Fujitsu MB3878 Manual Do Utilizador

14

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The charging voltage (DC/DC output voltage) can be set by connecting external voltage setting resistors (R3,
R4) to the -INE3 terminal. Be sure to select a resistor value that allows you to ignore the on resistor (70 

Ω

, 1mA)

of the internal FET connected to the OUTD terminal (pin 11).

 

Battery charging voltage:

V

O

V

O

 (V)  

=

  (R3 

+

 R4)  

/

 R4 

×

 4.2 (V) 

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The charge current (output control current) value can be set with the voltage at the +INE1 terminal (pin 9).

If a current exceeding the set value attempts to flow, the charge voltage drops according to the set current value.

Battery charge current setting voltage : +INE1 

+INE1 (V) = 25 

×

 I1 (A) 

×

 R

S

 (

Ω

)

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Upon activation, the IC starts charging the capacitor (Cs) connected to the CS terminal (pin 22).

The error amplifier causes soft-start operation to be performed with the output voltage in proportion to the CS
terminal voltage regardless of the load current of the DC/DC converter.

Soft-start time: ts (Time taken for the output voltage to reach 100 %)

ts (s)  :=  4.2 

×

 C

S 

(

µ

F)

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The trianguar wave oscillator frequency can be set by the timing resistor (R

T

)

 

connected the RT

 

terminal (pin 17).

Triangular wave oscillator frequency: f

OSC

f

OSC  

(kHz)  := 13630 / R

T 

(k

Ω

)

< Error Amp.3 >

−

+

+

4.2 V

R3

V

O

R4

−

INE3

OUTD

CS

16

B

11

22