Supply Voltage Power-Up Sequence; Sequence For 1.4 / 1.0 Ghz Devices; Sequence For 650 Mhz Devices - Intel IXP28XX Manual

IXP28XX Network Processor
Power Ratings and Requirements
2.2
Caution: The IXP28XX network processors each have a prescribed supply voltage bring-up sequence that
2.2.1
Note: The 1.8 V and 1.5 V supplies can come up in any order before or after the 2.5 V, 1.3 V, and 3.3 V
Note: No 3.3 V devices should drive any of the IXP2800/IXP2850 pins until its 3.3 V supply is up and
2.2.2
Note: The 1.8 V and 1.5 V supplies can come up in any order before or after the 2.5 V, 1.2 V, and 3.3 V
Note: No 3.3 V devices should drive any of the IXP2800/IXP2850 pins until its 3.3 V supply is up and
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Supply Voltage Power-up Sequence

must be followed, or permanent damage to the device may result. This section provides the bring-
up sequence for 1.4 /1.0 GHz devices

Sequence for 1.4 / 1.0 GHz Devices

The sequence for the 1.4 / 1.0 GHz B-stepping devices is as follows:
1. The 2.5 V supply must come up before the 1.3 V supply.
2. The 1.3 V supply must come up after the 2.5 V supply and must not start to ramp until the
2.5-V supply has exceeded 1 V.
3. The 3.3 V supply must come up only after the 2.5 V and 1.3 V supplies are up and stable.
It is expected that all supplies will be up and stable within the maximum power-up time
requirement of 700 ms. Additionally, the maximum time from when the 2.5 V supply is up and
stable to when the 1.3 V supply begins to ramp should not exceed 200 ms.
supplies.
stable.

Sequence for 650 MHz Devices

The sequence for the 650 MHz B-stepping devices is as follows:
1. The 2.5 V supply must come up before the 1.2 V supply.
2. The 1.2 V supply must come up after the 2.5 V supply and must not start to ramp until the
2.5 V supply has exceeded 1 V.
3. The 3.3 V supply should begin to ramp after the 2.5 V and 1.2 V supplies are up and stable.
It is acceptable to ramp the 1.2 V and 3.3 V supplies together as long as the two supplies rise
linearly together and do not deviate by more than 10% of the nominal ramp rate until both
supplies reach their respective final voltage levels.
It is expected that all supplies will be up and stable within the maximum power-up time
requirement of 700 ms. Additionally, the maximum time from when the 2.5 V supply is up and
stable to when the 1.2 V supply begins to ramp should not exceed 200 ms.
supplies.
stable.
(Section 2.2.1) and 650 MHz devices (Section 2.2.2).
Hardware Design Guide