Datasheet

LM2524D, LM3524D
www.ti.com SNVS766E –JUNE 2009–REVISED MAY 2013
Figure 23. Relation of Switch Timing to Inductor Current in Step-Down Regulator
(4)
Neglecting V
SAT
, V
D
, and settling ΔI
L
+
= ΔI
L
−
;
(5)
where T = Total Period
The above shows the relation between V
IN
, V
o
and duty cycle.
(6)
as Q1 only conducts during t
ON
.
(7)
The efficiency, η, of the circuit is:
(8)
ηMAX will be further decreased due to switching losses in Q1. For this reason Q1 should be selected to have the
maximum possible f
T
, which implies very fast rise and fall times.
Calculating Inductor L1
(9)
Since ΔI
L
+ = ΔI
L
−
= 0.4I
o
Solving the above for L1
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