Load switches

Load switches offer simple and straightforward solutions for managing inrush current. Compared to discrete solutions, the integrated soft-start in load switches enables better control over inrush current, helping to avoid power supply dips and voltage droop. Available in compact and cost-competitive 4-pin or 6-pin packages, load switches enable smaller, simpler designs with fewer components. Load switches also integrate additional features like quick output discharge for controlled power down. With both controlled power up and power down, load switches offer a simple way to have greater management over low-voltage power distribution.

In systems with limited battery budget, it is critical to manage overall system leakage current. Load switches are available in models with low quiescent current (when device is enabled) and low shutdown current (when device is disabled). This variety enables designers to select the optimal load switch based on how often a given load is on or off. Since battery size is often limited by the overall system size (like in a consumer wearable), many TI low-leakage load switches are also available in ultra-compact WCSP or QFN packages. Choosing a load switch with low-leakage current reduces idle power consumption and overall battery drain, enabling longer system lifetime.

When a processor or FPGA has precise requirements for inrush current, turn-on time and turn-off time, it can be difficult to manage with discrete solutions or sequencers. Implementing load switches into the power path allows independent control of timing for each rail. With adjustable soft start and adjustable quick output discharge, load switches are able to better conduct both power up and power down sequences. Load switches with power good (PG) pins enable greater control when sequencing multiple load switches. Bias voltage (Vbias) pins enable lower Vin voltages for use on low-voltage processor and FPGA rails.

In high-efficiency 3.3V systems (like optical modules), power budgets are limited and each component consumes valuable voltage headroom. By using a load switch with low on-resistance, the voltage drop is minimized, allowing more voltage headroom for downstream rails and transient events. Low on-resistance also helps minimize power losses and temperature rise, enabling higher performance and reliability.

While soft-start manages inrush current during turn-on, current limiting (ILIM) or short-circuit protection (SCP) protect against overcurrent events after startup. ILIM and SCP use different fault triggers, but both respond by clamping current to a fixed value until the device reaches thermal shutdown. Current-limited load switches can be fixed or adjustable (with external resistor) and often include fault reporting pins and standard safety certifications. Current limiting is valuable for protecting USB-A ports, preventing high-discharge damage to batteries and protecting downstream loads. Reverse current blocking (RCB) is another common protection feature, preventing reverse current flow between USB devices or power sources.