8.3.3.1 Overcurrent Protection (OCP)

When output current exceeds OCP trigger level, corresponding channel will be automatically turned off. nFault pin will be set low and corresponding OCP flag in fault register will be set to 1.

Over current faults are automatically cleared whenever the corresponding output is turned off by setting the Data register bit to ‘0’. Alternatively, a Fault Reset special command will also clear this value. In either case, once all bits in the Fault register are clear, nFAULT is released.

8.3.3.2 Open Load Detection (OL)

When any output is in off status (the corresponding Data Register bit is set to ‘0’), a current sink pulls the node down with approximately 30 µA. If the voltage on the pin is sensed to be less than 1.2 V, then an open load condition is reported. nFAULT is driven low and the OL bit of the fault register (F8:F1) corresponding to the specific channel is set.

Open load faults are automatically cleared whenever the corresponding output is turned on by setting the Data register bit to ‘1’. Alternatively, a Fault Reset special command will also clear this value. In either case, once all bits in the Fault register are clear, nFAULT is released.

8.3.3.3 Thermal Shutdown (TSD)

If the die temperature exceeds safe limits, all outputs 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. The nFAULT pin will be released after operation has resumed.

8.3.3.4 Undervoltage Lockout (UVLO)

If at any time the voltage on the VM pin 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 VM rises above the UVLO threshold. nFAULT will not be asserted in this condition.

8.3.3.5 Digital Noise Filter

The DRV8860 features an internal noise filter on all digital inputs. In a noisy system, noise may disturb the serial daisy-chain interface. Without an input filter, this noise may result in an unexpected behavior or output state. The digital input filter is capable of removing unwanted noise frequencies while allowing fast communication over the serial interface.

8.5.1.1 Data Writing Waveform

Figure 9. Writing Data Register – Single Device

Figure 10. Writing Data Register – Daisy Chan

Figure 11. Writing Data Register – Data Flow

8.5.1.2 Fault Register Reading Waveform

Figure 12. Reading Fault Register – Single Device

Figure 13. Reading Fault Register – Daisy Chain

Figure 14. Reading Fault Register – Data Flow

8.5.1.3 Special Command

Besides output ON/OFF control and fault status reading back, DRV8860 has special functions to make system more robust or power efficient. These functions will need special command to initiate the device or configure the internal registers.

There are 5 Special Commands:

1. Write Control Register command
2. Read Control Register command
3. Read Data Register command
4. Fault Register Reset command
5. PWM Start command

Special wave form pattern on CLK and LATCH pin will issue the special command, as below

Figure 15. Special Command

8.5.1.3.1 Special command: Write Control Register

When Write-Control-Register command is issued, the following serial data will be latched into timing and duty control register.

Figure 16. Writing Control Register – Single Device

Figure 17. Writing Control Register – Daisy Chain

Figure 18. Writing Control Register – Data Flow

8.5.1.3.2 Special command: Read Control Register

When Read-Control-Register command is issued, control register content will be copied to internal shift register and following CLK will shift this content out from DOUT pin. This provides a mechanism for system to verify the control register is correctly programmed.

Figure 19. Read Control Register – Single Device

Figure 20. Read Control Register – Daisy Chain

Figure 21. Read Control Register – Data Flow

8.5.1.3.3 Special command: Read Data Register

When Read-Data-Register command is issued, internal output data register content will be copied to internal shift register and following CLK will shift this content out from DOUT pin. This provides a mechanism for system to verify the output data is correctly programmed. It makes system more robust in noisy system.

Figure 22. Reading Data Register – Single Device

Figure 23. Reading Data Register – Daisy Chain

Figure 24. Reading Data Register – Data Flow

8.5.1.3.4 Special command: Fault Register Reset

When Fault-Register-Reset command is issued, internal 16bit fault register will be cleared. System can use this method to clear out all fault condition in every chained device at once.

Figure 25. Fault Register Reset

8.5.1.3.5 Special command: PWM Start

When Fault-Register-Reset command is issued, output channel will ignore energizing time and directly enter into PWM mode following the setting in control register.

Figure 26. PWM Start Command

8.5.1.4 Output Energizing and PWM Control

The device output is defined by two stages: Energizing Phase and PWM Phase.

During the Energizing phase, the channel is turned on with 100% duty cycle for a duration set by Control register bits C4:C1.

In PWM chopping phase, with the PWM Duty Cycle defined by Control register bits C7:C5.

The behavior of each bit in the Control Register is described in Table 2.

There are five operation cases as described in Figure 27 through Figure 31.

The output is turned on with 100% duty cycle.

Figure 27. Case 1: Timer Enable Bit (C8) is 0 (Default Value)

The output is turned on in PWM chopping mode with duty cycle defined by Control register bits C7:C5.

Figure 28. Case 2: Timer Enable Bit (C8) is 1 and Energizing Timing Bits (C4:C1) are 0000

The output is turned on in Energizing mode with 100% duty cycle for a duration set by Control register bits C4:C1. After the timer expires, the output switches to PWM chopping mode with PWM Duty Cycle defined by Control register bits C7:C5.

Figure 29. Case 3: Timer Enable Bit (C8) is 1, Energizing Timing Bits (C4:C1) are NOT 0000, and PWM Duty Bits (C7:C5) are NOT 000

The output is turned on in Energizing mode with 100% duty cycle for a duration set by Control register bits C4:C1. After the timer expires, the output is turned off.

Figure 30. Case 4: Timer Enable Bit (C8) is 1, Energizing Timing Bits (C4:C1) are NOT 0000, and PWM Duty Bits (C7:C5) are 00

8.5.1.4.1 PWM Start Special Command Used

The output is turned on in Energizing mode with 100% duty cycle, and a timer is enabled with duration set by Control register bits C4:C1. If the PWM Start special command is received before the timer expires, then the output switches to PWM chopping mode with PWM Duty Cycle defined by Control register bits C7:C5. If the timer expires and no PWM Start is received, then the device will stay in Energizing mode regardless of other PWM Start commands.

Figure 31. Case 5: Timer Enable Bit (C8) is 0, Energizing Timing Bits (C4:C1) are NOT 0000, and PWM Duty Bits (C7:C5) are NOT 000