ASSP Power Supply Applications With Power Mode Switching Function
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DS04-27221-2E
ASSP Power Supply Applications
With Power Mode Switching Function
2-ch DC/DC Converter With Synchronous Rectifier
MB3821
DESCRIPTION
MB3821 pulse width modulation (PWM) type 2-channel DC/DC converter with synchronous rectification designed voltage, high efficiency operation high precision high frequency applications, ideal down conversion. normal/low-power mode selection provided, ideal internal power supply (3.3V, applications with substantial load current variation, such notebook computers.
FEATURES
Synchronous rectification High efficiency (normal power mode, load (low power mode, load Built-in power mode selector circuit Reference voltage accuracy 2.5V Built-in error input control type soft start circuit Totem pole type output N-ch MOSFET applications Built-in timer-latch type short protection circuit
PACKAGE
24-pin, Plastic SSOP
(FPT-24P-M03)
MB3821
ASSIGNMENT
(TOP VIEW)
-IN1
VREF CSCP -IN2 OUT1-2 OUT2-2
(CH1)
OUT1-1 OUT2-1 GND(0)
(CH2)
(FPT-24P-M03)
MB3821
DESCRIPTION
Symbol -IN1 OUT1-1 OUT2-1 GND(0) OUT2-2 OUT1-2 -IN2 CSCP VREF Descriptions Triangular wave oscillator frequency setting capacitance connection pin. Triangular wave oscillator frequency setting resistance connection pin. Ground pin. Capacitor connection Channel soft start (also channel control). Channel error amplifier inverted input pin. Channel error amplifier output Mode select pin. level switch power mode. Totem pole type output (external main side gate drive). Channel external main side source connection pin. Channel boot capacitance connection pin. Channel totem pole output (external main side gate drive). Ground output circuit. Power supply output circuit. Channel totem pole output (external synchronous rectifier side gate drive). Channel boot capacitance connection pin. Channel external main side source connection pin. Channel totem pole output (external main side gate drive). Power supply control pin. switch standby mode. Channel error amplifier output pin. Channel error amplifier inverted input pin. Channel soft start capacitance connection pin(also channel control). Timer-latch short circuit protection capacitance connection pin. Reference power supply, control circuit power supply pin. Reference voltage output pin.
MB3821
BLOCK DIAGRAM
Error Amp. -IN1 1.26 Comp.2 Drive Comp.1 Drive
OUT1-1
OUT2-1
Error Amp. -IN2 1.26 Comp.2 Drive OUT2-2 Comp.1 Drive OUT1-2
Comp. CSCP Latch UVLO bias bias Power (2.5 ON/OFF
VREF
MB3821
ABSOLUTE MAXIMUM RAGINGS
Parameter Power supply voltage Bias voltage Output current Output peak current Power dissipation Storage temperature Symbol Tstg Conditions Duty +25°C Rating Min. Max. 740* +125 Unit
packages mounted epoxy board cm). WARNING: Semiconductor devices permanently damaged application stress (voltage, current, temperature, etc.) excess absolute maximum ratings. exceed these ratings.
RECOMMENDED OPERATING CONDITIONS
Parameter Power supply voltage Bias voltage Reference voltage output current Input voltage Output current Output peak current Timing capacitance Timing resistance Oscillator frequency Soft-start capacitance Short detection capacitance Boot capacitance Operating ambient temperature Symbol fOSC CSCP SEL, Duty (Normal mode) (Low power mode) Conditions Value Min. -300 Typ. 0.01 Max. 15000 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 FUJITSU representatives beforehand.
MB3821
ELECTRICAL CHARACTERISTICS
(VCC +25°C) Parameter Output voltage Reference voltage block Output voltage temperature variation Input stability Load stability Short-circuit output current Under voltage lockout protection circuit block(U.V.L.O) Threshold voltage Hysteresis width Reset voltage Symbol VREF VREF /VREF Line Load VRST Conditions VREF -30°C +85°C VREF -1.0 VREF Value Min. 2.45 Typ. 2.50 0.5* 0.18 Max. 2.55 Unit
4,21 4,21 4,21
Soft-start block
Charge current Input standby voltage Threshold voltage
VSTB ICSCP tSCP VSTB fOSC VLOW ISEL f/fdv
4,21 4,21 4,21 8,11, 500pF, 14,17 CSCP 0.01
-1.4 0.63 -1.4
-1.0 0.68 -1.0
-0.6 0.73 -0.6 12.2
Short circuit detection block
Input source current Short detection time Input standby voltage Input latch voltage Oscillator frequency Mode select voltage Input current Frequency stability voltage Frequency stability temperature
power mode Normal mode
Triangular wave oscillator block
500pF, 8,11, 14,17 4.5V
f/fdt
500pF, 8,11, 14,17 -30°C +85°C
Standard design value.
(Continued)
MB3821
(Continued)
(VCC +25°C) Parameter Threshold voltage temperature stability Error amplifier block Input bias current Voltage gain Frequency bandwidth Output voltage Output source current Output sink current Comp. block Threshold voltage Symbol ISOURCE ISINK Conditions Value Min. 1.235 -200 VREF Typ. 1.260 0.5* 800* Max. 1.285 Unit
6,19 6,19 -30°C +85°C 5,20 6,19 6,19 6,19 6,19 6,19 6,19 8,11 14,17 Duty cycle Duty cycle
Dead time control block
Maximum duty cycle
8,11, 14,17
Output block (Drive)
Output voltage (Main side)
VDIODE ICTL ICCS
8,17 8,17
Output voltage (Synchronous rectifier side) Diode voltage
11,14 11,14 active mode standby mode (Normal mode) (Low power mode)
Control block General
input voltage Input current Standby current
Power supply current
Standard design value.
MB3821
TYPICAL CHARACTERISTICS
Power supply current power supply voltage Power supply current (mA)
Power supply current power supply voltage Power supply current (mA)
Power supply voltage Reference voltage power supply voltage
Power supply voltage Reference voltage power supply voltage
Reference voltage VREF
Reference voltage VREF
Power supply voltage Reference voltage ambient temperature
Power supply voltage Reference voltage control voltage
Reference voltage VREF
-0.5 -1.0 -1.5 -2.0
Reference voltage VREF
Ambient temperature (°C)
Control voltage VCTL
(Continued)
MB3821
(Continued)
Control current control voltage
Select current select voltage
Select current ISEL (µA)
Control current ICTL (µA)
Control voltage VCTL Triangular wave upper lower limit voltage triangular wave oscillator frequency Triangular wave upper lower limit voltage Triangular wave upper lower limit voltage
16.0
Select voltage VSEL Triangular wave upper lower limit voltage ambient temperature
Upper
Upper
Lower
Lower
Triangular wave oscillator frequency fOSC (Hz) Triangular wave oscillator frequency capacitance Triangular wave oscillator frequency fOSC (Hz)
Ambient temperature (°C) Triangular wave oscillator frequency fOSC (Hz) Triangular wave oscillator frequency capacitance
capacitance
capacitance
(Continued)
MB3821
(Continued)
Duty oscillator frequency (ch1)
Duty oscillator frequency (ch1)
Duty
Duty
Triangular wave oscillator frequency fOSC (Hz)
Triangular wave oscillator frequency fOSC (Hz)
Oscillator frequency fOSC (Hz) Triangular wave oscillator frequency timing resistance
Oscillator frequency fOSC (Hz) Triangular wave oscillator frequency timing resistance
15000
15000
Triangular wave oscillator frequency fOSC (kHz)
Timing resistance Triangular wave oscillator frequency power supply voltage
Triangular wave oscillator frequency fOSC (kHz)
Timing resistance Triangular wave oscillator frequency power supply voltage
Power supply voltage
Power supply voltage
MB3821
(Continued)
Triangular wave oscillator frequency fOSC (kHz) Triangular wave oscillator frequency fOSC (kHz) Triangular wave oscillator frequency ambient temperature
Triangular wave oscillator frequency ambient temperature
Ambient temperature (°C) Error amplifier,gain phase frequency (ch1)
-135 -180
Ambient temperature (°C)
Phase (deg)
Gain (dB)
2.52 1.26
Error amplifier
Frequency (Hz) Power dissipation ambient temperature Power dissipation (mW)
Ambient temperature (°C)
MB3821
FUNCTIONAL DESCRIPTION
DC/DC Converter Function
Reference voltage circuit (Ref) reference voltage circuit generates temperature-compensated reference voltage 2.50 using voltage supplied from power supply terminal (pin 23). This voltage used reference voltage internal circuits reference voltage also supplied external device from VREF terminal (pin maximum current 1mA. Triangular-wave oscillator circuit (OSC) connecting frequency setting capacitor resistor (pin (pin terminals, possible generate desired triangular oscillation waveform. triangular wave input comparator within Error amplifier This amplifier detects output voltage DC/DC converter outputs control signal accordingly. system provided with stable phase compensation connecting feedback resistor capacitor between error amplifier create desired level loop gain. Also, connecting soft start capacitance terminal, which inverted input error amplifier, possible prevent current surges when power supply started. using error amplifier soft start detection, possible operate with fixed soft start interval independent output load converter. comparators (PWM Comp.1, Comp.2) Comp.1 Comp.2 voltage-pulse width modulators that control output duty according input voltage. Comp.1 controls pulse width main side output circuit, Comp.2 controls pulse width synchronous rectifier side output circuit. triangular wave generated triangular wave oscillator compared error amplifier output voltage, intervals when error amplifier voltage higher than triangular wave, main side output transistor switched synchronous rectifier side output transistor switched off. Also, Comp.1 maximum duty cycle approximately (normal mode). Output circuit (Drive) output circuits comprised totem-pole configuration both main side synchronous rectifier side, drive external N-ch MOSFET. Mode select circuit (SEL) terminal (pin either channel normal mode power mode. power mode triangular oscillator frequency approximately 1/10 normal mode, reducing internal power consumption chip enabling high efficiency power supply light load levels. Power supply control circuit (CTL) terminal (pin used power supply on/off control (standby power consumption less).
Protection Functions
Under Voltage Lockout Circuit (UVLO) Power-on surge states sudden drops supply voltage cause control operate abnormally, leading destruction damage system elements. under voltage lockout circuit detects internal reference voltage level from supply voltage, shuts output transistors that inactive interval becomes 100%, holding CSCP terminal (pin voltage level. Operation restored soon supply voltage exceeds under voltage lockout circuit threshold voltage.
MB3821
Timer-Latch Short Circuit Protection Circuit (SCP) This circuit detects output voltage level from error amplifier. When error amplifier output voltage exceeds approximately 2.1V, timer circuit activated charges external capacitor CSCP terminal (pin 22). error amplifier output does return normal range before capacitor voltage reaches approximately 0.7V, latch circuit activated sets both main synchronous rectifier side output pins level. After short protection circuit been activated, reset simply restarting power supply. (See "METHOD SETTING TIME CONSTANT TIMER LATCH SHORT-CIRCUIT PROTECTION CIRCUIT".)
MB3821
METHOD SETTING SOFT START TIME
provide soft start preventing current surges power-on, soft start capacitors (Cs1, Cs2) connected both channels, (pin (pin CH2. When started (when (pin goes level, UVLO threshold voltage), transistors switch pins begin charging external soft start capacitors (Cs1, Cs2) error amplifier contributes soft start with proportionate output voltage voltage regardless load current DC/DC converter. soft start time calculated following formula. Soft start time (time 100% output) tS(sec) 1.26 (µF)
Soft start circuit
-IN1 1.26 Error Amp.1
Output stage
OUT1-1
Output stage
OUT2-1
-IN2 1.26 Error Amp.2
Output stage
OUT1-2
Comp. bias Latch bias (2.5V) Power ON/OFF
Output stage
OUT2-2
CSCP
CSCP
UVLO
MB3821
TREATMENT WITHOUT USING TERMINAL
When soft start circuit, open terminal (pin terminal (pin 22).
Treatment When Using
MB3821
METHOD SETTING TIME CONSTANT TIMER-LATCH SHORT-CIRCUIT PROTECTION CIRCUIT
short detection comparator (SCP comparator) constantly compares error amplifier output level reference voltage. While switching regulator load conditions stable channels, short detection comparator output remains level, transistor CSCP terminal (pin held input standby voltage (VSTB= 50mV). load conditions change rapidly short-circuiting load, causing output voltage drop, output from short detection comparator goes level. This causes transistor turn external short protection capacitor CSCP connected CSCP charge Short Detection Time tSCP(sec) CSCP (µF) When capacitor CSCP charged threshold voltage latch set, external turned (inactive interval 100%). this point, latch input closed CSCP terminal held input latch voltage mV).
Timer-latch short-circuit protection circuit
-IN1 1.26 Error Amp.1
Output stage
OUT1-1
Output stage
OUT2-1
-IN2 1.26 Error Amp.2
Output stage
OUT1-2
Comp. bias bias (2.5V) Power ON/OFF
Output stage
OUT2-2
CSCP
CSCP
Latch
UVLO
MB3821
TREATMENT WITHOUT USING CSCP TERMINAL
When timer latch short-circuit protection circuit, connect CSCP terminal (pin with shortest distance.
Treatment When Using
CSCP
Channel Control Method
On/off controls either channel enabled setting pins. Setting Conditions setting Open Open Open Open Channel output state
MB3821
METHOD SETTING OSCILLATOR FREQUENCY
Oscillator Frequency timing capacitor (CT) connected (pin timing resistor (RT) connected (pin Oscillator frequency Normal mode
fOSC (kHz) 1000000 CT(pF) RT(k)
power mode
fOSC (kHz) 100000 CT(pF) RT(k)
RB415D Drive Si9410 OUT2-1 OUT1-1 Error Amp. Comp.1 Comp.2 Drive RB415D Comp.1 Drive OUT1-2 Error Amp. Si9410 1.26 Comp.2 Drive CH2>> Comp. bias Latch UVLO bias Power (2.5 ON/OFF VREF Si9410 CH1>> Si9410 1.26 <5.0
S-81250 Reg.
ON/OFF
0.022
-IN1
APPLICATION EXAMPLE
VXCS1
2SK1299
DE5SC3ML <3.3
0.022
ON/OFF
-IN2
VXCS2
OUT2-2
2SK1299
DE5SC3ML
CSCP
Si9410 Siliconix Output ON/OFF signal CTL= CTL= DE5SC3ML SHINDENGEN ELECTRIC MANUFACTURING Co., Ltd. RB415D ROHM Co., 2SK1299 SANYO Electric Co., Ltd. S-81250 Seiko Instruments Inc.
Mode select signal Normal mode SEL= power mode SEL=
MB3821
MB3821
REFERENCE DATA
Load characteristic
Conversion efficiency load current
output output OFF)
Conversion efficiency load current
output (3.3V output OFF)
VXCS1 VXCS2
Conversion efficiency
0.001
Conversion efficiency
VXCS1 VXCS2
Normal mode (SEL=
Normal mode (SEL=
power mode (SEL=
power mode (SEL=
0.005 0.01 0.05
0.001
0.005
0.01
0.05
Load current
Load current
Normal mode
Conversion efficiency Input voltage
Conversion efficiency Input voltage
Conversion efficiency
Conversion efficiency
output output OFF)
output (3.3 output OFF)
VXCS1 VXCS2
VXCS1 VXCS2
Input voltage
Input voltage
(Continued)
MB3821
(Continued))
power mode
Conversion efficiency Input voltage
Conversion efficiency Input voltage
Conversion efficiency
Conversion efficiency
output output OFF)
VXCS1 VXCS2
output (3.3 output OFF)
VXCS1 VXCS2
Input voltage
Input voltage
MB3821
USAGE PRECAUTIONS
Never setting exceeding maximum rated conditions.
Exceeding maximum rated conditions cause permanent damage LSI. Also, recommended that recommended operating conditions observed normal use. Exceeding recommended operating conditions adversely affect reliability.
this device within recommended operating conditions.
Recommended operating conditions values within which normal operation warranted. Standard electrical characteristics warranted within range recommended operating conditions within listed conditions each parameter.
Printed circuit board ground lines should with consideration common impedance. Take appropriate static electricity measures.
Containers semiconductor materials should have anti-static protection made conductive material. After mounting, printed circuit boards should stored shipped conductive bags containers. Work platforms, tools, instruments should properly grounded. Working personnel should grounded with resistance between body ground.
ORDERING INFORMATION
Part number MB3821PFV Package 24-pin plastic LQFP (FPT-24P-M03) Remarks
MB3821
PACKAGE DIMENSION
48-pin Plastic LQFP (FPT-24P-M03)
These dimensions include resin protrusion.
7.75±0.10(.305±.004)
1.25 -0.10 .049 -.004
+0.20 +.008
(Mounting height)
0.10(.004)
5.60±0.10
INDEX (.220±.004)
7.60±0.20 (.299±.008)
6.60(.260)
0.65±0.12(.0256±.0047)
0.22 -0.05 .009
+0.10 +.004 -.002
0.15 -0.02 .006 -.001
+0.05 +.002
Details part 0.10±0.10(.004±.004) (STAND OFF)
7.15(.281)REF
0.50±0.20 (.020±.008)
1994 FUJITSU LIMITED F24018S-2C-2
Dimensions (inches)
MB3821
FUJITSU LIMITED
further information please contact:
Japan FUJITSU LIMITED Corporate Global Business Support Division Electronic Devices KAWASAKI PLANT, 4-1-1, Kamikodanaka Nakahara-ku, Kawasaki-shi Kanagawa 211-8588, Japan Tel: 81(44) 754-3763 Fax: 81(44) 754-3329
Rights Reserved. contents this document subject change without notice. Customers advised consult with FUJITSU sales representatives before ordering. information circuit diagrams this document presented examples semiconductor device applications, intended incorporated devices actual use. Also, FUJITSU unable assume responsibility infringement patent rights other rights third parties arising from this information circuit diagrams. FUJITSU semiconductor devices intended standard applications (computers, office automation other office equipment, industrial, communications, measurement equipment, personal household devices, etc.). CAUTION: Customers considering products special applications where failure abnormal operation directly affect human lives cause physical injury property damage, where extremely high levels reliability demanded (such aerospace systems, atomic energy controls, floor repeaters, vehicle operating controls, medical devices life support, etc.) requested consult with FUJITSU sales representatives before such use. company will responsible damages arising from such without prior approval. 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. products described this document represent goods technologies subject certain restrictions export under Foreign Exchange Foreign Trade Japan, prior authorization Japanese government will required export those products from Japan.
http://www.fujitsu.co.jp/
North South America FUJITSU MICROELECTRONICS, INC. Semiconductor Division 3545 North First Street Jose, 95134-1804, Tel: (408) 922-9000 Fax: (408) 922-9179 Customer Response Center Mon. Fri.: (PST) Tel: (800) 866-8608 Fax: (408) 922-9179
http://www.fujitsumicro.com/
Europe FUJITSU MIKROELEKTRONIK GmbH Siebenstein 6-10 D-63303 Dreieich-Buchschlag Germany Tel: (06103) 690-0 Fax: (06103) 690-122
http://www.fujitsu-ede.com/
Asia Pacific FUJITSU MICROELECTRONICS ASIA #05-08, Lorong Chuan Tech Park Singapore 556741 Tel: (65) 281-0770 Fax: (65) 281-0220
http://www.fmap.com.sg/
F9905 FUJITSU LIMITED Printed Japan
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