SHINDENGEN MD3221N

CAT. No. U100 -1
Synchronous Rectification
DC-DC Converter Power IC
MD3221N
Application Manual
SHINDENGEN ELECTRIC MFG. CO., LTD.
↓Click!
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.
CAUTION
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.
■ 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
MD3221N Synchronous Rectification DC-DC Converter Power IC
Contents
↓Click!
1 Cautions for Use ....................... 1
6 Cautions for Pattern Design ..... 16
Primary Circuit Pattern Design
2 Outline ...................................... 3
Control Circuit Pattern Design
Features
7 Application Circuit Examples ... 17
Product Code
Standard Connection Diagram
Component Examples
Pin Layout
8 Dimension Drawing ................ 18
Pin Functions
9 Mounting ................................. 19
3 Specifications ........................... 5
Absolute maximum ratings
Substrate Mounting Example
Recommended Operating Conditions
Cautions for Mounting
Electrical Characteristics
10 External Protection Circuits ... 20
Internal Block Diagrams
Connection of Input Protection Devices
4 Selection of Primary Components and Pin Connections ... 7
Connection of Over-voltage Protection Circuit
Selecting the Output Choke Coil
11 Characteristics ....................... 21
Selecting the Output Condenser
Selecting the Input Condenser
Output voltage : 3.3V
Selecting the Regenerative Diode
●
Efficiency and Loss Characteristics
●
Line Regulation
●
Load Regulation
Setting the Output Voltage
●
Temperature Characteristics
Selecting the Oscillation Frequency
●
Start-up Characteristics
The Soft Start Function
●
R / C Start-up Characteristics
5 Functions ................................ 10
The Remote ON / OFF Function
Efficiency by Output Voltage
The Reference Voltage
●
The Over-current Protection Function
Efficiency by Output Voltage
Efficiency at Frequency of 100KHz
Short-circuit Protection
●
Efficiency and Losses
The Curre nt Limiting Function
12 Packaging ............................... 23
The Overheat Protection Function
Error Amp Gain Adjustment
Tape and Reel
Bootstrap
Packing
The L Cut (cut off detect ) Function
Ordering and Dimensions
2
↓Click!
2 Outline
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
◆Standard Connection Diagram
●
Basic Circuit
Wiring for 3.3V output
Efficiency and circuit loss characteristics
5V input, 3.3V output
100
24
VB
VDD
VOUT
18~21
+ V0
Efficiency η[%]
OCL+ 25
OCL- 27
32 S/S
ampOUT 28
1
R/C
+
+
amp- 29
5
80
1.6
70
1.4
60
1.2
50
1
40
0.8
30
0.6
20
0.4
10
0.2
ampIN 30
LC
2.5V/3.3V 31
Vref OSC GND P.GND1 P.GND2
2
1.8
11~14
MD3221N
6 VCC
90
3
4,26
8
16
0
G
G
0
0
0.5
1
1.5
2
2.5
3
Output current Io [A]
※ f = 300kHz
3
Circuit loss P [W]
+ Vi
7
Vboot
2
◆Pin Layout
□
□
□
□
□
32 : S/S
31 : 2.5V/3.3V
30 : ampIN
29 : amp28 : ampOUT
27 : OCL26 : GND
25 : OCL+
24 : VB
23 : VGH
22 : N/C
21 : VDD
20 : VDD
19 : VDD
18 : VDD
17 : N/C
SHINDENGEN
MD3221N
R/C : 1
Vref : 2
OSC : 3
GND : 4
LC : 5
Vcc : 6
Vboot : 7
P.GND1 : 8
VGL : 9
N/C : 10
VOUT : 11
VOUT : 12
VOUT : 13
VOUT : 14
N/C : 15
P.GND2 : 16
◆Pin Functions
Pin number
Symbol
Function description
1
R/C
Remote ON / OFF control
2
Vref
Internal reference voltage output
3
OSC
Oscillation frequency select
4,26
GND
Control circuit GND
5
LC
Cut-off detect select
6
Vcc
Control circuit power supply
7
Vboot
8
P.GND1
9
V GL
Low side MOSFET gate. Please do not conect the pin anywhere.
11∼14
V OUT
Output
16
P.GND2
18∼21
V DD
High side MOSFET power supply
23
V GH
High side MOSFET gate. Please do not conect the pin anywhere.
24
VB
25
OCL +
Over-current + ve detect at external resistance detection
27
OCL-
Over-current - ve detect at external resistance detection
28
ampOUT
29
amp -
Internal error amplifier inverted input
30
ampIN
Internal voltage detect resistor output
31
2.5V / 3.3V
32
S/S
Soft start condenser connection
10,15,17,22
N/C
Non-connection ( not connected internally )
Low side MOSFET drive circuit power supply
Low side MOSFET drive circuit GND
Low side MOSFET sources
High side MOSFET drive circuit power supply
Internal error amplifier output
2.5V / 3.3V output select
Refer to '7. Selection of Primary Components and Pin Connections' and '10. Functions' for function descriptions and pin connections.
4
↓Click!
3 Specifications
◆Absolute maximum ratings
◆Recommended Operating Conditions
Power supply voltage (voltage at V CC )
22V
Input voltage range
4.5∼20V
High side MOSFET input voltage
22V
Settable output voltage range
0.8∼14V
Average output current
3A
Peak output current
4A
Voltage between V B and V OUT
5.5V
- 30mA
Allowable applied output current at Vboot
- 3mA
Allowable applied current at Vref
Storage temperature
- 30∼85℃
Ambient temperature range
- 50∼150℃
Temperature at contacts
150℃
◆Electrical Characteristics
Item
High side MOSFET
Drain-source breakdown voltage
Drain breaking current
Drain-source ON resistance
Source-drain diode forward voltage
Low side MOSFET
Drain-source breakdown voltage
Drain breaking current
Drain-source ON resistance
Source-drain diode forward voltage
Control IC current consumption
Current consumption (at f=100kHz)
Current consumption (at f=300kHz)
Current consumption (remote OFF)
UVLO
Start-up voltage
Stop voltage
Start-up-stop voltage hysteresis
Bootstrap
BOOT pin voltage
Power supply voltage variation
Voltage load variation
Reference voltage
Internal reference voltage
Power supply voltage variation
Voltage load variation
Oscillator circuit
Internal oscillation frequency 1 (f=100kHz)
Internal oscillation frequency 2 (f=300kHz)
Maximum duty ratio (f=300kHz)
Remote control
Remote ON voltage
Remote OFF voltage
Short-circuit current
Ta = 25℃ unless specified otherwise.
Condition
Min.
Typ.
Max.
Unit
ID = 1mA, VGS = 0V
VDS= 22V, VGS = 0V
ID = 1.2A, VGS = 4.5V
IS = 1.2A, VGS = 0V
22
−
−
−
−
−
22
−
−
10
55
1.5
V
μA
mΩ
V
ID = 1mA, VGS = 0V
VDS = 22V, VGS = 0V
ID = 1.2A, VGS = 4.5V
IS = 1.2A, VGS = 0V
22
−
−
−
−
−
22
−
−
10
55
1.5
V
μA
mΩ
V
Vcc = 4.5∼20V
Vcc = 4.5∼20V
Vcc = 4.5∼20V
−
−
−
3.3
5
25
3.9
5.9
50
mA
mA
μA
−
4.1
4.3
4.5
V
−
−
3.6
−
3.8
0.5
4.0
−
V
V
Vcc = 5V
Vcc = 4.5∼20V
Vcc = 5V
3.84
−
−
4
−
−
4.16
30
30
V
mV
mV
Vcc = 5V
Vcc = 4.5∼20V
Vcc = 5V
3.84
−
−
4
−
−
4.16
30
30
V
mV
mV
Vcc = 5V
Vcc = 5V
Vcc = 5V
85
255
85
100
300
90
115
345
95
kHz
kHz
％
Vcc = 5V
Vcc = 5V
Vcc = 5V
-0.2
2
−
−
−
2
0.7
Vcc
10
V
V
μA
5
Item
Soft start
Current at soft start pin
Error amp
Error amp reference voltage
Over-Current protection detector
Threshold current at ON resistance detection
Threshold voltage at external resistance detection
Timer latch circuit
Timer current
Voltage at S/S pin prior to timer operation
Latch threshold voltage
Output voltage detector
Output voltage detect accuracy (set at 0.8V)
Output voltage detect accuracy (set at 2.5V)
Output voltage detect accuracy (set at 3.3V)
Over temperature protection detector
Overheat protection operation temperature
Condition
Min.
Typ.
Max.
Unit
Vcc = 5V
-3
-2.5
-2
μA
Vcc = 5V
0.784
0.800
0.816
V
Vcc = 5V
Vcc = 5V
3
85
−
100
−
115
A
mV
Vcc = 5V
Vcc = 5V
Vcc = 5V
-40
2.75
3.3
-33
2.9
3.45
-26
3.05
3.6
μA
V
V
Vcc = 4.5∼20V
Vcc = 4.5∼20V
Vcc = 4.5∼20V
0.784
2.425
3.200
0.800
2.500
3.300
0.816
2.575
3.400
V
V
V
−
−
140
−
℃
◆Internal Block Diagrams
● Block
Diagram
Vcc
Vref
6
2
Vboot VB
7
24
VGH
VDD
23
18~21
+
R/C 1
(L.Active)
BANDGAP
REFERENCE
1.26V±1%
ON/OFF
CONTROL
+
THERMAL
SHUTDOWN
Vref
UVLO
-
CURRENT
LIMIT1
-
VCC
+
32
+
-
+
LATCH
Q R S
S/S
VOUT
-
S R Q
LATCH
11~14
INVL
+
+
-
ampOUT 28
amp- 29
ERROR-AMP
-
+
4,26
GND
PWM-COMP
OCL-
+
CURRENT
LIMIT2
S R Q
LATCH
OSC
3
31
30
25
CURRENT
LIMIT3
Vref
-
VOUT
+
27
ampIN
OCLOSC
2.5V/3.3V
OCL+
S R Q
LATCH
5
8
LC
P.GND1
9
16
VGL P.GND2
※N/C : 10,15,17,22
※ ( Resistance )
6
↓Click!
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.
● Standard
Connection Diagram
C4
D1
+ Vi
C3
7
24
Vboot
VB
VDD
18~21
6 VCC
L1
+V0
VOUT
MD3221N
11~14
OCL+ 25
OCL- 27
32 S/S
ampOUT 28
R3
1 R/C
C1
+
C7
C2
C6
D2
C5
+
amp- 29
5
ampIN 30
LC
Vref
OSC
2
3
2.5V/3.3V 31
GND P.GND1 P.GND2
4,26
8
16
C8
G
G
◆Selecting the Output Choke Coil (inductor) (L1)
（Ｖi（max）−VO）×VO
L1＝
［H］
ΔI ×Ｖi（max）×f
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 ΔI is
approximately 30% of the maximum output current
when the input voltage is at its maximum.
Vi（max）：Maximum input voltage［V］
VO
：Output voltage［V］
ΔI
：30% of maximum output current［A］
) Hz］
f
：Oscillation frequency (100kHz or 300kHz［
IO
● Current
：Maximum output current［A］
Waveform in Output Choke Coil ( L1)
ΔI
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 ΔI is between 20% and 40% of the
output current is recommended.
Io
0
7
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.
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 overcurrent 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 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 ＞
−
D（1−D）× IO［A］
◆Selecting the Output Condenser (C5)
D＝
An output condenser is required to reduce output ripple
and thus obtain a stable DC voltage. The converter
output ripple voltage is determined by ΔI and
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.
Z C＜
−
Irip
VO
Vi
D
IO
Vrip
［Ω］
ΔI
VO
Vi
：Allowable ripple current［A］
：Output voltage［V］
：Input voltage［V］
：Duty ratio
：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.
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
8
The substrate wiring between the input condenser
to V DD 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 V F is 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） I R =0.1mA（max）
M1FM3 ( Shindengen )
30V, 2.1A VF =0.4V（max） I R =0.05mA（max）
9
↓Click!
5 Functions
◆Setting the Output Voltage
R5＝1k［Ω］
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
R4＝
V O ：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.
for 2.5V Output
L1
VOUT
R5×（VO −0.8）
［Ω］
0.8
+ V0
11~14
● Wiring
OCL+ 25
for Variable Output
OCL- 27
MD3221N
L1
2.5V/3.3V 31
VOUT
−
＋
+ V0
11~14
ampIN
0.8V
R4
MD3221N
30
amp-
amp-
−
29
29
＋
R5
0.8V
● Wiring
for 3.3V Output
L1
VOUT
11~14
+ V0
OCL+ 25
OCL- 27
MD3221N
◆Selecting the Oscillation Frequency
2.5V/3.3V 31
−
＋
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.
ampIN
0.8V
30
amp29
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.
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)
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.
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.
10
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
● Relationship
Between Soft Start Voltage and Input/Output Voltage
Vi
Switching
2.9V
Vss
Vref
2
300kHz
OSC 3
MD3221N
100kHz
GND 4
Vo
It is necessary to monitor output voltage V O is
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.
◆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
● Relationship Between S/S Condenser and Output Voltage Start-up Time
Start-up time (ms)
100
Vo/Vi=0.1
Vo/Vi=0.3
Vo/Vi=0.5
Vo/Vi=0.7
10
1
Start Circuit
0.1
0.001
0.010
0.100
1.000
S/S condenser capacitance (µF)
Is/s
Select a high value for capacitance of the condenser
connected to the S / S pin if latch is halted at start-up.
32
S/S
C2
MD3221N
◆The Remote ON / OFF Function ( R/C )
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.
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
11
To turn the timer latch off, use the R / C function to
switch OFF the MD3221N, or switch OFF the power
supply voltage.
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
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
Control Circuit
Itimer
32
S/S
1
R/C
C2
C
MD3221N
MD3221N
Vi
◆The Reference Voltage ( Vref )
Over-current
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.
3.45V
2.9V
Vss
Vo
＊Note that this voltage differs from the error amp
reference voltage.
In the process of increasing the output voltage at startup, 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.
◆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 overcurrent 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.
12
◆Short-circuit Protection
◆The Overheat Protection Function
The short-circuit protection function described above
operates when the output pin is completely shortcircuited, or if power is switched on in the shortcircuited 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 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.
◆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.
● Error
Amp Gain Adjustment Circuit
28
ampOUT
As shown in the diagram, the voltage drop across the
inserted resistor ( R2 ) is detected at 100mV.
C6
R3
MD3221N
29
amp-
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)
◆Bootstrap
L1
VOUT
11~14
R2
+ V0
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 VB and VOUT
pins as part of the power supply.
OCL+
MD3221N
25
−
＋
27
OCL-
The capacitance of C3 must be sufficient in relation
to the capacitance of the MOSFET gate. Use a
ceramic condenser of approximately 0.1μF.
13
（1）
Power Saving Mode ( L cut ON )
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.
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.
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 VF of the diode D1
when the VF of 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 V F. ( refer to '17. Application
Circuit Exanples )
● Bootstrap
● L1
Current Waveform at Low-load
Circuit
LC function ON
0
LC function OFF
D1
0
C3
C4
7
24
Vboot
VB
MD3221N
11∼14
VOUT
● Input
Current ( Vi ＝ 20V ) at Low-load
30
Input current (mA)
25
◆The L Cut ( cut off detect ) Function
20
15
LC : off
10
LC : on
5
0
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).
0
10
20
30
40
50
Output current (mA)
（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.
The MD3221N allows selection of two operating
modes in the cut-off region.
14
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
LC : OFF
LC : ON
Conditions : Vi = 5V, Vo=3.3V, output current 0A 3A
X axis : 100μs/div.
Y axis : 50mV/div.
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-cutoff region.
15
↓Click!
6 Cautions for Pattern Design
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.
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.
◆Primary Circuit Pattern Design
● Wiring
Pattern Illustration
Vi
The MD3221N is designed to radiate heat
through the substrate pattern. In particular, both
the V DD and V OUT 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.
+VO
VDD
VOUT
VCC
MD3221N
GND
P.GND2
◆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.
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 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 V CC 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 SBD pattern is connected next. Connect
the anode to P.GND2, and the cathode to V OUT .
A long pattern in this case will not only result in
considerable noise, but will also cause a drop in
efficiency.
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.
16
↓Click!
7 Application Circuit Examples
5V input, 2.5V output, 3A
● Application
300Hz operating frequency, R / C, LC : OFF
Circuit Example
HSU119
C4 : 0.1μF
C3 : 0.1μF
7
24
Vboot
VB
L1 : 4.7μH
Vi : 5V
VO : 2.5V/3A
VOUT
VDD
18~21
11~14
MD3221N
6 VCC
OCL+ 25
OCL- 27
C7:
1μF
32 S/S
C2:
0.01μF
ampOUT 28
1
R3:
100kΩ
R/C
C1:
68μF +
amp- 29
D2 : D1FM3
C6:
1000pF
+
C5:
330μF×2
ampIN 30
5
2.5V/3.3V 31
LC
Vref
OSC
GND
2
3
4,26
P.GND P.GND
1
2
8
16
C8 : 1μF
G
G
◆Component Examples
Component code
Rating
Type
C1
High-polymer organic semiconductor electrolytic condenser
10V, 68μF, Irip.1.7A
C2
Ceramic condenser
25V, 0.01μF
C3
Ceramic condenser
25V, 0.1μF
C4
Ceramic condenser
25V, 0.1μF
C5
High-polymer organic semiconductor electrolytic condenser
6.3V, 330μF, ESR：40mΩ × 2P
C6
Ceramic condenser
25V, 1000pF
C7
Ceramic condenser
10V, 1μF
C8
Ceramic condenser
10V, 1μF
D1
Switching diode
HSU119〔80V, 300mA, VF =1.2V (max)〕
D2
Schottky barrier diode
D1FM3〔30V, 3A, VF =0.4V (max)〕
L1
Inductor
4.7μH
R3
Resistor
100kΩ
17
↓Click!
8 Dimension Drawing
● Dimension
Drawing ( SSOP32 )
14.1MAX
+0.1
13.6 -
Company Name
+0.1
0.2 -0.05
■■■■■
9.95 -
7.5 -
MD3221N
+0.3
17
+0.1
32
1
Lot No.
16
（0.8）
0.35
+
-0.1
+0.2
0.16 M
0.8
+0.2
2.3 -
A Portion
+0.1
2.2 -
+0.1
Detail of A Portion S＝15/ 1
0.1 -
0.10
0.4 -
0゜
∼10゜
Type No.
Unit：mm
18
↓Click!
9 Mounting
◆Substrate Mounting Example
TP2
L1
K
C3
C2
D1
JP7
JP4
R5
C9
5
JP5
JP8
C5
C5−2
JP6
C5−1
C5
JP3
C4
R4−2
R4
R4−1
C8
JP2
C6
K
R7
R/C ＋VO
1
D2
C7
GND
C11
C12
＋VIN
32
IC1
JP1 R3
C10
R6
CN1
R2−2
R2
1
R1
01N07
C1−2
R2−1
R2
C1−1
TP1
MD3221N
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.
◆Cautions for Mounting
Both flow and reflow is applicable when mounting.
The recommended temperature profile for reflow
soldering is shown below.
● Recommended
Ensure that the following requirements are met
when using a soldering iron.
Tip temperature : 300℃ maximum
Soldering time : 5 sec. maximum
Temperature Profile
● Soldering
Pad Reference Pattern
10±1s
240℃max
30±10s
235±5℃
200℃
9.53
150±10℃
1.4
パ
ッ
ケ
ー
ジ
表
面
の
温
度
90±30s
0.8
0.5
時 間
Unit : mm
19
↓Click!
10 External Protection Circuits
◆Connection of Input Protection Devices
◆Connection of Over-voltage Protection Circuit
While the MD3221N incorporates both over-current
protection and overheat protection functions, these
protection circuits may not operate normally if a
fault or a malfunction develops in the IC. A
protective device ( eg a fuse ) should be inserted in
the + ve input line to prevent overheating and
consequent smoke or fire as a result of excess
input current.
The MD3221N does not incorporate an over-voltage
protection circuit. One of the modes supported is such
that the input voltage will appear unchanged at the output
despite operation being halted if the IC is damaged for
any reason. Such damage to the load may result in smoke
and fire, and an over-voltage protection circuit should
therefore be added to prevent such problems.
A representative example of an over-voltage
protection circuit is shown in the diagram below.
Select the rated current of the fuse etc in
consideration of factors such as the DC-DC
converter input current and current capacity of
the input power supply.
● External
The over-voltage protection circuit is inserted on
the load side of the output smoothing condenser.
Protection Circuits
Protection device (eg fuse)
Over-voltage protection circuit
L1
18~21
+
11~14
VOUT
VDD
F20
R20
MD3221N
DC
input
D20
+
GND
P.GND1,2
4,26
8,16
D21
THY20
Load
C5
R21
C20
-
Component number
Component
Output voltage
2.5V
3.3V
5V
F20
Protection device (eg fuse)
R20
Resistor
0.1W 22Ω
R21
Resistor
0.1W 100Ω
C20
Ceramic condenser
D20
Diode
D21
Zener diode
THY20
Thyristor
9V
12V
Select in accordance with load current.
0.33μF
M1FL20U 200V 1.1A
HZM2.7N B1 HZM3.6N B1 HZM5.6N B1
HZM11N B1
3P4J−Z 400V 3A
20
HZM15N B1
↓Click!
11 Characteristics
◆Output voltage : 3.3V
Conditions
● Efficiency
LC：OFF, f ＝300kHz, L ＝12μH
and Loss Characteristics ( f ＝300kHz )
● Temperature
1.8
80
1.6
1.4
Vi=5V
Vi=8V
Vi=12V
Vi=20V
60
50
1.2
1
40
0.8
30
0.6
20
0.4
10
0.2
0
3.36
Output voltage Vo [V]
90
70
3.32
3.28
3.24
0
0
0.5
1
1.5
2
2.5
3.2
-30
3
Output current Io [A]
● Line
Characteristics at Vi ＝5V, IO ＝3A
3.4
2
Circuit loss P [W]
Efficiency η[%]
100
Ta ＝25℃ unless specified otherwise.
-10
10
30
50
70
90
Ambient temperature Ta [˚C ]
Regulation at I O ＝3A
● Start-up
Characteristics at Vi ＝5V, I O ＝3A
3.4
CH1 : Input voltage
Output voltage Vo [V]
3.36
3.32
CH2 : S/S pin voltage
3.28
CH3 : Output voltage
3.24
X axis : 10ms/div.
3.2
0
5
10
15
Y axis : CH1 : 5V/div.、CH2 : 2V/div.、CH3 : 2V/div.
20
Input voltage Vi [V]
● Load
Regulation at Vi ＝5V
●R/C
Start-up Characteristics at Vi ＝5V, I O ＝3A
3.4
CH1 : R/C pin voltage
Output voltage Vo [V]
3.36
3.32
CH2 : S/S pin voltage
3.28
CH3 : Output voltage
3.24
X axis : 10ms/div.
3.2
0
0.5
1
1.5
2
2.5
Y axis : CH1 : 5V/div.、CH2 : 2V/div.、CH3 : 2V/div.
3
Output current Io [A]
21
◆Efficiency by Output Voltage
◆Efficiency at Frequency of 100KHz
Conditions
Conditions
LC：OFF, f ＝300kHz, L ＝12μH
Ta＝25℃
LC：OFF, f ＝100kHz, L ＝22μH
Ta＝25℃
Output voltage : VO ＝0.8V, 1.2V, 1.8V, 2.5V, 3.3V
Output voltage : 3.3V
● Efficiency
● Efficiency
100
100
90
2
90
1.8
80
1.6
70
80
Efficiency η[%]
Efficiency η[%]
and Losses ( f ＝100kHz )
70
Vo=3.3V
Vo=2.5V
Vo=1.8V
Vo=1.2V
Vo=0.8V
60
1.4
Vin=5V
Vin=8V
Vin=12V
Vin=20V
60
1.2
50
1
40
0.8
30
0.6
20
0.4
10
0.2
50
40
0
0
0.5
1
1.5
2
2.5
3
0
0.5
1
1.5
2
Output current Io [A]
Output current Io [A]
22
2.5
3
0
Circuit loss P [W]
by Output Voltage at Vi ＝5V
↓Click!
12 Packaging
◆Tape & Reel
● Tape
Material : PVC + Carbon
Dimensions Comply with JIS, C-0806-3
(2.8)
14.2
SHINDENGEN
MD3221N
□□□□□
11.5±0.1
2.0±0.1
2.2±0.1
0.3±0.1
24.0±0.9
±0.1
4.0
φ1.5+0.1
0
１PIN Side
1.75±0.1
12.0±0.1
φ2.1±0.1
10.4
3.1±0.1
Direction of Feed
Unit : mm
● Reel
Material : Polystyrene
Dimensions
Comply with JEITA, ET-7200
・Label
PS
Type No.
φ13±0.2
Date Code
φ80±1
φ330±2
０
0.２
2
０
0.４
4
０
0.６
6
０
0.８
8
Code No.
Quantity
Manufacturer
JEITA.RRM.24.D
Label
25.5±0.5
±0.1
29.4
● Leader
Unit : mm
and Trailer
Trailer (Over 120)
Top cover (Over 400)
Device
Leader (Over 120)
23
Unit : mm
◆Packing
・Marking
Type No.
Code No.
H
Date Code
Quantities
W
Label
D
Unit : mm
・Tape & Reel : 6,000pcs ( 3 Reels ) / Outer Carton
◆Ordering and Dimensions
Package
SSOP32
Code No.
4072
Minimum Ordering
Quantities
2000
Quantities Per
Inner Carton
(pcs.)
2000
Quantities per
Outer Carton
pcs./Carton Weight (kg)
6000
7.6
Outer Carton (mm)
D
W
H
363
363
160
※Please consolidate ordering quantities at basic ordering quantity unit.
24
U.S.A
Shindengen America, Inc.
Head Office
2985 E. Hillcrest Drive, Suite 140
Westlake Village, CA91362, U.S.A.
Phone:(1)-805-373-1130 Fax:(1)-805-373-3710
Chicago Office
411 Business Center Drive, Suite 112
Mt. Prospect, IL 60056 U.S.A.
Phone:(1)-847-827-7100 Fax:(1)-847-827-7122
Europe
Shindengen UK Ltd.
Howard Court, 12 Tewin Road,
Welwyn Garden City, Hertfordshire. AL7 IBW
Phone:(44)-1707-332-992 Fax:(44)-1707-332-955
German Branch Office
Kaiser-Strasse 25, D-40479 Dusseldorf, Germany
Phone:(49)-211-491968-0 Fax:(49)-211-4986499
Asia
Shindengen Singapore PTE Ltd.
159, Sin Ming Road #04-07, Amtech Building Singapore 575625
Phone:65-6552-3635 Fax:65-6552-4210
Shindengen (H.K.) Co., Ltd.
Head Office
Suite 3206, 32/F, Tower 1, The Gateway, 25 Canton Road, TST,
Kowloon, Hong Kong
Phone:(852)-2317-1884 Fax:(852)-2314-8561
Taipei Branch
Room N1010, 10F, Chia-Hsin Bldg. 2 No. 96, SEC. 2, Chung Shan N.
RD Taipei, Taiwan R.O.C.
Phone:886-2-2560-3990 Fax:886-2-2560-3991
Shanghai Liaison Office
W504, Sun Plaza, No.88 Xianxia Road Shanghai 200336, China
Phone:86-21-6270-1173 Fax:86-21-6270-0419
Shindengen Electric Mfg. Co., Ltd.
Seoul Office
Korea City Air-Terminal Bldg. 606, 159-6 Samsung-Dong
Kangnam-ku, Seoul, Korea
Phone:82(2)551-1431 Fax:82(2)551-1432
Taiwan Representative Office
Room N1010, 10F, Chia-Hsin Bldg.No.96,Sec.2 Chung Shan N. Road,
Taipei, Taiwan R.O.C.
Phone:886(2)2560-3990 Fax:886(2)2560-3991
Malaysia Regional Office
Suite A202, 2nd Floor, West Wing, Wisma Tractors No.7
Jalan SS 16/1, 47500 Subang Jaya, Selangor, Malaysia
Phone:60-3-5633-0834 Fax:60-3-5633-1179
SHINDENGEN
ELECTRIC MFG. CO., LTD.
Ikebukuro office:
Ikebukuro. YS Bldg., 1-13-23, Minami-Ikebukuro, Toshimaku, Tokyo 171-0022, Japan
Phone : ( 81)-03-5951-8105, 8130
Fax : ( 81)-03-5951-8090
URL：http://www.shindengen.co.jp/top_e/index.html
This product is classified as the integrated circuit specified in Item 7 in the Attached Table No. 1 to the Export Trade Control Order and in Article 6 of the
Ordinance of the Ministry of International Trade and Industry.
* This product is subject to the KNOW regulation.
May 2002
02500 (NQ)