Battery output current limit

How are current limits calculated?

The current limits are estimated using this validated cell model and the CLE profiles are generated at the different operating conditions. For these estimates, the pulse duration is fixed at Δt = 1s and the cut-off voltage at Vcut-off = 3 V.

What is a brick wall current limit?

In a brick-wall current limit, the upper boundary is defined and the LDO supplies current incrementally until the limit current limit is reached. Once the current limit is exceeded, the output voltage is not regulated and is determined by the resistance for the load circuitry (RLOAD) and the output current limit (ILIMIT) (Figure 2 Figure 2. (1)

What is a current limit in an LDO?

Current limit in an LDO is defined by establishing an upper boundary for the current supplied. Unlike a constant current source, LDOs supply current on demand but can also control the total power regulated. Current limiting is achieved through internal circuitry controlling the output stage transistors inside the LDO. See Figure 1.

What happens if a current limit is exceeded?

After the current limit is exceeded and VOUT begins to reduce (assuming a constant RLOAD), both IOUT and the power dissipation reduce. This adds a bit of complexity for non-ohmic devices that draw a constant current and could trigger a lockout condition in which the powered device continues to reduce VOUT and the LDO continues to reduce IOUT.

When does a current limited load switch start limiting current?

A current limited load switch would start limiting current as soon as the system current exceeds the set limit. Some load switch families like the TPS2294x devices offer various current limits, response delay times and auto-restart features. The TPS22948 offers a current limit specified for HDMI output port applications.

What is the difference between short circuit protection and current limiting?

Short circuit protection and current limiting use different triggers and references to protect against high current events. In both cases the response of the switch is the same. The load switch clamps the current to a fixed value until the device heats up and the die reaches the thermal shutdown threshold and turns off.