SI-8000Y
Application Note
Full Mold Chopper Type Switching Regulator IC
SI-8000Y Series
2nd Edition May 2010
SANKEN ELECTRIC CO., LTD.
SI-8000Y
－－－
Contents
－－－
1. General Description
1-1 Features
－－－－－－－－－－
3
1-2 Applications
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3
1-3 Type
－－－－－－－－－－
3
2-1 Package Information
－－－－－－－－－－
4
2-2 Ratings
－－－－－－－－－－
5
2-3 Circuit Diagram
－－－－－－－－－－
7
3-1 Terminal List
－－－－－－－－－－
10
3-2 Functional Description of Terminal
－－－－－－－－－－
10
4-1 Operational Description
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11
4-2 Overcurrent Protection / Thermal Shutdown
－－－－－－－－－－
12
5-1 External Components
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14
5-2 Pattern Design Notes
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21
5-3Output Voltage Setting
－－－－－－－－－－
22
5-4 Operation Waveform Check
－－－－－－－－－－
25
5-5 Thermal Design
－－－－－－－－－－
26
6-1 Soft Start
－－－－－－－－－－
30
6-2 Output ON / OFF Control
－－－－－－－－－－
31
6-3 Spike Noise Reduction
－－－－－－－－－－
32
6-5 Reverse Bias Protection
－－－－－－－－－－
32
7. Typical Characteristics
－－－－－－－－－－
33
8. Terminology
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35
2. Specification
3. Terminal Description
4. Operational Description
5. Cautions
6. Applications
2
SI-8000Y
1. General Description
The SI-8000Y is a buck switching regulator IC of a current control system. Since the switching transistor
includes a low ON resistance Nch MOSFET, a highly efficient DC/DC converter can be realized. In
addition, the current control system is adopted to downsize the LC filter. The soft start function is also
included and by connecting an external capacitor, the soft start can be set to alleviate the in-rush current at
startup.
● 1-1 Features
-
Compact size and large output current of 8A
The maximum output current is 8A for the outline of TO220F class.
-
High efficiency of 86% (VIN = 30V / IO = 3A)
Heat dissipation is small due to high efficiency to allow for the downsizing of a heat sink.
-
Built-in functions for overcurrent and thermal shutdown
A current limiting type protection circuit against overcurrent and overheat is built in. (automatic
restoration type)
-
Soft start function (capable of ON/OFF output)
By setting constant of an external capacitor, it is possible to delay the rise speed of the output
voltage. In-rush current at startup can be alleviated. ON/OFF control of the output is also possible
by connecting collector-opened transistor.
-
No insulation plate required
No insulation plate is required, when it is fitted to the heat sink, because it is of full molding type.
● 1-2 Applications
For amusements power supplies, power supplies for OA equipment, stabilization of secondary output
voltage of regulator and on-board local power supplies.
● 1-3 Type
-
Type: Semiconductor integrated circuits (monolithic IC)
-
Structure: Resin molding type (transfer molding)
3
SI-8000Y
2. Specification
DWG No: TG3A-2116
● 2-1 Package Information
Unit: mm
c
a
８０１０Ｙ
b
1 2 3 4 5 6 7
端子配列
Pin Assignment
1.BS
1.2.SW
BS
2.3.IN
SW
4.GND
3. IN
5.COMP
4.6.FB
GND
5.7.EN/SS
COMP
6.FB
7. EN/SS
a: Type No
b: Lot Number
1st letter: The last digit of year
2nd letter: Month
1 to 9 for Jan. to Sep.
O for Oct.
N for Nov.
D for Dec.
3rd and 4th letter: Date
01 to 31
c: Logo
*1: The dimensions don’t include the gate burr.
*2: It shows the dimensions measured at the top of lead.
Weight of product: about 2.3g
External Terminal Processing: Sn-3Ag-0.5Cu dipping
4
SI-8000Y
● 2-2 Rating
Table1 Absolute Maximum Rating
Parameter
Symbol
Rating
Unit
VIN
4.5
V
BVDSS
55
V
Pd1
20.8
W
Pd2
1.8
W
Junction Temperature
Tj
-30 - 150
°C
Storage Temperature
Tstg
-40 – 150
°C
Θj-c
6
°C/W
Θj-c
66.7
°C/W
Input Voltage VIN
*1
D-S voltage
on high side power MOS
Allowable Power Dissipation
at infinite heat dissipation
Allowable Power Dissipation
without heat sink
Thermal resistance
(Junction and case)
Thermal resistance
(Junction and ambient)
*1: It is maximum applied voltage including VIN serge.
Table 2 Recommended Conditions
Rating
Parameter
Symbol
Unit
MIN
MAX
Condition
Input Voltage
VIN
*2
43 *4
V
Output Current
Iout
0
8.0
A
Junction Temperature in Operation
Tjop
-30
135
°C
Operation Temperature
Top
-30
85
°C
*3
Output Voltage
Vo
1
15
V
Only for SI-8010Y
*3
*2: It is whichever higher VIN = 8V or VIN = VOUT × 1.3
*3: It should be used within the thermal derating limit.
*4: In the case of VIN >40V, a snubber circuit should be provided between IN - SW and SW - GND.
5
SI-8000Y
Table 3 Electrical Characteristics
Ratings
Parameter
Symbol
Reference Voltage
(Output Voltage)
VREF
（Vout）
Temperature Coefficient
For Reference Voltage
ΔVREF/ΔT
(ΔVo/ΔT)
Efficiency *6
η
Operational Frequency
fo
Line Regulation
VLine
Load Regulation
VLoad
Overcurrent Protection
Start Current
IS
Circuit Current
in Non-operation 1
Iq
Circuit Current
in Non-operation 2
Flow-out
Current
at
EN/SS
Low
Terminal
*7
Low level
Voltage
Iq (off)
MIN
SI-8010Y *5
TYP
MAX
0.98
1
1.02
MIN
MAX
4.9
5
5.1
VIN = 30V, Io = 0.1A
V
VIN = 30V, Io = 0.1A
±0.1
±0.5
VIN = 30V, Io = 0.1A, Ta = 0 - 100°C
VIN = 30V, Io = 0.1A, Ta = 0 - 100°C
86
86
VIN = 30V, Io = 3A
VIN = 30V, Io = 3A
130
130
VIN = 30V, Io = 3A
VIN = 30V, Io = 3A
30
90
30
kHz
90
mV
VIN = 10 - 43V, Io = 3A
90
VIN = 30V, Io = 0.1 - 8A
30
90
mV
VIN = 30V, Io = 0.1 - 8A
8.1
8.1
A
VIN = 20V
VIN = 20V
8
8
VIN = 30V, Io = 0A, VEN/SS = open
VIN = 30V, Io = 0A, VEN/SS = open
250
250
500
VIN = 30V, VEN/SS = 0V
VIN = 30V ,VEN/SS = 0V
500
10
uA
30
μA
VIN = 30V ,VEN/SS = 0V
0.5
VC/EL
mA
VIN = 30V, VEN/SS = 0V
30
VIN = 30V
0.5
V
VIN = 30V
*5: When Ta=25°C, Vo = 5V, R1 = 8kΩ, R2 = 2kΩ
*6: Efficiency is calculated by the following equation.
(%)
mV/°C
%
30
VIN = 10 - 43V, Io = 3A
10
ISSL
Unit
SI-8050Y
TYP
Vo Io
100
Vin Iin
*7: Pin no.7 is an EN/SS terminal and soft start can be made by connecting to a capacitor. Also, the output
can be stopped by setting the EN/SS terminal voltage below VSSL. The switch-over of potential of EN/SS
terminal can be made by the open collector driving of the transistor.
In the case that both soft start and ON/OFF of transistor are used, since the discharge current of C6 flows
across the transistor of ON/OFF, protection such as current limiting etc. should be made if the capacitance
of C6 is large. The EN/SS terminal is pulled up to the internal power supply of IC therefore no external
voltage can be applied. In the case of no use, the EN/SS terminal should be made open.
6
SI-8000Y
● 2-3 Circuit Diagram
2-3-1 Internal Equivalent Circuit
SI-8010Y
VIN
SI-8010Y
C2
3
５
IN
Pre
REG
OSC
Σ３
C1
Current
Sense
Amp
Boot
5vREG
６
1
BS
C5
7
３
EN/
SS
３
C6
UVLO
TSD
OCP
EN/SS
DRIVE
PWM
LOGIC
４
L1
2
VO
SW
C3
D1
R1
5 COMP
８
1.0V
７
C4
6
FB
Amp
R2
C7
R3
GND
１
4
Fig.1
SI-8050Y
VIN
C2
3
C1
IN
Pre
REG
OSC
Σ
Current
Sense
Amp
Boot
5vREG
1
BS
C5
7
C6
EN/
SS
UVLO
TSD
OCP
EN/SS
DRIVE
PWM
LOGIC
L1
2
SW
D1
VO
C3
6
5 COMP
1.0V
C4
Amp
FB
C7
R3
GND
4
Fig.2
7
SI-8000Y
2-3-2 Typical Connection Diagram
SI-8010Y
*1
Csn1
Rsn1
Vin
C1
IN
7
C2
EN/SS
C6
C5
1
3
BS
SI-8010Y
COMP
GND
5
4
C7
FB
R1
6
Csn2
D1
C4
Vo
L1
2
SW
C3
R2
*1
Rsn2
R3
GND
GND
Fig.3
C1: 2200μF/50V
C2: 4.7μF/50V (RPER11H475K5 by MURATA)
C3: 470μF/25V
C4: 1200pF (Vo = 5V)
C5: 0.22μF/50V
C6: 0.1 - 1uF
C7: 680pF (Vo = 5V)
L1: 47μH
D1: FMB-26L by Sanken
R1: 8kΩ (Vo = 5V)
R2: 2kΩ
R3: 39kΩ (Vo = 5V)
Csn1,2 = 2200pF (VIN >40V) *1
Rsn1,2 = 10
*1 In the case of VIN >40V, a snubber circuit should be provided between IN - SW and SW - GND.
8
SI-8000Y
SI-8050Y
*1
Csn1
Rsn1
Vin
C1
IN
7
C2
C5
1
3
EN/SS
C6
BS
Vo
L1
SI-8050Y
COMP
GND
5
4
C7
2
SW
FB
6
C3
D1
Csn2
C4
*1
R3
Rsn2
GND
GND
Fig.4
C1: 2200μF/50V
C2: 4.7μF/50V (RPER11H475K5 by MURATA)
C3: 470μF/25V
C4: 1200pF
C5: 0.22μF/50V
C6: 0.1 - 1uF
C7: 680pF
L1: 56μH
D1: FMB-26L by Sanken
R3: 39kΩ
Csn1,2 = 2200pF (VIN >40V)*1
Rsn1,2 = 10Ω (VIN >40V)*1
*1 In the case of VIN >40V, a snubber circuit should be provided between IN - SW and SW - GND.
9
SI-8000Y
3. Terminal Description
● 3-1 Terminal List
Table 4
SI-8010Y/8050Y
Terminal
Symbol
Description
1
BS
High side boost terminal
2
SW
Switching output terminal
3
VIN
Input terminal
4
GND
GND terminal
5
COMP
Phase compensation terminal
6
FB
Feedback voltage terminal
7
EN/SS
Soft start and ON/OFF terminal
● 3-2 Functional Description of Terminal
-
BS (terminal No. 1)
It is an internal power supply for driving the gate of high side switch Nch - MOS. A capacitor of
0.22nF (recommended) is connected between the SW terminal and BS terminal to drive the high
side Nch - MOS.
-
SW (terminal No. 2)
It is a switching output terminal which supplies power to the output.
-
VIN (terminal No. 3)
It is an input voltage of IC.
-
GND (terminal No. 4)
It is a grand terminal.
-
Comp (terminal No. 5)
It is a phase compensation terminal for controlling the loop stably.
-
FB (terminal No. 6)
It is a terminal for setting the output voltage. The output voltage is set by R1 and R2 for
SI-8010Y.
-
EN/SS (terminal No. 7)
A capacitor is connected to this terminal to set the soft start of output voltage. In the case that the
IC is turned ON/OFF, an open collector transistor is connected to turn OFF by making it low.
10
SI-8000Y
4. Operational Description
● 4-1 Operational Description
The SI-8000Y is composed of an error amplifier which compares the division of resistance with the
reference voltage of 1V. The current control feedback is a loop which feeds back the inductor current for
PWM control and the inductor current shunted by using a sense MOS is detected by a current sense
amplifier. With respect to the slope compensation, in consideration of current control system, in order to
avoid the sub harmonic oscillation, slope compensation is made for the current control slope. As shown in
Fig.5, in the SI-8000Y, by means of voltage control feedback, current control feedback and calculation of
slope compensation, the PWM control by current control system is made.
VIN
SI-8010Y
C2
3
C1
IN
Pre
REG
OSC
Σ
Current
Sense
Amp
Boot
5vREG
7
C6
EN/
SS
UVLO
TSD
OCP
EN/SS
1
BS
PWM
LOGIC
C5
M1
DRIVE
L1
2
SW
C3
D1
M2
VO
R1
6
5 COMP
1.0V
C4
Amp
FB
R2
C7
R3
GND
4
Fig.5 Current Control PWM Chopper Regulator Basic Configuration
Since the SI-8000Y is a current control regulator, the COMP terminal voltage is proportional to the peak
value of the inductor current. When the ULVO is released or the EN/SS terminal exceeds the threshold
value (about 1.5V), the switching operation is made. At first, switching operation is made in MIN ON duty
or MAX ON duty and the high side switch (hereinafter called as M1) and the switch for BS capacitor
charging (hereinafter called as M2) turn ON and OFF alternately. M1 is a switching MOS which provides
power to the output, while M2 charges the capacitor C5 for boost which drives M1.
At M1: ON / M2: OFF, inductor current is increased by applying voltage to the SW switch and inductor,
and the output of the current detection amplifier which detects it also rises. The signal to which the output
of this current detection amplifier and the Ramp compensation signal are added is compared with the
11
SI-8000Y
output of the error amplifier by the current comparator (CUR COMP). When the added signal exceeds the
output of the error amplifier (COMP terminal voltage), the output of the current comparator becomes “H”
to reset the RS flip-flop. Then, M1 turns off and M2 turns on. Thereby, the regenerated current flows
through the external SBD (D1).
In the SI-8000Y, the reset signal is generated at each cycle to reset the RS flip-flop. In the case the added
signal does not exceed the COMP terminal voltage, the RS flip-flop is reset without fail by the signal of the
10% OFF Duty circuit.
● 4-2 Overcurrent Protection / Thermal Shutdown
Output Voltage
As VO drops, the oscillation frequency
is decreased.
Output Current
Fig.6 Output Voltage Characteristics in Overcurrent
The SI-8000Y integrates a current limiting type overcurrent protection circuit. The overcurrent protection
circuit detects the peak current of a switching MOSFET and when the peak current exceeds the set value,
the ON time of the transistor is compulsorily shortened to limit the current by lowering the output voltage.
In addition, when the output voltage is lowered, the increase of current at low output voltage is prevented
by dropping the switching frequency to about 25KHz. When the overcurrent condition is released, the
output voltage will be automatically restored.
出力電圧
Output Voltage
Restoration
Setting
復帰設定温度
Temperature
Protection Setting Temperature
保護設定温度
接合温度
Junction Temperature
Fig.7 Output voltage Characteristics in Thermal Shutdown
12
SI-8000Y
The thermal shutdown circuit detects the semiconductor junction temperature of the IC and when the
junction temperature exceeds the set value (around 160°C), the output transistor is stopped and the output is
turned OFF. When the junction temperature drops from the set value for overheat protection by around
25°C, the output transistor is automatically restored.
* Note for thermal shutdown characteristic
This circuit protects the IC against overheat resulting from the instantaneous short circuit, but it should be
noted that this function does not assure the operation including reliability in the state that overheat
continues due to long time short circuit.
13
SI-8000Y
5. Cautions
● 5-1 External Components
5-1-1 Choke coil L1
The choke coil L1 plays a main role in the chopper type switching regulator. In order to maintain the stable
operation of the regulator, such dangerous state of operation as saturation state and operation at high
temperature due to heat generation must be avoided.
The following points should be taken into consideration for the selection of the choke coil.
a) The choke coil should be fit for the switching regulator.
The coil for a noise filter should not be used because of large loss and generated heat.
b) For the peak detection current control, the inductance current may fluctuate at the cycle of integral
multiple of switching operation frequency.
Such phenomenon is called as sub harmonic oscillation and it may theoritically occur in the peak detection
current control mode.
Therefore, in order to assure stable operation, the inductance current is compensated inside the IC, and it is
required to select a proper inductance value to the output voltage.
VIN(V)
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
120
L=100ｕＨ
L=82uH
L=68uH
L=56uH
L=47uH
L=33uH
1
2
3
4
5
6
7
8
9
Ｖｏｕｔ
10
11
12
13
14
15
Fig.8 The selection range of the inductance L value to avoid the sub harmonic oscillation
14
SI-8000Y
Since the SI-8010Y sets Vout by an external resistor, it is required to optimize the inductance value subject
to setting conditions.
In the SI-8050Y, when the external resistor is added to make Vout variable for rising, it is also required to
adjust the inductance value.
In the case that Vo is changed, it is required to reset complementary constants (C4, C7, R3). (Refer to page
18.)
The pulse current of choke coil ΔIL and the peak current ILp are expressed by the following equation:
(Vin Vout) Vout
－－－（A）
L Vin f
IL
－－－（B）
ILp
Iout
2
IL
From this equation, you will see that as the inductance L of choke coil is decreased, ΔIL and ILP are
increased. In the event that the inductance is too small, the fluctuation of choke coil current is larger,
resulting in unstable operation of the regulator.
Care should be taken of decrease of inductance of choke coil due to magnetic saturation of overload, load
short circuit etc.
High inductance
Low inductance
Fig.9 Relation between Ripple current ILP and Output Current IO
c) The rated current shall be met.
The rated current of the choke coil must be higher than the maximum load current to be used. When the
load current exceeds the rated current of the coil, the inductance is sharply decreased to the extent that it
causes saturation state at last. Please note that overcurrent may flow since the high frequency impedance
becomes low.
d) Noise shall be low.
In the open magnetic circuit core which is of drum shape, since magnetic flux passes outside the coil, the
peripheral circuit may be damaged by noise. It is recommended to use the toroidal type, EI type or EE type
coil which has a closed magnetic circuit type core as much as possible.
5-1-2 Input Capacitor C1, C2
The input capacitor is operated as a bypass capacitor of the input circuit to supply steep current to the
15
SI-8000Y
regulator during switching and to compensate the voltage drop of the input side. Therefore, the input
capacitor should be connected as close as to the regulator IC. Especially for C2, a ceramic capacitor or film
capacitor which has good frequency characteristics should be used to be laid out near the IN – GND
terminal of the product.
Even in the case that the rectifying capacitor of the AC rectifier circuit is located in the input circuit, the
input capacitor cannot play a role of the rectifying capacitor unless it is connected near the SI-8000Y.
The selection of C1 shall be made in consideration of the following points:
a) The requirement of withstand voltage shall be met.
b) The requirement of the allowable ripple voltage shall be met.
IIN
C1電流波形
VIN
1.VIN
Ripple
Current
ﾘｯﾌﾟﾙ電流
0
Iv
Ip
C1
Ton
T
Fig.10 Current Flow of C1
D
Ton
T
Fig. 11 Current Waveform of C1
The ripple current of the input capacitor is increased in accordance with the increase of the load
current.
If the withstanding voltages or allowable ripple voltages are exceeded or used without derating, it is in
danger of causing not only the decreasing the capacitor lifetime (burst, capacitance decrease, equivalent
impedance increase, etc) but also the abnormal oscillations of regulator.
Therefore, the selection with sufficient margin is needed.
The effective value of ripple current flowing across the input capacitor can be calculated by the following
equation (2):
Irms 1.2
Vo
Io
Vin
－－(2)
For instance, where VIN = 20V, Io = 3A and Vo= 5V,
Irms 1.2
5
3 0.9 A
20
Therefore, it is necessary to select the capacitor with the allowable ripple current of 0.9A or higher.
5-1-3 Output Capacitor C3
The output capacitor C3 composes a LC low pass filter together with a choke coil L1 and functions as a
16
SI-8000Y
rectifying capacitor of switching output.
The current equivalent to the pulse current ΔIL of the choke coil current is charged and discharged in the
output capacitor.
Therefore, it is necessary to meet the requirements of withstand voltage and allowable ripple current with
sufficient margin like the input capacitor.
IL
Vout
L1
ESR
C2電流波形
Io
ﾘｯﾌﾟﾙ電流
Ripple current
0
RL
⊿IL
C2
Fig.10 C3 current flow
Fig.11 C3 current curve
The ripple current of the output capacitor is equal to the ripple current of the choke coil and does
not vary even if the load current increases or decreases.
The ripple current effective value of the output capacitor is calculated by the equation (3).
Irms
IL
－－－(3)
2 3
When ΔIL = 0.5A,
Irms
0.5
2 3
≒ 0.14 A
Therefore a capacitor having the allowable ripple current of 0.14A or higher is required.
In addition, the output ripple voltage Vrip of the regulator is determined by a product of the pulse current
ΔIL of the choke coil current (= C2 charging/discharging current) and the equivalent series resistance ESR
of the output capacitor.
Vrip IL C2ESR
－－－(4)
It is therefore necessary to select a capacitor with low equivalent series resistance ESR in order to lower the
output ripple voltage. As for general electrolytic capacitors of same product series, the ESR shall be lower,
for the products of higher capacitance with same withstand voltage, or with higher withstand voltage
(almost proportional to larger externals) with same capacitance.
When ΔIL=0.5A, Vrip=40mV,
C 2esr 40 0.5 80m
As shown above, a capacitor with the ESR of 80mΩ or lower should be selected. In addition, since the ESR
varies with temperature and increases at low temperature, it is required to examine the ESR at the actual
operating temperatures. It is recommended to contact capacitor manufacturers for the ESR value since it is
17
SI-8000Y
peculiar to capacitors. However, in the case that an output capacitor with extremely small ESR (30 mΩ or
less) is used, it may be used by reviewing phase compensation constants of the Comp terminal(Refer to
page 18).
5-1-4 The flywheel Diode D1
The flywheel diode D1 is to discharge the energy which is stored in the choke coil at switching OFF.
For the flywheel diode, the Schottky barrier diode must be used. If a general rectifying diode or fast
recovery diode is used, the IC may be damaged by applying reverse voltage due to the recovery and ON
voltage.
In addition, since the output voltage from the SW terminal (pin 2) of the SI-8000Q series is almost
equivalent to the input voltage, the flywheel diode with the reverse withstand voltage of the input voltage or
higher should be used.
If a ferrite bead is inserted into a fly wheel Di for noise prevention, excessive negative potential will be
generated, therefore please refrain from doing so by all means.
5-1-5 Phase compensation elements C4, C7, R3
The stability and responsiveness of the loop are controlled through the COMP terminal.
The COMP terminal is an output of the internal trans-conductance amplifier.
The series combination of a capacitor and resistor sets the combination of pole and zero which determines
characteristics of the control system. The DC gain of voltage feedback loop can be calculated by the
following equation:
Adc Rl Gcs AEA
VFB
Vout
Here, VFB is feedback voltage (1.0V). AEA is the voltage gain of error amplifier, GCS trans-inductance of
current detection and R1 a load resistance value. There are 2 important poles. One is produced by a phase
compensation capacitor (C4) and an output resistor of the error amplifier.
Another one is produced by a output capacitor (C3) and a load resistor. These poles appear at the following
frequencies:
GEA
2 C 4 AEA
1
fp2
2 C 3 Rl
fp1
Here, GEA is the trans-conductance of error amplifier. In this system, one zero is important. This zero is
produced by phase compensation capacitor C3 and phase compensation resistance R3. This zero appears in
the following frequencies:
fz1
1
2 C 4 R3
If the output capacitor is large and/or ESR is large like an electrolytic capacitor, this system may have
another important zero. This zero is produced by the ESR and capacitance of the output capacitor C3. And
18
SI-8000Y
it exists in the following frequencies:
fESR
1
2 C 3 RESR
In this case, the third pole which is set by the phase compensation capacitor (C7) and phase compensation
resistor (R3) is used to compensate the effect of ESR zero on the loop gain.
This pole exists in the following frequencies:
p3
1
2 C 7 R3
The objective of design of phase compensation is to form the converter transfer function to obtain the
desired loop gain. The system crossover frequency where the feedback loop has a single gain is important.
The lower crossover frequency will produce the slower line and load transient. In the meantime, the higher
crossover frequency may cause instability of the system. The selection of the most suitable phase
compensation element is described below.
Table 5
Parameter
Symbol
Value
Unit
Error Amplifier Voltage Gain
AEA
300
V/V
Error Amplifier Trans-conductance
GEA
800
μA/V
Current Sense Amplifier Impedance
1/GCS
0.16
V/A
1. A phase compensation resistor (R3) is selected to set the resistor at the desired crossover frequency.
The calculation of R3 is made by the following equation:
R3
2 C3 fc Vout 2 C3 0.1 fs Vout
GEA GCS VFB
GEA GCS
VFB
Here, fc is a desired crossover frequency. It should be one tenth or lower of the normal switching frequency
(fs).
2. In order to achieve the desired phase margin, a phase compensation capacitor (C4) is selected.
For the application having a representative inductance value, adequate phase margin is provided by setting
the zero compensation of one fourth or lower of the crossover frequency.
C4 is calculated by the following equation.
C4
4
2 R3 fc
R3 is a phase compensation resistor.
3. It is required to judge whether the second compensation capacitor C7 is necessary or not.
It will be necessary, when the ESR zero of the output capacitor is located at a frequency which is lower
than the half of the switching frequency.
19
SI-8000Y
Namely, it is necessary, when the following equation is applicable.
fs
1
(C3: capacitance of output capacitor)
2 C3 RESR 2
In this case, the second compensation capacitor C7 is added and the frequency fp3 of ESR zero is set.
C6 is calculated from the following equation.
C7
C 3 RESR
R3
5-1-6 Example of calculation of C4, C7 and R3
-
Calculation of R3
R3 is calculated by the following equation.
R3
2 C 3 fc Vout
GEA GCS VFB
From Table 5,
GEA: 800 × 10-6 , GCS: 6.25 (reciprocal number of 1/GCS = 0. 16)
fc: 13 × 103 (1/10 of oscillating frequency)
C3: capacitance of output capacitor, VOUT: set Vo, VFB: 1V
When CO = 560μF at VO = 5V,
R3 = { (2 × 3.14 × 560 × 10-6 × 13 × 103) / (800 × 10-6 × 6.25) } × (5/1)
= 45.718kΩ
As an approximated value, it is 43kΩ which is less than the calculated value.
-
Calculation of C4
C4
4
2 R3 fc
C4 = 4 / (2 × 3.14 × 43 × 103 × 13 × 103) = 1139 × 10-12
= 1139pF
As an approximated value, it is 1200pF or so which is larger than the calculated value.
-
Calculation of C7
C7
C 3 RESR
RESR: ESR of C3 (COUT)
R3
When calculated as C3 = 560μF and assumed as RESR = 50mΩ
C7 = (560 × 10-6 × 0.05) / 43 × 103 = 651 × 10-12
= 651pF
As an approximated value, it is 680 pF or so which is more than the calculated value.
The constants for each output setting voltage in the case that aluminum electrolytic capacitors are used are
shown in the following table.
20
SI-8000Y
Reference Comp terminal phase compensation constants (C4, C7, R3)
Table 6 Constants for each setting voltage (CO = 470μF)
Vo (V)
R3 (kΩ）
C4 (pF)
C7 (pF)
3.3
27
2000
1000
5
39
1200
620
9
68
680
340
12
91
580
255
Table 7 Constants for each setting voltage (CO = 1000μF)
Vo (V)
R3 (kΩ）
C4 (pF)
C7 (pF)
3.3
54
1000
1000
5
82
620
620
9
150
330
360
12
200
270
270
● 5-2 Pattern Design Notes
5-2-1 High Current Line
Since high current flows in the bold lines in the connection diagram, the pattern should be as wide and
short as possible.
Vin
C1
C2
IN
7
EN/SS
C6
C7
C5
1
3
BS
Vo
L1
2
SW
SI-8050Y
COMP
GND
5
4
FB
6
C3
D1
C4
R3
GND
GND
21
SI-8000Y
5-2-2 Input/ Output Capacitor
The input capacitor C1, C2 and the output capacitor C3 should be connected to the IC as close as possible.
If the rectifying capacitor for AC rectifier circuit is on the input side, it can be used as an input capacitor.
However, if it is not close to the IC, the input capacitor should be connected in addition to the rectifying
capacitor. Since high current is discharged and charged through the leads of input/output capacitor at high
speed, the leads should be as short as possible. A similar care should be taken for the patterning of the
capacitor.
C1,C2
C1,C2
Improper Pattern Example
Proper Pattern Example
● 5-3 Output Voltage Setting
5-3-1 Output Voltage Setting for SI-8010Y
The FB terminal is a feedback detection terminal for controlling the output voltage. It is recommended to
connect it as close as possible to the output capacitor C3. When they are not close, the abnormal oscillation
may be caused due to the poor regulation and increase of switching ripple.
Since the SI-8010Y is of variable type, the output voltage set-up is achieved by connecting R1 and R2.
ISENSE should be set to be around 2mA.
(The ISENSE lower limit is 1.6mA, and the upper limit is not defined. However, it is necessary to consider
that the consumption current shall increase according to the IFB value, resulting in lower efficiency.)
R1, R2 and output voltage are calculated from the following equations:
ISENSE = VFB / R2 (VFB = 1.0V ±2%)
R1 = (Vo – VFB) / ISENSE
, R2
= VFB / ISENSE
Vout = R1 × (VFB / R2) + VFB
The wiring of FB terminal, R1 and R2 that run parallel to the
flywheel diode should be avoided, because switching noise may
interfere with the detection voltage to cause abnormal oscillation.
It is recommended to implement the wiring from the FB terminal
to R1 and R2 as short as possible.
ISENSE
22
SI-8000Y
-
Mounting Board Pattern Example
Recommended pattern
Backside GND plane
*It is so important in term of the pattern design to lay out C2 and D1 near the product.
*For optimum operation conditions, the GND line shall be wired at one point, centered on No. 4 terminal
and each part shall be wired in the shortest distance.
5-3-2 Variable Output Voltage for SI-8050Y
Even for SI-8050Y with fixed output voltage, the output voltage can be increased by adding a resistor to
the No. 6 FB terminal (not applicable to voltage drop).
SW
FB 6
G4
４
Ivos
IVFB
ＦＢ
The output voltage adjustment resistors Rex1 and 2 are calculated by the following equation.
Vout'Vos
S IV FB
V FB
Re x 2
( S 1) IV FB
Re x1
S: Stability coefficient
Stability coefficient S means the ratio of Rex 2 to the FB terminal in-flow current Ivos. The larger is S, the
more is the variation of temperature characteristic and output voltage improved. (Normally, about 5 - 10)
IVOS on SI-8050Y should be 1mA ±20%.
23
SI-8000Y
The tolerance of the output voltage including variation of Rex 1, Rex 2, Ivos, VFB is shown below.
-
Maximum output voltage (Vout MAX)
Vout' MAX ＝VFB MAX ＋Rex1MAX(
VFB MAX
＋IvosMAX ）
Rex2MIN
VFBMAX: The maximum value of set output voltage. The MAX value of set output voltage should be put,
shown in the electrical characteristics of the specifications.
Rex1MAX: The maximum value of Rex1. It is obtained from the tolerance of the resistor.
Rex2 MIN: The minimum value of Rex2. It is obtained from the tolerance of the resistor.
IvosMAX: The maximum in-flow current of FB terminal, 1.2mA
-
The minimum output voltage (VoutMIN)
Vout' MIN＝VFB MIN＋Rex1MIN(
VFB MIN
＋IvosMIN ）
Rex2MAX
VFBMIN: The minimum value of the set output voltage. Please fill in the MIN value of the set output
voltage which is shown in the electrical characteristics of the specifications.
Rex1 MIN: The minimum value of Rex1. It will be obtained from the tolerance of the resistor.
Rex2MAX: The maximum value of Rex2. It will be obtained from the tolerance of the resistor.
IvosMIN: The minimum in-flow current of FB terminal, 0.8mA.
In the case of VO = 12V, Rex2 = 1250Ω, Rex1 = 1400Ω based on equation above.
24
SI-8000Y
● 5-4 Operation Waveform Check
It can be checked by the waveform between the pin 2 and 4 (waveform between SW and GND) of the
SI-8000Y whether the switching operation is normal or not.
The examples of waveforms at normal and abnormal operations are shown below:
1. Normal Operation (continuous area)
2. Normal Operation (discontinuous area)
3. When C1 is distant from IC
4. When C3 is distant from IC
The continuous area is an area where the DC component of the triangular wave is superimposed on the
current flowing across the choke coil and the discontinuous area is an area where the current flowing across
the choke coil is intermittent (a period of zero current may happen.) because the current flowing across the
choke coil is low.
Therefore, when the load current is high, the area is a continuous area and when the same current is low,
the area is a discontinuous area.
In the continuous area, the switching waveform is formed in the normal rectangular waveform (waveform
1) and in the discontinuous area, damped oscillation is caused in the switching waveform (waveform 2), but
this is a normal operation without any problem.
In the meantime, when the IC is far from C1, C2 and C3, jitter which disturbs the ON – OFF time of
switching will happen, as shown in the waveforms (3, 4). As described above, C1, C2 and C3 should be
connected close to the IC.
25
SI-8000Y
● 5-5 Thermal Design
5-5-1 Calculation of Heat Dissipation
The relation among the power dissipation Pd of regulator, junction temperature Tj, case temperature Tc,
heat sink temperature Tfin and ambient temperature Ta is as follows:
Pd (Power dissipation)
Pd(損失)
Tj:ｼﾞｬﾝｸｼｮﾝ
Junction temperature
(125°C MAX)
Tj
温度
(125℃ MAX)
Chip
チップ
θ jc(接合
－ｹｰｽ
間熱抵抗)
θjc:
Thermal
resistance
between junction and case 5°C / W
5℃ /W
Case
ケース
Tc: ｹｰｽ
Case温度(内部
temperatureﾌﾚｰﾑ
(internal
Tc
温 frame temperature)
度)
放熱器
Heat
sink
θi:
Thermal放熱器間熱抵抗)
resistance between case and heat sink) 0.4 – 0.6°C / W
θ i(ｹｰｽ－
0.4～ 0.6℃ /W
T
fin:放熱器温度
Heat sink temperature
Tfin
θfin:
Heat sink thermal resistance
θ fin(放熱器熱抵抗)
Ta:
temperature
Ta Ambient
周囲温度
Tj Tc
jc
Tj Tfin
Pd
jc i
Tj Ta
Pd
jc i fin
Pd
The TjMAX is an inherent value for each product, therefore it must be strictly observed. For this purpose, it
is required to design the heat sink in compliance with PdMAX, TaMAX (determination of θfin). The heat
derating graphically describes this relation.
The designing of the heat sink is carried out by the following procedure:
1) The maximum ambient temperature Ta MAX in the set is obtained.
2) The maximum power dissipation PdMAX is obtained.
100
VOUT
Pd VOUT Io
1 Vf Io1
VIN
x
* ηx= efficiency (%), Vf= diode forward voltage
3) The size of heat sink is determined from the intersection of the heat derating.
The required thermal resistance of the heat sink can be also calculated. The thermal resistance required for
the heat sink is obtained by the following equation:
i fin
Tj Ta
jc
Pd
26
SI-8000Y
An example of heat calculation for using SI-8010Y under the conditions of VIN = 20V, Io = 6A and Ta =
60°C is shown below.
Where efficiency η = 87.5%, Vf = 0.55V from the typical characteristics, when calculated as Tjmax =
125°C,
5
100
Pd 5 6
1 0.55 6 1 ≒1.81W
87.5
20
125 60
fin
6 ≒ 30ﾟC / W
1.81
As a result, the heat sink with the thermal resistance of 30°C /W or less is required. As described above, the
heat sink is determined, but the derating of 10 - 20% or more is used. Actually, heat dissipation effect
significantly changes depending on the difference in component mounting. Therefore, heat sink
temperature or case temperature should be checked with the heat sink mounted.
SI-8000Y Derating curve
SI-8000Y 減定格曲線
ｼﾘｺｰﾝｸﾞﾘｰｽはG746を使用（信越化学)
Silicon
Grease: G746
Silicone Grease G746(Shin-Etsu
無限大放熱板
Infinity heat sink
22
(Shin-Etsu
Chemical)
Kagaku)
放熱板：ｱﾙﾐﾆｳﾑ
20
Heat
Al
Heatsink:
sink：Al
許容損失 Pd （W）
Power Dissipation Pd (W)
Power Dissipation
18
16
200㎜×200㎜×2㎜(2.3℃/W)
14
12
100㎜×200㎜×2㎜(5.2℃/W)
10
8
75㎜×75㎜×2㎜(7.6℃/W)
6
4
No-FIN
2
0
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Ambient
Temperature Ta (°C)
周囲温度 Ta ℃
27
SI-8000Y
SI-8010Y Output Current Io – Product Power Dissipation Pd calculated with efficiency data
製品 Pd W
Product Power Dissipation Pd (W)
SI-8010Y
Vo=3.3v
SI-8010Y
Io-製品Pd
Io - Pd (Vo = 3.3V)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Vin=8v
Vin=10v
Vin=15v
Vin=24v
Vin=30v
Vin=35v
Vin=43v
0
2
4
6
8
製品 Pd W
Product Power Dissipation Pd (W)
Iout A
SI-8010Y
Vo=5v
SI-8010Y
Io-製品Pd
Io - Pd (Vo = 5V)
6
5
Vin=8v
4
Vin=10v
Vin=15v
3
Vin=20v
2
Vin=24v
1
Vin=30v
0
Vin=35v
0
2
4
6
8
Vin=43v
Iout A
製品Pd W
Product Power Dissipation Pd (W)
SI-8010Y
SI-8010Y
Vo=12v
Io-製品
Io - Pd (Vo =Pd
12V)
8
7
6
5
4
3
2
1
0
Vin=15v
Vin=20v
Vin=30v
Vin=35v
Vin=43v
0
2
4
6
8
Iout A
28
SI-8000Y
5-5-2 Installation to Heat sink
Selection of silicon grease
When the SI-8000Y is installed to the heat sink, silicon grease should be thinly and evenly coated between
the IC and heat sink. Without coating, thermal resistance is significantly increased because of contact
failure due to micro concavity/convexity between the backside of the IC and the surface of the heat sink to
accelerate the heating of the IC, resulting in shorter life of the IC.
In some kind of silicon grease to be used, oil component may be separated to penetrate into the IC,
resulting in the deformation of packages or the adverse effect on built-in elements.
Any other silicon grease than one based on the modified silicon oil shall not be used.
The recommended silicon greases are as follows:
Sanken’s recommended silicon greases:
Types
Suppliers
G746
Shin-Etsu Chemical Co., Ltd.
SC102
Toray Silicone Co., Ltd.
YG6260
Momentive Performance Materials Inc.
Tightening torque of fixing screws
In order to keep the thermal resistance between the IC and the heat sink at low level without damaging the
IC package, it is necessary to control the torque of fixing screws in a proper way.
Even if silicon grease is coated, the thermal resistance θi increases if the tightening torque is not enough.
Change rate of
thermal resistance (%)
熱抵抗変化率（%）
For the SI-8000Y, 58.8 - 68.6Ncm (6.0 - 7.0 kg cm) are recommended.
110
105
100
95
90
0
20
40
60
締め付けトルク（N・cm）
Tightening
Torque (N cm)
80
100
* 1. The change rate of thermal resistance in the case that 58.8N cm (6kg cm) is expressed as
100% is shown above.
* 2. The silicon grease G746 shall be used.
29
SI-8000Y
6. Applications
● 6-1 Soft Start
When a capacitor is connected to terminal 7 (EN/SS), the soft start is activated when the input voltage is
applied or EN/SS terminal is opened. Unless soft start is applied, excessive in-rush current will flow at
startup, therefore it is recommended to set soft start without fail.
VOUT rises in relation with the charging voltage of Css when soft start is activated. Therefore, the rough
estimation of enable time is done by the time constant calculation of Css charging.
The capacitor Css controls the rise time by controlling the OFF period of PWM control. The rise time tss is
calculated approximately by the following equation:
tss = (Css × Vss) / IssL (sec)
Or EN/SS terminal is opened.
4.4v
T2
3v
1.5v
EN/SS terminal
EN /SS端子
T1
VOUT
V out
Since the EN/SS terminal is pulled up (4.4V TYP) with the internal power supply of IC, the external
voltage can not be applied.
In the SI-8000Y, VOUT starts rising, when the voltage of EN/SS terminal is about 1.5V and when it goes up
to about 3V, it does not rise any more.
It takes longer to discharge CSS after turning VIN off if capacitance of CSS is increased. The discharge of CSS
is made, when Q1 is ON or VIN falls to 0V. It is recommended to use CSS at the value of about 10μF or less.
ISSL:
Charging current of CSS {10μA or so (real value)}
VSSA:
Voltage at which CSS rises and VOUT is stabilized (about 3V)
VSSB:
Voltage at which CSS rises and VOUT starts rising (about 1. 5V)
CSS:
Capacitance of capacitor connected to SS terminal
T1 = (CSS x VSSB)/ISSL (sec)
The time from release of terminal to start of rising
T2 = (CSS x VSSA)/IAAL (sec)
The time from release of terminal to startup of VOUT
30
SI-8000Y
SI-8000Y C
Enable time
SS –
SI-8000Y
Css
vs起動時間
(Vo
=
5V,
Co
=
1000μF)
Vo=5v設定 Co：1000uF
10000
起動時間
ms
time [ms]
Enable
1000
ｔ2
100
ｔ1
10
1
0.001
0.01
0.1
Css uF
1
10
In the case that a transistor Q1 for ON/OFF control is not connected, CSS is discharged from the IN
terminal, when Vin falls. Therefore, in the case of restart (rise of Vin) after fall of Vin and drop of Vo, but
prior to the complete drop of Vin, the discharge of Css is not made and the soft start may not be applied.
This situation can be resolved by connecting a discharge circuit as shown in the below figure.
Circuit of Discharging CSS
● 6-2 Output ON/ OFF Control
The output ON / OFF control is possible using the EN/SS (No.7) terminal. The output is turned OFF when
the terminal 5 voltage falls below VSSL (0.5V) by opening collector or so.
Since the EN/SS terminal is pulled up (4.4V TYP) with the internal power supply of IC, the external
voltage cannot be applied.
31
SI-8000Y
● 6-3 Spike Noise Reduction
In order to reduce the spike noise, it is possible to compensate the output waveform of the SI-8000Y and
the recovery time of the diode by a capacitor, but it should be noted that the efficiency is also slightly
reduced.
Around 10Ω
Around 1000pF
3.
Around 10Ω
4.
Around 1000pF
Without Noise Reducing Circuit
With Noise Reducing Circuit
*When the spike noise is observed with an oscilloscope, the lead wire may function as an antenna and the
spike noise may be observed extremely higher than usual because the probe GND lead wire is long. In
order to monitor spike noise, it is necessary to disconnect the lead wire of probe and connect wire to the
base of the output capacitor by soldering for measurement.
● 6-4 Reverse Bias Protection
A diode for reverse bias protection will be required between input and output when the output voltage is
higher than the input terminal voltage, such as in battery chargers.
SI-8000S,SS
SI-8000Y
32
SI-8000Y
7. Typical Characteristics
Eff η (%)
SI-8010Y 効率 Eff Vo=3.3V Ta=RT
100
95
90
85
Vin=8v,12v,20v,30v,40v
80
75
70
65
60
0
1
2
3
4
Iout(A)
5
6
7
8
6
7
8
Eff η (%)
SI-8010Y ES3 S5 Eff Vo=5V Ta=RT
100
95
90
85
Vin=8v,12v,20v,30v,40v
80
75
70
65
60
0
1
2
3
4
Iout(A)
5
SI-8010Y ES3 S5 Eff Vo=12V Ta=RT
SI-8001FFE
100
Eff η (%)
95
90
Vin=15v,20v,30v,40v
85
80
75
70
0
1
2
3
4
Iout(A)
5
6
7
8
33
SI-8000Y
Ta = 25°C, R2 = 2kΩ at Vo = 5V if no specific comment
34
SI-8000Y
8. Terminology
-
Jitter
It is a kind of abnormal switching operations and is a phenomenon that the switching pulse width varies in
spite of the constant condition of input and output. The output ripple voltage peak width is increased when
a jitter occurs.
-
Recommended Conditions
It shows the operation conditions required for maintaining normal circuit functions. It is required to meet
the conditions in actual operations.
-
Absolute Maximum Ratings
It shows the destruction limits. It is required to take care so that even one item does not exceed the
specified value for a moment during instantaneous or normal operation.
-
Electrical Characteristics
It is the specified characteristic value in the operation under the conditions shown in each item. If the
operating conditions are different, it may be out of the specifications.
-
PWM (Pulse Width Modulation)
It is a kind of pulse modulation systems. The modulation is achieved by changing the pulse width in
accordance with the variation of modulation signal waveform (the output voltage for chopper type
switching regulator).
-
ESR (Equivalent Series Resistance)
It is the equivalent series resistance of a capacitor. It acts in a similar manner to the resistor
series-connected to the capacitor.
35
SI-8000Y
Notice
・The contents of this description are subject to change without prior notice for improvement etc. Please
make sure that any information to be used is the latest one.
・Any example of operation or circuitry described in this application note is only for reference, and we are
not liable to any infringement of industrial property rights, intellectual property rights or any other rights
owned by third parties resulting from such examples.
・In the event that you use any product described here in combination with other products, please review the
feasibility of combination at your responsibility.
・Although we endeavor to improve the quality and reliability of our product, in the case of semi-conductor
components, defects or failures which occur at a certain rate of probability are inevitable.
The user should take into adequate consideration the safety design in the equipment or the system in order to
prevent accidents causing death or injury, fires, social harms etc..
・Products described here are designed to be used in the general-purpose electronic equipment (home
appliances, office equipment, communication terminals, measuring equipment etc.).
If used in the equipment or system requiring super-high reliability (transport machinery and its control
equipment, traffic signal control equipment, disaster/crime prevention system, various safety apparatus etc.),
please consult with our sales office. Please do not use our product for the equipment requiring ultrahigh
reliability (aerospace equipment, atomic control, medical equipment for life support etc.) without our written
consent.
・The products described here are not of radiation proof type.
・The contents of this brochure shall not be transcribed nor copied without our written consent.
36