Shindengen MD3221N Instructions for use

SynchronousRectification
DC-DC Converter Power IC
MD3221N
ApplicationManual
CAT. No. U100 -1
SHINDENGEN ELECTRIC MFG. CO., LTD.
查询MD3221N供应商 捷多邦，专业PCB打样工厂，24小时加急出货

1
UsingtheMD3221NDCtoDCConverterPowerIC
Thank you for purchasing the MD3221N DC to DC Converter Power IC. This manual contains important
information on the safe use of the MD3221N. Your safety is most important to our company. Please read these
instructions carefully before using this device.
CAUTION
The improper use of this device can result in serious injury or death.
Expensive damage to this and other equipment can result. Failure to observe the cautions in
this Manual can also result in minor injuries and annoying equipment damage.
The MD3221N is intended for use with general electronic equipment (office automation,
communication, measurement, household, etc.) It is not intended for use with equipment whose
failure might result in the death or injury of those depending upon it (medical treatment, air
navigation, railroad, cargo handling, nuclear power, etc.)
If you intend to use the MD3221N with other than the general equipment listed above, please consult
with our company.
Under no conditions attempt to repair or modify this device by yourself. Doing so can result in
electric shock, equipment breakage, fire, and unreliable (and dangerous) equipment operation.
Abnormal operating conditions may result in excessive voltage at the output terminal or excessive
voltage drops elsewhere in the device. Take steps to prevent load mishandling and breakage
(overvoltage and overcurrent prevention) at the final point in the equipment chain.
Overvoltage protection
The MD3221N is not equipped with an overvoltage protection function. In the event excessive
voltage appears within a module, the high input voltage may remain together with a high output
voltage even when the equipment is turned off. Smoke and flame may appear. To prevent this, be sure
to install some sort of overvoltage protection circuitry before using the equipment.
Before providing electrical power to the device, check that the polarity of the input and output
terminals is correct (check for misconnections). If circuit protection circuitry is cut off from the rest
of the equipment, smoke and flames may appear.
Be sure that input voltage level is maintained at the specified level. This may require the installation
of a voltage regulator to the input line. Voltage fluctuations may result in the appearance of smoke
and flames.
If a breakdown or other abnormal condition occurs during equipment use, immediately stop power to
the equipment. Contact our company at your earliest possible convenience.
CAUTION
■The information appearing in this Manual is the latest available at the time of publication. We reserve the right to make changes to the device
without prior notice. Therefore, your device may differ slightly from that described in this Manual.
■Every effort has been made to make the information in this Manual accurate and reliable. However, our company takes no responsibility for
injuries or damage incurred when using the device as described in this Manual. Neither do we take responsibility for damages incurred as a
result of patent or other defined rights.
■We do not give consent for a third person to use our patent or other rights based on this material. We do not guarantee these rights.
■No part of this material may be reproduced or copied without the specific written consent of our company.
■This device fully meets the reliability and quality control standards described in our company's catalog. If this device is to be used in a situation
where its misuse or failure might cause serious injury or death, consult with our company.
■Reliability and quality control standards for this device are considered adequate when it is used with the following types of end equipment.
Computer - Office automation - Communication terminal - Measurement • Machine tools - Audio-visual - Games and other amusements -
Household appliance - Personal items - Industrial robot.
Special applications where the device may or may not be suitable include the following.
Transportation and conveyance (cargo loading) equipment- Primary communications equipment - Traffic signal control equipment - Fire and
burglary alarms - Various safety devices - Medical equipment
Other special applications where the device reliability is not considered high enough include the following.
Atomic energy control systems - Aviation equipment- Aeronautics and space equipment - Ocean depth sounding equipment - Life
supportequipment
■Our company makes a constant effort to improve the quality and reliability of our products. However, it is the customer's responsibility to
provide safety. Take the appropriate steps to prevent personal injury, fire, and damage by providing redundancy equipment, fire containment
equipment, and devices to protect personnel and equipment from operational mistakes.
1
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2
MD3221NSynchronousRectificationDC-DCConverterPowerIC
CautionsforUse....................... 1
Outline ...................................... 3
Features
ProductCode
StandardConnectionDiagram
PinLayout
PinFunctions
Specifications........................... 5
Absolutemaximumratings
RecommendedOperatingConditions
ElectricalCharacteristics
InternalBlockDiagrams
SelectionofPrimaryComponentsandPinConnections
... 7
SelectingtheOutputChokeCoil
SelectingtheOutputCondenser
SelectingtheInputCondenser
SelectingtheRegenerativeDiode
Functions................................ 10
SettingtheOutputVoltage
SelectingtheOscillationFrequency
TheSoftStartFunction
TheRemoteON/OFFFunction
TheReferenceVoltage
TheOver-currentProtectionFunction
Short-circuitProtection
TheCurrentLimitingFunction
TheOverheatProtectionFunction
ErrorAmpGainAdjustment
Bootstrap
TheLCut(cutoffdetect)Function
CautionsforPatternDesign
..... 16
PrimaryCircuitPatternDesign
ControlCircuitPatternDesign
ApplicationCircuitExamples
... 17
ComponentExamples
DimensionDrawing ................ 18
Mounting................................. 19
SubstrateMountingExample
CautionsforMounting
ExternalProtectionCircuits ... 20
ConnectionofInputProtectionDevices
ConnectionofOver-voltageProtectionCircuit
Characteristics ....................... 21
Outputvoltage:3.3V
●
EfficiencyandLossCharacteristics
●LineRegulation
●LoadRegulation
●TemperatureCharacteristics
●Start-upCharacteristics
●R/CStart-upCharacteristics
EfficiencybyOutputVoltage
●EfficiencybyOutputVoltage
EfficiencyatFrequencyof100KHz
●EfficiencyandLosses
Packaging............................... 23
TapeandReel
Packing
OrderingandDimensions
10
12
9
8
7
61
2
3
4
5
11
Contents
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3
2Outline
TheMD3221Nisanon-insulatedDC-DCconverter
powerICincorporatingadedicatedmainswitch
MOSFETandasynchronousrectificationMOSFET.
IntegrationofacontrolICandapowerdeviceina
singlechipminimizestheeffectsofwiringand
simplifieslarge-currentpowersupplycircuitdesign.
ThePWM-controlledoutputvoltagemaybeset
overawiderangeof0.8Vto14V,and2.5V/ 3.3Vmay
besetwithouttheuseofanexternalresistor.A
widerangeofinputvoltages(4.5Vto20V)are
possible,and5Vinputandbatteryinputarealso
accommodated.Anover-currentprotectioncircuitis
incorporatedtodetectvoltagedropwiththeON
resistanceoftheinternalMOSFETandthusprovide
asimpleDC-DCconverterofhighefficiency.The
oscillationfrequencyisselectedfromthe100kHzor
300kHzsetinternally,notonlyreducingthenumber
ofexternalcomponentsrequired,butalsofacilitating
flexibledesigninapplications.Asurfacemount
S/SOP32packageisusedtoensureasmallandthin
powersupplycircuit.
◆Features
□Inputvoltagerangeof4.5Vto20V.
□
Adjustableoutputvoltagerangeof0.8Vto14V.
□InternalpowerMOSFET
□
Highefficiencyof96%(Vi=5V,Vo=3.3V,Io=1A
)
□
Over-Currentprotectionfunction(externalresistornotrequired)
□Overtemperatureprotectionfunction
□RemoteON/OFFfunction
(currentconsumptionatOFF:Typ .25μA)
□Switchingfrequencyof100kHzor300kHz
(externalC.Rnotrequired)
□TheLCut(Cutoffderect)function
□Ambienttemperaturerange:
− 30℃ to85℃
◆ProductCode
MD3221N 4072
Specificationcode
Productname
++
G
+Vi
1
MD3221N
LC
Vboot
OCL+
OCL
-
2.5V/3.3V
ampIN
ampOUT
amp
-
P.GND2
GNDOSC
R/C
S/S
VCC
VDD
P.GND1
VOUT
VB
Vref
6
32
1
5
724
25
27
28
29
11~14
30
31
832 16
4,26
+V0
G
18~21
Efficiencyandcircuitlosscharacteristics
5Vinput,3.3Voutput
※f=300kHz
Efficiencyη[%]
Circuitloss P [W]
Outputcurrent Io[A]
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
32.521.510.50
0
10
20
30
40
50
60
70
80
90
100
◆StandardConnectionDiagram
●BasicCircuit
Wiringfor3.3Voutput
↓Click!

4
Referto'7.SelectionofPrimaryComponentsandPinConnections'and'10.Functions'forfunctiondescriptionsandpinconnections.
VGL : 9
N/C : 10
VOUT : 11
VOUT : 12
VOUT : 13
VOUT : 14
N/C : 15
P.GND2 : 16
23 : VGH
22 : N/C
21 : VDD
20 : VDD
19 : VDD
18 : VDD
17 : N/C
R/C : 1
Vref : 2
OSC : 3
GND : 4
LC : 5
Vcc : 6
Vboot : 7
P.GND1 : 8
24 : VB
25 : OCL+
26 : GND
27 : OCL
-
28 : ampOUT
29 : amp
-
30 : ampIN
31 : 2.5V/3.3V
32 : S/S
SHINDENGEN
MD3221N

□
□
□
□
□

◆PinLayout
Pinnumber Symbol
1R/C
2Vref
3OSC
4,26 GND
5
Vcc
6
P.GND1
8
LC
P.GND2
11〜14
16
18〜21
25
amp
-
ampIN
S/S
29
30
32
VOUT
VDD
Functiondescription
RemoteON / OFFcontrol
Internalreferencevoltageoutput
Oscillationfrequencyselect
ControlcircuitGND
Controlcircuitpowersupply
LowsideMOSFETdrivecircuitGND
Vboot
7LowsideMOSFETdrivecircuitpowersupply
Cut-offdetectselect
LowsideMOSFETsources
ampOUT
28 Internalerroramplifieroutput
OCL
-
27 Over-current
- vedetectatexternalresistancedetection
Internalerroramplifierinvertedinput
Internalvoltagedetectresistoroutput
Softstartcondenserconnection
N/C10,15,17,22 Non-connection(notconnectedinternally)
2.5V / 3.3V31 2.5V / 3.3Voutputselect
Output
9VGL LowsideMOSFETgate.Pleasedonotconectthepinanywhere.
HighsideMOSFETpowersupply
OCL+Over-current+vedetectatexternalresistancedetection
24 VBHighsideMOSFETdrivecircuitpowersupply
23 VGH HighsideMOSFETgate.Pleasedonotconectthepinanywhere.

◆PinFunctions

5
3Specifications
◆Absolutemaximumratings
Powersupplyvoltage(voltageatV
CC
)
22V
HighsideMOSFETinputvoltage 22V
Averageoutputcurrent 3A
Peakoutputcurrent 4A
VoltagebetweenVBandVOUT 5.5V
AllowableappliedoutputcurrentatVboot
-
30mA
AllowableappliedcurrentatVref
-
3mA
Storagetemperature
-
50〜150℃
Temperatureatcontacts 150℃
◆ RecommendedOperatingConditions
Inputvoltagerange 4.5〜20V
Settableoutputvoltagerange 0.8〜14V
Ambienttemperaturerange
-
30〜85℃
Item
Drain-sourcebreakdownvoltage
HighsideMOSFET
LowsideMOSFET
ControlICcurrentconsumption
UVLO
Bootstrap
Referencevoltage
Oscillatorcircuit
Remotecontrol
Drainbreakingcurrent
Drain-sourceONresistance
Source-draindiodeforwardvoltage
Drain-sourcebreakdownvoltage
Drainbreakingcurrent
Drain-sourceONresistance
Start-upvoltage
Stopvoltage
Start-up-stopvoltagehysteresis
Currentconsumption(atf
=
100kHz)
BOOTpinvoltage
Powersupplyvoltagevariation
Voltageloadvariation
Powersupplyvoltagevariation
Voltageloadvariation
Internalreferencevoltage
Internaloscillationfrequency1(f
=
100kHz)
Condition
ID
=
1mA,VGS
=
0V
VDS
=
22V,VGS
=
0V
ID
=
1.2A,VGS
=
4.5V
IS
=
1.2A,VGS
=
0V
ID
=
1mA,VGS
=
0V
VDS
=
22V,VGS
=
0V
ID
=
1.2A,VGS
=
4.5V
Vcc
=
4.5〜20V
Vcc
=
4.5〜20V
Vcc
=
4.5〜20V
−
Vcc
=
5V
Vcc
=
4.5〜20V
Vcc
=
5V
Vcc
=
5V
Min.
22
22
−
−
−
−
−
−
−
−
−
22
−
−
−
−
22
−
−
−
4.1
3.84
−
−
85
Typ.
3.3
5
25
4.3
4
−
−
100
Max.
10
55
1.5
−
10
55
1.5
3.9
5.9
50
4.5
4.16
30
30
115
Vcc
=
5V 85 90 95
Unit
V
μA 
mΩ
V
V
μA
mΩ
V
mA
mA
μA
V
Currentconsumption(atf
=
300kHz)
− 3.6 3.8 4.0 V
Currentconsumption(remoteOFF)
− − 0.5 − V
RemoteONvoltage
Vcc
=
5V 3.84 4 4.16 V
RemoteOFFvoltage
Vcc
=
4.5〜20V − − 30 mV
Short-circuitcurrent
Vcc
=
5V − − 30 mV
V
Vcc
=
5V 255 300 345 kHz
mV
mV
Internaloscillationfrequency2(f
=
300kHz)
Maximumdutyratio(f
=
300kHz)
kHz
Vcc
=
5V
-
0.2 − 0.7 V
％
Vcc
=
5V 2−Vcc V
Vcc
=
5V − 210
μA
Source-draindiodeforwardvoltage IS
=
1.2A,VGS
=
0V
Ta
=
25℃unlessspecifiedotherwise.
◆ElectricalCharacteristics
↓Click!

6
Item
Currentatsoftstartpin
Softstart
ThresholdcurrentatONresistancedetection
Latchthresholdvoltage
Outputvoltagedetectaccuracy(setat3.3V)
Erroramp
Errorampreferencevoltage
Over-Currentprotectiondetector
Thresholdvoltageatexternalresistancedetection
Timerlatchcircuit
Timercurrent
Overtemperatureprotectiondetector
Overheatprotectionoperationtemperature
Outputvoltagedetector
Condition
Vcc
=
5V
Vcc
=
5V
Vcc
=
5V
Vcc
=
5V
Vcc
=
5V
Vcc
=
5V
Vcc
=
4.5〜20V
Vcc
=
4.5〜20V
Vcc
=
4.5〜20V
Min.
-
3
0.800
−
0.784
3
-
40
2.75
3.3
-
2.5
-
33
2.9
3.45
100
-
2
85


Typ.
0.8000.784
2.425
3.200
2.500
3.300
Max.
0.816
115
−
-
26
3.05
3.6
0.816
2.575
3.400
Unit
μA
V
mV
μA
V
V
V
A
V
V
Outputvoltagedetectaccuracy(setat0.8V)
− − 140 − ℃
Outputvoltagedetectaccuracy(setat2.5V)
VoltageatS/Spinpriortotimeroperation Vcc
=
5V
R/C
(L.Active)
S/S
UVLO
INVL
※N/C : 10,15,17,22
※ (Resistance)
CURRENT
LIMIT2
CURRENT
LIMIT3
CURRENT
LIMIT1
PWM-COMP
ampIN OCL-
OCL-
2.5V/3.3V OCL+
amp-
OSC
Vref
VOUT
Vref
VDDVGH
VOUT
VBVbootVrefVcc
LC P.GND1
ampOUT
ERROR-AMP
VGL P.GND2
GND
ON/OFF
CONTROL
BANDGAP
REFERENCE
1.26V±1%
THERMAL
SHUTDOWN
VCC LATCH
Q R S
S R Q
LATCH
S R Q
LATCH
S R Q
LATCH
OSC
+
-
-
+
-
+
-
+
-
+
+
-
+
-
+
-
+
-
+
33130 2527
4,26
28
29
32
1
62 23
18~21
247
11~14
8916 5
◆InternalBlockDiagrams
●BlockDiagram

7
4
SelectionofPrimaryComponentsandPinConnections
ThecharacteristicsoftheDC-DCconverterareinfluencedbytheICitself,andalsosignificantlybythe
peripheralcomponentsofthecircuit.
Awell-designedcircuitisnecessarytomakethemostofthepotentialoftheMD3221N.Itisthereforenecessary
toclarifythespecificationsoftherequiredpowersupply,andtoselectcomponentsasfollows.
◆ SelectingtheOutputChokeCoil(inductor)( L1)
Thechokecoilhasanimportanteffectonpower
supplyperformance.Asaripplecurrentflowsinthe
inductorasshowninthediagrambelow,the
inductanceshouldbeselectedtoensurethatΔIis
approximately30%ofthemaximumoutputcurrent
whentheinputvoltageisatitsmaximum.
●CurrentWaveforminOutputChokeCoil(L1)
Vi（max）：Maximuminputvoltage［V］
VO：Outputvoltage［V］
ΔI：30%ofmaximumoutputcurrent［A］
f：
Oscillationfrequency(100kHzor300kHz) ［Hz］
IO：Maximumoutputcurrent［A］
Theinductorisgenerallyselectedonthebasis
ofthecalculation,howeverinsomecasesthe
natureoftheproductmayrequireaninductor
which differs from the calculated value. An
inductorinwhichΔIisbetween20%and40%ofthe
outputcurrentisrecommended.
++
+Vi +V0
GG
1
MD3221N
C4
C2
C8
C7
C1 C5
C6
R3
D1
D2
C3
L1
LC
Vboot
OCL+
OCL
-
2.5V/3.3V
ampIN
ampOUT
amp
-
P.GND2
GNDOSC
R/C
S/S
VCC
VDD
P.GND1
VOUT
VB
Vref
6
32
1
5
7 24
25
27
28
29
11~14
30
31
832 16
4,26
18~21
●StandardConnectionDiagram
（Ｖi（max）−VO）×VO
L1＝ ［H］
ΔI ×Ｖi
（max）×f
ΔI
0
Io
↓Click!

8
Ifahigherinductancevalueisselectedtheoutput
ripplevoltageisreduced,howeverasthecurrentrating
dropsthesizeoftherequiredinductorisincreased.
Ontheotherhand,ifalowerinductancevalueis
selectedthesizeoftherequiredinductorisreduced
while peak current is increased, thus slightly
increasingthelosswhenaloadisapplied.
WhiletheMD3221Nincorporatesanover-current
protectionfunction,theinductorselectedmustbesuch
thatmagneticsaturationdoesnotoccurattheover-
currentdetectionpoint.
Asamagneticfieldisgeneratedinthevicinityofthe
inductor,componentlayoutandpatterndesignmust
besuchastoensurethattheydonotaffectthe
controlcircuit.Toroidalorclosedmagneticcircuitpot
typeinductorsarerecommendedforapplicationslikely
to be affected by magnetic field leakage and
radiatednoise.
◆
SelectingtheOutputCondenser(C5)
Anoutputcondenserisrequiredtoreduceoutputripple
andthusobtainastableDCvoltage.Theconverter
outputripplevoltageisdeterminedbyΔIand
condenserimpedance.Theoutputcondenseris
selectedinrelationtotheimpedance.Selecttheoutput
condenserbased on thedesiredoutput ripple
voltageusingthefollowingequation.
Zc ：Condenserimpedance［Ω］
Vrip：Outputripplevoltage［V］
ΔI：30%ofmaximumoutputcurrent［A］
Thedesiredripplevoltageisobtainedifacondenser
withanimpedancelessthanthatcalculatedwiththe
aboveequationisselectedfromthecatalog.
In addition to a low impedance, the output
condensermustalsohaveareasonablecapacitance.
Controlwillreadilybecomeunstableandampgain
adjustmentwillprovedifficultifcapacitanceislow.
Aluminumelectrolyticcondensersandfunctional
high-polymer electrolytic condensers are of
sufficientlyhighcapacitancesothatitneednotbe
consideredwhenselectingonthebasisofthe
equationabove.Theuseofsuchcondensers,rather
than ceramic or film condensers, is therefore
recommended.Ontheotherhand,concurrentuseof
ceramicorfilmcondensersiseffectiveineliminating
highfrequencynoise.
◆SelectingtheInputCondenser(C1)
Asalargeripplecurrentflowsintheinputcondenser
itisnecessarytoconsidertheallowablevalueforripple
current.Selectaninputcondenserwithanallowable
ripplecurrentexceedingthevaluecalculatedinthe
equationbelow.
Irip ：Allowableripplecurrent［A］
VO：Outputvoltage［V］
Vi ：Inputvoltage［V］
D：Dutyratio
IO：Outputcurrent［A］
DistheratiobetweentheONintervalandthe
OFFinterval,andIripisatamaximumwhenthis
value is 0.5. The capacitance of the input
condenserneednotbeparticularlyhigh,however
careisrequiredifaceramicorfilmcondenseris
used.Aslargeripplevoltagesaregeneratedinthe
inputcondenserduringcharginganddischarge,a
particularly low input voltage may result in
operation becoming unstable. As this ripple
voltageisreturnedtotheinputlineothercircuits
poweredfromthesamelinemaybeaffected.
Interferencemayoccur,particularlywhenusing
multipleDC-DCconverters,andinsuchcasesan
inductorofafewμHisinsertedinthestagebefore
theinputcondensertoeliminatetheproblem.
Vrip
ZC［Ω］
ΔI
VO
D＝ Vi
Irip D（1−D）× IO［A］
＜
−
＞
−

9
Thesubstratewiringbetweentheinputcondenser
toVDD andP.GND2 issubjecttothegreatest
variationincurrent,andwiringdesignshould
thereforefocusprimarilyonreducingitsimpedance
totheabsoluteminimum.Referto'16.Cautions
forPatternDesign'fordetails.
◆
SelectingtheRegenerativeDiode(D2)
TheMD3221Nemployssynchronousrectification
usingaregenerativeMOSFET,andrequiresa
diodetobypasstheregenerativecurrentduring
thedead-timeinterval.Ifthisdiodeisnotpresent
regenerativecurrentflowsintheMOSFETbody
diodeduringthedead-timeinterval,resultingin
increasedlossesandnoise.ASchottkybarrier
diodewithlowVFisidealforuseinpreventing
currentflowinginthebodydiode,howeveritis
importantthatthisdiodehasalowleakagecurrent
topreventthermalrunaway.
Recommendedcomponent:
D1FM3(Shindengen)
30V, 3AVF=0.4V
（max） IR=0.1mA
（max）
M1FM3(Shindengen)
30V, 2.1AVF=0.4V（max） IR=0.05mA（max）

10
5Functions
◆SettingtheOutputVoltage
MD3221Noutputvoltagemaybesetbetween0.8V
and14V.Whensetto2.5Vor3.3Vtheinternal
dividingresistorisusedandanexternalresistorisnot
required.Outputvoltageissetwithaminimum
accuracyof±3%.
●Wiringfor2.5VOutput
●Wiringfor3.3VOutput
Theinternaldividingresistorisconnectedacrossthe
OCL and GND pins, with the dividing point
connectedtotheampINpin.TheampINpinshould
thereforebeconnectedtotheamp
- pinexternally.
Anexternaldividingresistorisrequiredifoutput
voltageistobesettootherthan2.5Vor3.3V.Asthe
errorampreferencevoltageis0.8Vthevalueforthe
dividingresistorisdeterminedwiththeequation
below.
VO：Outputvoltage［V］
Asthereferencevoltagehasaminimumaccuracy
of ±2%.Theaccuracyofthesetoutputvoltageis
determinedbytheaccuracyofthereference
voltagesandtheaccuracyoftheresistor.
●WiringforVariableOutput
◆ SelectingtheOscillationFrequency
TheMD3221Nincorporatesaninternaloscillator,and
an external C.R is therefore not required. The
oscillationfrequencymaybesettoeither100kHzor
300kHz.
Switchinglossesinswitchingpowersuppliesgenerally
increaseas theoscillation frequency increases,
however the MD3221N is designed to provide
sufficientlyhighefficiencyat300kHz.Furthermore,
thenumberofperipheralcomponents(egtheinductor)
isminimized,andthusastandardcircuitusingthe
300kHzfrequencyprovidesbenefitsintermsofbothcost
andspace.Useofthe100kHzfrequencyiseffectivein
termsofreducinghigh-frequencynoise,andismore
effectivethanthe300kHzfrequencyatlow-loadat
whichswitchinglossesdominate.
−
＋
MD3221N
OCL+
OCL
-
2.5V/3.3V
0.8V ampIN
amp
-
VOUT
L1
11~14
25
27
31
30
29
+V0
−
＋
MD3221N
0.8V
amp
-
R4
R5
VOUT
L1
11~14 +V0
29
−
＋
MD3221N
OCL+
2.5V/3.3V
0.8V ampIN
amp
-
VOUT
L1
11~14
25
27
31
30
29
+V0
OCL
-
R5×（VO−0.8）
R4＝ ［Ω］
0.8
R5＝1k［Ω］
↓Click!

11
TheOSCpinisusedinsettingtheoscillation
frequency.The300kHzfrequencyisselectedby
connectingtheOSCpintotheVrefpin,and100kHz
byconnectingittotheGNDpin.
●FrequencySwitching
◆TheSoftStartFunction
TheMD3221Nincorporatesasoftstartfunctionto
prevent overshoot at start-up and to reduce
electricalstressonthedevice.Asshowninthe
diagrambelow,thecondenser(C2)isconnected
acrosstheS/SandGNDpins.Asthedutyratiois
limitedbythevoltageattheS / S pin,gradual
chargingofthiscondenserallowsafixedrateof
increaseintheoutputvoltage.
●SoftStartCircuit
Asshowninthediagram,theS / Spinischargedata
fixedcurrent.Whenthevoltageatthispinreaches0.5V,
mainswitchoscillationbeginsandoutputvoltage
increases.AsthevoltageattheS / Spinincreasesto
aconstantvalueof2.9Vtheoutputvoltagemust
reachthesetvoltageduringthatinterval.Ifthe
capacitanceoftheoutputcondenseristoohigh,the
increaseintheoutputvoltagedoesnotfollowthe
increaseattheS / Spin,thuspreventingstart-upinsome
cases.
●
RelationshipBetweenSoftStartVoltageandInput/OutputVoltage
ItisnecessarytomonitoroutputvoltageVOis
alwaysstartedupinadvancetotheS/Sterminal
voltage.(Refertothechartabove)
Asshowninthegraphbelow,thecapacitanceofthe
condenserconnectedtotheS/Spindeterminesthe
start-uptime.
●
RelationshipBetweenS/SCondenserandOutputVoltageStart-upTime
Selectahighvalueforcapacitanceofthecondenser
connectedtotheS/Spiniflatchishaltedatstart-up.
◆ TheRemoteON /OFF Function (R/C)
AnexternalsignalmaybeusedforON / OFFcontrol
oftheMD3221N.TheMD3221NisswitchedONwhen
theR / CpinissettoL(0.7Vorlower),andswitched
OFFwhenitissettoH(2Vorhigher),orisopen.
CurrentconsumptionatOFFisapproximately25μA.
AstheR / Cpinispulledupinternallyitmaybeused
asanopencollector,thuseliminatingtheneedfor
applicationofanexternalvoltage.Anyexternal
MD3221N
Vref 300kHz
100kHz
OSC
GND
2
3
4
Vi
Vss
Vo
2.9V
MD3221N
S/S
C2
Is/s
32
Vo/Vi=0.1
Vo/Vi=0.3
Vo/Vi=0.5
Vo/Vi=0.7
0.001
0.1
1
10
100
0.010 0.100 1.000
S/Scondensercapacitance(µF)
Start-uptime(ms)

12
voltageappliedmustbenohigherthanVCC.
When the remote ON /OFF function is used, a
condenserisconnectedacrosstheR / CandGNDpins
to prevent malfunctioning due to noise. If the
capacitanceofthiscondenseristoohigh,theoutput
voltagewillbeproducedinstantaneouslywhenaninput
voltageisappliedwhiletheMD3221NisOFF.The
capacitanceofthiscondensershouldbeapproximately
1/ 3ofthatoftheS / Scondenser(C2)asobtainedfrom
thegraphin'SoftStartFunction'(P11).
●RemoteControlCircuit
◆TheReferenceVoltage(Vref)
TheMD3221Nprovidesaninternaltemperature
compensatedreferencevoltage(4V)whichmaybe
usedasareferencevoltageupto1mAforexternal
circuits.Acondenser (C8)ofapproximately0.1μF
isconnectedacrosstheVrefandGNDpinsto
preventmalfunctioningduetonoise.
＊Notethatthisvoltagediffersfromtheerroramp
referencevoltage.
◆ TheOver-currentProtectionFunction(timerlatch)
TheMD3221Nincorporatesanover-currentprotection
function.Astheover-currentconditionisdetectedwith
theuseofthevoltagedropresultingfromtheON
resistanceoftheinternalMOSFET,anexternal
detectionresistanceisnotrequired.Whentheover-
currentconditionisdetectedthecondenser (C2)
connectedtotheS/ Spinischargedagain,and
whenalevelof3.45Visreachedthelatchishalted.
Toturnthetimerlatchoff,usetheR/ Cfunctionto
switchOFFtheMD3221N,orswitchOFFthepower
supplyvoltage.
ThisfunctionalsoemploystheS/ Spincondenseras
atimer.Determinethecapacitanceofthis condenser
inreferencetothesectiononsoftstart.
●Over-currentProtection
Intheprocessofincreasingtheoutputvoltageatstart-
up,theconvertergenerallychargestheoutput
condenserresultingintheover-currentcondition.When
theover-currentprotectioncircuitoperatesthelatch
ishaltedandstart-upbecomesimpossible.The
MD3221Ntimercircuitislockedtopreventits
operationuntilthevoltageattheS/Spinreaches2.9V,
andwhentheS / Spinisfullychargedthelockis
clearedandthetimercircuitisreadyforoperation.
If,however,theoutputvoltagedoesnotrisebythe
timetheS/Spinischargedto2.9V,theover-current
protectioncircuitoperatesandthelatchishalted.The
outputvoltagemustthereforereachthesetvoltage
beforethevoltageattheS /Spinreaches2.9V.
MD3221N
C
R/C
1
MD3221N
S/S
C2
Itimer
32
Over-current
3.45V
2.9V
Vss
Vo
Vi

13
◆Short-circuitProtection
Theshort-circuitprotectionfunctiondescribedabove
operateswhentheoutputpiniscompletelyshort-
circuited,orifpowerisswitchedonintheshort-
circuitedcondition,howeverasanextremelyhigh
currentflowsintheconverterthelatchcircuitmaynot
operateduetonoiseresultingfromthisshort-circuit
current.Aprotectioncircuitindependentofthe
MD3221N should therefore be provided to
accommodatesuchcases(referto'20.External
ProtectionCircuits').
◆TheCurrentLimitingFunction
(externalresistancedetection)
Inadditiontoover-currentprotectionusingthetimer
latch,theMD3221Nincorporatesafunctiontolimit
outputcurrent.Connectionofanexternalresistor
facilitatesincorporationofdroopcharacteristicsforthe
outputatanydesiredcurrentvalue.Limitingthe
maximumoutputpowersimplifiesstart-upwhenthe
currentsupplycapacityoftheinputpowersupplyislow.
Asshowninthediagram,thevoltagedropacrossthe
insertedresistor(R2)isdetectedat100mV.
Thetimerlatchisdisabledwhendroopcharacteristics
areincorporatedintheoutputusingthisfunction.When
theimpedanceattheloadsideapproacheszero,
currentincreasesandthetimerlatchoperatesto
protectthecircuit.TheOCL+andOCL
-
shouldbe
shortedifthisfunctionisnotused.
●
CircuitforCurrentLimitingFunction(externalresistancedetection)
◆TheOverheatProtectionFunction
TheMD3221Nincorporatesanoverheatprotection
function.Theoscillatorishaltedwhenthejunction
temperaturereaches140℃ duetooperationunder
adverseconditions.Theoscillatorbeginsoperation
againwhenthetemperaturedropsto110℃.Areset
signalisnotrequired.
◆ErrorAmpGainAdjustment
Errorampgainadjustmentiseffectiveinensuring
stableoperationofthepowersupplycircuitandgood
transientresponse.Astheappropriateconstant
varies with the components used (eg output
condenser),theMD3221Nhasanexternalerroramp
input/outputpinforadjustmentfollowingselection
oftheprimarycomponents.
●ErrorAmpGainAdjustmentCircuit
◆Bootstrap
TheMD3221NemploysanN-chMOSFETinthe
high-side switch. The load supply circuit is
bootstrappedtothegateofthisMOSFET.A
condenser(C3)isconnectedacrosstheVBandVOUT
pinsaspartofthepowersupply.
ThecapacitanceofC3mustbesufficientinrelation
tothecapacitanceoftheMOSFETgate.Usea
ceramiccondenserofapproximately0.1μF.
MD3221N
OCL+
OCL
-
VOUT
L1 R2
+V0
−
＋
25
11~14
27
MD3221N
ampOUT
R3
C6
29
amp -
28

14
TheloadappliedtoC3issupplementedfromthe
VbootpinviaD1witheachpulsecycle.Thisis
backedupbyC4,whilesimultaneouslystabilizingthe
voltageattheVbootpin.ThecapacitanceofC4should
thereforebeequaltoorgreaterthanthatofC3.
ThevoltageattheVbootpiniscontrolledto4V.As
C3ischargedwithavoltagewhichislessthan
this4VbyanamountequaltotheVFofthediodeD1
whentheVFofthisdiodeishigh,thegatedrivevoltage
dropsandthepreviousperformanceisthennot
obtained.Astheaveragecurrentisintheorderofa
fewmA,asmallsignaldiodeissufficient,however
itisimportanttoavoidadiodewithahighvoltage
resistanceandhighVF.(referto'17.Application
CircuitExanples)
●BootstrapCircuit
◆TheLCut(cutoffdetect)Function
Aspreviouslydescribed,acontinuouscurrent
normallyflowsin the chokecoil.Thiscurrent
includes a ripple current determined by the
inductanceandinput/ outputvoltageofthechokecoil.
Astheaveragevalueistheoutputcurrent,whenthe
outputcurrentislessthanΔ1/2atlow-loadthe
currentbecomesdiscontinuous(cut-off).
TheMD3221Nallowsselectionoftwooperating
modesinthecut-offregion.
（1）PowerSavingMode(LcutON)
ThismodeisONwhentheLCandVrefpinsare
connected(H).Whenthechokecoilcurrentis
cut-offtheONrangeisnarrowedandtheaverage
current drops. As the current flowing in the
MOSFETisreducedthelossesatlow-loadare
reduced,howevervariationin the ON range
increasesandtransientresponsedeterioratesin
proportion.Aspowersavingisbeneficialathighinput
voltages,benefitsat5Vareminimalanditistherefore
recommendedthat(2)CurrentRegenerationMode
(LcutOFF)beusedatlowvoltages.
●L1CurrentWaveformatLow-load
●InputCurrent(Vi ＝20V)atLow-load
（2）CurrentRegenerationMode(LcutOFF)
ThismodeisOFFwhentheLCandGNDpinsare
connected(L).Thecurrentinthechokecoilflows in
thereversedirection,thusregeneratingenergyand
resultinginacontinuouscurrentevenatno-load.
MD3221N
Vboot
C4
VOUT
VB
7 24
11〜14
C3
D1
LCfunctionON
LCfunctionOFF
0
0
10
5
0
010
Outputcurrent(mA)
Inputcurrent(mA)
20 30 40 50
LC :off
LC :on
30
25
20
15

15
AstheONrangeremainsconstantirrespectiveofthe
loadapplied,astableresponseisobtainedevenunder
rapidchangesinloadfromtheno-loadcondition.On
the other hand, as the actual current value
increases,inputcurrentatlow-loadincreases
slightlyincomparisonwiththatatLcutON.
●TransientResponsewithLCON/OFF
Transientresponsemaybeoptimizedwitherror
ampgainadjustment(referto13'ErrorAmpGain
Adjustment'fordetails).Forthegraphabove,
two1200μFaluminumelectrolyticcondensers(C5)
wereusedfortheoutputcondenser,a100pF
condenserforC6,anda1MΩ resistorforR3.
Loadcurrentisextremelylow,andthedifference
showninthediagramisobtainedatthetransient
responsefromthechokecoilcurrentcut-offregion
(uptoapproximately15%ofthemaximumoutput
current),howeverthereisalmostnodifferencein
transientresponseduetoLCON/OFFinthenon-cut-
offregion.
Conditions:Vi=5V, Vo=3.3V, output current 0A 3A
X axis : 100μs/div.
Yaxis:50mV/div.
LC :ON
LC :OFF

16
6CautionsforPatternDesign
◆PrimaryCircuitPatternDesign
●WiringPatternIllustration
Inthemaincircuit,thepatternbetweentheinput
condenserandVDD,andbetweenP.GND2andthe
inputcondenser,aresubjecttothegreatest
variationsincurrent.Particularattentionshould
thereforebegiventoensurethatthesepatterns
areasthickandasshortaspossible.Theuseof
through-holesinthesepatternsistobeavoided.
Voltage drop due to the DC resistance of
through-holesmayresultinachangeinthe
over-currentdetectionpointinsomecases.
TheSBDpatternisconnectednext.Connect
theanodetoP.GND2,andthecathodetoVOUT.
Alongpatterninthiscasewillnotonlyresultin
considerablenoise,butwillalsocauseadropin
efficiency.
The choke coil and output condenser are
connected next. As this pattern carries a
continuouscurrent,voltagedropratherthan
noiseistheimportantconsideration.Along
patterninthiscasewillresultinavoltagedropdue
to pattern DC resistance, and reduced
efficiency.
The MD3221N is designed to radiate heat
throughthesubstratepattern.Inparticular,both
theVDD andVOUT pinsareallocatedeachtofour
pins,andconnecteddirectlytotheinternallead
frame.Allofthesepinsmaythereforebeusedto
ensurealargepatternareaandthusprovide
foreffectiveradiationofheat.
◆ControlCircuitPatternDesign
Thecontrolcircuitpatternmustbedesignedto
ensurethatitisnotsubjecttonoise,electric
fields,andmagneticfieldfromthechokecoil.
TheGNDpinisthecontrolICGND.Connectthis
pinclosetotheinputcondenser.TheVCC pinisthe
control circuit input pin. Always connect a
condenser (C7)acrosstheVCC andGNDpinsto
eliminatenoise.
TheVrefpinprovidesthereferencevoltageforthe
internallogiccircuitoftheIC.Noiseatthispinmay
result in a malfunction. Always connect a
condenser (C8)tothispatterntoeliminatenoise.
TheP.GND1pinisthelowsidedriverGNDandis
connectedtotheP.GND2pin.Ensurethatthesepins
areconnectedclosetothe
- vepinoftheinput
condenser.
SubstratepatterndesignhasamajoreffectonDC-DCconvertercharacteristics.AstheMD3221Nswitches
alargecurrentveryrapidly,alargeinductancecomponentinthepatternwillprovideasourceofnoise.Itis
thereforeveryimportanttoensurethattheprimarycircuitpatternisasthickandshortaspossible.
MD3221N
VOUT
+VO
Vi
P.GND2
GND
VCC
VDD
↓Click!

17
7ApplicationCircuitExamples
5Vinput,2.5Voutput,3A 300Hzoperatingfrequency,R/C,LC:OFF
++
Vi:5V VO: 2.5V/3A
G G
1
MD3221N
LC
Vboot
C4 : 0.1μF
C7:
1μF
C1:
68μF
C2:
0.01μF
C8:1μF
C3 : 0.1μF
C5:
330μF×2
C6:
1000pF
L1 : 4.7μH
HSU119
D2 : D1FM3
R3:
100kΩ
OCL+
OCL
-
2.5V/3.3V
ampIN
ampOUT
amp
-
P.GND
2
GNDOSC
R/C
S/S
VCC
VDD
P.GND
1
VOUT
VB
Vref
6
32
1
5
724
25
27
28
29
11~14
30
31
832 16
4,26
18~21
●ApplicationCircuitExample
Componentcode Type
C1
High-polymerorganicsemiconductorelectrolyticcondenser
C2 Ceramiccondenser
C3 Ceramiccondenser
C4 Ceramiccondenser
C5
Ceramiccondenser
C6
Ceramiccondenser
C8
High-polymerorganicsemiconductorelectrolyticcondenser
Inductor
D2
L1
R3
Schottkybarrierdiode
Resistor
Rating
10V,68μF,Irip.1.7A
25V,0.01μF
25V,0.1μF
25V,0.1μF
25V,1000pF
10V,1μF
Ceramiccondenser
C7 10V,1μF
6.3V,330μF,ESR：40mΩ×2P
4.7μH
D1FM3〔30V,3A,VF=0.4V(max)〕
D1 Switchingdiode HSU119〔80V,300mA,VF=1.2V(max)〕
100kΩ
◆ComponentExamples
↓Click!

18
8DimensionDrawing
Unit：mm
7.5
9.95
+ -
0.1
+
-
0.3
32 17
+
-
0.1
13.6
14.1MAX
116
+
-
0.1
0.35 0.16 M
0.8
（0.8）
LotNo.
0
゜
〜10゜
0.2
+
-
0.2

+0.1
-
0.05
0.4
APortion
DetailofAPortionS ＝ 15/1
0.10
2.2+
-
0.1
0.1+
-
0.1
2.3+
-
0.2
■■■■■
MD3221N
CompanyName
TypeNo.
●DimensionDrawing(SSOP32)
↓Click!

19
9Mounting
L1
C8
TP2
32
MD3221N
11
IC1
TP1TP1TP1 C1
− 1
C5C5
− 1C5C5 − 2C5 − 1C5 − 2
5
R/C ＋VO ＋VINGND
CN11
C1
− 201N07
C11C11C11
C12C12C12
R6
C6
C7C7 JP3JP3
JP1JP1 JP2JP2
R3R3
C4C4
D1D1
R1R1
C2C2 C10C10
JP5JP5 JP8JP8
C7 JP3
JP1 JP2
R3
C4
D2
K
KK
C3C3
C9C9R7R7
R2R2−1
R2R2−2
R4R4−2
C3
D1
R5
C9R7
R4−1
R1
C2 C10
JP4
JP7
JP6
JP5 JP8
R2−1
R2−2
R4−2
◆SubstrateMountingExample
◆CautionsforMounting
Bothflowandreflowisapplicablewhenmounting.
Asthispatterndoesnotincorporateanover-currentprotectioncircuitorinputfusetheymustbeaddedseparately
ifthecircuitistobeusedinpractice.
Therecommendedtemperatureprofileforreflow
solderingisshownbelow.
●RecommendedTemperatureProfile
Ensurethatthefollowingrequirementsaremet
whenusingasolderingiron.
Tiptemperature:300℃ maximum
Solderingtime:5sec.maximum
●SolderingPadReferencePattern
パ
ッ
ケ
ー
ジ
表
面
の
温
度

時 間
240℃max
200℃
235±5℃
150±10℃
10±1s
30±10s
90±30s
0.5
0.8
9.53
1.4
Unit:mm
↓Click!