33993 datasheet(13/28 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33993

FUNCTIONAL DEVICE OPERATION

LOGIC COMMANDS AND REGISTERS

PROGRAMMABLE SWITCH REGISTER

Inputs SP0 to SP7 may be programmable for switch-to-

battery or switch-to-ground. These inputs types are defined

using the settings command (refer to Table 5). To set an SPn

input for switch-to-battery, a logic [1] for the appropriate bit

must be set. To set an SPn input for switch-to-ground, a logic

[0] for the appropriate bit must be set. The MCU may change

or update the Programmable Switch Register via software at

any time in Normal mode. Regardless of the setting, when the

SPn input switch is closed a logic [1] will be placed in the

Serial Output Response Register (refer to Table 16,

page 17).

WAKE-UP/INTERRUPT REGISTER

The Wake-Up/Interrupt Register defines the inputs that

are allowed to wake the 33993 from Sleep mode or set the

INT pin 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 6). 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 33993 has two levels of switch 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 7).

Programming the metallic bit to logic [0] will set the switch

wetting current to 2.0 mA. Programming the metallic bit to

logic [1] will set the switch contact wetting current to 16 mA.

The MCU may change or update the Wetting Current

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

Table 5. Settings Command

Settings Command

Not used

Battery/Ground Select

sp7

sp6

sp5

sp4

sp3

sp2

sp1

sp0

Table 6. 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

16 mA Switch Wetting Current

2.0 mA Switch Sustain Current

20 ms Wetting Current Timer

33993 Datasheet(PDF) 13 Page - Freescale Semiconductor, Inc

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