MC33972ATEW Freescale Semiconductor, MC33972ATEW Datasheet - Page 15

• Manufacturer Part Number: MC33972ATEW
• Description: IC SWITCH DETECT SPI 32-SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MC33972ATEW

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 7. Wake-up / Interrupt Command
WETTING CURRENT REGISTER
2.0 mA (see
the switch contact current level
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 register via software at
any time in Normal mode.
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.
Table 8. Metallic Command
WETTING CURRENT TIMER REGISTER
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 to 2.0 mA. The wetting current
timer may be disabled for a specific input. When the timer is
disabled, 16 mA of current will continue to flow through the
Table 9. Wetting Current Timer Enable Command
Analog Integrated Circuit Device Data
Freescale Semiconductor
23
23
23
0
0
0
0
0
0
The 33972 has two levels of switch contact current, 16 and
Wetting current is designed to provide higher levels of
Each switch input has a designated 20 ms timer. The timer
Wetting Current Timer Commands
Wake-up /Interrupt Command
22
22
22
0
0
0
0
0
0
Metallic Command
21
21
21
0
0
0
0
0
0
Figure
20
20
20
0
0
0
0
0
0
11). The metallic command is used to set
19
19
19
0
0
0
0
0
1
18
18
18
1
1
0
0
1
0
17
17
(Table
17
1
1
0
0
1
0
16
16
16
0
1
0
1
1
0
8). Programming the
15
15
X
X
X
X
15
X
X
14
14
X
X
14
X
X
X
X
sg13 sg12 sg11 sg10 sg9
sg13 sg12 sg11 sg10 sg9
sg13 sg12 sg11 sg10 sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0
13
13
X
X
13
X
12
12
X
X
12
X
11
11
X
X
11
X
closed switch contact. With multiple wetting current timers
disabled, power dissipation for the IC must be considered.
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
10
10
X
The MCU may change or update the wetting current timer
X
10
X
Figure 11. Contact Wetting and Sustain Current
X
9
X
9
X
9
Command Bits
Command Bits
Command Bits
Switch Contact Voltage
sg8
sg8
X
8
8
X
8
X
20 ms Wetting Current Timer
sp7
sg7
sp7
sg7
sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0
7
7
7
16 mA Switch Wetting Current
sp6
sg6
sp6
sg6
2.0 mA Switch Sustain Current
6
6
6
FUNCTIONAL DEVICE OPERATION
sp5
sg5
sp5
sg5
5
5
5
sp4
sg4
sp4
sg4
4
4
4
(Table
OPERATIONAL MODES
sp3
sg3
sp3
sg3
3
3
3
9).
sp2
sg2
sp2
sg2
2
2
2
sp1
sg1
sp1
sg1
1
1
1
33972
sp0
sg0
sp0
sg0
0
0
0
15