High-side and Low-side switches are commonly used in embedded circuits to control power to the load. This helps in many ways and the major advantage is power saving. In a low side, load is connected between the power rail and switch and in high side switch load is connected between ground and switch. In the above circuit diagram, R1,R2 are the loads and M1, M3 are MOSFETs which act as switches. Control to MOSFET is from a host controller. In some of the high power loads, there are specially designed switch controllers which control the switches. The switch controller is further controlled by the host controller.
We can see from the above circuits that N-channel MOSFET is used for Low-side switch and P-channel MOSFET is used for High-side switch. N-channel MOSFET can also be used for High-side switch but requires a complex control mechanism.
MAX14922 is one example of high-side switch controller where N-channel MOSFET is used.
- Low-side switch can be used to control heavier loads (high current) as N-channel MOSFET can carry more current than P-channel MOSFET. We all know mobility of N-channel MOSFET is more than P-channel MOSFET
- High-side switch are used in cases where there is a single supply and multiple loads are to be switched at a time.
- Low-side is preferred when there are multiple rails connecting to loads.
- When there is a PWM based control for MOSFET, Low-side switch is preferred
There are switches available in the market with diagnosis and protection features. The features include,
- Over voltage protection
- Under voltage lockout
- Over temperature protection
- Reverse polarity protection
- Overload protection (short circuit protection)
- ESD protection
- Ground disconnection protection
- Auto restart after fault diagnosis
These above features help designers to have minimal circuit with good amount of protection features. IPS1025HF is one example of such high-side switch.
]]>
0 Comments