74.7.9 Main Crystal Oscillator

Table 74-54. Main Crystal Oscillator Characteristics
Symbol	Parameter	Conditions	Min	Max	Unit
V_DDIN33	Supply voltage range (VDDIN33)⁽¹⁾	–	3.0	3.6	V
I_VDDIN33	Current consumption (VDDIN33)⁽²⁾	–	–	2.8	mA
t_START	Start-up time⁽²⁾		–	10	ms
f_OSC	Operating frequency range	–	12	48	MHz
Duty	Duty cycle⁽²⁾	–	40	60	%
C_PARA	Internal parasitic capacitance⁽²⁾	Between XIN and XOUT	1		pF

Note:

This oscillator is powered by the 2.5V regulated output of the VDDOUT25 regulator, which is supplied from VDDIN33.
Simulation data

Three sets of crystal characteristics are supported with this oscillator corresponding to three operating frequency ranges:

Set 1: Crystal frequency is between 12 and 20 MHz. See Table 74-55.
Set 2: Crystal frequency is between 20 and 30 MHz. See Table 74-56.
Set 3: Crystal frequency is between 30 and 48 MHz. See Table 74-57.

When choosing a crystal, one and only one of these sets must be completely satisfied.

Table 74-55. Recommended Crystal Characteristics (Set 1)
Symbol	Parameter	Conditions	Min	Max	Unit
f₀	Fundamental frequency	–	12	20	MHz
C_CRYSTAL	Load capacitance	–	6	17.5	pF
C_SHUNT	Shunt capacitance	–	–	3	pF
ESR	Equivalent series resistance	–	–	100	Ω
C_M	Motional capacitance	–	1.3	3.2	fF
P_ON	Drive level	–	150	–	μW

Table 74-56. Recommended Crystal Characteristics (Set 2)
Symbol	Parameter	Conditions	Min	Max	Unit
f₀	Fundamental frequency	–	20	30	MHz
C_CRYSTAL	Load capacitance	–	6	12.5	pF
C_SHUNT	Shunt capacitance	–	–	3	pF
ESR	Equivalent series resistance	–	–	100	Ω
C_M	Motional capacitance	–	1.3	3.2	fF
P_ON	Drive level	–	300	–	μW

Table 74-57. Recommended Crystal Characteristics (Set 3)
Symbol	Parameter	Conditions	Min	Max	Unit
f₀	Fundamental frequency	–	30	48	MHz
C_CRYSTAL	Load capacitance	–	6	10	pF
C_SHUNT	Shunt capacitance	With ESR_MAX = 60Ω	–	3	pF
C_SHUNT	Shunt capacitance	With ESR_MAX = 80Ω	–	1	pF
ESR	Equivalent series resistance	With C_{SHUNT_MAX} = 1 pF	–	80	Ω
ESR	Equivalent series resistance	With C_{SHUNT_MAX} = 3 pF	–	60	Ω
C_M	Motional capacitance	–	1.3	3.2	fF
P_ON	Drive level	–	400	–	μW

Figure 74-45. Main Crystal Oscillator

C_LEXT = 2 x (C_CRYSTAL – C_PARA – C_PCB / 2).

where C_PCB is the single-ended (ground referenced) parasitic capacitance of the printed circuit board (PCB) on XIN and XOUT tracks. For example, if the crystal is specified for a 12.5 pF load, with C_PCB=1 pF (on XIN and on XOUT), C_LEXT = 2 x (12.5 - 1 - 0.5) = 22 pF.