USB84604 datasheet(39/61 Pages) MICROCHIP

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 2014-2016 Microchip Technology Inc.

DS60001295C-page 39

USB84604

8.5

Link Power Management (LPM)

The device supports the L0 (On), L1 (Sleep), and L2 (Suspend) link power management states per the USB 2.0 Link

Power Management Addendum. These supported LPM states offer low transitional latencies in the tens of microsec-

onds versus the much longer latencies of the traditional USB suspend/resume in the tens of milliseconds. The supported

LPM states are detailed in Table 8-1. For additional information, refer to the USB 2.0 Link Power Management Adden-

dum.

8.6

Suspend (SUSPEND)

When enabled, the SUSPEND signal can be used to indicate that the entire hub has entered the USB suspend state

and that VBUS current consumption should be reduced in accordance with the USB specification [ 2]. Selective suspend

set by the host on downstream hub ports have no effect on this signal because there is no requirement to reduce current

consumption from the upstream VBUS. Suspend can be used by the system to monitor and dynamically adjust how

much current the PMIC draws from VBUS to charge the battery in the system during a USB session. Because it is a

level indication, it will assert or negate to reflect the current status of suspend without any interaction through the

SMBus.

A negation of this signal indicates no level suspend interrupt and device has been configured by the USB Host. The full

configured current can be drawn from the USB VBUS pin on the USB connector for charging - up to 500 mA - depending

on descriptor settings. When asserted, this signal indicates a suspend interrupt or that the device has not yet been con-

figured by USB Host. The current draw can be limited by the system according to the USB specification. The USB spec-

ification limits current to 100 mA before configuration, and up to 12.5 mA in USB suspend mode.

TABLE 8-1:

LPM STATE DEFINITIONS

State

Description

Entry/Exit Time to L0

Suspend

Entry: ~3 ms

Exit: ~2 ms

Sleep

Entry: ~65 µs

Exit: ~100 µs

Fully Enabled (On)

Note:

State change timing is approximate and is measured by change in power consumption.

Note:

System clocks are stopped only in suspend mode or when power is removed from the device.

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