DRV8307_15 Datasheet, PDF (11/34 Pages) Texas Instruments – DRV8307 Brushless DC Motor Controller

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Feature Description (continued)
Hall
Differential
Voltage
0V
DRV8307
SLVSCK2 – APRIL 2014
V_HYS
Hall Amplifier
Output
(Internal)
Figure 3. Hall Amplifier Hysteresis
In addition to hysteresis, the Hall inputs are deglitched with a circuit that ignores any extra Hall transitions for a
period of 20 μs after sensing a valid transition. This prevents PWM noise from being coupled into the Hall inputs,
which can result in erroneous commutation.
If excessive noise is still coupled into the Hall comparator inputs, it may be necessary to add capacitors between
the + and – inputs of the Hall comparators, and (or) between the input or inputs and ground.
The ESD protection circuitry on the Hall inputs implements a diode to VREG. Because of this diode, the voltage
on the Hall inputs should not exceed the VREG voltage.
Since VREG is disabled in standby mode (ENABLEn inactive), the Hall inputs should not be driven by external
voltages in standby mode. The DRV8307 device specifies if the Hall sensors are powered from VREG or VSW;
however, if the Hall sensors are powered externally, they should be disabled when the DRV8307 is put into
standby mode. In addition, the Hall sensors should be powered-up before enabling the motor, or an invalid Hall
state may cause a delay in motor operation.
8.3.2 HALLOUT Output
The HALLOUT terminal indicates the speed of the motor. It follows the transitions observed from the HALL U hall
sensor. Figure 4 shows the HALLOUT signal.
HALL_U
HALL_V
HALL_W
HALLOUT
Figure 4. HALLOUT Relationship to Hall Transitions
8.3.3 Enable, Reset, and Clock Generation
The ENABLEn terminal is used to start and stop motor operation. The ENABLEn terminal is active low.
When ENABLEn is active, operation of the motor is enabled. When ENABLEn is made inactive, the motor
coasts. After motor rotation has stopped (when no transitions occur on the HALLOUT terminal for a period of 1
s), the DRV8307 device enters a low-power standby state.
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