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| 型號(hào)： | MC33972DWB |
| 廠商： | MOTOROLA INC |
| 元件分類： | 其它接口 |
| 英文描述： | Multiple Switch Detection Interface with Suppressed Wake-Up |
| 中文描述： | SPECIALTY INTERFACE CIRCUIT, PDSO32 |
| 封裝： | PLASTIC, SOIC-32 |
| 文件頁數(shù)： | 20/28頁 |
| 文件大?。?/td> | 506K |
| 代理商： | MC33972DWB |
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33972
20
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
APPLICATIONS
Introduction
The 33972’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 33972 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 10
shows how the 33972 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 10. 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 33972 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 19.)
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 16 mA for each input added to
the switch contact. The second option is to simply add an
external resistor pullup 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 pullup and pulldown
currents must be reduced to prevent excessive power
dissipation at the contact. Programming for a lower current
settings is provided in the
Device Operation
Section beginning
on page 12 under
Table 3
, Metallic Command.
Analog Sensor Inputs (Ratiometric)
The 33972 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 V
DD
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 2.0 mA
pullup, or analog with 16 mA pullup.
Figure 11
, page 21, shows
how the 33972 may be used to provide a ratiometric reading of
variable resistive input.
V
DD
V
PWR
V
DD
SI
SO
INT
SCLK
CS
MOSI
SCLK
CS
MISO
INT
VBAT
SP0
SP1
SP7
SG1
SG0
SG12
SG13
WAKE
33972
MCU
16
mA
2.0
mA
V
PWR
V
PWR
16 mA
IOC[7:0]
Input Capture
Timer Port
X
Reg
Hall-Effect
Sensor
2.5 k
16
mA
2.0
mA
V
PWR
V
PWR
2.5 k
VBAT
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
.
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| MC33972EWR2 | 功能描述:多路器開關(guān) IC MSDISW RoHS:否 制造商:Texas Instruments 通道數(shù)量:1 開關(guān)數(shù)量:4 開啟電阻（最大值）:7 Ohms 開啟時(shí)間（最大值）: 關(guān)閉時(shí)間（最大值）: 傳播延遲時(shí)間:0.25 ns 工作電源電壓:2.3 V to 3.6 V 工作電源電流: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UQFN-16 |
| MC33972TEW | 功能描述:接口 - 專用 MULTI-SW DETECT W/SUPRES RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59 |
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