To increase battery working lifetime, video processing circuit is in shutdown mode most time and woken up and start to work when there is a trigger event such as PIR trigger, or regular task, or remote network request. Video processing circuit is consisted of ISP SOC, image sensor, Flash, ambient sensing, IR/White flash LED, IR cut and so on. Due to the fact that the video processing circuit are working in shutdown mode most of the time, more attention is shown to shutdown current and power efficiency. Actually, although video processing circuit working time is not too much,the video processing circuit are also a major source of energy consumption.

Efficiency of low voltage output is easily overlooked, especially since there are some similar voltage output efficiency. For example, 0.8 V efficiency is needed in design but only given 1.2 V voltage output efficiency in SPEC. Mostly, the lower voltage output, the worse the efficiency is. So, reference power efficiency is only needed when voltage output is larger than the SPEC given.

TPS62A02 is a 2-A buck with very good efficiency in low-voltage output.

Figure 4-4 TPS62A02 Efficiency

Figure 4-5 TPS62A02 Output 0.8 V Efficiency

TPS62A02 shutdown current is typical 10 nA. TPS62A02 is also a very good feature for shutdown mode.

TLV62568 is a very low-cost 1-A buck component with a good power efficiency. Shutdown current is typical 100 nA

Figure 4-6 TLV62568 Efficiency

Sometimes, a load switch is a good option for shutting down some non working circuit in most time. TPS22919 is a low cost 1.5-A load switch. The load switch quiescent current is 8 uA, and shutdown current is 2 nA.