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参数资料
| 型号： | MC33794DWB/R2 |
| 厂商： | MOTOROLA INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | Electric Field Imaging Device |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO54 |
| 封装： | PLASTIC, SOICW-54 |
| 文件页数： | 8/23页 |
| 文件大小： | 574K |
| 代理商： | MC33794DWB/R2 |
33794
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
16
ISO-9141
This circuit connects to an ISO-9141 bus to allow remote
communications. ISO_IN is data from the bus to the MCU and
ISO_OUT is data to drive onto the bus from the MCU.
POR/WD
This circuit is a combined power-on reset and watchdog
timer. The RST output is held low until a certain amount of time
after the VCC output has remained above a minimum operating
threshold. If VCC falls below the level at any time, RST is pulled
low again and held until the required time after VCC has returned
high. An overvoltage circuit is also included, which will force a
reset if VCC rises above a maximum voltage. The watchdog
function also can force RST low if too long an interval is allowed
to pass between positive transitions on WD_IN.
VCC REG
This circuit converts an unregulated voltage from VIN to a
regulated 5.0 V source, which is used internally and available
for other components requiring a regulated voltage source.
VDD REG
This is a regulator for analog devices that require more than
5.0 V. This is used by the device and some current is available
to operate op-amps and other devices. By having this higher
voltage available, some applications can avoid the need for a
rail-to-rail output amplifier and still achieve the 0 V-to-5.0 V
output for a digital-to-analog converter input. VDDMON is a
divided output from VDD, which allows a 0 V-to-5.0 V ADC to
measure VDD.
CONTROL LOGIC
This contains the logic that decodes and controls the MUXes
and some of the test modes.
APPLICATION INFORMATION
The 33794 is intended to be used where an object’s size and
proximity are to be determined. This is done by placing
electrodes in the area where the object will be. The proximity of
an object to an electrode can be determined by the increase in
effective capacitance as the object gets closer to the electrode
and modifies the electric field between the electrode and
surrounding electrically common objects. The shape and size of
an object can be determined by using multiple electrodes over
an area and observing the capacitance change on each of the
electrodes. Those that don’t change have nothing near them,
and those that do change have part of the object near them.
The voltage measured is an inverse function of the
capacitance between the electrode being measured and the
surrounding electrodes and other objects in the electric field
surrounding the electrode. Increasing capacitance results in
decreasing voltage. The value of series resistance (22 k) was
chosen to provide a nearly linear relationship at 120 kHz over a
range of 10 pF to 100 pF.
The measured value will change with any change in
frequency, series resistance, driving voltage, or detector
sensitivity. These can change with temperature and time. The
proper use of REF_A and REF_B will allow much of the
changes to be compensated for.
A typical measurement algorithm would start by measuring
the voltage for two known value capacitors (attached to REF_A
and REF_B). The value of these capacitors would be chosen to
be near the minimum and maximum values of capacitance
expected to be seen at the electrodes. These reference
voltages and the known capacitance values are then used with
the electrode measurement voltage to determine the
capacitance seen by the electrode. This method can be used to
detect short- and long-term changes due to objects in the
electric field and significantly reduce the effect of temperature-
and time-induced changes.
The 33794 does not contain an ADC. It is intended to be
used with an MCU that contains one. Offset and gain have been
added to the 33794 to maximize the sensitivity over the range
of 0 pF to 100 pF. An 8-bit ADC can resolve around 0.4 pF of
change and a 10-bit converter around 0.1 pF. Higher resolution
results in more distant detection of smaller objects.
DC loading on the electrodes should be avoided. The signal
is generated with a DC offset that is more than half the peak-to-
peak level. This keeps the signal positive above ground at all
times. The detector uses this voltage level as the midpoint for
detection. All signals below this level are inverted and added to
all signals above this level. Loading of the DC level will cause
some of the positive half of the signal to be inverted and added
and will change the measurement.
If it is not possible to assure that the electrodes will always
have a high DC resistance to ground or a voltage source, a
series capacitor of about 10 nF should be connected between
the IC electrode pins and the electrodes.
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相关代理商/技术参数 |
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| MC33794EK | 功能描述:近程传感器 ODS 54LD RoHS:否 制造商:Vishay Semiconductors 感应方式:Optical 感应距离:1 mm to 200 mm 电源电压:2.5 V to 3.6 V 安装风格:SMD/SMT 输出配置:Digital 最大工作温度:+ 85 C 最小工作温度:- 25 C 系列:VCNL3020 |
| MC33794EKR2 | 功能描述:近程传感器 ODS 54LD RoHS:否 制造商:Vishay Semiconductors 感应方式:Optical 感应距离:1 mm to 200 mm 电源电压:2.5 V to 3.6 V 安装风格:SMD/SMT 输出配置:Digital 最大工作温度:+ 85 C 最小工作温度:- 25 C 系列:VCNL3020 |
| MC33797BPEW | 功能描述:功率驱动器IC Four Channel Squib Dr RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube |
| MC33797BPEWR2 | 功能描述:功率驱动器IC Four Channel Squib Dr RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube |
| MC33813AE | 功能描述:功率驱动器IC 1 CYL SM ENG CONTROL IC RoHS:否 制造商:Micrel 产品:MOSFET Gate Drivers 类型:Low Cost High or Low Side MOSFET Driver 上升时间: 下降时间: 电源电压-最大:30 V 电源电压-最小:2.75 V 电源电流: 最大功率耗散: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Tube |
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