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MB3887
3. Soft-Start Function
Soft-start block (SOFT)
Connecting a capacitor to the CS terminal (pin 22) prevents rush currents when the IC is turned on. Using an error amplifier for
■SETTING THE CHARGING VOLTAGE
The charging voltage (DC/DC output voltage) can be set by connecting external voltage setting resistors (R3, R4) to the −INE3 terminal (pin 16) . Be sure to select a resistor value that allows you to ignore the
Battery charging voltage : VO
VO (V) = | (R3 + R4) / R4 ⋅ 4.2 (V) |
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| B | VO |
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| R3 |
| <Error Amp3> |
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| −INE3 | − |
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| 16 | |
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| + |
| R4 |
| + |
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| 11 | 4.2 V |
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| OUTD | |
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| 22 |
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| CS |
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■METHOD OF SETTING THE CHARGING CURRENT
The charge current (output limit 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) = 20 ⋅ I1 (A) ⋅ RS (Ω)
■METHOD OF SETTING THE TRIANGULAR WAVE OSCILLATION FREQUENCY
The triangular wave oscillation frequency can be set by the timing resistor (RT) connected the RT terminal (pin 17) .
Triangular wave oscillation frequency : fOSC fOSC (kHz) =: 13630 / RT (kΩ)
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