6.11 Crystal Input Characteristics (SEC_REF)
VDD_SEC = 1.71 to 1.89 V, 2.375 V to 2.625 V, 3.135 V to 3.465 V, TA = –40°C to 85°CPARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT |
Mode of oscillation |
| Fundamental |
|
Frequency |
See note (1) |
10 |
| 30.72 |
MHz |
See note (2) |
30.73 |
| 50 |
MHz |
Equivalent Series Resistance (ESR) |
10 MHz |
| | 150(4) |
Ω |
25 MHz |
| | 70(5) |
50 MHz |
| | 30(6) |
On-chip load capacitance |
1.8-V / 3.3-V SEC_REFP |
3.5 |
4.5 |
5.5 |
pF |
1.8-V SEC_REFN |
5.5 |
7.25 |
8.5 |
3.3-V SEC_REFN |
6.5 |
7.34 |
8.5 |
Drive level |
See note (3) |
| | 200 |
µW |
(1) Verified with crystals specified for a load capacitance of CL = 8 pF, the PCB related capacitive load was estimated to be 2.3 pF, and completed with a load capacitors of 4 pF on each crystal pin connected to GND. XTALs tested: NX3225GA 10MHz EXS00A-CG02813 CRG, NX3225GA 19.44MHz EXS00A-CG02810 CRG, NX3225GA 25MHz EXS00A-CG02811 CRG, and NX3225GA 30.72MHz EXS00A-CG02812 CRG.
(2) For 30.73 MHz to 50 MHz, TI recommends to verify sufficient negative resistance and initial frequency accuracy with the crystal vendor. The 50-MHz use case was verified with a NX3225GA 50MHz EXS00A-CG02814 CRG. To meet a minimum frequency error, the best choice of the XTAL was one with CL = 7 pF instead of CL = 8 pF.
(3) Maximum drive level measured was 145 µW; XTAL should at least tolerate 200 µW
(4) With NX3225GA_10M the measured remaining negative resistance on the EVM is 6430 Ω (43 x margin)
(5) With NX3225GA_25M the measured remaining negative resistance on the EVM is 1740 Ω (25 x margin)
(6) With NX3225GA_50M the measured remaining negative resistance on the EVM is 350 Ω (11 x margin)