TWR-MC-LV3PH Freescale Semiconductor, TWR-MC-LV3PH Datasheet - Page 7

• Manufacturer Part Number: TWR-MC-LV3PH
• Description: Power Management IC Development Tools Low-volt 3-phase MC
• Manufacturer: Freescale Semiconductor
• Type: Motor / Motion Controllers & Driversr

Specifications of TWR-MC-LV3PH

• Rohs: yes
• Product: Tower Systems
• Tool Is For Evaluation Of: MC33937A
• Input Voltage: 12 V to 24 V
• Output Voltage: 3.3 V, 5 V
• Description/function: Part of the Tower Systems
• Dimensions: 3.54 in x 3.18 in
• Interface Type: SPI
• Output Current: 8 A

The under voltage function is implemented internally. The supply voltage is also sensed internally. If this voltage is lower
than 8V, the hold off circuit is evaluated and an interrupt is generated if set. The MC33927 safety functions keep the driver
operating properly and within safe limits. Current limiting by itself, however, does not necessarily ensure that a board is
operating within safe thermal limits. The MC33927 has a thermal warning feature. If the temperature rises above 170°C on
one of the three detectors, then an interrupt is generated if set.
The MC33927 driver has also other safety features such as desaturation detection, phase error, framing error, write error after
the lock, and exiting RST. All these features can be configured through SPI to trigger interrupts. Detailed information is
available in the driver datasheet.
3.8 Back EMF Signals
Back EMF signals are included to support sensorless algorithms for brushless DC motors and dead time distortion correction
for sinusoidal motors. The raw phase voltage is scaled down by a voltage divider consisting of R47 and R48 (phase A).
Output from this divider produces back EMF sense voltage BEMF_SENSE_A. Resistor values are chosen such that a 36.3 V
of phase voltage corresponds to a 3.3 V AD input. BEMF_SENSE_A is terminated to the elevator main port.
3.9 Phase Current Sensing
Sampling resistors provide phase current information for all three phases. Because these resistors sample current in the lower
phase legs, they do not directly measure phase current. However, given phase voltages for all three phases, phase current can
be constructed mathematically from the lower phase leg values. This information can be used in vector-control algorithms for
AC induction motors. Referencing the sampling resistors to the negative motor rail makes the measurement circuitry
straightforward and inexpensive. Current is sampled by resistor R7 (phase A) and amplified by the differential amplifier
U5A. This circuit provides a voltage output suitable for sampling on AD inputs. An AD8656 is used as a differential
amplifier. When R38 = R41 and R39 = R42 and R40 = R46, the gain is given by:
The input voltage is shifted up by +1.65V_REF to accommodate both positive and negative current swings. A ±400-mV
voltage drop across the shunt resistor corresponds to a measured current range of ±8 A. As a source for +1.65V_REF, a
Precision Shunt Voltage Reference LM4041 is used.
3.10 LED Indication
This module also contains eight LED indicators.
Freescale Semiconductor, Inc.
LED
D14
D16
D18
D15
D17
D19
D5
D7
User LED diode for user-defined purposes
Indicates that the +5V level is properly generated
PWM_AT indication LED
PWM_AB indication LED
PWM_BT indication LED
PWM_BB indication LED
PWM_CT indication LED
PWM_CB indication LED
TWR-MC-LV3PH User’s Guide, Rev. 1, 07/2012
Table 2. LED indicators
Description
high level
low level
high level
low level
high level
low level
high level
Activated On
Hardware Features
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