MB3885PFV Просмотр технического описания (PDF) - Fujitsu

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MB3885PFV

1-channel DC/DC Converter IC with Synchronous Rectifier

Fujitsu 

MB3885

s PRECAUTIONS RELATED TO SUPPLY VOLTAGE RANGE

Although the supply voltage range listed under recommended operating requirements is 5.5V-18V, generation

of heat limits the maximum operating supply voltage since the IC’s internal loss varies with the frequency of

oscillation and FET’s total gate charge. When using the MB 3885 in an application, caution must be taken in

relation to supply voltage range.

As shown below, IB (average current) can be determined from the total gate charge Qg1, Qg2, charged from the

gate capacitance (Ciss1, Ciss2, Crss1, Crss2) of the external FET Q1, Q2, by the following formula.

IB (A) = I1 + I2

= Ibias1 ×

T1 Qg1

T2 Qg2

T + T + Ibias2 × T + T

(Ibias1 = Ibias2 =: 2 mA)

Because IC current consumption other than IB is 6.5 mA, power consumption can be determined from the

following formula.

Power consumption : Pc

Pc (W) =: 0.0065 × VCC + VCC × IB − 1 / 2 × VB × IB

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