MB39A113 Datasheet, PDF (34/51 Pages) Fujitsu Component Limited. – ASSP for Power Supply Applications (Secondary Battery)

MB39A113
Example) Using the RB053L-30
VR (DC reverse voltage) = 30 V, average output current = 3.0 A, peak surge current = 70 A
VF (forward voltage) = 0.42 V, at IF = 3.0 A
16.8 V output
Vo
IDi ≥ Io × (1−
)
VIN
≥ 3 × (1−0.672)
≥ 0.984 A
12.6 V output
Vo
IDi ≥ Io × (1−
)
VIN
≥ 3 × (1−0.572)
≥ 1.284 A
16.8 V output
Vo
IDip ≥ (Io +
tOFF)
2L
≥ 3.6 A
12.6 V output
Vo
IDip ≥ (Io +
tOFF)
2L
≥ 3.6 A
• Smoothing capacitor
The smoothing capacitor is an indispensable element for reducing ripple voltage in output. In selecting a smooth-
ing capacitor, it is essential to consider equivalent series resistance (ESR) and allowable ripple current. Higher
ESR means higher ripple voltage, so that to reduce ripple voltage it is necessary to select a capacitor with low
ESR. Note, however, that the use of a capacitor with low ESR has substantial effects on loop phase character-
istics, and impairing system stability. Care should also be taken to use a capacity with sufficient margin for
allowable ripple current. In this application the 20SVP22M (OS-CON^TM : SANYO) are used.
The ESR, capacitance value, and ripple current can be obtained by the following formulas.
Equivalent series resistance : ESR
∆Vo
1
ESR ≤
−
∆IL
2πfCL
Capacitance value : CL
∆IL
CL ≥
2πf (∆Vo−∆IL × ESR)
Ripple current : ICLrms
(VIN−Vo) tON
ICLrms ≥
2√3L
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