Low power load switch for biometric devices
Advanced Analogic Technologies introduced the AAT4702, a highly integrated load switch that requires half the board footprint of discrete alternatives and consumes a 15 micro-A quiescent current.
Packaged in a compact 8-pin, 2×2-mm FTDFN package, the AAT4702 is a current-limited P-channel metal-oxide-semiconductor field-effect transistor (MOSFET) power switch with an integrated LDO regulator that offers a variety of protection features including auto restart, reverse current blocking and a fault flag to deliver the highest available level of load current protection in a load switch.
The AAT4702’s load switch current limit is set at 150 mA as a default, but it is programmable up to 1A via an external set resistor. To further protect system loads or peripheral circuits from over-current conditions, the new load switch adds an auto-restart function that wakes up and re-enables the device every 40 ms to check for the continued existence of an over-current condition. If the over-current condition remains, the AAT4702 stays in shutdown mode with both the load switch and LDO regulator output pulled low to ground. This allows the device to automatically resume operation once the over-current condition ends, eliminating the risk of damage.
An integrated FAULT flag feature that indicates an over-current or over-temperature condition is also available, adding a 5 ms blanking time to prevent reports of false events. The AAT4702 also adds reverse current blocking to protect the load switch from reverse current potentials when the device is shut down. The integrated load switch/LDO operates from inputs ranging from 2.4V to 5.5V.
The LDO integrated into the AAT4702 delivers a regulated 1.8V supply voltage with plus or minus 2 percent accuracy at load levels up to 100 mA. It may be powered either directly from an input source supply or via the load switch output. Quiescent current for the AAT4702 is 15 micro A typical, by far the lowest specification in the industry for integrated solutions of this type. Shutdown current is less than 1 micro A.
The switch is available in a compact 8-pin, 2×2-mm FTDFN package and is priced at $0.59 in 1K quantities.