POWER MANAGEMENT (CON’T)

Copyright Semtech 2000-2001

DOC7-TS2-S840-DS-102

www.semtech.com

5

Critical Suspend

Ext Mouse

power down

Normal State

_PWR_DOWN=0

_PWR_DOWN=1

and XPWRS=1

_PWR_DOWN=0

_PWR_DOWN=1

and XPWRS=1

_PWR_DOWN=1

and XPWRS=0

_PWR_DOWN=1

and XPWRS=0

Figure 2: System-coordinated Power Management

System-coordinated Power

Management

Normal Operation State:

In normal operation state, both the

_PWR_DOWN and XPWRS pins are

SPI/Serial operations are controlled

Critical Suspend:

At any time, the Host may negate

the _PWR_DOWN pin in order to

into a "critical suspend" mode. This

signal can be activated (driven low)

due to specific conditions of the

Host's operations (for example, a

discharged battery), or due to

actions of the Operating System or

BIOS.

During the "critical suspend", the

down all of the pointing activities.

External PS/2 power down:

monitors the state of the power

supply rail for the external PS/2

pointing device through the XPWRS

pin. If the IC senses that the external

PS/2 device has been powered-

down by the host, it will actively

eliminate shot-through current in the

input buffers for the clock and data

lines by driving both low.

initialize the external PS/2 pointing

device when the power to the

external PS/2 port is restored.

resistive touch screen sensors. The sensor interface has the following

features:

Touch detection

The IC periodically checks touch pressure applied to the panel. If there is

no touch, the IC will not perform measurements and will not send data to

system. When touch pressure is detected, the IC further qualifies and

determines the amount of pressure. Semtech’s proprietary, patent-pending

touch detection algorithm performs this test very quickly, accommodating

sensors with various plate-to-plate capacitances.

TOUCH SCREEN SENSOR INTERFACE