SLOSE71 April 2020 – December 2020 DRV8955
PRODUCTION DATA
The MODE pin configures the half-bridges such that one, two or four solenoid loads can be driven by the device. Higher load currents can be supported by paralleling half-bridges. Table 7-2 shows the four possible settings -
MODE | Number of Half-bridges | Independent High-z Control | RdsON (HS + LS) | Maximum ITRIP | Input Control Pins | Current Control |
---|---|---|---|---|---|---|
0 | Four | No | 330 mΩ | 2.5 A | IN1, IN2, IN3, IN4 | VREF12 controls the ITRIP for OUT1 and OUT2, VREF34 controls the ITRIP for OUT3 and OUT4. |
1 | Two (Connect OUT1 and OUT2 together, and OUT3 and OUT4 together) | No | 160 mΩ | 5 A | IN2 controls OUT1 and OUT2, IN4 controls OUT3 and OUT4 | VREF12 controls the ITRIP for OUT1 and OUT2, VREF34 controls the ITRIP for OUT3 and OUT4. |
Hi-z | One (connect all four OUT pins together) | No | 80 mΩ | 10 A | IN4 controls the combined output | VREF12 must be shorted to VREF34 to control the ITRIP for output load. |
330kΩ to GND |
Four (independent High-z) | Yes | 330 mΩ | No ITRIP control available. | IN1, IN2, IN3, IN4, EN1, EN2, EN3, EN4 |
The current for each output has to be controlled by the input PWM pulse width. The VREF and TOFF pins are reassigned as enable (ENx) pins in this mode. |
The INx input pins directly control the state (high or low) of the OUTx outputs. When MODE pin is connected to a 330k resistor to GND, the ENx input pins enable or disable the OUTx drivers, as shown below.
nSLEEP | INx | OUTx | DESCRIPTION |
---|---|---|---|
0 | X | Hi-Z | Sleep mode; Half-bridge disabled (Hi-Z) |
1 | 0 | L | OUTx Low-side ON |
1 | 1 | H | OUTx High-side ON |
nSLEEP | INx |
ENx | OUTx | DESCRIPTION |
---|---|---|---|---|
0 | X |
X | Hi-Z | Sleep mode; Half-bridge disabled (Hi-Z) |
1 |
X |
0 |
Hi-Z |
Individual outputs disabled (Hi-Z) |
1 | 0 |
1 | L | OUTx Low-side ON |
1 | 1 |
1 | H | OUTx High-side ON |
When MODE pin is connected to a 330k resistor to GND, the inputs can also be used for PWM control of, for example, the speed of a DC motor. When controlling a winding with PWM, when the drive current is interrupted, the inductive nature of the motor requires that the current must continue to flow. This is called recirculation current. To handle this recirculation current, the H-bridge can operate in two different states, fast decay or slow decay. In fast decay mode, the H-bridge is disabled and recirculation current flows through the body diodes; in slow decay, the motor winding is shorted.
To PWM using fast decay, the PWM signal is applied to the ENx pin; to use slow decay, the PWM signal is applied to the INx pin. The following table is an example of driving a DC motor using OUT1 and OUT2 as an H-bridge:
IN1 | EN1 |
IN2 | EN2 |
FUNCTION |
---|---|---|---|---|
PWM |
1 |
0 |
1 |
Forward PWM, slow decay |
0 |
1 |
PWM |
1 | Reverse PWM, slow decay |
1 |
PWM |
0 |
PWM | Forward PWM, fast decay |
0 |
PWM |
1 |
PWM | Reverse PWM, fast decay |