LAN9730 datasheet(202/222 Pages) MICROCHIP

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LAN9730/LAN9730i

DS00001946A-page 202

 2012-2015 Microchip Technology Inc.

7.5.2

POWER SEQUENCE TIMING

Power supplies must adhere to the following rules:

• All power supplies of the same voltage must be powered up/down together.

• There is no power-up sequencing requirement, however all power supplies must reach operational levels within

the time periods specified in Table 7-14.

• There is no power-down sequencing or timing requirement, however the device must not be powered for an

extended period of time without all supplies at operational levels.

• Do not drive input signals without power supplied to the device.

• It is acceptable for the 3.3 V supplies to remain powered up while the 1.2 V supplies are at zero volts for a period

not to exceed 750 ms. In this case, nRESET must be asserted while 1.2 V is off, and must remain asserted for a

minimum of 50 ms after the 1.2 V supplies reach operational level. Configuration straps must meet the require-

ments specified in Section 7.5.4, "Reset and Configuration Strap Timing," on page 203.

Note:

When operating with an external 1.2 V power source, the 1.2 V input must not exceed the 3.3 V source by

more than 0.4 V.

Note:

Violation of these specifications may damage the device.

Note:

A Power-On Reset (POR) occurs whenever power is initially applied to the device, or if power is removed

and reapplied to the device. A timer within the device will assert the internal reset for approximately 22 ms.

FIGURE 7-2:

POWER SEQUENCE TIMING

TABLE 7-14:

POWER SEQUENCE TIMING VALUES

Symbol

Description

Min.

Typ.

Max.

Unit

tpon

Power supply turn on time

750

All 3.3 V Power

Supply Pins

All 1.2 V Power

Supply Pins

tpon

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