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ZHCSJB5B September 2019 – December 2019 DRV8904-Q1 , DRV8906-Q1 , DRV8908-Q1 , DRV8910-Q1 , DRV8912-Q1

UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.

封裝選項

機械數據 (封裝 | 引腳)

PWP|24
- MPDS372A

散熱焊盤機械數據 (封裝 | 引腳)

PWP|24
- PPTD407

訂購信息

8.3.3.5.2 Low-current OLD

Low-current open-load detection is another type of active open-load detection in the DRV89XX-Q1 devices. In low-current open-load detection, the current detection threshold is around 10x lower than the active open-load detection scheme. This feature gives the user flexibility to detect a valid open-load condition when driving loads that require low current.

As shown in Figure 58, if the low-side MOSFET is in operating condition (switched-ON) and the current flowing in the particular MOSFET is lower than the low-current active open-load current threshold (I_{OLD_LOW}) for at least open-load detection deglitch time (t_OLD), then an open-load condition is detected. The OLD bit in the IC status (IC_STAT) register is set, the HBX_LS_OLD bit in the open-load status register (OLD_STAT_X) is set and nFAULT pin is driven low during an open-load detect. Normal operation resumes (driver operation and the nFAULT pin is released) when the open-load condition is removed and CLR_FLT command is issued. The OLD bit remains set until cleared through the CLR_FLT bit.

DRV8904-Q1 DRV8906-Q1 DRV8908-Q1 DRV8910-Q1 DRV8912-Q1 drv89xx-LCOLD.gif

Figure 58. Low-Current OLD

NOTE

The low-current OLD has following limitations

This feature is only applicable for the current flowing in low-side FET.
Once this mode is enabled the corresponding over-current threshold for the low-side FET is also reduced by 11 times (~120 mA min.).
The R_DS(on) of the low side FET will increase by 11 times (~7.5 Ω typical), hence the thermal performance has to be monitored. However, for the lower current the thermal dissipation is limited.

Figure 59 shows the flowchart for implementing the low-current active OLD in continuous mode of operation. Following are the steps to configure and detect the low-current active OLD in the DRV89XX-Q1 device.

Enable OLD by setting the OLD_OP bit in OLD_CTRL_2 register. This setting will ensure that the OUTX outputs continue to operate when and OLD fault occurs.
Enable the full-bridge operation by setting the individual HBX_HS_EN/HBX_LS_EN bits in operation control (OP_CTRL_1, OP_CTRL_2 and OP_CTRL_3) registers.
Check for the nFAULT pin status and the OLD fault in the IC_STAT register.
If the nFAULT pin is low and the OLD fault is high, then check for the individual HBX_HS_OLD/HBX_LS_OLD bits in OLD status (OLD_STAT_1, OLD_STAT_2 and OLD_STAT_3) registers.
Disable OLD using the HBX_OLD_DIS bits for the OUTX pins acting as high-side drivers.
Enable the low-current OLD mode for the half-bridge which low-side is operating by using the HBX_LOLD_EN bit in OLD control (OLD_CTRL_3 and OLD_CTRL_4) registers. This will also disable the high-side OLD for the particular half-bridge.
Wait for the open-load deglitch time (t_OLD).
Issue the clear fault command (CLR_FLT) to release the nFAULT pin and clear the OLD bits if low-current OLD is not detected.
If the OLD bit is high and the nFAULT pin is not released (low), then low-current OLD fault is detected.

NOTE

The low-current OLD is applicable only for low-side FETs. The user has to enable the low-current OLD mode for the corresponding low-side FET.

DRV8904-Q1 DRV8906-Q1 DRV8908-Q1 DRV8910-Q1 DRV8912-Q1 drv89xx-LCOLD_flowchart.gif

Figure 59. Flowchart for Enabling Low-Current OLD (Continuous Mode)