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MB3878 nnnn ABSOLUTE MAXIMUM RAGINGS Rating Parameter Symbol Conditions Unit Min Max Power supply voltage VCC VCC, VCC (O) 28 V Output current IOUT 60 mA Peak output current IOUT Duty £ 5 % (t = 1 / fOSC · Duty) 500 mA 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, temperature,
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MB3878 nnnn ELECTRICAL CHARACTERISTICS (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Pin Parameter Symbol Conditions Unit No. Min Typ Max Ta = +25 C 4.995 5.000 5.045 V Output voltage VREF 6 Ta = - 30 C to +85 C 4.945 5.000 5.055 V Reference Input stability Line 6 VCC = 7 V to 25 V 310 mV voltage block Load stability Load 6 VREF = 0 mA to - 1 mA 110 mV (Ref) Short-circuit Ios 6 VREF = 1 V - 25 - 15 -5mA output current VCC = VCC (O) , VTLH 18 6.1 6.4 6.7 V VCC =
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MB3878 (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Pin Parameter Symbol Conditions Unit No. Min Typ Max VTH1 16 FB3 = 2 V, Ta = +25 C 4.167 4.200 4.233 V Threshold voltage FB3 = 2 V, VTH2 16 4.158 4.200 4.242 V Ta = - 30 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 2.0* MHz bandwidth Error amplifier VFBH 15 4.7 4.9 V block Output voltage (Error Amp.3) VFBL 15 20 200 mV Output
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MB3878 (Continued) (Ta = +25 C, VCC = 19 V, VCC (O) = 19 V, VREF = 0 mA) Value Pin Parameter Symbol Conditions Unit No. Min Typ Max VOUTCH 2, 10 4.7 4.9 V Output voltage VOUTCL 2, 10 20 200 mV Current detection amplifier block Output source ISOURCE 2, 10 OUTC1 = OUTC2 = 2 V - 2.0 - 0.6 mA (Current Amp.1, current Current Amp.2) Output sink ISINK 2, 10 OUTC1 = OUTC2 = 2 V 150 300 m A current 5, 7, VTL Duty cycle = 0 % 1.4 1.5 V PWM comparator 15 block Threshold voltage 5, 7,
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MB3878 nnnn TYPICAL CHARACTERISTICS Power supply current vs. power supply voltage Reference voltage vs. power supply voltage 12 10 Ta = +25 C Ta = +25 C CTL = 5 V CTL = 5 V 10 VREF = 0 mA 8 8 6 6 4 4 2 2 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. VREF load current Reference voltage vs. ambient temperature 10 2.0 Ta = +25 C VCC = 19 V VCC = 19 V 1.5 CTL = 5 V CTL = 5 V VREF = 0 mA 8 1.0 D 0.5 6 0.0 4 - 0.5 - 1.0 2 - 1
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MB3878 Triangular wave oscillator frequency vs. Triangular wave oscillator frequency vs. timing resistor power supply voltage 340 1 M Ta = +25 C Ta = +25 C VCC = 19 V 330 CTL = 5 V CTL = 5 V RT = 47 kW 320 310 300 100 k 290 280 270 260 250 10 k 240 0 5 10 15 20 25 10 k 100 k 1 M Timing resistor RT (W ) Power supply voltage VCC (V) Error amplifier threshold voltage vs. Triangular wave oscillator frequency ambient temperature (Error Amp.3) 5.0 340 VCC = 19 V VCC = 19 V 4.0 330 CTL = 5 V D
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MB3878 (Continued) Error amplifier gain and phase vs. frequency Ta = +25 C 40 AV 180 VCC = 19 V 5.2 V 240 kW 20 90 f 10 kW 1 m F IN 2.4 kW -+ 8 - 0 0 f OUT (4) 7 + (5) 9 10 kW - 20 - 90 (3) Error Amp.1 2.5 V (Error Amp.2) - 40 - 180 1 k 10 k 100 k 1 M 10 M Frequency f (Hz) Current detection amplifier gain and phase vs. frequency Ta = +25 C f 40 180 VCC = 19 V 20 AV 90 13 + 0 0 OUT f (24) · 25 10 - (2) 12 - 20 - 90 (1) Current Amp.1 12.6 V 12.55 V (Current Amp.2) - 40 - 180 1 k 10 k 100 k 1
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MB3878 nnnn 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 (5.0V Typ) used as the reference supply voltage for the IC’s internal circuitry. This pin 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 triangular w
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MB3878 (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 Amp. 1 to Error Amp. 3) 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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MB3878 nnnn 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. Be sure to select a resistor value that allows you to ignore the on resistor (70 W , 1mA) of the internal FET connected to the OUTD terminal (pin 11). Battery charging voltage: VO VO (V) = (R3 + R4) / R4 · 4.2 (V) VO B R3 < Error Amp.3 > - INE3 16 - + + R4 11 4.2 V OUTD 22 CS nnnn METHOD OF SETTING THE CHARGING CURR
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MB3878 nnnn 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 adaptor power constant when the partial potential point A of the AC adaptor voltage (Vcc) becomes lower than the voltage at the -INE2 terminal. AC adaptor detected voltage setting: Vth Vth (V) = (R1 + R2) / R2 · - INE2 - INE2 setting voltage range : 1.176 V to 4.2 V (equivalent to 7 V to 25
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MB3878 nnnn PROCESSING WITHOUT USE OF THE CS PIN If the soft-start function is not used, the CS terminal (pin 22) should be left open. Open 22 CS When no soft-start time is specified. nn NOTE ON AN EXTERNAL REVERSE-CURRENT PREVENTIVE DIODE nn • Insert a reverse-current preventive diode at one of the three locations marked * to prevent reverse current from the battery. • When selecting the reverse current prevention diode, be sure to consider the reverse voltage (VR) and reverse current (IR) of
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+ MB3878 nnnn APPLICATION EXAMPLE 1 W m - m - m m - m m - W W - m - W - - - m · - · - W - - - - - W W W W W W W W W W W W W W W 17 R8 100 k INE1 8 OUTC1 10 A 13 + R9 25 10 k INC1 IIN B 12 VCC (O) VIN + R14 R12 21 AC Adaptor 1.3 k 30 k +INE1 + C5 9 C1 R16 0.1 F R13 R15 22 F 200 k FB1 110 30 k + 7 A B + OUT Q2 + INE2 Drive 20 Q1 C8 4 I1 BATT SW 10000 pF OUTC2 R10 2 L1 RS 30 k VCC 12 H 0.033 VREF +INC
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MB3878 nnnn PARTS LIST (for APPLICATION EXAMPLE 1) COMPONENT ITEM SPECIFICATION VENDOR PARTS No. VISHAY Q1 FET Si4435DY SILICONIX Si4435DY Q2 FET 2N7002 VISHAY 2N7002 SILICONIX D1 Diode MBRS130LT3 MOTOROLA MBRS130LT3 L1 Coil 12 m H 4.0 A, 38 mW SUMIDA CDRH124-12 m H C1 OS Condenser 22 m F 25 V (10 %) C2, C3 OS Condenser 100 m F 25 V (10 %) CS Ceramics Condenser 2200 pF 10 % C5 Ceramics Condenser 0.1 m F 16 V C6 Ceramics Condenser 1500 pF 10 % C7 Ceramics Condenser 0.1 m F 25 V C8 Ceramics
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MB3878 nnnn REFERENCE DATA Conversion efficiency vs. charge current Conversion efficiency vs. charge voltage (Fixed voltage mode) (Fixed current mode) 100 100 VIN = 19 V VIN = 19 V 98 98 BATT charge voltage = 12.6 V fOSC = 277.9 kHz BATT : Electronic load, 96 h (%) = (VBATT · IBATT) / (VIN · IIN) · 100 96 h h (Product of KIKUSUI PLZ-150W) 94 94 92 92 90 90 88 88 86 86 84 84 82 82 80 80 10 m 100 m 1 10 0 2 4 6 8 10 12 14 16 BATT charge current IBATT (A) BATT charge voltage VBATT (V) BATT
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+ MB3878 nnnn APPLICATION EXAMPLE 2 W W m - m - m m - m m - W W - m - W - - - m · - · - W - - - - - W W W W W W W W W W W W W - W W W W - 20 AC Adaptor R8 VIN 100 k INE1 8 OUTC1 10 5600 pF A 13 + 25 R9 INC1 B 12 VCC (O) 10 k + R14 R12 21 System 1.3 k 30 k +INE1 RS2 + C5 9 0.033 C1 R15 0.1 F R16 R13 22 F 110 FB1 200 k 30 k + 7 A B + OUT Q2 + Drive 20 Q1 INE2 4 SW BATT R23 100 k OUTC2 2 L1 RS1 VIN VI
