MB39A102 Datasheet, PDF (18/24 Pages) Fujitsu Component Limited. – Evaluation Board

MB39A102
The following subsections show the component selection methods with the following common parametric values.
2. CH1 : Output 2.5 V (Downconversion Type)
VIN (Max) = 6.0 V, Io = 250 mA, fosc = 500 kHz
(1) P-ch MOS FET (MCH3309 (SANYO product) )
VDS = −20 V, VGS = ±10 V, ID = −1.5 A, RDS (ON) = 340 mΩ (Max) , Qg = 3.2 nC
• Drain current: Peak value
The peak drain current of this FET must be within its rated current.
If the FET’s peak drain current is ID, it is obtained by the following formula.
VO
= VIN ×
tON
t
tON =
t×
VO
VIN
=
1
fOSC
×
VO
VIN
ID
≥ IO +
VIN (Max) −VO
2L
× tON
≥ 0.25 +
6−2.5
2×22×10^−6
×
1
500×10³
× 0.417
≥ 0.316 A
• Drain-source voltage / Gate-source voltage
The source-drain and gate-source voltages of the FET should be in the rated voltage value of FET.
The FET source-drain voltage (VDS) and gate-source voltage (VGS) are obtained by the following formula.
VDS ≤ −VIN (Max)
≤ −6 V
VGS ≥ VIN (Max)
≥ 6V
(2) Schottky Barrier Diode (SBS004 (SANYO product) )
VF (forward voltage) = 0.35 V (Max) : at IF = 1 A, VRRM (repeated peak reverse voltage) = 15 V
IF (mean output current) = 1 A, IFSM (surge forward current) = 10 A
• Diode current: Peak value
The peak diode current must be within its rated current.
If the peak diode current is IFSM, it is obtained by the following formula.
IFSM
≥
IO +
VO
2L
× tOFF
≥ 0.25 +
2.5
2×22×10^−6
×
1
500×10³
×
(1−0.417)
≥ 0.316 A
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