of 160/2 = 80 MHz. The resultant device
operating speed is 80/2 = 40 MIPS.
operating speed is 80/2 = 40 MIPS.
EQUATION 8-3:
XT WITH PLL MODE
EXAMPLE
EXAMPLE
FIGURE 8-2:
dsPIC33FJ32GP202/204 and dsPIC33FJ16GP304 PLL BLOCK DIAGRAM
TABLE 8-1:
CONFIGURATION BIT VALUES FOR CLOCK SELECTION
F
OSC
F
IN
M
N1
N2
⋅
----------------------
⎝
⎠
⎛
⎞
⋅
=
F
CY
F
OSC
2
-------------
1
2
2
---
10000000
32
⋅
2
2
⋅
-------------------------------------
⎝
⎠
⎛
⎞
40 MIPS
=
⋅
=
=
Oscillator Mode
Oscillator Source
POSCMD<1:0>
FNOSC<2:0>
See Note
Fast RC Oscillator with Divide-by-N
(FRCDIVN)
(FRCDIVN)
Internal
xx
111
1, 2
Fast RC Oscillator with Divide-by-16
(FRCDIV16)
(FRCDIV16)
Internal
xx
110
1
Low-Power RC Oscillator (LPRC)
Internal
xx
101
1
Secondary (Timer1) Oscillator (SOSC)
Secondary
xx
100
1
Primary Oscillator (HS) with PLL
(HSPLL)
(HSPLL)
Primary
10
011
—
Primary Oscillator (XT) with PLL
(XTPLL)
(XTPLL)
Primary
01
011
—
Primary Oscillator (EC) with PLL
(ECPLL)
(ECPLL)
Primary
00
011
1
Primary Oscillator (HS)
Primary
10
010
—
Primary Oscillator (XT)
Primary
01
010
—
Primary Oscillator (EC)
Primary
00
010
1
Fast RC Oscillator with PLL (FRCPLL)
Internal
xx
001
1
Fast RC Oscillator (FRC)
Internal
xx
000
1
Note 1: OSC2 pin function is determined by the OSCIOFNC Configuration bit.
2: This is the default oscillator mode for an unprogrammed (erased) device.
0.8-8.0 MHz
Here
(1)
100-200 MHz
Here
(1)
Divide by
2, 4, 8
Divide by
2-513
Divide by
2-33
Source (Crystal, External Clock
PLLPRE
X
VCO
PLLDIV
PLLPOST
or Internal RC)
12.5-80 MHz
Here
(1)
F
OSC
Note 1: This frequency range must be satisfied at all times.
F
VCO
N1
M
N2