MAX15118 Datasheet, PDF (16/23 Pages) Maxim Integrated Products – High-Efficiency, 18A, Current-Mode Synchronous Step-Down Regulator with Integrated Switches

MAX15118
High-Efficiency, 18A, Current-Mode Synchronous
Step-Down Regulator with Integrated Switches
Skip Mode Frequency and Output Ripple
Enable skip mode in battery-powered systems for high effi-
ciency at light loads. In skip mode the switching frequency
(fSKIP), as illustrated in Figure 1, is cal­culated as follows:
where:
f_SKIP
=
t _ON
+
1
t _OFF1
+
t _OFF2
t _ON
=
V_IN
L
− V_OUT
× I_{SKIP_LIMIT}
t
OFF1
=
L
×
I_{SKIP_LIMIT}
V_OUT
and:
t _OFF2
=
∆Q _OUT
I_LOAD
t _OFF2
=
L
× I_{SKIP_LIMIT}
×



V_IN
1
+¹
- V_OUT V_OUT
I_LOAD



×
I_{SKIP_LIMIT}


2
−
I_LOAD



Output ripple in skip mode is:
V_{OUT_RIPPLE}
=
 L × I_{SKIP_LIMIT}
_{COUT × (VIN - VOUT)}
+

R _{ESR_COUT }

( ) ^{× I}_{SKIP_LIMIT} ^{- I}_LOAD
IL
VOUT
ISKIP-LIMIT
tON
tOFF1
tOFF2 = n × tCK
Figure 1. Skip Mode Waveform
ILOAD
VOUT_RIPPLE
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