10.1.7.8 Main Crystal Oscillator

Table 10-48. Main Crystal Oscillator Characteristics
Symbol	Parameter	Conditions	Min	Typ	Max	Unit
V_DDIN33	Supply voltage range (VDDIN33)⁽¹⁾	–	3.0	–	3.6	V
I_VDDIN33	Current consumption (VDDIN33)⁽²⁾	–	–	–	2.6	mA
t_START	Startup time⁽²⁾	–	–	–	10	ms
f_OSC	Operating frequency range	–	12	–	48	MHz
Duty	Duty cycle	–	40	50	60	%
C_PARA	Parasitic load capacitance⁽²⁾	On 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

The Main crystal oscillator supports a Bypass mode. See Input AC Characteristics.

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 10-49.
Set 2: Crystal frequency is between 20 and 30 MHz. See Table 10-50.
Set 3: Crystal frequency is between 30 and 48 MHz. See Table 10-51.

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

Table 10-49. Recommended Crystal Characteristics (Set 1)
Symbol	Parameter	Conditions	Min	Typ	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 10-50. Recommended Crystal Characteristics (Set 2)
Symbol	Parameter	Conditions	Min	Typ	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 10-51. Recommended Crystal Characteristics (Set 3)
Symbol	Parameter	Conditions	Min	Typ	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} = 1pF	–	–	80	Ω
ESR	Equivalent series resistance	With C_{SHUNT_MAX} = 3pF	–	–	60	Ω
C_M	Motional capacitance	–	1.3	–	3.2	fF
P_ON	Drive level	–	400	–	–	μW

Figure 10-40. Main Crystal Oscillator Schematic

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. As an 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.