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FUJITSU SEMICONDUCTOR
DATA SHEET
ASSP
For Power Supply Applications (Secondary battery)
DC/DC Converter IC for Charging
MB3878
DESCRIPTION
The MB3878 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
adaptor in order to keep its power constant (dynamically-controlled charging).
The charging method enables quick charging, for example, with the AC adaptor during operation of a notebook PC
The MB3878 provides a broad power supply voltage range and low standby current as well as high efficiency,
making it ideal for use as a built-in charging device in products such as notebook PC.
This product is covered by US Patent Number 6,147,477.
FEATURES
• Detecting a voltage drop in the AC adaptor and dynamically controlling the charge current
(Dynamically-controlled charging)
• Output voltage setting using external resistor : 1 cell to 4 cells
• High efficiency
• Wide range of operating supply voltages : 7 V to 25 V
• Output voltage setting accuracy : 4.2V
• Built-in frequency setting capacitor enables frequency setting using external resistor only
• Oscillator frequency range : 100kHz to 500kHz
PACKAGE
: 94
0.8% (per cell)
24-pin plastic SSOP
(FPT-24P-M03)
DS04-27706-2E
(Continued)
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Summary of Contents for Fujitsu MB3878
- Page 1 FUJITSU SEMICONDUCTOR DS04-27706-2E DATA SHEET ASSP For Power Supply Applications (Secondary battery) DC/DC Converter IC for Charging MB3878 DESCRIPTION The MB3878 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.
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Page 2: Pin Assignment
MB3878 (Continued) • Built-in current detector amplifier with wide in-phase input voltage range : 0 V to Vcc • In standby mode, leave output voltage setting resistor open to prevent inefficient current loss • Built-in standby current function : 0 A (standard) •... - Page 3 MB3878 PIN DESCRIPTION Pin No. Symbol Descriptions INC2 Current detection amplifier (Current Amp. 2) input pin. OUTC2 Current detection amplifier (Current Amp. 2) output pin. INE2 Error amplifier (Error Amp. 2) non-inverted input pin. INE2 Error amplifier (Error Amp. 2) inverted input pin. Error amplifier (Error Amp.
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Page 4: Table Of Contents
MB3878 BLOCK DIAGRAM INE1 OUTC1 <Current Amp.1> <Error VREF Amp.1> INC1 INC1 VCC (O) INE1 <PWM Comp.> <OUT> Drive INE2 OUTC2 <Error <Current Amp.2> Amp.2> VREF INC2 Bias INC2 Voltage 5 V) <VH> INE2 2.5 V 1.5 V <UVLO> <Error Amp.3>... -
Page 5: Ine1
No warranty is made with respect to uses, operating conditions, or combinations not represented on the data sheet. Users considering application outside the listed conditions are advised to contact their FUJITSU representatives beforehand. -
Page 6: Ine1
MB3878 ELECTRICAL CHARACTERISTICS 25 C, VCC 19 V, VCC (O) 19 V, VREF 0 mA) Value Parameter Symbol Conditions Unit 25 C 4.995 5.000 5.045 Output voltage 30 C to 85 C 4.945 5.000 5.055 Reference Input stability Line 7 V to 25 V voltage block Load stability Load... -
Page 7: Outc1
MB3878 25 C, VCC 19 V, VCC (O) 19 V, VREF 0 mA) Value Parameter Symbol Conditions Unit 2 V, Ta 25 C 4.167 4.200 4.233 Threshold voltage 2 V, 4.158 4.200 4.242 30 C to 85 C Input current INE3 INE3 Voltage gain... - Page 8 MB3878 (Continued) 25 C, VCC 19 V, VCC (O) 19 V, VREF 0 mA) Value Parameter Symbol Conditions Unit 2, 10 OUTCH Output voltage 2, 10 Current detection OUTCL amplifier block Output source 2, 10 OUTC1 OUTC2 2 V SOURCE (Current Amp.1, current Current Amp.2)
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Page 9: Inc1
MB3878 TYPICAL CHARACTERISTICS Power supply current vs. power supply voltage Reference voltage vs. power supply voltage 25 C 25 C VREF 0 mA Power supply voltage V Power supply voltage V Reference voltage vs. VREF load current Reference voltage vs. ambient temperature 25 C 19 V 19 V... - Page 10 MB3878 Triangular wave oscillator frequency vs. Triangular wave oscillator frequency vs. timing resistor power supply voltage 25 C 25 C 19 V 47 k 100 k 10 k 10 k 100 k Timing resistor R Power supply voltage V Error amplifier threshold voltage vs. Triangular wave oscillator frequency ambient temperature (Error Amp.3) 19 V...
- Page 11 MB3878 (Continued) Error amplifier gain and phase vs. frequency 25 C VCC 19 V 5.2 V 240 k 10 k 2.4 k 10 k Error Amp.1 2.5 V (Error Amp.2) 10 k 100 k 10 M Frequency f (Hz) Current detection amplifier gain and phase vs.
- Page 12 MB3878 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.
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Page 13: Ine3
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 output voltage. -
Page 14: Outd
MB3878 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 , 1mA) of the internal FET connected to the OUTD terminal (pin 11). - Page 15 MB3878 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) INE2...
- Page 16 MB3878 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 When no soft-start time is specified. NOTE ON AN EXTERNAL REVERSE-CURRENT PREVENTIVE DIODE • Insert a reverse-current preventive diode at one of the three locations marked * to prevent reverse current from the battery.
- Page 17 MB3878 APPLICATION EXAMPLE 1...
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Page 18: Inc1
MB3878 PARTS LIST (for APPLICATION EXAMPLE 1) COMPONENT ITEM SPECIFICATION VENDOR PARTS No. VISHAY Si4435DY SILICONIX Si4435DY 2N7002 VISHAY 2N7002 SILICONIX Diode MBRS130LT3 MOTOROLA MBRS130LT3 Coil 12 H 4.0 A, 38 m SUMIDA CDRH124-12 H OS Condenser 22 F 25 V (10 C2, C3 OS Condenser 100 F... - Page 19 MB3878 REFERENCE DATA Conversion efficiency vs. charge current Conversion efficiency vs. charge voltage (Fixed voltage mode) (Fixed current mode) 19 V 19 V charge voltage BATT 12.6 V f 277.9 kHz BATT : Electronic load, (VIN IIN) (Product of KIKUSUI PLZ-150W) BATT BATT 10 m...
- Page 20 MB3878 APPLICATION EXAMPLE 2...
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Page 21: Inc2
MB3878 PARTS LIST (for APPLICATION EXAMPLE 2) COMPONENT ITEM SPECIFICATION VENDOR PARTS No. Si4435DY VISHAY SILICONIX Si4435DY 2N7002 VISHAY SILICONIX 2N7002 Diode MBRS130LT3 MOTOROLA MBRS130LT3 Dual Op-amp MB47358 Our Company MB47358 4.0 A, Coil 12 H SUMIDA CDRH124-12 H 38 m OS Condenser 22 F 25 V (10 ) - Page 22 MB3878 USAGE PRECAUTIONS • Printed circuit board ground lines should be set up with consideration for common impedance. • Take appropriate static electricity measures. • Containers for semiconductor materials should have anti-static protection or be made of conductive material. • After mounting, printed circuit boards should be stored and shipped in conductive bags or containers. •...
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Page 23: Package Dimension
Details of "A" part +0.20 1.25 –0.10 (Mounting height) +.008 .049 –.004 0.25(.010) 0~8° "A" 0.65(.026) +0.08 0.24 –0.07 0.13(.005) +.003 .009 0.50±0.20 0.10±0.10 –.003 (.020±.008) (.004±.004) (Stand off) 0.60±0.15 (.024±.006) 0.10(.004) 0.10(.004) 2001 FUJITSU LIMITED F24018S-c-3-4 Dimensions in mm (inches) - Page 24 (2) for use requiring extremely high reliability (i.e., submersible repeater and artificial satellite). Please note that Fujitsu will not be liable against you and/or any third party for any claims or damages arising in connection with above-mentioned uses of the products.