ASSP Power Management Applications 1-channel DC/DC Converter

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ASSP Power Management Applications 1-channel DC/DC Converter

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DS04-27227-2Ea
ASSP Power Management Applications
1-channel DC/DC Converter
with Synchronous Rectifier
MB3885
DESCRIPTION
MB3885 1-channel DC/DC converter using pulse width modulation (PWM) synchronous rectification, designed down conversion applications. This device power supply with high output drive capacity. Synchronous rectification also provides high efficiency. addition, regulator built reduce number system components. result ideal built-in power supply driving products with high speed CPU's such home game devices notebook PC's. This product covered Patent Number 6,147,477.
FEATURES
Synchronous rectification high efficiency Supply voltage range Built-in high-precision reference voltage circuit Error Amp. threshold voltage 1.25 Oscillator frequency range Built-in soft-start circuit with error Amp. input control Totem pole type output N-ch MOSFET
PACKAGE
20-pin Plastic SSOP
(FPT-20P-M03)
Copyright©2002-2008 FUJITSU MICROELECTRONICS LIMITED rights reserved 2002.9
MB3885
ASSIGNMENTS
(TOP VIEW)
N.C. N.C. CSCP -INE +INE
N.C. N.C. VREF SGND PGND OUT2 OUT1
(FPT-20P-M03)
MB3885
DESCRIPTIONS
Symbol N.C. N.C. CSCP -INE +INC OUT1 OUT2 PGND SGND VREF N.C. N.C. connection connection Timer latch short protection capacitor connection terminal Triangular wave oscillator frequency setting capacitor connection terminal Triangular wave oscillator frequency setting resistor connection terminal Soft-start capacitor connection terminal (Also used output control) Error Amp. output terminal Error Amp. inverted input terminal Overvoltage comparator non-inverted input terminal Reference voltage, control circuit power supply terminal Output circuit bias output terminal Output bootstrap terminal Insert capacitor between terminals, bootstrap internal output transistor. Totem pole output terminal (External main side gate drive) External main side source connection terminal Totem pole output terminal. (External synchronous rectifier side gate drive) Ground terminal Ground terminal Reference voltage output terminal connection connection Description
MB3885
BLOCK DIAGRAM
Reg.
Error Amp. 1.25 Comp. Comp.1 Comp.2 Latch Drive2
-INE
Drive1
OUT1
+INC
1.47
OUT2 PGND
Comp.
bias Latch
CSCP
bias (2.5 VREF
UVLO
Power
SGND
MB3885
ABSOLUTE MAXIMUM RATINGS
Parameter Supply voltage Boot voltage Output current Peak output current Power dissipation Storage temperature Symbol Tstg Conditions terminal Duty fOSC Duty) Rating 555* +125 Unit
package mounted dual-sided epoxy board (10cm 10cm). WARNING: Semiconductor devices permanently damaged application stress (voltage, current, temperature, etc.) excess absolute maximum ratings. exceed these ratings.
MB3885
RECOMMENDED OPERATING CONDITIONS
Value -100 -700 0.01 15000
Parameter Supply voltage Boot voltage Reference voltage output current Bias output current Input voltage Output current Peak output current Oscillator frequency Timing resistor Timing capacitor Boot capacitor Reference voltage output capacitor Bias output capacitor Soft-start capacitor Short detection capacitor Operating ambient temperature
Symbol VINC fOSC CREF CSCP
Conditions terminal VREF terminal terminal -INE terminal +INC terminal Duty fosc Duty) VREF terminal terminal
Unit
WARNING: recommended operating conditions required order ensure normal operation semiconductor device. device's electrical characteristics warranted when device operated within these ranges. Always semiconductor devices within their recommended operating condition ranges. Operation outside these ranges adversely affect reliability could result device failure. warranty made with respect uses, operating conditions, combinations represented data sheet. Users considering application outside listed conditions advised contact their representatives beforehand.
MB3885
ELECTRICAL CHARACTERISTICS
(VCC VREF Parameter Symbol VREF Output voltage Reference Input stability Voltage Block Load stability [Ref] Short output current Bias Voltage Block [VB] Undervoltage Lockout Circuit Block [UVLO] Soft-start Block [CS] Short Detection Comparator Block [SCP] Triangular Wave Oscillator Block [OSC] VREF/ VREF Line Load Conditions VREF VREF Value 2.475 2.500 0.5* 2.525 Unit
Output voltage
4.95
5.05
5.15
Threshold voltage Hysteresis width Reset voltage Charge current Threshold voltage Input source current Short detection time Oscillator frequency Frequency temperature variation rate
VRST
0.2*
ICSCP tSCP fOSC fOSC/ fOSC VTH1 VTH2
CSCP 0.01
0.63 -1.4
0.68 -1.0
0.73 -0.6 12.2
-INE
Error Block [Error Amp.]
Threshold voltage Input bias current Voltage gain
1.241 1.2375 -200
1.2500 1.2500
1.259 1.2625
Standard design value (Continued)
MB3885
(VCC VREF Parameter Frequency band width Error Block [Error Amp.] Output voltage Output source current Output sink current Threshold Comparator voltage Block [PWM Comp.1, Comp.2] Dead time Adjustment Block [DTC] Symbol VFBH VFBL ISOURCE ISINK Duty cycle Conditions Value 800* -100 Unit
Duty cycle
1.81
Maximum duty cycle
Duty fOSC Duty) Duty fOSC Duty) OUT1 -100 OUT1 Duty fOSC Duty) Duty fOSC Duty) OUT2 -100 OUT2
Output current (main side)
ISOURCE1 ISINK1 VOH1 VOL1
-700* 900* -750* 900*
Output voltage (main side) Output Block [Drive]
Output current ISOURCE2 (synchronous rectifier side) ISINK2 Output voltage (synchronous rectifier side) Diode voltage VOH2 VOL2
Standard design value (Continued)
MB3885
(Continued) (VCC VREF Symbol Conditions OUT1 OUT2 OPEN, OUT2 OUT1 OUT1 OUT2 OPEN, OUT1 OUT2 +INC Value Unit
Parameter
Output Block [Drive] Dead time
Overvoltage Detection Comparator Block [OVP] General
Threshold voltage Input bias current Power supply current
1.44
1.47
1.50
+INC
-200
MB3885
TYPICAL CHARACTERISTICS
Supply Current Supply Voltage
Reference voltage VREF Supply current (mA) Supply voltage Supply voltage
Reference Voltage Supply Voltage
VREF
Reference Voltage Ambient Temperature
Reference voltage VREF -0.5 -1.0 -1.5 -2.0 VREF
Ambient temperature (°C)
Triangular wave upper/lower limit voltage
Triangular wave upper/lower limit voltage
Triangular Wave Upper/Lower Limit Voltage Triangular Wave Oscillator Frequency
Upper limit
Triangular Wave Upper/Lower Limit Voltage Ambient Temperature
Upper limit Lower limit
Lower limit
Triangular wave oscillator frequency fosc (Hz)
Ambient temperature (°C)
(Continued)
MB3885
Triangular Wave Oscillator Frequency Timing Capacitor
Triangular wave frequency fOSC (Hz) Triangular wave frequency fOSC (Hz)
Triangular Wave Oscillator Frequency Timing Resistor
15000
1000
10000
100000
Timing capacitor (pF)
Timing resistor
Triangular Wave Oscillator Frequency Supply Voltage
Triangular wave frequency fOSC (Hz) Supply voltage Triangular wave frequency fOSC (Hz)
Triangular Wave Oscillator Frequency Ambient Temperature
Ambient temperature (°C)
Error Gain, Phase Frequency
Frequency (Hz) -180
Phase (deg.)
Gain (dB)
1.25
Error Amp.
(Continued)
MB3885
(Continued)
Power Dissipation Ambient Temperature
Power dissipation (mW)
Ambient temperature (°C)
MB3885
FUNCTION DESCRIPTION
DC/DC Converter Function
Reference Voltage Block reference voltage circuit takes voltage feed from power supply terminal (pin generates temperature compensated reference voltage (2.5 Typ) reference voltage power supply control unit. Also, external load current obtained from power supply VREF terminal (pin maximum Triangular Wave Oscillator Block triangular waveform with amplitude generated connecting timing capacitor resistor terminal (pin terminal (pin respectively. triangular oscillator waveform input IC's internal comparator, well supplied externally from terminal. Error Block (Error Amp.) error Amp. amplifier that detects output voltage from DC/DC converter outputs control signal. error Amp. broad in-phase input voltage range Vcc-1.8 that easily external power supply. addition, arbitrary loop gain connecting feedback resistor capacitor between error Amp. output inverter input pin, providing stable phase compensation system. Also, power-on rush current prevented connecting soft-start capacitor between error Amp. noninverted input pins terminal (pin soft-start function operates with stable soft-start time that dependent output load DC/DC converter. Comparator Block (PWM Comp.) This voltage pulse width modulator that controls output duty according input voltage. Main side Turns output intervals which error Amp. output voltage higher than triangular wave voltage. Synchronous rectifier side Turns output intervals which triangular wave voltage lower than error Amp. voltage. Output Block output block totem pole configuration both main side synchronous rectifier side, drive external N-ch MOSFET. Also, high output drive capability (700 duty provides high gate-source capacitor, enabling on-resistor devices.
MB3885
Control Functions
Output ON/OFF control provided using terminal (pin setting functions. Output On/Off Setting Functions terminal voltage level Output state Hi-Z
Protective Functions
Timer Latch Short Circuit Protection (SCP) short circuit protection comparators read output voltage levels. output voltage falls below short detection voltage, timer circuit activated start charging external capacitor Cscp connected CSCP terminal (pin When capacitor voltage reaches approximately 0.68 output turns off, setting idle interval 100%. Once protection circuit activated, reset turning power supply again. (See "Setting Timer Latch Short Circuit Protector Time Constant.") Undervoltage Lockout Circuit Block (UVLO) Transient status during normal power-on momentary drops supply voltage cause abnormal operation control leading damage degradation system components. undervoltage lockout circuit prevents such abnormal operations reading internal reference voltage level switching output off, setting idle interval 100% holding CSCP terminal (pin level. System operation restored when supply voltage rises back about undervoltage lockout circuit threshold voltage. Overvoltage Protection Block (OVP) overvoltage protection circuit uses overvoltage comparator (OVP Comp.) read output voltage levels from DC/DC converter. output voltage exceeds threshold voltage latch set, turning main side FET. Once protector circuit activated, reset switching power supply again.
MB3885
SETTING TIMER LATCH SHORT CIRCUIT PROTECTOR TIME CONSTANT
error Amp. output level constantly compares operation with short circuit protection comparator reference voltage. When DC/DC comparator load conditions stable, short circuit protection comparator output level, transistor CSCP terminal (pin held input standby voltage (VSTB load conditions change rapidly, such during load short, causing output voltage drop, short circuit protection comparator output goes level. This causes transistor shut off, charging short circuit protection capacitor Cscp (connected CSCP terminal) Short detection time tscp 0.68 Cscp (µF) When capacitor Cscp charted threshold voltage (VTH 0.68 latch set, turning external (setting idle interval 100%) this time latch input closed CSCP terminal held input latch voltage
Error Amp. OUT1
-INE
1.25
Drive
Drive
OUT2
Comp.
CSCP
bias
CSCP
Latch
UVLO
Timer Latch Short Circuit Protection Circuit
MB3885
PROCESSING WITHOUT USING CSCP TERMINAL
When timer latch short circuit protection circuit used, CSCP terminal (pin should shorted SGND using shortest possible connection.
SGND
CSCP
Operation Without Using CSCP Terminal
MB3885
SOFT-START TIME SETTING
soft-start function prevents rush current events when power turned connecting soft-start capacitors (Cs) terminal (pin When activated (Vcc UVLO threshold voltage) terminals begin charging externally connected soft-start capacitors (Cs) Because error Amp. output (FB) determined ratio lower non-inverted input terminals (1.25 terminal voltage) inverted input terminal voltage (-INE) soft-start interval (when terminal voltage 1.25 determined ratio -INE terminal voltage terminal voltage. Thus DC/DC converter output voltage proportion rise terminal voltage soft-start capacitor connected terminal charges. soft-start time determined following formula. Soft-start time (time output 100%) 0.125 (µF)
terminal voltage Error. block comparison voltage -INE voltage
1.25
Soft start time
MB3885
VREF
-INE
1.25
Error Amp.
UVLO
Soft-start Block
MB3885
PROCESSING WITHOUT USING TERMINALS
When soft-start function used, terminal (pin should left open.
"Open"
Operation Without Soft-start Setting
OSCILLATOR FREQUENCY SETTING
oscillator frequency connecting timing capacitor (CT) terminal (pin timing resistor (RT) terminal (pin Oscillator frequency 893000 fosc (kHz) (pF)
OUTPUT VOLTAGE SETTING
-INE 1.25 Error Amp. 1.25
MB3885
OVERVOLTAGE PROTECTION CIRCUIT VOTAGE SETTING
Overvoltage conditions DC/DC converter output voltage detected connecting external resistance from DC/DC converter output voltage +INC terminal (pin respective overvoltage protection comparator circuits (OVP comp.) When output voltage DC/DC converter rises above detection voltage, overvoltage protection comparator (OVP Comp.) output goes level, setting latch shutting off. Detection voltage VOVP 1.47 Once protection circuit been activated, reset lowering voltage below reset voltage (1.7 Min)
+INC1
1.47
Comp.
MB3885
PRECAUTIONS RELATED SUPPLY VOLTAGE RANGE
Although supply voltage range listed under recommended operating requirements 5.5V-18V, generation heat limits maximum operating supply voltage since IC's internal loss varies with frequency oscillation FET's total gate charge. When using 3885 application, caution must taken relation supply voltage range. shown below, (average current) determined from total gate charge Qg1, Qg2, charged from gate capacitance (Ciss1, Ciss2, Crss1, Crss2) external following formula. Ibias1 Ibias2 (Ibias1 Ibias2
Because current consumption other than power consumption determined from following formula. Power consumption 0.0065
MB3885
OUT1 Ciss2 Crss1 Ciss1 Crss2
Drive Drive
OUT2 PGND
VOUT1
VOUT2
Bias current Ibias1
Bias current Ibias2
Using above formulas determine power consumption, settings should made with reference "Power Consumption Input Voltage" following page, well "Power dissipation Ambient Temperature."
MB3885
Power Consumption Input Voltage Parameters)
1.00 Power consumption 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Input voltage fOSC
Power Consumption Input Voltage (fosc Parameters)
1.00 Power consumption 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 fOSC fOSC fOSC fOSC fOSC
0.00 Input voltage
MB3885
Reg. OUT1 Drive1 OUT2 PGND Error Amp. Comp.1 Comp. Latch 1.47 Drive2 Comp.2
APPLICATION CIRCUIT
0.022 -INE
Output On/Off signal 1.25
+INC
Comp. bias
CSCP UVLO
Latch
bias
0.01
(2.5 Power VREF SGND
MB3885
COMPONENT LIST
COMPONENT ITEM Diode Diode Coil Condenser Ceramics Condenser Ceramics Condenser Ceramics Condenser Ceramics Condenser Ceramics Condenser Ceramics Condenser Ceramics Condenser Ceramics Condenser Electrolytic Condenser Ceramics Condenser Ceramics Condenser Resistor Resistor Resistor Resistor Resistor Resistor Resistor SPECIFICATION (Max) 0.35 (Max) (Max) 0.022 0.01 VENDOR ROHM ROHM PARTS IRF7811 RB051L-40 RB495D RLF12545T -2R7N8R7
Notes International Rectifier Corp. ROHM Rohm, Ltd. TDK, Ltd.
MB3885
REFERENCE DATA
Conversion Efficiency Load Current Characteristics
output
Conversion efficiency
Load current
MB3885
PRECAUTIONARY INFORMATION
Printed circuit board ground lines should designed with consideration common impedance. Take sufficient countermeasures should taken protect against static electricity. Always place semiconductors containers that have anti-static provisions, conductive. After mounting, boards should placed conductive bags containers storage handling. Working surfaces, tools, measurement equipment should grounded. Persons handling semiconductors should grounded directly with resistance
apply negative voltages. Application negative voltage -0.3 greater create parasitic transistor effects device, leading abnormal operation.
ORDERING INFORMATION
Part Number MB3885PFV Package Plastic SSOP 20-pin (FPT-20P-M03) Remarks
MB3885
PACKAGE DIMENSION
20-pin, Plastic SSOP (FPT-20P-M03)
6.50±0.10(.256±.004)
Note These dimensions include resin protrusion. Note Pins width pins thickness include plating thickness.
0.17±0.03 (.007±.001)
4.40±0.10
INDEX
6.40±0.20 (.173±.004) (.252±.008)
Details part 1.25 -0.10 .049 -.004 LEAD
+0.20 +.008
(Mounting height)
0.65(.026)
0.24±0.08 (.009±.003) 0.13(.005)
0~8° 0.10±0.10 (Stand off) (.004±.004) 0.25(.010)
0.10(.004)
0.50±0.20 (.020±.008) 0.45/0.75 (.018/.030)
1999 FUJITSU LIMITED F20012S-3C-5
Dimensions (inches)
MB3885
MEMO
MB3885
MEMO
MB3885
MEMO
FUJITSU MICROELECTRONICS LIMITED
Shinjuku Dai-Ichi Seimei Bldg. 7-1, Nishishinjuku 2-chome, Shinjuku-ku, Tokyo 163-0722, Japan Tel: +81-3-5322-3347 Fax: +81-3-5322-3387 http://jp.fujitsu.com/fml/en/ further information please contact: North South America FUJITSU MICROELECTRONICS AMERICA, INC. 1250 Arques Avenue, Sunnyvale, 94085-5401, U.S.A. Tel: +1-408-737-5600 Fax: +1-408-737-5999 http://www.fma.fujitsu.com/ Europe FUJITSU MICROELECTRONICS EUROPE GmbH Pittlerstrasse 63225 Langen, Germany Tel: +49-6103-690-0 Fax: +49-6103-690-122 Korea FUJITSU MICROELECTRONICS KOREA LTD. KOSMO TOWER, 1002 Daechi-Dong, Kangnam-Gu,Seoul 135-280 Korea Tel: +82-2-3484-7100 Fax: +82-2-3484-7111 http://www.fmk.fujitsu.com/ Asia Pacific FUJITSU MICROELECTRONICS ASIA LTD. Lorong Chuan, #05-08 Tech Park, Singapore 556741 Tel: +65-6281-0770 Fax: +65-6281-0220 FUJITSU MICROELECTRONICS SHANGHAI CO., LTD. Rm.3102, Bund Center, No.222 Road(E), Shanghai 200002, China Tel: +86-21-6335-1560 Fax: +86-21-6335-1605 http://cn.fujitsu.com/fmc/ FUJITSU MICROELECTRONICS PACIFIC ASIA LTD. 10/F., World Commerce Centre, Canton Road Tsimshatsui, Kowloon Hong Kong Tel: +852-2377-0226 Fax: +852-2376-3269 http://cn.fujitsu.com/fmc/tw
Rights Reserved. contents this document subject change without notice. Customers advised consult with sales representatives before ordering. information, such descriptions function application circuit examples, this document presented solely purpose reference show examples operations uses FUJITSU MICROELECTRONICS device; FUJITSU MICROELECTRONICS does warrant proper operation device with respect based such information. When develop equipment incorporating device based such information, must assume responsibility arising such information. FUJITSU MICROELECTRONICS assumes liability damages whatsoever arising information. information this document, including descriptions function schematic diagrams, shall construed license exercise intellectual property right, such patent right copyright, other right FUJITSU MICROELECTRONICS third party does FUJITSU MICROELECTRONICS warrant non-infringement third-party's intellectual property right other right using such information. FUJITSU MICROELECTRONICS assumes liability infringement intellectual property rights other rights third parties which would result from information contained herein. products described this document designed, developed manufactured contemplated general use, including without limitation, ordinary industrial use, general office use, personal use, household use, designed, developed manufactured contemplated accompanying fatal risks dangers that, unless extremely high safety secured, could have serious effect public, could lead directly death, personal injury, severe physical damage other loss (i.e., nuclear reaction control nuclear facility, aircraft flight control, traffic control, mass transport control, medical life support system, missile launch control weapon system), requiring extremely high reliability (i.e., submersible repeater artificial satellite). Please note that FUJITSU MICROELECTRONICS will liable against and/or third party claims damages arising connection with above-mentioned uses products. semiconductor devices have inherent chance failure. must protect against injury, damage loss from such failures incorporating safety design measures into your facility equipment such redundancy, fire protection, prevention over-current levels other abnormal operating conditions. Exportation/release products described this document require necessary procedures accordance with regulations Foreign Exchange Foreign Trade Control Japan and/or export control laws. company names brand names herein trademarks registered trademarks their respective owners.
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ASSP Power Management Applications 1-channel DC/DC Converter

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