Hi,
I'm trying use a new crystal with TM4C1290NCZAD and would like to seek your comment on the new part.
The crystal is the 32.768 KHz crystal selection for the TM4C1290NCZAD Hibernate module.
1. Based on the crystal spec the TM4C1290NCZAD Datasheet, C1 and C2 each is calculated to be around 13pF. Since C1 and C2 are each <18pF, the OSCDRV should be set to ‘0’ and the maximum ESR required from the Crystal should be 50kOhm (for OSCDRV=0). Am I correct? My ESR crystal specification is at 70kOhm.
2. The maximum output drive level of the crystal can go up to 0.5uW above the 0.25uW requirement of the TM4C1290NCZAD datasheet.
3. The datasheet mentions that calculation of C1 and C2 is based on the following formula: CL = (C1 *C2 )/(C1+C2 ) + CPKG + CPCB. It does not seem to include the crystal shunt capacitance C0 in the formula. Is this correct?
Given the above conditions, what are the risk to the performance of the TM4C1290NCZAD hibernation module?
Table 1. Crystal Specification
|
Nominal Frequency |
32.768 KHz |
|
Frequency Tolerance |
+20ppm |
|
Shunt Capacitance C0 |
1.5pF |
|
Motional Capacitance C1 |
6.7fF |
|
Drive Level DL |
0.5uW (Max 0 |
|
Load Capacitance |
9pF |
|
ESR |
70Kohm
|
