10.1 Transient Protection

In the case of a short circuit and overload current limit when the device interrupts current flow, the input inductance generates a positive voltage spike on the input, and the output inductance generates a negative voltage spike on the output. The peak amplitude of voltage spikes (transients) is dependent on the value of inductance in series to the input or output of the device. Such transients can exceed the absolute maximum ratings of the device if steps are not taken to address the issue. Typical methods for addressing transients include:

• Minimize lead length and inductance into and out of the device.
• Use a large PCB GND plane.
• Use a Schottky diode across the output to absorb negative spikes.
• Use a low-value ceramic capacitor C_IN = 0.001 μF to 0.1 μF to absorb the energy and dampen the transients.

The approximate value of input capacitance can be estimated with Equation 18:

Equation 18.

where

• V_(IN) is the nominal supply voltage
• I_(LOAD) is the load current
• L_(IN) equals the effective inductance seen looking into the source
• C_(IN) is the capacitance present at the input

Some applications may require the addition of a Transient Voltage Suppressor (TVS) to prevent transients from exceeding the absolute maximum ratings of the device.

The circuit implementation with optional protection components (a ceramic capacitor, TVS and Schottky diode) is shown in Figure 67.

Figure 67. Circuit Implementation with Optional Protection Components