MB3886

Manufacturer Part NumberMB3886
Description2-channel Dc/dc Converter Ic With Overcurrent Protection Symmetrical-phase Type
ManufacturerFujitsu Microelectronics, Inc.
MB3886 datasheet
 


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FUJITSU SEMICONDUCTOR
DATA SHEET
ASSP
For Power Supply Applications (General Purpose DC/DC Converter)
2-Channel DC/DC Converter IC
with Overcurrent Protection Symmetrical-Phase Type
MB3886
DESCRIPTION
The MB3886 is a symmetrical-phase type of two-channel, DC/DC converter IC using pulse width modulation
(PWM) , incorporating an overcurrent protection circuit (requiring no current sense resistor) and an overvoltage
protection circuit. Providing high output driving capabilities, the MB3886 is suitable for down-conversion.
The MB3886 adopts both synchronous rectification to provide high efficiency and symmetrical phasing (two anti-
phase triangular waves) which contributes to making the input capacitor small.
The MB3886 contains a 5-volt regulator resulting in a reduced number of components used. It also contains a
variety of protection features which output the protection status upon detection of an overvoltage or overcurrent
while reducing the number of external protective devices required.
The result is an ideal built-in power supply for driving products with high speed CPU’s such as home TV game
devices and notebook PC’s.
This product is covered by US Patent Number 6,147,477.
FEATURES
• Overcurrent protection circuit (requiring no current sense resistor) and overvoltage protection circuit
• Power-supply voltage range : 5.5 V to 18 V
• Synchronous rectification system providing high efficiency
• PSIG pins (open-drain) to output the protection status
PACKAGE
30-pin plastic SSOP
(FPT-30P-M02)
DS04-27228-2E
(Continued)

MB3886 Summary of contents

  • Page 1

    ... The MB3886 adopts both synchronous rectification to provide high efficiency and symmetrical phasing (two anti- phase triangular waves) which contributes to making the input capacitor small. The MB3886 contains a 5-volt regulator resulting in a reduced number of components used. It also contains a variety of protection features which output the protection status upon detection of an overvoltage or overcurrent while reducing the number of external protective devices required. The result is an ideal built-in power supply for driving products with high speed CPU’ ...

  • Page 2

    ... MB3886 (Continued) • Symmetrical-phase system reducing the input capacitor loss • Built-in channel control function • Reference voltage : 3 • Error amplifier threshold voltage : 1.25 V • Oscillator frequency range : 10 kHz to 500 kHz • Built-in circuit for load-independent soft-start and discharge control • Totem-pole type output for N-ch MOSFET ...

  • Page 3

    ... Reference voltage, control circuit power supply terminal 27 VREF O Reference voltage output terminal 28 ILIM2 I CH2 overcurrent detection resistor connection terminal CH2 control terminal 29 CTL2 I “H” level : CH2 ON state “L” level : CH2 OFF state and protection status reset 30 PSIG2 O CH2 protection status output terminal MB3886 Description 3 ...

  • Page 4

    ... MB3886 BLOCK DIAGRAM 9 FB1 INE1 CS1 7 VREF 10 A 3.8 k INC1 10 2 CTL1 PSIG1 1 FB2 INE2 CS2 24 VREF INC2 29 CTL2 1.47 V PSIG2 30 SCP Comp CSCP 25 4 VCC 26 Error Amp.1 PWM Comp.1 1.25 V OVP Comp.1 Latch1-1 Dead Time CTL1 R Modulation1 1 ...

  • Page 5

    ... WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings. Conditions Min CB terminal Duty Duty) OSC cm) . MB3886 Rating Unit Max 120 mA 800 mA 770* mW 125 ...

  • Page 6

    ... MB3886 RECOMMENDED OPERATING CONDITIONS Parameter Power-supply voltage Boot voltage Reference voltage output current Bias output current Input voltage Output voltage Output current Peak output current Oscillator frequency Timing resistor Timing capacitor Boot capacitor Reference voltage output capacitor Bias output capacitor Soft-start capacitor ...

  • Page 7

    ... RST 9.1 k LIM 10, 21 INC TH I 10, 21 INC CTL RST 1, 30 PSIG PSIG MB3886 0 mA, VREF 0 mA Values Unit Min Typ Max 3.465 3.500 3.535 V 0 5.0 5.1 5.2 ...

  • Page 8

    ... MB3886 Parameter 10. Soft-start Circuit Block Charge current [CS] Threshold voltage Input bias current Voltage gain 11. Error Amp. Block Frequency [Error Amp.] bandwidth Output voltage Output source current Output sink current 12. PWM Comparator Threshold Block voltage [PWM Comp.] 13. Dead Time Maximum duty Control Block ...

  • Page 9

    ... V, VB Pin Conditions No. 13 11, 14 OUT1 OUT2 OPEN 20 Output ON state Output OFF state OFF 2, 29 CTL 26 CC MB3886 0 mA, VREF 0 mA Values Unit Min Typ Max 0.9 1 100 170 REF 0 0 ...

  • Page 10

    ... MB3886 TYPICAL CHARACTERISTICS Supply Current vs. Supply Voltage Supply voltage V Reference Voltage vs. Ambient Temperature 2 1.5 1 0.5 0 0 Ambient temperature Triangular Waveform Oscillation Frequency vs. Timing Capacitor 1000 100 100 1000 Timing capacitor C 10 Reference Voltage vs ...

  • Page 11

    ... Power Dissipation vs. Ambient Temperature 800 770 VCC 12 V 700 600 500 400 300 200 100 0 80 100 40 20 Ambient Temperature MB3886 vs. Ambient Temperature VCC 9 330 100 Ambient Temperature VCC 12 V 240 k (23) ...

  • Page 12

    ... MB3886 FUNCTIONAL DESCRIPTION 1. DC/DC Converter Functions (1) Reference voltage Block The reference voltage circuit generates a temperature-compensated reference voltage (typically 3.5 V) using the voltage supplied from the power supply terminal (pin 26) . The voltage is used as the reference voltage for the IC’s internal circuitry. The reference voltage can be used to supply a load current external device through the VREF terminal (pin 27) ...

  • Page 13

    ... THE OVERVOLTAGE DETECTION VOLTAGE”.) Channel On/Off Setting Conditions Channel output state CTL2 CH1 L OFF OFF H ON connected between the drain and the ILIM2 LIM2 MB3886 CH2 OFF OFF ON ON while holding the CSCP connected between the main- LIM1 13 ...

  • Page 14

    ... MB3886 SETTING THE OUTPUT VOLTAGE SETTING THE OSCILLATION FREQUENCY The oscillation frequency can be set by connecting the timing capacitor (C resistor ( the RT terminal (pin Oscillation frequency : f OSC 870000 f (kHz OSC C (pF (FB2) 22 FB1 9 Error ( INE2) 23 Amp. 8 INE1 ...

  • Page 15

    ... Discharge time : toff (time to output 10 ) toff ( 0.0126 3.4 V 1.25 V Error Amp. 0.125 Soft-start time ts OPEN CTL signal L and C ) connected to the CS1 and CS2 terminals and C ) charged at about 3.4 V using the internally set terminal voltage Voltage compared to INE voltage Discharge time toff MB3886 15 ...

  • Page 16

    ... MB3886 (FB2) 22 FB1 ( INE2) 23 INE1 (CS2) 24 CS1 (CTL2) 29 CTL1 TREATMENT OF UNUSED CS PINS When the soft-start function is not used, the CS1 terminal (pin 7) and CS2 terminal (pin 22) should be left open. "Open" 16 VREF VREF SW1 (SW2 3.8 k < Soft-start circuit > ...

  • Page 17

    ... When the overcurrent protection circuit is not used, the ILIM1 terminal (pin 3) and ILIM2 terminal (pin 28) should be shorted to the SGND terminal (pin 6) using the shortest possible connection. < Operation Without Using the ILIM Terminals > and R ) connected between the main-side FET’s LIM1 LIM2 (Vin ( (V) 2 Vin (V) f (Hz) L (H) OSC 3 ILIM1 ILIM2 28 6 SGND MB3886 17 ...

  • Page 18

    ... MB3886 TREATMENT OF UNUSED PSIG PINS When the PSIG terminals are not used, the PSIG1 terminal (pin 1) and PSIG2 terminal (pin 30) should be shorted or open to the SGND terminal (pin PSIG1 6 SGND < Operation Without Using the PSIG Terminals > 18 "Open" PSIG2 30 1 PSIG1 " ...

  • Page 19

    ... When the timer-latch short-circuit protection circuit is not used, the CSCP terminal (pin 25) should be shorted to SGND using the shortest possible connection. < Operation Without Using the CSCP Terminal > 0. the protection circuit sets the latch mV) . The protection circuit shuts off both channels I 6 SGND CSCP 25 MB3886 : = 50 STB 19 ...

  • Page 20

    ... MB3886 SETTING THE OVERVOLTAGE DETECTION VOLTAGE An overvoltage output from the DC/DC converter can be detected by connecting external resistors from the DC/ DC converter output voltage to the INC1 terminal (pin 10) and INC2 terminal (pin 21) of the overvoltage comparators (OVP Comp. 1 and 2) . When the DC/DC converter output voltage rises and the detection voltage exceeds the setting voltage, the output of the overvoltage comparator (OVP Comp becomes the “ ...

  • Page 21

    ... Unlatched, : Not unlatched CH1 OUT2-1 PSIG1 OUT1 Active Active Active Active Unlatching Conditions Channels unlatched CTL2 CH1 OPEN OPEN L L OPEN OPEN L L MB3886 CH2 OUT2-2 PSIG2 Active Active CH2 21 ...

  • Page 22

    ... MB3886 NOTE ON IC’S INTERNAL POWER CONSUMPTION The oscillation frequency and the total gate charge of FETs largely affects the internal dissipation of the IC. Pay attention to the following point with respect to the internal power consumption of the IC when applications are used. I (mean current) is obtained from the following equation, assuming Qg1 and Qg2 as the total gate charges ...

  • Page 23

    ... IC taking account of the “Power Dissipation vs. Ambient Temperature” characteristic in the “TYPICAL CHARACTERISTICS” section CB1 Crss Crss 1 2 OUT1 Ciss 1 VS1 Ciss 2 OUT2-1 14 PGND 15 t Bias current Ibias1 Bias current Ibias2 MB3886 ...

  • Page 24

    ... MB3886 Power Consumption vs. Input Voltage (Qg Parameters) 1.2 1.1 1.0 0.9 0 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Power Consumption vs. Input Voltage (fosc Parameter) 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 OSC SW1 SW2 Input voltage Vin (V) f 500 kHz OSC SW1 ...

  • Page 25

    ... SAMPLE CIRCUIT MB3886 25 ...

  • Page 26

    ... MB3886 PARTS LIST COMPONENT ITEM Q1, Q3 FET Q2, Q4 FETKY TM D1, D3 Diode L1 Coil L2 Coil C2 OS-CON TM C3, C5, C6, C8 Ceramics Condenser TM C4 OS-CON C7 OS-CON TM C9 Ceramics Condenser C10 Ceramics Condenser C11, C13, C16 Ceramics Condenser C12 Ceramics Condenser C14 Ceramics Condenser C15 Ceramics Condenser ...

  • Page 27

    ... Conversion Efficiency vs. Load Current (CH2) 100 output 90 SW1 ON SW2 OFF 100 m 1 Load current I ( 100 m 1 Load current I (A) L MB3886 Vin 8.5 V Vin 10 V Vin Vin 8.5 V Vin 10 V Vin ...

  • Page 28

    ... The worker must put on a grounding device containing 250 k • Do not apply a negative voltage. - Applying a negative voltage of 0 less to an LSI may generate a parasitic transistor, resulting in malfunction. ORDERING INFORMATION Model name MB3886PFV resistors in series. Package 30-pin plastic SSOP (FPT-30P-M02) ...

  • Page 29

    ... NOM "A" +0.10 +0.05 0.22 0.15 –0.05 –0.02 +.004 +.002 .009 .006 –.002 –.001 Details of "A" part 0.10±0.10(.004±.004) 0 10° Dimensions in mm (inches) MB3886 (Mounting height) (STAND OFF) 0.50±0.20 (.020±.008) 29 ...

  • Page 30

    ... MB3886 FUJITSU LIMITED All Rights Reserved. The contents of this document are subject to change without notice. Customers are advised to consult with FUJITSU sales representatives before ordering. The information and circuit diagrams in this document are presented as examples of semiconductor device applications, and are not intended to be incorporated in devices for actual use. Also, ...