Dear Sir
Could I use LM74610-Q1 for 2x1.5V=3V Alkaline application ,this mean when vin down to 1.6V ,the charge pump of LM74610 is still workable
Hsiao,
The LM74610 is a controller device, designed mainly for automotive high current applications. Which doesn't mean it can not be used in other applications such as battery chargers and AC adapters. The bi-directional current nature of automotive battery (and some other batteries or AC adapters) allow current flow out and into the battery which works great for LM74610.
The LM74610 controller constantly monitors the voltage across the Source and Drain of the MOSFET. If the output voltage goes higher than the input, which happens in the case of reverse polarity, the LM74610 shut down the MOSFET by hardly pulling down the gate.
The shutting down of gate happens if the the LM74610 detects any reverse current flow from the output to the battery. There has to be reverse current flow for atleast 1usec for the LM74610 to react and pull the gate down. If you forcefully stop this reverse current or use a battery that doesn't allow current sinking, the shut down period can be up to 2sec. The MOSFET will only shut down when the Vcap completely discharges. Here is an example scenario:
Notice when the voltage dips from 6V to -10V, the input current has a negative spike for a very short period of time. This spike triggered the fast shutdown. Even if the voltage doesn't go to negative value and a reverse current flows due to voltage interruption in the presence of a large output cap, the reverse current will still flow for a small time and LM74610 will shut down as shown in the fig below:
500mA current is certainly enough to justify the use of LM74610, however you have to make sure that the design is robust and the IC will protect the downstream circuity int he event of reverse current flow.
Hope this explanation helps.
