參數(shù)資料
型號(hào)： 33991
廠商： Motorola, Inc.
英文描述： Gauge Driver Integrated Circuit
中文描述： 儀表驅(qū)動(dòng)集成電路
文件頁(yè)數(shù)： 27/36頁(yè)
文件大小： 660K
代理商： 33991
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33991
27
Return to Zero Calibration
Many stepper motor applications require the integrated
circuit (IC) detect when the motor is stalled after commanded to
return to the zero position for calibration purposes. Stalling
occurs when the pointer hits the end stop on the gauge bezel,
usually at the zero position. It is important when the pointer
reaches the end stop it immediately stops without
bouncing
away from the stop.
The 33991device provides the ability to automatically and
independently return each of the two pointers to the zero
position via the RTZR and RTZCR SPI commands. During an
RTZ event, all commands related to the gauge being returned
are ignored, exceptwhenthe RTZRbit D1isused todisable the
event, or when the RTZR bits D3 and D2 are changed in order
to look at different RTZ accumulator bits. Once an RTZ event is
initiated, the device will report back via the SO pin, indicating an
RTZ is underway.
The RTZCR command is used to set the RTZ pointer speed,
choose an appropriate blanking time and preload the
integration accumulator with an appropriate offset. Reaching
the end stop, the device reports the RTZ success to the
microcontroller via the SO pin. The RTZ automatically disables
allowing other commands to be valid. In the event the master
determines an RTZ sequence is not working properly, for
example the RTZ taking too long, it can disable the command
via the RTZR bit D1.
RTZCR bits D12:D5 are written to preload the accumulator
with a predetermined value assuring an accurate pointer stall
detection. This preloaded value is determined during
application development by disabling the automatic shutdown
feature of the device withthe RTZR bit D4. This operating mode
allows the master to monitor the RTZ event using the
accumulator information availablein theSO status bits D15:D8.
Once the optimal value is determined, the RTZ event can be
turned off using the RTZR bit D1.
During an RTZ event, the pointer is returned counter-clock-
wise (CCW) using full steps at a constant speed determined by
the RTZCR D3:D0 bits during RTZ configuration. See Figure 9.
Full steps are used because only one coil of the motor is being
driven at any time. The coil not being driven is used to
determine whether the pointer is moving. If the pointer is
moving, a back EMF signal can be processed and detected in
the non-driven coil. This is achieved by integrating the signal
present on an opened end of the non-driven coil while
grounding the opposite end.
The IC automatically prepares the non-driven coil at each
step, waits for a predetermined blanking time, then processes
the signal for the duration of the full step. When the pointer
reaches the stop and no longer moves, the dissipating back
EMF is detected. The processed results are placed in the RTZ
accumulator, then compared to a decision threshold. If the
signal exceeds the decision threshold, the pointer is assumed
to be moving. When the threshold value is not exceeded, the
drive sequence is stopped when RTZR bit D4 is logic [0]. If bit
D4 is logic [1], the RTZ movement will continue indefinitely until
the RTZR bit D1 is used to stop the RTZ event.
A pointer not on a full step location, or in magnetic alignment
prior to the RTZ event, may result in a false RTZ detection.
More specifically, an RTZ event beginning from a non-full step
position may result in an abbreviated integration, interpreted as
a stalled pointer. Similarly, if the magnetic fields of the
energized coils and the rotor are not aligned prior to initiating
the RTZ, the integration results may mistakenly indicate the
pointer has stopped moving.
Advancing the pointer by at least 24 microsteps clock-wise
(CW) to the nearest full step position, e.g., 24,30, 36, 42, 48
...prior to initiating an RTZ, ensures the magnetic fields are
aligned. Doing that increases the chances of a successful
pointer stall detection. It is important the pointer be in a static,
or commanded position before starting the RTZ event. Since
the time duration and the number of steps the pointer moves
prior to reaching the commanded position can vary depending
on its status at the time a position change is communicated, the
master should assure sufficient time has elapsed prior to
starting an RTZ. If an RTZ is desired after first enabling the
outputs, or after forcing a reset of the device, the pointer should
first be commanded to move 24 microstep steps clock-wise
(CW) to the nearest full step location. Because the pointer was
in a static position at default, the master could determine the
number of microsteps the device took by monitoring and
counting the ST4 (ST5) status bit transitions, confirming the
pointer is again in a static position.
Only one gauge at a time can be returned to the zero
position. An RTZ should not begin until the gauge to be
calibrated is at a static position and its pointer is at a full step
position. Anattempt to calibrate a gauge whilethe other isin the
process of an RTZ event, will be ignored by the device. In most
applications of the RTZR command, it is possible to avoid a
visually obvious sequential calibration by first bringing the
pointer back to the previous zero position and then re-
calibrating the pointers.
After completion of a RTZ, the 33991 automatically assigns
the zero step position to the full step position at the end stop
location. Because the actual zero position could lie anywhere
within the full step where the zero was detected, the assigned
zero position could be within a window of ±0.5
°
. An RTZ can be
used to detect stall, even if the pointer already rests on the end
stop when an RTZ sequence is initiated; however, it is
recommended the pointer should be advanced by at least 24
microsteps to the nearest full step prior to initiating the RTZ.
F
Freescale Semiconductor, Inc.
Go to: www.freescale.com
n
.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
33-991 制造商:Ideal Industries Inc 功能描述:LTKII,350MHZ,CAT6 W/CAT6 ADPT
3399-1 制造商:3M 功能描述:3399-1
33992 制造商:Ideal Industries Inc 功能描述:LTKII500MHZ,CAT6A W/CAT6A ADPT
33992510000001 功能描述:電纜組件 CABLE KIT RoHS:否 制造商:Molex 產(chǎn)品:Power Assemblies 類型:Cable Assembly 連接器端口 A:No Connector 連接器端口 A 管腳計(jì)數(shù):4 連接器端口 B:No Connector 連接器端口 B 管腳計(jì)數(shù): 型式:Male 線規(guī) - 美國(guó)線規(guī)（AWG）:20, 28 長(zhǎng)度:0.305 m 顏色:Black, Red
33993 制造商:Ideal Industries Inc 功能描述:LTKII1000MHZ,CAT7A W/CAT6AADPT
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