Datasheet

Table Of Contents

LMZ31530

www.ti.com

SLVSBC7B –OCTOBER 2013–REVISED DECEMBER 2013

Overcurrent Protection

For protection against load faults, the LMZ31530 incorporates cycle-by-cycle overcurrent limiting control. The

inductor current is monitored during the OFF state and the controller maintains the OFF state during the period in

that the inductor current is larger than the overcurrent trip level. In cycle-by-cycle mode, applying a load that

exceeds the regulator's overcurrent threshold limits the output current and reduces the output voltage as shown

in Figure 26. If the overcurrent condition remains and the output voltage drops below 70% of the set-point, the

LMZ31530 shuts down. Following shutdown, the module periodically attempts to recover by initiating a soft-start

power-up as shown in Figure 26. This is described as a hiccup mode of operation, whereby the module

continues in a cycle of successive shutdown and power up until the load fault is removed. During this period, the

average current flowing into the fault is significantly reduced which reduces power dissipation. Once the fault is

removed, the module automatically recovers and returns to normal operation as shown in Figure 27.

Figure 26. Overcurrent Limiting (Hiccup) Figure 27. Removal of Overcurrent (Hiccup)

Current Limit (ILIM) Adjust

The current limit of this device can be adjusted lower by connecting a resistor, R

ILIM

, between the ILIM pin (pin 6)

and PGND. To adjust the typical current limit threshold, as listed in the electrical characteristics table, refer to

Table 6.

Table 6. Current Limit Adjust Resistor

Current Limit Reduction R

ILIM

(kΩ)

10 % 825

20 % 487

30 % 324

Thermal Shutdown

The internal thermal shutdown circuitry forces the device to stop switching if the junction temperature exceeds

145°C typically. The device reinitiates the power up sequence when the junction temperature drops below 135°C

typically.

Product Folder Links: LMZ31530