at91cap7e ATMEL Corporation, at91cap7e Datasheet - Page 210

• Manufacturer Part Number: at91cap7e
• Description: Customizable Microcontroller
• Manufacturer: ATMEL Corporation

Figure 24-4. Divider and PLL Block Diagram
24.1.5.1
Figure 24-5. PLL Capacitors and Resistors
210
AT91CAP7E
PLL Filter
MAINCK
The PLLA requires connection to an external second-order filter through the PLLRCA pin.
24-5
PLLB has its own internal filter which is tuned for optimum operation with a 12 MHz input clock
frequency and an output frequency of 96 MHz for generating the USB clock. Use of any other
frequency for the input clock or output setting for PLLB will likely result in increased jitter and
reduced quality of the PLLB output clock.
Values of R, C1 and C2 to be connected to the PLLRC pin must be calculated as a function of
the PLL input frequency, the PLL output frequency and the phase margin. A trade-off has to be
found between output signal overshoot and startup time.
SLCK
shows a schematic of this filter.
C2
Divider B
Divider A
C1
R
DIVB
DIVA
PLLRC
GND
PLLRCA
MULB
MULA
PLLBCOUNT
PLLACOUNT
Counter
Counter
PLL B
PLL A
PLL B
PLL A
PLL
OUTB
OUTA
LOCKB
LOCKA
PLLBCK
PLLACK
8549A–CAP–10/08
Figure