DRV8829_15 Datasheet, PDF (10/27 Pages) Texas Instruments – DRV8829 5-A 45-V Single H-Bridge Motor Driver

DRV8829
SLVSA74E – MAY 2010 – REVISED SEPTEMBER 2015
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Feature Description (continued)
7.3.4.2 Thermal Shutdown (TSD)
If the die temperature exceeds safe limits, all FETs in the H-bridge will be disabled and the nFAULT pin will be
driven low. Once the die temperature has fallen to a safe level operation will automatically resume.
7.3.4.3 Undervoltage Lockout (UVLO)
If at any time the voltage on the VM pins falls below the undervoltage lockout threshold voltage, all circuitry in the
device will be disabled and internal logic will be reset. Operation will resume when V_M rises above the UVLO
threshold.
7.3.5 Current Regulation
The current through the motor winding is regulated by a fixed-frequency PWM current regulation, or current
chopping. When the H-bridge is enabled, current rises through the winding at a rate dependent on the DC
voltage and inductance of the winding. Once the current hits the current chopping threshold, the bridge disables
the current until the beginning of the next PWM cycle.
For stepping motors, current regulation is normally used at all times, and can changing the current can be used
to microstep the motor. For DC motors, current regulation is used to limit the start-up and stall current of the
motor.
If the current regulation feature is not needed, it can be disabled by connecting the ISENSE pins directly to
ground and the VREF pins to V3P3.
The PWM chopping current in each bridge is set by a comparator which compares the voltage across a current
sense resistor connected to the ISEN pin, multiplied by a factor of 5, with a reference voltage. The reference
voltage is input from the xVREF pins, and is scaled by a 5-bit DAC that allows current settings of zero to 100% in
an approximately sinusoidal sequence.
The full-scale (100%) chopping current is calculated in Equation 1.
V
I = ₅^¾ _{R CHOP}
REFX
· _ISENSE
(1)
Example:
If a 0.25-Ω sense resistor is used and the VREFx pin is 2.5 V, the full-scale (100%) chopping current will be
2.5 V / (5 × 0.25 Ω) = 2 A.
Five input pins (I0 - I4) are used to scale the current in the bridge as a percentage of the full-scale current set by
the VREF input pin and sense resistance. The I0 - I4 pins have internal pulldown resistors of approximately 100
kΩ. The function of the pins is shown in Table 1.
Table 1. Current Scalar Logic
I[4..0]
0x00h
0x01h
0x02h
0x03h
0x04h
0x05h
0x06h
0x07h
0x08h
0x09h
0x0Ah
0x0Bh
0x0Ch
RELATIVE CURRENT
(% FULL-SCALE CHOPPING CURRENT)
0% (Bridge disabled)
5%
10%
15%
20%
24%
29%
34%
38%
43%
47%
51%
56%
10
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