11.2.1 Power-Up Sequencing

This section defines the requirements for a power-up sequencing from a power-on reset condition. There are two acceptable power sequences for the device.

The first sequence stipulates the core voltages starting before the IO voltages as shown below.

1. CVDD
2. CVDD1, CVDDT1, VDDAHV, AVDDAx, DVDD18
3. DVDD15
4. VDDALV, VDDUSB, VP, VPTX
5. DVDD33

The second sequence provides compatibility with other TI processors with the IO voltage starting before the core voltages as shown below.

1. VDDAHV, AVDDAx, DVDD18
2. CVDD
3. CVDD1, CVDDT1
4. DVDD15
5. VDDALV, VDDUSB, VP, VPTX
6. DVDD33

The clock input buffers for SYSCLK, ARMCLK, ALTCORECLK, DDR3ACLK, DDR3BCLK, PASSCLK, and SRIOSGMIICLK use CVDD as a supply voltage. These clock inputs are not failsafe and must be held in a high-impedance state until CVDD is at a valid voltage level. Driving these clock inputs high before CVDD is valid could cause damage to the device. Once CVDD is valid, it is acceptable that the P and N legs of these clocks may be held in a static state (either high and low or low and high) until a valid clock frequency is needed at that input. To avoid internal oscillation, the clock inputs should be removed from the high impedance state shortly after CVDD is present.

If a clock input is not used, it must be held in a static state. To accomplish this, the N leg should be pulled to ground through a 1-kΩ resistor. The P leg should be tied to CVDD to ensure it will not have any voltage present until CVDD is active. Connections to the IO cells powered by DVDD18 and DVDD15 are not failsafe and should not be driven high before these voltages are active. Driving these IO cells high before DVDD18 or DVDD15 are valid could cause damage to the device.

The device initialization is divided into two phases. The first phase consists of the time period from the activation of the first power supply until the point at which all supplies are active and at a valid voltage level. Either of the sequencing scenarios described above can be implemented during this phase. The figures below show both the core-before-IO voltage sequence and the IO-before-core voltage sequence. POR must be held low for the entire power stabilization phase.

This is followed by the device initialization phase. The rising edge of POR followed by the rising edge of RESETFULL triggers the end of the initialization phase, but both must be inactive for the initialization to complete. POR must always go inactive before RESETFULL goes inactive as described below. SYSCLK1 in the following section refers to the clock that is used by the CorePacs. See Figure 11-7 for more details.