LAN9730 Datasheet, PDF (202/222 Pages) SMSC Corporation – High-Speed Inter-Chip (HSIC) USB 2.0

LAN9730/LAN9730i
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:
Note:
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.
Violation of these specifications may damage the device.
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
t_pon
All 3.3 V Power
Supply Pins
All 1.2 V Power
Supply Pins
TABLE 7-14: POWER SEQUENCE TIMING VALUES
Symbol
t_pon
Description
Power supply turn on time
Min.
Typ.
Max.
Unit
0
750
ms
DS00001946A-page 202
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