SLVSGI0C September 2022 – June 2024 DRV8411
PRODUCTION DATA
The DRV8411 has two identical H-bridge motor drivers. The input pins, AINx and BINx, control the corresponding outputs, AOUTx and BOUTx, respectively. Table 8-4 shows how the inputs control the H-bridge outputs.
nSLEEP | xIN1 | xIN2 | xOUT1 | xOUT2 | DESCRIPTION |
---|---|---|---|---|---|
0 | X | X | High-Z | High-Z | Low-power sleep mode |
1 | 0 | 0 | High-Z | High-Z | Coast/ fast decay; H-bridge disabled to High-Z |
1 | 0 | 1 | L | H | Reverse (Current OUT2 → OUT1) |
1 | 1 | 0 | H | L | Forward (Current OUT1 → OUT2) |
1 | 1 | 1 | L | L | Brake; low-side slow decay |
The inputs can be set to constant voltages for 100% duty cycle drive, or they can be pulse-width modulated (PWM) for variable motor speed. When using PWM, switching between driving (forward or reverse) and slow-decay states typically works best. For example, to drive a motor forward with 50% of the maximum RPM, IN1 = 1 and IN2 = 0 during the driving period or PWM "on" time, and IN1 = 1 and IN2 = 1 during the PWM "off" time.
Alternatively, the coast mode (IN1 = 0, IN2 = 0) for fast current decay is also available. To PWM using fast decay, the PWM signal is applied to one xIN pin while the other is held low, as shown below.
xIN1 | xIN2 | DESCRIPTION |
---|---|---|
PWM | 0 | Forward PWM, fast decay |
1 | PWM | Forward PWM, slow decay |
0 | PWM | Reverse PWM, fast decay |
PWM | 1 | Reverse PWM, slow decay |
Figure 8-1 shows how the motor current flows through the H-bridge. The input pins can be powered before VM is applied.
When an output changes from driving high to driving low, or driving low to driving high, dead time is automatically inserted to prevent shoot-through. The tDEAD time is the time in the middle when the output is High-Z. If the output pin is measured during tDEAD, the voltage depends on the direction of current. If the current is leaving the pin, the voltage is a diode drop below ground. If the current is entering the pin, the voltage is a diode drop above VM. This diode is the body diode of the high-side or low-side FET.
The propagation delay time (tPD) is measured as the time between an input edge to output change. This time accounts for input deglitch time and other internal logic propagation delays. The input deglitch time prevents noise on the input pins from affecting the output state. Additional output slew delay timing accounts for FET turn on or turn off times (tRISE and tFALL).
Figure 8-2 below shows the timing of the inputs and outputs of the motor driver.