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參數(shù)資料
| 型號(hào)： | PC33975A |
| 廠商： | 飛思卡爾半導(dǎo)體(中國)有限公司 |
| 英文描述： | Multiple Switch Detection Interface with Suppressed Wake-Up and 32mA Wetting Current |
| 中文描述： | 多交換檢測(cè)接口，具有抑制喚醒和32毫安濕電流 |
| 文件頁數(shù)： | 22/32頁 |
| 文件大?。?/td> | 641K |
| 代理商： | PC33975A |
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Analog Integrated Circuit Device Data
Freescale Semiconductor
22
33975
TYPICAL APPLICATIONS
OPERATIONAL MODES
TYPICAL APPLICATIONS
The 33975’s primary function is the detection of open or
closed switch contacts. However, there are many features
that allow the device to be used in a variety of applications.
The following is a list of applications to consider for the IC:
Sensor Power Supply
Switch Monitor for Metallic or Elastomeric Switches
Analog Sensor Inputs (Ratiometric)
Power MOSFET/LED Driver and Monitor
Multiple 33975 Devices in a Module System
The following paragraphs describe the applications in
detail.
SENSOR POWER SUPPLY
Each input may be used to supply current to sensors
external to a module. Many sensors such as Hall effect,
pressure sensors, and temperature sensors require a supply
voltage to power the sensor and provide an open collector or
analog output.
Figure 12
shows how the 33975 may be used
to supply power and interface to these types of sensors. In an
application where the input makes continuous transitions,
consider using the
wake-up/interrupt command
to disable
the interrupt for the particular input.
Figure 12. Sensor Power Supply
METALLIC/ELASTOMERIC SWITCH
Metallic switch contacts often develop higher contact
resistance over time owing to contact corrosion. The
corrosion is induced by humidity, salt, and other elements
that exist in the environment. For this reason the 33975
provides two settings for contacts. When programmed for
metallic switches, the device provides higher wetting current
to keep switch contacts free of oxides. The higher current
occurs for the first 20 ms of switch closure. Where longer
duration of wetting current is desired, the user may send the
wetting current timer command
and disable the timer. Wetting
current will be continuous to the closed switch. After the time
period set by the MCU, the
wetting current timer command
may be sent again to enable the timer. The user must
consider power dissipation on the device when disabling the
timer. (Refer to the paragraph entitled
Temperature Monitor
,
page
21
.)
To increase the amount of wetting current for a switch
contact, the user has two options. Higher wetting current to a
switch may be achieved by paralleling SGn or SPn inputs.
This will increase wetting current by 32 mA for each input
added to the switch-to- ground contact and 16 mA for switch-
to-battery contacts. The second option is to simply add an
external resistor pull-up to the V
PWR
supply for switch-to-
ground inputs or a resistor to ground for a switch-to-battery
input. Adding an external resistor has no effect on the
operation of the device.
Elastomeric switch contacts are made of carbon and have
a high contact resistance. Resistance of 1.0 k
is common.
In applications with elastomeric switches, the pull-up and
pull-down currents must be reduced to prevent excessive
power dissipation at the contact. Programming for a lower
current settings is provided in the
Functional Device
Operation
Section beginning on page
14
under
Table 8
,
Metallic Command.
ANALOG SENSOR INPUTS (RATIOMETRIC)
The 33975 features a 22-to-1 analog multiplexer. Setting
the binary code for a specific input in the
analog command
allows the microcontroller to perform analog to digital
conversion on any of the 22 inputs. On rising edge of
CS
the
multiplexer connects a requested input to the AMUX terminal.
The AMUX terminal is clamped to max of VDD volts
regardless of the higher voltages present on the input
terminal. After an input has been selected as the analog, the
corresponding bit in the next SO data stream will be logic [0].
The input terminal, when selected as analog, may be
configured as analog with high impedance, analog with
4.0 mA pull-up, or analog with 32 mA pull-up.
Figure 13
,
page
23
, shows how the 33975 may be used to provide a
ratiometric reading of variable resistive input.
VDD
VPWR
V
DD
SI
SO
INT
SCLK
CS
MOSI
SCLK
MISO
INT
VBAT
SP0
SP1
SP7
SG1
SG0
SG12
SG13
WAKE
33975
CS
MCU
32
mA
4.0
mA
V
PWR
V
PWR
32 mA
IOC[7:0]
Input Capture
Timer Port
X
Reg
Hall-Effect
Sensor
32
mA
4.0
mA
V
PWR
V
PWR
VBAT
AMUX
0V
V
PWR
SG13
0V
V
DD
AMUX
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| PC33975AEK | Multiple Switch Detection Interface with Suppressed Wake-Up and 32mA Wetting Current |
| PC33975AR2 | Multiple Switch Detection Interface with Suppressed Wake-Up and 32mA Wetting Current |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| PC33975AEK | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:Multiple Switch Detection Interface with Suppressed Wake-Up and 32mA Wetting Current |
| PC33975AR2 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:Multiple Switch Detection Interface with Suppressed Wake-Up and 32mA Wetting Current |
| PC33981PNA/R2 | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:High-Frequency, High-Current, Self-Protected High-Side Switch (4.0 mз up to 60 kHz) |
| PC33984CHFKR2 | 制造商:Freescale Semiconductor 功能描述: |
| PC33989DW | 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:System Basis Chip with High Speed CAN Transceiver |
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