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| 型号： | MC33794DWB |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 3/18页 |
| 文件大小： | 0K |
| 描述： | IC SENSOR ELECTRIC FIELD 54-SOIC |
| 标准包装： | 26 |
| 类型： | 传感器接口 |
| 输入类型： | 逻辑 |
| 输出类型： | 逻辑 |
| 接口： | ISO9141 |
| 电流 - 电源： | 7mA |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 54-BSSOP（0.295"，7.50mm 宽）裸露焊盘 |
| 供应商设备封装： | 54-SOIC W EP |
| 包装： | 管件 |
Sensors
Freescale Semiconductor
11
MC33794
FUNCTIONAL DESCRIPTION
INTRODUCTION
The MC33794 is intended for use in detecting objects
using an electric field. The IC generates a low radio
frequency sine wave. The frequency is set by an external
resistor and is optimized for 120 kHz. The sine wave has very
low harmonic content to reduce potential interference at
higher harmonically related frequencies. The internal
generator produces a nominal 5.0 V peak-to-peak output that
is passed through an internal resistor of about 22 k. An
internal multiplexer routes the signal to one of 11 terminals
under control of the ABCD input terminals. A receiver
multiplexer simultaneously connected to the selected
electrode routes its signal to a detector, which converts the
sine wave to a DC level. This DC level is filtered by an
external capacitor and is multiplied and offset to increase
sensitivity. All of the unselected electrode outputs are
grounded by the device. The current flowing between the
selected electrode and the other grounded electrodes plus
other grounded objects around the electrode causes a
voltage drop across the internal resistance. Objects brought
into or out of the electric field change the current and resulting
voltage at the IC terminal, which in turn reduces the voltage
at LP_CAP and LEVEL.
A shield driver is included to minimize the effect of
capacitance caused by using coaxial cables to connect to
remote electrodes. By driving the coax shield with this signal,
the shield voltage follows that of the center conductor,
significantly reducing the effective capacitance of the coax
and maintaining sensitivity to the capacitance at the
electrode.
The MC33794 is made to work with and support a
microcontroller. It provides two voltage regulators, a Power-
ON-reset/out-of-range voltage detector, watchdog circuit,
lamp driver and sense circuit, and a physical layer ISO-9141
communications interface.
BLOCK DIAGRAM COMPONENTS
Refer to Figure 1, MC33794 Internal Block Diagram,
page 2, for a graphic representation of the block diagram
information in this section.
OSC
This section generates a high purity sine wave. The center
frequency is controlled by a resistor attached to R_OSC. The
normal operating frequency is around 120 kHz. A square
wave version of the frequency output is available at CLK.
Timing for the Power-ON Reset and watchdog (POR/WD)
circuit are derived from this oscillator’s frequency.
MUX OUT
This circuit directs the output of the sine wave to one of
nine possible electrode outputs or two reference terminals.
All unused terminals are automatically grounded (except the
two reference terminals). The selected output is controlled by
the ABCD inputs.
ELECTRODES E1-E9
These are the electrode terminals. They are connected
either directly or through coaxial cables to the electrodes for
measurements. Every electrode has a 2.8K (± 20%) resistor
in series with the external pad and the internal electronics.
Only one of these electrodes can be selected at a time for
capacitance measurement. All of the other unselected
electrodes are switched to ground by an internal switch that
has an internal on-resistance of approximately 700 . The
signal at the selected electrode terminal is routed to the
shield driver amplifier by an internal switch. All of the coaxial
cable shields should be isolated from ground and connected
SHIELD.
REF_A & REF_B ELECTRODES
These terminals can be individually selected like E1
through E9. Unlike E1 through E9, these terminals are not
grounded when not selected. Both terminals have a 2.8K
(± 20%) resistor in series with the external pad and the
internal electronics. The purpose of these terminals is to
allow known capacitors to be measured. By using capacitors
at the low and high end of the expected range, absolute
values for the capacitance on the electrodes can be
computed. These terminals can be used for electrodes E10
and E11 with the only difference is that these two electrodes
will not be grounded when not selected.
SHIELD DRIVE
This circuit provides a buffered version of the returned AC
signal from the electrode. Since it nearly has the same
amplitude and phase as the electrode signal, there is little or
no potential difference between the two signals thereby
cancelling out any electric field. In effect, the shield drives
and isolates the electrode signal from external virtual
grounds. A common application is to connect the Shield Drive
to the shield of a coax cable used to connect an electrode to
the corresponding electrode terminal. Another typical use is
to drive a ground plane that is used behind an array of touch
sensor electrodes in order to cancel out any virtual grounds
that could attenuate the AC signal.
MUX IN
This circuit connects the selected electrode, reference, or
one of two internal nodes to an amplifier/detector. The
selection is controlled by the ABCD inputs and follows the
driven electrode/reference when one is selected.
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相关代理商/技术参数 |
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|---|---|
| MC33794DWBR2 | 功能描述:IC SENSOR ELECTRIC FIELD 54-SOIC RoHS:否 类别:集成电路 (IC) >> 接口 - 传感器和探测器接口 系列:- 其它有关文件:Automotive Product Guide 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:74 系列:- 类型:触控式传感器 输入类型:数字 输出类型:数字 接口:JTAG，串行 电流 - 电源:100µA 安装类型:表面贴装 封装/外壳:20-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:20-TSSOP 包装:管件 |
| 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 |
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