The inrush period is an optional mode of the device where it can be configured to allow the device to handle different inrush currents such as bulbs, motor stall currents, or capacitive loads at the initial turn on of a channel. The inrush period can be configured through the CAP_CHRG_CHx, INRUSH_DURATION_CHx, and INRUSH_LIMIT_CHx bits in the ILIM_CONFIG_CHx registers. If the inrush period is enabled, it will take effect in both the ACTIVE state and the LIMPHOME mode if a channel is enabled in either of these states.

The device offers two different ovecurrent protection settings in the inrush period which can be set through the CAP_CHRG_CHx bits:

• No capacitive charging - immediate shutdown overcurrent protection (I_OCP) only
• Current limit regulation (I_{CL_REG})

The no capacitive charging setting, enables the device to have a different overcurrent protection (I_OCP) value in the inrush period compared to steady state to allow for bulb current inrush or motor stall current. Additionally, in the no capacitive charging setting, I2T protection (if enabled) is active if V_DS < V_{DS_LT_2V}. The current limit regulation mode, allows for the device to charge up large capacitances such as input capacitors on downstream ECUs. Depending on the CAP_CHRG_CHx bit settings, the values of the INRUSH_LIMIT_CHx will change. The overcurrent protection for each channel is independent and can be set on an per channel basis.

No Capacitive Charging - CAP_CHRG_CHx = 00

The no capacitive charging setting, enables the device to have a different immediate shutdown overcurrent protection (I_OCP) value in the inrush period compared to steady state operation to allow for different inrush events at startup such as bulb current inrush or motor stall current.

If CAP_CHRG_CHx [1:0] = 00, the immediate shutdown overcurrent protection (I_OCP) value in the inrush period is set by the INRUSH_LIMIT_CHx [3:0] bits and the duration is set by the INRUSH_DURATION_CHx [2:0] bits. Once the inrush period duration timer expires the immediate shutdown overcurrent protection (I_OCP) value will be set by the ILIMIT_SET_CHx [3:0] bits in steady state operation.

If CAP_CHRG_CHx [1:0] = 00, I2T protection (if enabled) and current sensing is available if V_DS < V_{DS_LT_2V}.

An example of this is shown in Figure 7-3.

Figure 7-3 No Capacitive Charging (CAP_CHRG_CHx [1:0] = 00) - Bulb Driving Example

Current limit regulation capacitive charging mode - CAP_CHRG_CHx [1:0] = 10

The device offers a current limit regulation capacitive charging mode to charge up large downstream capacitive loads such as bulk input capacitors on ECUs. If CAP_CHRG_CHx [1:0] = 10, the current limit regulation mode will clamp the output current when the channel is initially enabled at a value set by the INRUSH_LIMIT_CHx [3:0]. The device will limit the current continuously until the capacitive load has finished charging, the inrush period expires, or a thermal shutdown has occurred. The range of settings which can be programmed through the INRUSH_LIMIT_CHx [3:0] and are specified in the electrical characteristic table as I_{CL_REG}. If the VOUT voltage is greater than VBB - 2V and the inrush period timer has not expired, the device is able to slowly exit the current limit regulation without a large spike. An example of the current limit regulation capacitive charging mode and the slow exit before the inrush period timer expiration is shown in Figure 7-4.

Figure 7-4 Current Limit Regulation Capacitive Charging (CAP_CHRG_CHx [1:0] = 10) - ECU Input Bulk Capacitance Driving Example