33975 datasheet(15/32 Pages) FREESCALE

15 / 32 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

33975

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

WAKE-UP/INTERRUPT REGISTER

The Wake-Up/Interrupt Register defines the inputs that

are allowed to wake the 33975 from Sleep mode or set the

INT

terminal low in Normal mode. Programming the wake-up/

interrupt bit to logic [0] will disable the specific input from

generating an interrupt and will disable the specific input from

waking the IC in Sleep mode (refer to Table 7). Programming

the wake-up/interrupt bit to logic [1] will enable the specific

input to generate an interrupt with switch change of state and

will enable the specific input as wake-up. The MCU may

change or update the Wake-Up/Interrupt Register via

software at any time in Normal mode.

WETTING CURRENT REGISTER

The 33975 has two levels of switch-to-ground contact

current, 32 mA and 4.0 mA, and two levels of switch-to-

battery contact current, 16 mA and 2.0 mA (see Figure 10).

The metallic command is used to set the switch contact

current level (refer to Table 8). Programming the metallic bit

to logic [0] will set the switch wetting current to 2.0 mA/4.0

mA. Programming the metallic bit to logic [1] will set the

switch contact wetting current to 16 mA/32 mA. The MCU

may change or update the Wetting Current Register via

software at any time in Normal mode.

Wetting current is designed to provide higher levels of

current during switch closure. The higher level of current is

designed to keep switch contacts from building up oxides that

form on the switch contact surface.

Figure 10. Contact Wetting and Sustain Current

for Switch-to-Ground Input

WETTING CURRENT TIMER REGISTER

Each switch input has a designated 20 ms timer. The timer

starts when the specific switch input crosses the comparator

threshold (4.0 V). When the 20 ms timer expires, the contact

current is reduced from 16 mA to 2.0 mA for switch-to-battery

inputs and 32 mA to 4.0 mA for switch-to-ground inputs. The

wetting current timer may be disabled for a specific input.

When the timer is disabled, wetting current will continue to

flow through the closed switch contact. With multiple wetting

current timers disabled, power dissipation for the IC must be

considered.

The MCU may change or update the Wetting Current

Timer Register via software at any time in Normal mode. This

allows the MCU to control the amount of time wetting current

is applied to the switch contact. Programming the wetting

current timer bit to logic [0] will disable the wetting current

timer. Programming the wetting current timer bit to logic [1]

will enable the wetting current timer (refer to Table 9).

Table 7. Wake-Up /Interrupt Command

Wake-Up/Interrupt Command

Command Bits

sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0

sg1

sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0

Switch Contact Voltage

32 mA Switch Wetting Current

4.0 mA Switch Sustain Current

20 ms Wetting Current Timer

Table 8. Metallic Command

Metallic Command

Command Bits

sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0

sg1

sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0

33975 датащи(PDF) 15 Page - Freescale Semiconductor, Inc

33975 датащи(HTML) 15 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

датащи скачать

ссылки URL