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LM2830

SNVS454D – AUGUST 2006 – REVISED APRIL 2013

www.ti.com

CURRENT LIMIT

The LM2830 uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle, a

current limit comparator detects if the output switch current exceeds 1.75A (typ), and turns off the switch until the

next switching cycle begins.

THERMAL SHUTDOWN

Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature

exceeds 165°C. After thermal shutdown occurs, the output switch doesn’t turn on until the junction temperature

drops to approximately 150°C.

Design Guide

INDUCTOR SELECTION

(1)

The catch diode (D1) forward voltage drop and the voltage drop across the internal PMOS must be included to

calculate a more accurate duty cycle. Calculate D by using the following formula:

(2)

(3)

Lower inductor values decrease the size of the inductor, but increase the output ripple current. An increase in the

inductor value will decrease the output ripple current.

One must ensure that the minimum current limit (1.2A) is not exceeded, so the peak current in the inductor must

(4)

Figure 22. Inductor Current

(5)

In general,

(6)

If

operating conditions is 1.2A. One can either reduce

be safe enough. The typical current limit is 1.75A.

10

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