MCZ33991EG Freescale, MCZ33991EG Datasheet - Page 25

• Manufacturer Part Number: MCZ33991EG
• Manufacturer: Freescale

Specifications of MCZ33991EG

• Operating Current: 6mA
• Operating Temperature Classification: Automotive
• Package Type: SOIC W
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Compliant

with a longer time reference. For example, for the
120:1motor, the pulse would be 12 µs instead
longer step times necessary to generate pointer movements
meeting acceleration and velocity requirements. The
resolution of the pointer positioning decreases from 0.083°/
microstep (180:1) to 0.125°/microstep (120:1). The pointer
sweep range increases from approximately 340° to over
500°.
of the motor acceleration and velocity maximums, resulting in
missed steps.
RETURN TO ZERO CALIBRATION
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.
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 that is being
returned are ignored, except when the RTZR bit D1 is used
to disable 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 reports back via
the SO pin, indicating an RTZ is underway.
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 micro
controller 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.
with a predetermined value assuring an accurate pointer stall
Analog Integrated Circuit Device Data
Freescale Semiconductor
of 8 µs. The result of this slower calibration will result in the
Note: Be aware a fast calibration could result in violations
Many stepper motor applications require the integrated
The 33991 device provides the ability to automatically, and
The RTZCR command is used to set the RTZ pointer
RTZCR bits D12:D5 are written to preload the accumulator
VELOCITY
n =
0
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Figure 9. Deceleration Waveshaping
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POINTER DECELERATION WAVESHAPING
results in choppy movements when compared to air core
movements. Air core behavior can be simulated with
appropriate wave- shaping during deceleration only. This
shaping can be accomplished by adding repetitive steps at
several of the last step values. An example is illustrated in
Figure 8.
detection. This preloaded value is determined during
application development by disabling the automatic
shutdown feature of the device with the RTZR bit D4. This
operating mode allows the master to monitor the RTZ event,
using the accumulator information available in the SO status
bits D15: D8. Once the optimal value is determined, the RTZ
event can be turned OFF using the RTZR bit D1.
clockwise (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.
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 if RTZR bit
D4 is logic [0]. If bit D4 is logic [1], the RTZ movement will
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HOLDCNT =
Constant acceleration and deceleration of the pointer
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During an RTZ event, the pointer is returned counter-
The IC automatically prepares the non-driven coil at each
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STEPS
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TIMING DESCRIPTIONS AND DIAGRAMS
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DEVICE FUNCTIONAL DESCRIPTION
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33991
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