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FUJITSU SEMICONDUCTOR
DS04-27709-3E
DATA SHEET
ASSP For Power Supply Applications (Secondary battery)
DC/DC Converter IC
for Charging Li-ion battery
MB3887
n DESCRIPTION
The MB3887 is a DC/DC converter IC suitable for down-conversion, using pulse-width (PWM) charging and
enabling output voltage to be set to any desired level from one cell to four cells.
These ICs can dynamically control the secondary battery’s charge current by detecting a voltage drop in an AC
adapter in order to keep its powe
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MB3887 (Continued) • Output voltage setting using external resistor : 1 cell to 4 cells • High efficiency : 96% (VIN = 19 V, Vo = 16.8 V) • Wide range of operating supply voltages : 8 V to 25 V • Output voltage setting accuracy : 4.2 V – 0.74% (Ta = - 10 C to +85 C , per cell) • Charging current accuracy : – 5% • Built-in frequency setting capacitor enables frequency setting using external resistor only • Oscillation frequency range : 100 kHz to 500 kHz • Built-in current detection amplif
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MB3887 n PIN ASSIGNMENT (TOP VIEW) - INC2 : 1 24 : +INC2 OUTC2 : 2 23 : GND +INE2 : 3 22 : CS - INE2 : 4 21 : VCC (O) FB2 : 5 20 : OUT VREF : 6 19 : VH FB1 : 7 18 : VCC - INE1 : 8 17 : RT +INE1 : 9 16 : - INE3 OUTC1 : 10 15 : FB3 OUTD : 11 14 : CTL - INC1 : 12 13 : +INC1 (FPT-24P-M03) 3
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MB3887 n PIN DESCRIPTION Pin No. Symbol I/O Descriptions 1 - INC2 I Current detection amplifier (Current Amp2) input terminal. 2 OUTC2 O Current detection amplifier (Current Amp2) output terminal. 3 +INE2 I Error amplifier (Error Amp2) non-inverted input terminal. 4 - INE2 I Error amplifier (Error Amp2) inverted input terminal. 5 FB2 O Error amplifier (Error Amp2) output terminal. 6 VREF O Reference voltage output terminal. 7 FB1 O Error amplifier (Error Amp1) output terminal. 8 - INE1 I Error a
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MB3887 n BLOCK DIAGRAM 8 - INE1 OUTC1 10 VREF 13 + +INC1 - · 20 - 12 - INC1 + 21 VCC (O) +INE1 9 7 + FB1 + + Drive 20 OUT - - INE2 4 2 OUTC2 VCC VREF 24 + +INC2 - · 20 19 - Bias VH 1 - INC2 + Voltage (VCC - 6 V) 3 +INE2 2.5 V FB2 5 1.5 V VCC VREF (VCC UVLO) 215 kW 16 - - INE3 + + 35 kW 11 OUTD - 4.2 V 0.91 V (0.77 V) FB3 15 VREF UVLO VREF 10 VCC m A 4.2 V CS 22 18 VCC [ 14 CT
]
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MB3887 n ABSOLUTE MAXIMUM RATINGS Rating Parameter Symbol Conditions Unit Min Max Power supply voltage VCC VCC, VCC (O) terminal 28 V Output current IOUT 60 mA Duty £ 5 % Peak output current IOUT 700 mA (t = 1 / fOSC · Duty) Power dissipation PD Ta £ +25 C 740* mW Storage temperature TSTG - 55 +125 C * : The package is mounted on the dual-sided epoxy board (10 cm · 10 cm) . WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temp
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MB3887 n RECOMMENDED OPERATING CONDITIONS Value Parameter Symbol Conditions Unit Min Typ Max Power supply voltage VCC VCC, VCC (O) terminal 8 25 V Reference voltage output IREF - 1 0mA current VH terminal output current IVH 0 30 mA - INE1 to - INE3, +INE1, VINE 0 VCC - 1.8 V +INE2 terminal Input voltage +INC1, +INC2, - INC1, VINC 0 VCC V - INC2 terminal OUTD terminal VOUTD 0 17 V output voltage OUTD terminal IOUTD 0 2mA output current CTL terminal input voltage VCTL 0
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MB3887 n ELECTRICAL CHARACTERISTICS (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Sym- Pin Parameter Conditions Unit bol No. Min Typ Max VREF1 6Ta = +25 C 4.967 5.000 5.041 V Output voltage VREF2 6Ta = - 10 C to +85 C 4.95 5.00 5.05 V 1. Reference Input stability Line 6 VCC = 8 V to 25 V 310 mV voltage block Load stability Load 6 VREF = 0 mA to - 1 mA 110 mV [REF] Short-circuit output Ios 6 VREF = 1 V - 50 - 25 - 12 mA current VCC = VCC (O) , VTLH 18 6.2 6.4 6.6 V V
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MB3887 (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Sym- Pin Parameter Conditions Unit bol No. Min Typ Max VTH1 16 FB3 = 2 V, Ta = +25 C 4.183 4.200 4.225 V Threshold voltage FB3 = 2 V, VTH2 16 4.169 4.200 4.231 V Ta = - 10 C to +85 C Input current IINE3 16 - INE3 = 0 V - 100 - 30 nA Voltage gain AV 15 DC 100* dB Frequency BW 15 AV = 0 dB 2* MHz bandwidth 5-2. Error amplifier VFBH 15 4.7 4.9 V Output voltage block VFBL 15 20 200 mV [Error Amp3] Output
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MB3887 (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Sym- Pin Parameter Conditions Unit bol No. Min Typ Max +INC1 = +INC2 = VOUTC1 2, 10 3 V to VCC, 1.9 2.0 2.1 V D Vin = - 100 mV +INC1 = +INC2 = VOUTC2 2, 10 3 V to VCC, 0.34 0.40 0.46 V D Vin = - 20 mV Current detection voltage +INC1 = +INC2 = VOUTC3 2, 10 0 V to 3 V, 1.8 2.0 2.2 V D Vin = - 100 mV +INC1 = +INC2 = VOUTC4 2, 10 0 V to 3 V, 0.2 0.4 0.6 V D Vin = - 20 mV 6. Current 1, detection In-phase input 12, VCM 0
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MB3887 (Continued) (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Sym- Pin Parameter Conditions Unit bol No. Min Typ Max Output source OUT = 13 V, Duty £ 5 % ISOURCE 20 - 400* mA current (t = 1 / fOSC · Duty) Output sink OUT = 19 V, Duty £ 5 % ISINK 20 400* mA current (t = 1 / fOSC · Duty) 8. ROH 20 OUT = - 45 mA 6.5 9.8 W Output ON Output block resistor ROL 20 OUT = 45 mA 5.0 7.5 W [OUT] OUT = 3300 pF Rise time tr1 20 50* ns (Si4435 · 1) OUT = 3300 pF Fall
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MB3887 n TYPICAL CHARACTERISTICS Power supply current vs. Power supply voltage Reference voltage vs. Power supply voltage 6 6 Ta = +25 C CTL = 5 V 5 5 4 4 3 3 2 2 Ta = +25 C CTL = 5 V 1 1 VREF = 0 mA 0 0 0 5 10 15 20 25 0 5 10 15 20 25 Power supply voltage VCC (V) Power supply voltage VCC (V) Reference voltage vs. IREF load current Reference voltage vs. Ambient temperature 6 5.08 Ta = +25 C VCC = 19 V 5.06 VCC = 19 V CTL = 5 V 5 CTL = 5 V 5.04 4 5.02 3 5.00 4.98 2 4.96 1 4.94 0 4.92 0 5 1
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MB3887 Triangular wave oscillation frequency Triangular wave oscillation frequency vs. Timing resistor vs. Power supply voltage 1 M 340 Ta = +25 C Ta = +25 C 330 VCC = 19 V CTL = 5 V CTL = 5 V RT = 47 kW 320 310 100 k 300 290 280 270 10 k 260 0 5 10 15 20 25 10 100 1000 Timing resistor RT (kW ) Power supply voltage VCC (V) Triangular wave oscillation frequency Error amplifier threshold voltage vs. Ambient temperature vs. Ambient temperature 320 4.25 VCC = 19 V 315 VCC = 19 V 2.24 CTL = 5 V
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MB3887 Error amplifier gain and phase vs. Frequency Ta = +25 C 40 180 VCC = 19 V AV 4.2 V f 240 kW 20 90 10 kW 10 kW 1 m F + 8 0 0 f - 2.4 kW IN (4) 7 + (5) OUT 9 - 20 - 90 (3) Error Amp1 10 kW 10 kW (Error Amp2) - 40 - 180 1 k 10 k 100 k 1 M 10 M Frequency f (Hz) Error amplifier gain and phase vs. Frequency Ta = +25 C VCC = 19 V 4.2 V 40 180 AV 240 kW 10 kW f 10 kW 20 90 1 m F + 16 - 0 0 f 2.4 kW IN + 22 15 + OUT - 20 - 90 Error Amp3 10 kW 10 kW 4.2 V - 40 - 180 1 k 10 k 100 k 1 M 10 M Fre
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MB3887 (Continued) Power dissipation vs. Ambient temperature 800 740 700 600 500 400 300 200 100 0 - 40 - 20 0 20 40 60 80 100 Ambient temperature Ta ( C) 15 Power dissipation PD (mW)
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MB3887 n FUNCTIONAL DESCRIPTION 1. DC/DC Converter Unit (1) Reference voltage block (Ref) The reference voltage generator uses the voltage supplied from the VCC terminal (pin 18) to generate a tem- perature-compensated, stable voltage (5.0 V Typ) used as the reference supply voltage for the IC’s internal circuitry. This terminal can also be used to obtain a load current to a maximum of 1mA from the reference voltage VREF terminal (pin 6) . (2) Triangular wave oscillator block (OSC) The tria
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MB3887 (7) PWM comparator block (PWM Comp.) The PWM comparator circuit is a voltage-pulse width converter for controlling the output duty of the error amplifiers (Error Amp1 to Error Amp3) depending on their output voltage. The PWM comparator circuit compares the triangular wave generated by the triangular wave oscillator to the error amplifier output voltage and turns on the external output transistor during the interval in which the triangular wave voltage is lower than the error amplifier
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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 soft-start detection makes the soft-start time constant, being independent of the output load of the DC/DC converter. n 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
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MB3887 n METHOD OF SETTING THE SOFT-START TIME For preventing rush current upon activation of IC, the IC allows soft-start using the capacitor (Cs) connected to the CS terminal (pin 22) . When CTL terminal (pin 14) is placed under “H” level and IC is activated (VCC ‡ UVLO threshold voltage) , Q2 is turned off and the external soft-start capacitor (Cs) connected to the CS terminal is charged at 10 m A. Error Amp output (FB3 terminal (pin 15) ) is determined by comparison between the lower voltage
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MB3887 n AC ADAPTOR VOLTAGE DETECTION • With an external resistor connected to the +INE2 terminal (pin 3) , the IC enters the dynamically-controlled charging mode to reduce the charge current to keep AC adapter power constant when the partial potential point A of the AC adapter voltage (VCC) becomes lower than the voltage at the - INE2 terminal. AC adapter detection voltage setting : Vth Vth (V) = (R1 + R2) / R2 · - INE2 - INE2 4 - A VCC 3 + R1 +INE2 R2 n OPERATION TIMING DIAG
