STR5A450_技术文档

For Non-Isolated

Off-Line PWM Controllers with Integrated Power MOSFET

STR5A450 Series

Data Sheet

Description

Package

The STR5A450 Series is power ICs for switching

power supplies, incorporating a MOSFET and a current

mode PWM controller IC for non-isolated Buck

converter and Inverting converter topologies.

The operation mode is automatically changed, in

response to load, to the fixed switching frequency, to the

switching frequency control, and to the burst oscillation

mode. Thus the power efficiency is improved.

DIP8

S/OCP

FB

1

2

3

4

8

7

6

D/ST

GND

VCC

5

The product achieves high cost-performance power

supply systems with few external components.

Not to scale

Features

Selection Guide

● Buck converter

● Inverting converter

● Electrical Characteristics

f_OSC(AVG)= 60 kHz (typ.)

V_D/ST= 650V (max.)

● Current mode type PWM control

● Automatically changed operation mode in response to

load conditions

I_OUT(MAX)

(Universal, open

frame, V_OUT= 24 V)

*

Fixed switching frequency mode, 60 kHz (typ.)

Green mode, 23 kHz (typ.) to 60 kHz (typ.)

Burst oscillation mode

● Built-in Startup Function

reducing power consumption, and shortening the

startup time

● Built-in Error Amplifier

● Random Switching Function

● Leading Edge Blanking Function

● Soft Start Function

● Protections

R_DS(ON)

Products

(max.)

STR5A451D

STR5A453D

4.0 Ω

1.9 Ω

0.7 A

0.9 A

* The output power is actual continues current that is

measured at 50 °C ambient. The peak output current

can be 120 to 140 % of the value stated here. Thermal

design affects the output current. It may be less than

the value stated here.

Overcurrent Protection (OCP): adjustabe by an

external current detection resistor, including OCP

input compensation function

Overload Protection (OLP): Auto-restart

Overvoltage Protection (OVP): Auto-restart

Thermal Shutdown with hysteresis (TSD): Auto-restart

Recommended Operating Condition

Buck

Converter

Inverting

Converter

Input Voltage

AC 85 V to AC 265 V

D/ST Input

Voltage

Output Voltage

Range*

≥ 40 V

Typical Application (Buck Convertor)

> 11 V

< 27.5 V

> – 27.5 V

< – 11 V

STR5A450D

D1

D/ST

VCC

*Add a zener diode or a regulator to VCC pin when

target output voltage is high.

4

3

2

1

5

6

7

8

C4

C3

R1

GND

C2

R2 R3

FB

Applications

D2 V_OUT

S/OCP

(+)

L1

R_OCP

● White goods

U1

VAC

● Auxiliary power supply (lighting equipment with

microcomputer, etc.)

● Power supply for motor control (actuator, etc.)

● Telecommunication equipment (convertible from

48VDC to 15VDC)

D3

C1

C5

R4

(-)

TC_STR5A450_1_R1

● Other Switchung mode power supply, SMPS

STR5A450-DSE Rev.1.1

Oct. 19, 2016

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STR5A450 Series

Contents

Description ------------------------------------------------------------------------------------------------------1

1. Absolute Maximum Ratings-----------------------------------------------------------------------------3

2. Electrical Characteristics--------------------------------------------------------------------------------3

3. Performance Curves--------------------------------------------------------------------------------------5

3.1 Derating Curves -------------------------------------------------------------------------------------5

3.2 MOSFET Safe Operating Area Curves---------------------------------------------------------5

3.3 Ambient Temperature versus Power Dissipation Curves -----------------------------------6

3.4 Transient Thermal Resistance Curves ----------------------------------------------------------6

4. Block Diagram ---------------------------------------------------------------------------------------------7

5. Pin Configuration Definitions---------------------------------------------------------------------------7

6. Typical Applications--------------------------------------------------------------------------------------8

7. Physical Dimensions --------------------------------------------------------------------------------------9

8. Marking Diagram -----------------------------------------------------------------------------------------9

9. Operational Description ------------------------------------------------------------------------------- 10

9.1 Startup Operation of IC ------------------------------------------------------------------------- 10

9.2 Undervoltage Lockout (UVLO) ---------------------------------------------------------------- 10

9.3 Power Supply Startup and Soft Start Function --------------------------------------------- 10

9.4 Constant Voltage (CV) Control----------------------------------------------------------------- 11

9.4.1

9.4.2

Buck Converter Operation ---------------------------------------------------------------- 12

Inverting Converter Operation----------------------------------------------------------- 12

9.5 Leading Edge Blanking Function -------------------------------------------------------------- 13

9.6 Random Switching Function-------------------------------------------------------------------- 13

9.7 Operation Mode ----------------------------------------------------------------------------------- 13

9.8 Overcurrent Protection (OCP) ----------------------------------------------------------------- 14

9.8.1

9.8.2

OCP Operation ------------------------------------------------------------------------------ 14

OCP Input Compensation Function ----------------------------------------------------- 14

9.9 Overload Protection (OLP)---------------------------------------------------------------------- 14

9.10 Overvoltage Protection (OVP)------------------------------------------------------------------ 15

9.11 Thermal Shutdown (TSD) ----------------------------------------------------------------------- 15

10. Design Notes---------------------------------------------------------------------------------------------- 15

10.1 External Components ---------------------------------------------------------------------------- 15

10.1.1 Input and Output Electrolytic Capacitor----------------------------------------------- 16

10.1.2 Inductor --------------------------------------------------------------------------------------- 16

10.1.3 VCC Pin Peripheral Circuit--------------------------------------------------------------- 16

10.1.4 FB Pin Peripheral Circuit ----------------------------------------------------------------- 16

10.1.5 Freewheeling Diode ------------------------------------------------------------------------- 16

10.1.6 Bleeder Resistance -------------------------------------------------------------------------- 16

10.2 D/ST Pin--------------------------------------------------------------------------------------------- 16

10.3 Inductance Calculation--------------------------------------------------------------------------- 17

10.3.1 Parameter Definition ----------------------------------------------------------------------- 17

10.3.2 Buck Convertor------------------------------------------------------------------------------ 18

10.3.3 Inverting Convertor ------------------------------------------------------------------------ 23

10.4 PCB Trace Layout -------------------------------------------------------------------------------- 28

11. Reference Design of Power Supply ------------------------------------------------------------------ 30

11.1 Buck Converter------------------------------------------------------------------------------------ 30

11.2 Inverting Converter------------------------------------------------------------------------------- 31

Important Notes---------------------------------------------------------------------------------------------- 32

STR5A450-DSE Rev.1.1

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STR5A450 Series

1. Absolute Maximum Ratings

● The polarity value for current specifies a sink as "+," and a source as "−," referencing the IC.

● Unless otherwise specified, T_A= 25 °C, all D/ST pins (5 pin to 8pin) are shorted.

Parameter

Symbol

I_DPEAK

Test Conditions

Single pulse

Pins

Rating

3.6

Units

A

Notes

5A451D

5A453D

5A451D

5A453D

Drain Peak Current

8 – 1

5.2

I

_LPEAK= 2.13 A

53

1

)

Avalanche Energy⁽

E_AS

8 – 1

mJ

I_LPEAK= 2.46 A

72

S/OCP Pin Voltage

FB Pin Voltage

V_S/OCP

V_FB

1 – 3

2 – 3

4 – 3

4 – 5

− 2 to 5

− 0.3 to 7

− 0.3 to 32

− 0.3 to V_DSS

1.68

V

VCC Pin Voltage

D/ST Pin Voltage

V_CC

V_D/ST

5A451D

5A453D

2

(

)

MOSFET Power Dissipation

P_D1

8 – 1

W

1.76

Control Part Power Dissipation

Operating Ambient Temperature

Storage Temperature

P_D2

T_OP

T_stg

T_j

4 – 3

1.3

W

°C

–

− 40 to 125

150

Junction Temperature

⁽¹⁾Single pulse, V_DD= 99 V, L = 20 mH

⁽²⁾When embedding this hybrid IC onto the printed circuit board (cupper area in a 15mm×15mm)

2. Electrical Characteristics

● The polarity value for current specifies a sink as "+," and a source as "−," referencing the IC.

● Unless otherwise specified, T_A= 25 °C, all D/ST pins (5 pin to 8pin) are shorted.

Test

Conditions

Parameter

Symbol

Pins

Min.

Typ. Max. Units

Notes

Power Supply Startup Operation

Operation Start Voltage

V_CC(ON)

V_CC(OFF)

I_CC(ON)

4 – 3

13.6

7.3

–

15.0

8.0

–

16.6

8.7

V

Operation Stop Voltage

V_CC= 12 V

Circuit Current in Operation

3.0

mA

Startup Circuit Operation

Voltage

V_CC= 13.5 V

V_ST(ON)

I_CC(ST)

8 – 3

4 – 3

21

29

37

V

Startup Current

– 3.0 − 1.7 – 0.9

mA

PWM Operation

Average PWM Switching

Frequency

V_FB

f_OSC(AVG)

8 – 3

53

60

67

kHz

= V_FB(REF)–20mV

Switching Frequency Modulation

Deviation

Δf

8 – 3

2 – 3

–

7.1

–

kHz

V

Feedback Reference Voltage

V_FB(REF)

2.44

2.50

2.56

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STR5A450 Series

Test

Conditions

Parameter

Symbol

I_FB(OP)

Pins

2 – 3

1 – 3

8 – 3

Min.

Typ. Max. Units

Notes

Feedback Current⁽¹⁾

− 2.4 − 0.8

−

–

μA

V

V_FB= 2.3 V

S/OCP Pin Standby Threshold

voltage

V_OCP(STB)

D_MAX

–

0.11

62

Maximum ON Duty

56

69

%

Protection

Leading Edge Blanking Time⁽¹⁾

OCP Compensation Coefficient⁽¹⁾

OCP Compensation Limit Duty⁽¹⁾

t_BW

–

−

–

−

280

15.8

36

–

−

ns

mV/µs

%

DPC

D_DPC

OCP Threshold Voltage at Zero

ON-Duty

V_OCP(L)

V_OCP(H)

1 − 3

0.640 0.735 0.830

V

OCP Threshold Voltage

0.74

0.83

1.61

0.92

OCP Threshold Voltage During

V_OCP(LEB)

−

LEB (t_BW

)

OVP Threshold Voltage

V_CC(OVP)

t_OLP

I_OLP

4 – 3

8 – 3

27.5

53

29.3

70

31.3

88

V

V_FB= 0.41 V

V_CC= 9 V

OLP Delay Time at Startup

ms

Circuit Current in Overload

Protection

Delay Time of FB Pin Short

Protection at Startup

Standby Blanking Time at

Startup

4 – 3

8 – 3

–

300

17.5

3.0

–

V_FB= 0.2 V

V_FB= 2.6 V

t_FBSH

13.0

2.0

22.0

4.0

t_STB(INH)

ms

Thermal Shutdown Operating

T_j(TSD)

–

135

–

°C

Temperature⁽¹⁾

Thermal Shutdown Hysteresis⁽¹⁾

T_j(TSDHYS)

80

Power MOSFET

Drain-to-Source Breakdown

Voltage

I_DS= 50 µA

V_DS= V_DSS

V_DSS

I_DSS

8 – 1

650

−

V

Drain Leakage Current

−

–

−

–

50

4.0

1.9

250

μA

5A451D

5A453D

I_DS= 0.4 A

On Resistance

R_DS(ON)

t_f

8 – 1

Ω

Switching Time

ns

Thermal Characteristics

Thermal Resistance Junction to

Case ⁽²⁾

5A451D

5A453D

θ_j-C

–

18

°C/W

⁽¹⁾Design assurance

⁽²⁾Case temperature (T_C) measured at the center of the case top surface

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STR5A450 Series

3. Performance Curves

3.1 Derating Curves

100

80

60

40

20

0

80

60

40

20

0

25

50

75

100

125

150

0

25

50

75

100 125 150

Ambient Temperature, T_A(°C)

Junction Temperature, T_j(°C)

Figure 3-1. SOA Temperature Derating Coefficient

Curve

Figure 3-2. Avalanche Energy Derating Coefficient

Curve

3.2 MOSFET Safe Operating Area Curves

When the IC is used, the safe operating area curve should be multiplied by the temperature derating coefficient

derived from Figure 3-1. The broken line in the safe operating area curve is the drain current curve limited by

on-resistance.

Unless otherwise specified, T_A= 25 °C, Single pulse.

● STR5A451D

● STR5A453D

10

0.1ms

1

1ms

0.1

0.01

1

0.01

1

10

100

1000

10

100

1000

Drain-to-Source Voltage (V)

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STR5A450 Series

3.3 Ambient Temperature versus Power Dissipation Curves

● STR5A451D

● STR5A453D

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

P_D1= 1.68 W

P_D1= 1.76 W

0.0

0

25

50

75

100 125 150

25

50

75

100 125 150

Ambient Temperature, T_A(°C )

3.4 Transient Thermal Resistance Curves

● STR5A451D

10

1

0.1

0.01

1µ

10µ

100µ

1m

10m

100m

Time (s)

● STR5A453D

10

1

0.1

0.01

1µ

10µ

100µ

1m

10m

100m

Time (s)

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STR5A450 Series

4. Block Diagram

VCC

4

D/ST

5, 6, 7, 8

STARTUP

UVLO

OVP

TSD

REG

PROTECTION

DRV

PWM

OSC

S Q

R

OCP

Drain Peak Current

Compensation

FB

E/A

S/OCP

GND

Feedback

Control

2

1

LEB

V_FB(REF)

3

BD_STR5A450_R1

5. Pin Configuration Definitions

Name

Descriptions

Power MOSFET source and Overcurrent

Protection (OCP) signal input

Constant voltage control signal input and

overload protection signal input

S/OCP

D/ST

1

S/OCP

1

2

3

4

8

7

6

2

3

FB

D/ST

FB

GND

VCC

GND

Ground

Power supply voltage input for control part

and Overvoltage Protection (OVP) signal

input

4

VCC

D/ST

5

6

7

8

MOSFET drain and startup current input

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STR5A450 Series

6. Typical Applications

Figure 6-1 and Figure 6-2 are the example circuits.

To enhance the heat dissipation, the wide pattern layout of the D/ST pin (5 through 8 pin) is recommended.

When the absolute value of the output voltage | V_OUT| is 27.5 V or higher, add a zener diode DZ1 connected to D1 in

serial as shown in Figure 6-3. Using the maximum on-duty of 50 % in the steady state operation, the condition of |V_OUT

is shown below:

|

| V_OUT| : 11V < V_OUT− V_DZ1< 27.5V

1

|

| V_OUT| in response to the input voltage: For Buck toplogy, V_OUT≤ � × Input voltage

2

|

For Inverting topology, V_OUT≤ Input voltage

STR5A450D

D1

R1

D/ST

VCC

4

3

2

1

5

6

7

8

C4

C3

GND

C2

R3

R2

FB

D2

V_OUT

S/OCP

(+)

L1

R_OCP

U1

VAC

C1

D3

C5

R4

(-)

TC_STR5A450_2_R1

Figure 6-1. Buck Converter

STR5A450D

D1

D/ST

VCC

4

3

2

1

5

6

7

8

C4

C3

R1

GND

C2

R3

R2

D3

FB

V_OUT

S/OCP

(-)

R_OCP

U1

VAC

C1

L1

C5

D2

R4

(+)

TC_STR5A450_3_R1

Figure 6-2. Inverting Converter

STR5A450D

D1 DZ1

D2

VCC

(+)

4

3

C4

C3

GND

U1

TC_STR5A450_4_R1

Figure 6-3. Increasing the Absolute value of |V_OUT

|

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STR5A450 Series

7. Physical Dimensions

● DIP8

NOTES:

1) Units: mm

2) Pb-free. Device composition compliant with the RoHS directive

8. Marking Diagram

DIP8

8

5 A 4 5 × D

Part Number

S K Y M D

Lot Number

Y = Last Digit of Year (0-9)

M = Month (1-9,O,N or D)

D = Period of days (1 to 3)

1 : 1^stto 10^th

1

2 : 11^thto 20^th

3 : 21^stto 31^st

Sanken Control Number

STR5A450-DSE Rev.1.1

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STR5A450 Series

(Refer to Figure 9-1).

9. Operational Description

The voltage between VCC pin and GND pin in the

steady state operation is calculated as follows, where

V_FD1, V_FD2and V_FD3are the forward voltage of D1, D2

and D3 respectively:

All of the parameter values used in these descriptions

are typical values, unless they are specified as minimum

or maximum. With regard to current direction, "+"

indicates sink current (toward the IC) and "–" indicates

source current (from the IC).

(

)

(2)

V_CC= V_OUT+ V_FD3− V_FD1+ V_FD2(V)

The common items of Buck converter and Inverting

are desribed by using Buck conveter.

9.2 Undervoltage Lockout (UVLO)

9.1 Startup Operation of IC

Figure 9-2 shows the relationship of VCC pin voltage

and the circuit current, I_CC. When VCC pin voltage

increases to V_CC(ON)= 15.0 V, the control circuit starts

switching operation and the circuit current, I_CC, increases.

When VCC pin voltage decreases to V_CC(OFF)= 8.0 V,

the control circuit stops its operation by the

Undervoltage Lockout (UVLO) circuit, and reverts to

the state before startup.

Figure 9-1 shows the circuit around VCC pin.

Startup operation

U1

I_STRTUP

4

D1

D2

Normal operation

STARTUP

VCC

C4 C3

GND

3

V_OUT

(＋)

R_OCP

5~8

S/OCP

D/ST

L1

1

Circuit current, I_CC

C1

D3

R4

C5

(－)

Figure 9-1. VCC Pin Peripheral Circuit in Buck

Converter

VCC pin

voltage

V_CC

（

ON

（

OFF

）

The IC incorporates the startup circuit. The circuit is

connected to D/ST pin. When D/ST pin voltage reaches

the Startup Circuit Operation Voltage V_ST(ON)= 29 V,

the startup circuit starts operation.

Figure 9-2. Relationship between

VCC Pin Voltage and I_CC

During the startup process, the constant current,

I_CC(ST)= − 1.7 mA, charges C4 at VCC pin. When VCC

pin voltage increases to V_CC(ON)= 15.0 V, the control

circuit starts switching operation.

9.3 Power Supply Startup and Soft Start

Function

After switching operation begins, the startup circuit

turns off automatically so that its current consumption

becomes zero.

The Soft Start Function reduces the voltage and the

current stress of the internal power MOSFET and the

freewheeling diode, D3.

The approximate startup time t_STARTis calculated as

follows:

Figure 9-3 shows the startup waveforms. After the IC

starts, during the Standby Blanking Time at Startup,

t_STB(INH), the burst oscillation mode is disabled to operate

the soft start.

The IC activates the soft start circuitry during the

startup period. The soft start time is fixed to about 10.2

ms. During the soft start period, the overcurrent

threshold is increased step-wisely (7 steps). The IC

operates switching operation by the frequency

responding to FB pin voltage until the output reaches the

setting voltage.

V_CC(ON)− V_CC(INT)

t_START= C4 ×

(s)

(1)

ꢀI_CC(ST)

ꢀ

where,

t_STARTis the startup time of IC (s),

V_CC(INT)is the initial voltage on VCC pin (V).

When the internal power MOSFET turns off, the

output voltage, V_OUT, charges C4 through D1 and D2

Here, the t_LIMis defined as the period until FB pin

voltage reaches 1.6 V after the IC starts. When the t_LIM

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STR5A450 Series

reaches the OLP Delay Time at Startup, t_OLP, of 70 ms

and more, the IC stops switching operation. Thus, it is

necessary to adjust the value of output electrolytic

which enhances the response speed and the stable

operation.

The IC controls the peak value of the voltage of a

current detection resistor (V_ROCP) to be close to target

voltage (V_SC), comparing V_ROCPwith V_SCby internal FB

comparator. Feedback Control circuit receives the target

voltage, V_SC, reversed FB pin voltage by an error

amplifier (Refer to Figure 9-5 and Figure 9-6).

capacitor, C5 so that the t_LIMis less than t_OLP

.

If VCC pin voltage reaches V_CC(OFF)and a startup

failure occurs as shown in Figure 9-4, increase C4 value

or decrease C5 value. Since the larger capacitance

causes the longer startup time of IC, it is necessary to

check and adjust the startup process based on actual

operation in the application.

Since the Leading Edge Blanking Function (Refer to

Section 9.5) is disabled during the soft start period, the

on-time may be less than the Leading Edge Blanking

Time (t_BW= 280 ns).

U1

Feedback

Control

E/A

R2 R3

R1

FB

V_SC

FB comp

+

-

2

-

+

GND

3

1

PWM

Control

C3

L1

V_OUT

R_OCP

5~8

Startup of IC

VCC pin

D/ST

S/OCP

I_LON

(＋)

voltage

Normal opertion

Startup of SMPS

V_ROCP

t_START

D3

R4

(－)

C1

C5

V_CC(ON)

V_CC(OFF)

t_STB(INH)

Time

Figure 9-5. FB Pin Peripheral Circuit in Buck

Converter

Soft start period,

fixed to approximately 10.2 ms

D/ST pin

current, I_D

-

V_SC

+

V_ROCP

Time

t_LIM< t_OLP

FB pin voltage

V_FB(REF)

Voltage on both side of R_OCP

FB comparator

1.6V

Time

Drain current,

I_ON

Figure 9-3. Startup Waveforms

Figure 9-6. Drain Current I_Dand FB Comparator

in Steady State Operation

Startup success

IC starts operation

VCC pin

voltage

Target operating

voltage

V_CC(ON)

V_CC(OFF)

● Decreasing load

Increase with rising of

output voltage

When the output load decreases, the FB pin voltage

increases in response to the increase of the output

voltage. Since V_SCwhich is the output voltage of

internal error amplifier becomes low, the peak value

of V_ROCPis controlled to become low, and the peak of

the drain current decreases. This control prevents the

output voltage from increasing.

Startup failure

Time

Startup time of IC, t_START

Figure 9-4. VCC Pin Voltage During Startup Period

● Increasing load

When the output load increases, the control circuit

operates the reverse of the former operations. Since

V_SCbecomes high, the peak drain current increases.

This control prevents the output voltage

from decreasing.

9.4 Constant Voltage (CV) Control

The constant voltage (CV) control for power supply

output adopts the peak-current-mode control method

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STR5A450 Series

2) PWM Off-Time Period

9.4.1 Buck Converter Operation

When the internal power MOSFET turns off, the

back electromotive force occurs in the inductor, L1,

the freewheeling diode, D3, is forward biased and

turns on. Thus, the I_LOFFcurrent flows as shown in

Figure 9-7.

Figure 9-7 shows the output current path in the Buck

converter. Figure 9-8 shows the operational waveforms.

D1

D2

4

2

U1

VCC

FB

As shown in Figure 9-8, after the average switching

C4

⁄

period, 1 f_OSC(AVG)), the power MOSFET turns on

again, and the event moves to the previous 1).

GND

C3

3

1

I_L

The output current is equal to the average inductor

current of L1.

R_OCP

V_OUT

(＋)

L1

5~8

V_L

I_LON

(MOSFET ON)

C1

I_LOFF

(MOSFET OFF)

V_IN

D3

R4

9.4.2 Inverting Converter Operation

C5

Figure 9-9 shows the output current path in the

Inverting converter. Figure 9-10 shows the operational

waveforms.

(－)

Figure 9-7. Output Current Path in Buck Converter

D1

D2

U1

4

2

VCC

FB

C4

MOSFET

ON

V_L

OFF

GND

C3

3

1

V_IN-V_RON-V_OUT

R_OCP

D3

V_OUT

(－)

5~8

0

)

t

-(V_OUT+V_FD3

C1

I_LI_LOFF

(MOSFET OFF)

C5

V_L

I_LON

(MOSFET ON)

V_IN

I_L

R4

L1

t

(＋)

I_LON

Figure 9-9. Output Current Path in Inverting Converter

t

I_LOFF

MOSFET

1/f_OSC(AVG)

ON

V_L

OFF

V_IN-V_RON

Figure 9-8. Operational Waveforms in Buck Converter

0

t

-(V_OUT+V_FD3

)

In the Buck converter, the PWM control is described

in the following.

I_L

1) PWM On-Time Period

t

When the internal power MOSFET turns on, the I_LON

current flows as shown in Figure 9-7, and the

inductor, L1, stores some energy.

Since the I_LONflows through the current detection

resistor, R_OCP, the voltage of R_OCPis detected as the

I_LON

t

I_LOFF

current detection voltage, V_ROCP

.

FB pin voltage is the voltage divided C3 voltage by

voltage dividing resistors, and the target voltage, V_SC,

is given by FB pin voltage.

1/f_OSC(AVG)

Figure 9-10. Operational Waveforms in Inverting

Converter

When V_ROCPreaches V_SC, the power MOSFET turns

off.

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In the Inverting converter, the PWM control is

described in the following.

9.6 Random Switching Function

The switching frequency is randomly modulated by

superposing the modulating frequency on f_OSC(AVG). This

function reduces the conduction noise compared with

other products without this function, and simplifies noise

filtering of the input lines of power supply.

1) PWM On-Time Period

When the internal power MOSFET turns on, the I_LON

current flows as shown in Figure 9-9, and the

inductor, L1, stores some energy.

Since the I_LONflows through the current detection

resistor, R_OCP, the voltage of R_OCPis detected as the

current detection voltage, V_ROCP

.

9.7 Operation Mode

FB pin voltage is the voltage divided C3 voltage by

voltage dividing resistors, and the target voltage, V_SC,

is given by FB pin voltage.

When V_ROCPreaches V_SC, the power MOSFET turns

off.

As shown in Figure 9-12, when the output power is

decreasing, together with the decrease of the drain

current I_Dof the internal power MOSFET, the operation

mode is automatically changed to the fixed switching

frequency mode (60 kHz), to the Green mode controlled

the switching frequency (23 kHz to 60 kHz), and to the

burst oscillation mode controlled by an internal

oscillator. In the Green mode, the number of switching

is reduced. In the burst oscillation mode, the switching

operation is stopped during a constant period. Thus, the

switching loss is reduced, and the power efficiency is

improved (Refer to Figure 9-13).

2) PWM Off-Time Period

When the internal power MOSFET turns off, the

back electromotive force occurs in the inductor, L1,

the freewheeling diode, D3, is forward biased and

turns on. Thus, the I_LOFFcurrent flows as shown in

Figure 9-9

As shown in Figure 9-10, after the average

⁄

switching period, 1 f_OSC(AVG), the power MOSFET

When the output load becomes lower, FB pin voltage

increases and S/OCP pin voltage decreases. The S/OCP

pin voltage reaches to the S/OCP pin standby threshold

voltage, V_OCP(STB)= 0.11 V, the burst oscillation mode is

activated.

turns on again, and the event moves to the previous

1).

The output current is equal to the average current of

I_LOFFof L1.

As shown in Figure 9-13, the burst oscillation mode

consists of the switching period and the non-switching

period. The oscillation frequency during the switching

period is the Minimum Frequency of about 23 kHz.

9.5 Leading Edge Blanking Function

The constant voltage control for power supply output

adopts the peak-current-mode control method. The peak

drain current is detected by the current detection resistor,

R_OCP. Just in turning on the internal power MOSFET,

the steep surge current would occur.

If the Overcurrent Protection (OCP) responds to the

voltage caused by that surge current, the power

MOSFET may be turned off.

Switching

frequency

f_OSC

60 kHz

Normal

operation

About 23 kHz

Green mode

Burst oscillation

To prevent that response, the OCP threshold voltage

increases during Leading Edge Blanking (t_BW= 280 ns)

just after the power MOSFET turns on, and this prevents

the OCP detection from responding to the surge voltage

in turning-on (Refer to Section 9.8.1).

Output power, P_O

Figure 9-12. Switching Frequency in Response to P_O

t_BW

Switching period

I_D

R_OCPvoltage

Non-switching period

Time

Switching operation of about 23 kHz

Surge pulse voltage width at turning on

Figure 9-11. Leading Edge Blanking

Figure 9-13. Switching Waveform

at Burst Oscillation Mode

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1.0

9.8 Overcurrent Protection (OCP)

9.8.1 OCP Operation

V_OCP(H)

V_OCP(L)

Overcurrent Protection (OCP) detects each drain peak

current level of a power MOSFET on pulse-by-pulse

basis, and limits the output power when the voltage on

the current detection resistor, R_OCP, reaches to OCP

threshold voltage.

During Leading Edge Blanking Time shown in Figure

0.5

9-11, the OCP

threshold

voltage becomes

0

6

ONTime (µs)

V_OCP(LEB)= 1.61 V which is higher than the normal OCP

threshold voltage. Changing to this threshold voltage

prevents the OCP detection from responding to the surge

voltage in turning-on the power MOSFET. This function

operates as protection at the condition including output

shorted.

Figure 9-14. Relationship between ONTime and OCP

Threshold Voltage after Compensating

When the power MOSFET turns on, the surge voltage

width of the S/OCP pin should be less than t_BW. To

prevent surge voltage, pay extra attention to R_OCPtrace

layout (Refer to Section 10.4).

9.9 Overload Protection (OLP)

When the voltage on the current detection resistor,

R_OCP, reaches the OCP threshold voltage, the internal

power MOSFET turns off. Figure 9-15 shows the

characteristic of output voltage and current.

The output voltage decreases in the overload state,

and FB pin voltage also decreases. When the period

keeping FB pin voltage less than 1.6 V continues for

OLP Delay Time at Startup, t_OLP= 70 ms, the Overload

Protection (OLP) is activated, and the IC stops switching

9.8.2 OCP Input Compensation Function

ICs with PWM control usually have some propagation

delay time. The steeper the slope of the actual drain

current at a high AC input voltage is, the larger the

detection voltage of actual drain peak current is,

compared to V_OCP. Thus, the peak current has some

variation depending on AC input voltage in OCP state.

To reduce the variation of peak current in OCP state, the

Input Compensation Function is built-in.

operation. Thus, VCC pin voltage decreases to V_CC(OFF)

,

and the control circuit stops operation. After that, the

startup circuit is activated, VCC pin voltage increases to

V_CC(ON)by the startup current, and the control circuit

operates again. Thus, the intermittent operation by

UVLO is repeated in the OLP state (Refer to Figure

9-16).

This function compensates the OCP threshold voltage

so that it depends on AC input voltage, as shown in

Figure 9-14.

When AC input voltage is low, the OCP threshold

voltage is controlled to become high. Thus this control

reduces the difference of peak drain current between at

low AC input voltage and at high.

When the on-time is 6 µs or more, the OCP threshold

voltage is V_OCP(H)of 0.83 V. When the on-time is less

than 6 µs, that is V_OCPshown in Equation (3).

This intermittent operation reduces the stress of parts

including the power MOSFET and the freewheeling

diode. In addition, this operation reduces power

consumption because the switching period in this

intermittent operation is much shorter than the

oscillation stop period.

When the abnormal condition is removed, the IC

returns to normal operation automatically.

V_OCP= V_OCP(L)+ DPC × 10³× ONTime

(3)

Output voltage,

V_OUT

Where,

V_OCP(L): OCP Threshold Voltage at Zero ON Duty (V)

DPC: OCP Compensation Coefficient (mV/μs)

ONTime: On-time of power MOSFET (μs)

CV mode

Output current, I_OUT

Figure 9-15. Overload Characteristics

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startup current, and the control circuit operates again.

The intermittent operation by TSD and UVLO is

repeated in the TSD state.

After the fault condition is removed, the IC returns to

normal operation automatically.

Non-switching interval

VCC pin voltage

V_CC(ON)

V_CC(OFF)

Junction temperature,

Return

to normal operation

TSD is active

T_j

T_j(TSD)

Drain current,

I_D

t_OLP

T_j(TSD)−T_j(TSD)HYS

ON

Bias Assist Function

Figure 9-16. OLP Operational Waveform

OFF

VCC pin voltage

V_CC(ON)

V_CC(BIAS)

V_CC(OFF)

9.10 Overvoltage Protection (OVP)

When the voltage between VCC pin and GND pin

increases to V_CC(OVP)= 29.3 V or more, the Overvoltage

Protection (OVP) is activated and the IC stops switching

operation. The intermittent operation by UVLO is

repeated in the OVP state. Refer to Section 9.9 about the

intermittent operation by UVLO.

Drain current,

I_D

Figure 9-17. TSD Operational Waveforms

When the abnormal condition is removed, the IC

returns to normal operation automatically.

The approximate value of output voltage V_OUT(OVP)in

the OVP condition is calculated by using Equation (4).

10. Design Notes

V_OUT(OVP)= V_CC(OVP)+ V_FD1+ V_FD2− V_FD3

(4)

10.1 External Components

where,

V_OUT(OVP)is voltage of between V_OUT(+) and V_OUT(−),

V_FD1is the forward voltage of D1 in Figure 9-1,

V_FD2is the forward voltage of D2, and

Take care to use properly rated, including derating as

necessary, and proper type of components.

V_FD3is the forward voltage of D3.

Figure 10-1 shows the peripheral circuit of IC in Buck

converter.

D1

9.11 Thermal Shutdown (TSD)

D/ST

VCC

GND

4

3

2

1

5

6

7

8

C4

C3

R1

Figure 9-17 shows the Thermal Shutdown (TSD)

operational waveforms.

C2

R2 R3

FB

When the junction temperature of the IC control

circuit increases to T_j(TSD)= 135 °C (min.) or more, the

TSD is activated, and the IC stops switching operation.

The TSD has a temperature hysteresis. While the

junction temperature of the control circuit is more than

T_j(TSD)−T_j(TSD)HYS, the Bias Assist Function is enabled

when VCC pin voltage decreases to about 9.4 V. While

this function is activated, the startup current is supplied

to VCC pin in order to keep V_CC(OFF)or more, and the IC

holds stopping.

While the junction temperature is T_j(TSD)−T_j(TSD)HYSor

less, the Bias Assist Function is disabled, and VCC pin

voltage decreases to V_CC(OFF)or less. Thus, the control

circuit stops operation. After that, the startup circuit is

activated, VCC pin voltage increases to V_CC(ON)by the

D2 V_OUT

S/OCP

(+)

L1

R_OCP

U1

VAC

D3

C1

C5

R4

(-)

Figure 10-1. Peripheral Circuit of IC in

Buck Converter

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depends on the value of output electrical capacitor, C5.

Usually the value of C3 is 0.022 μF to 0.22 μF. When

C3 value is set larger, the line regulation becomes better,

however, the dynamic response of the output voltage

becomes worse. Be careful of that value.

10.1.1 Input and Output Electrolytic

Capacitor

Apply proper derating to ripple current, voltage, and

temperature rise.

The voltage dividing resistor of R1, R2 and R3 is

determined by the reference voltage, V_FB(REF)= 2.50 V,

the output voltage, V_OUT, and so on. The following

Equation (6) shows the relationship of them.

The target value of R1 is about 10 kΩ to 22 kΩ. R2

and R3 should be adjusted in actual operation condition.

The V_Fof D2 and D3 affects the output voltage. Thus,

the diodes of low V_Fshould be selected.

The value of output electrolytic capacitor, C5, should

be fulfilled the following conditions:

- The specification of output ripple

- Enough shorter output voltage rising time in startup

than the OLP Delay Time at Startup, t_OLP= 70 ms.

- Low impedance types, designed for switch mode

power supplies, is recommended.

The ESR of C5 should be set in the range of

Equation (5).

R1 + R2 + R3

|

V_OUT≅ V_FB(REF)

×

+ V_FD2− V_FD3

R1

∆V_OR

(5)

Z_CO

<

I_LRP

|

V_OUT−V_FD2+ V_FD3

⇒ R2 + R3 = ꢁ

− 1ꢂ × R1 (6)

where,

V_FB(REF)

Z_COis the ESR of electrolytic capacitor at the

operation frequency (Since the ESR in general

catalogs is mostly measured at 100 kHz, check the

frequency characteristic.),

ΔV_ORis the output ripple voltage specification, and

I_LRPis the ripple current of inductor (Refer to

Section 10.3).

where,

V_FD2is the forward voltage of D2, and

V_FD3is the forward voltage of D3.

10.1.5 Freewheeling Diode

D3 in Figure 10-1 is the freewheeling diode.

When the internal power MOSFET turns on, the

recovery current flows through D3. The current affects

power loss and noise much. The V_Faffects the output

voltage. Thus, the diode of fast recovery and low V_F

should be selected.

10.1.2 Inductor

Apply proper design margin to core temperature rise

by core loss and copper loss.

The inductor should be designed so that the inductor

current does not saturate. Refer to Section 10.3 about the

inductance. The value should be the minimum

considered a negative tolerance of inductance and a

decline of DC superposition characteristics.

10.1.6 Bleeder Resistance

The on-time must be longer than the Leading Edge

Blanking Time to control the output voltage constantly.

In the universal input voltage design, the on-time is

easy to become short in the condition of maximum AC

input voltage and light load. Be careful not to choose too

small value for the inductance (The recommended value

is 100 μH or more).

For light load application, the bleeder resistor, R4, in

Figure 10-1 should be connected to both ends of

output capacitor, C5, to prevent the increase of output

voltage.

The value of R4 should be satisfied with Equation (7),

and should be adjusted in actual operation condition.

|

V_OUT

(7)

R4 ≤

3mA

10.1.3 VCC Pin Peripheral Circuit

The reference value of C4 in Figure 10-1 is generally

10 to 47 μF. Refer to Section 9.1 about the startup time.

10.2 D/ST Pin

10.1.4 FB Pin Peripheral Circuit

When the voltage or the current of the D/ST pins

shown in

Figure 10-1 exceeds the Absolute Maximum Ratings,

the internal power MOSFET connected to the D/ST pin

would be permanently damaged.

As shown in Figure 10-1, FB pin is input the voltage

divided the voltage between V_OUT(+) and GND pin by

resistors.

C3 is the smoothing capacitor. The value of C3

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10.3 Inductance Calculation

10.3.1 Parameter Definition

Since this calculation is just on paper, it is necessary

to take account of margins and to check operations on

actual operation in the application.

The following parameters refer to the circuit of Figure

6-1 and Figure 6-2.

V_{DCIN_MIN}is minimum DC input voltage at C2,

V_{DCIN_MAX}is maximum DC input voltage at C2,

V_OUTis output voltage,

I_OUTis output current,

V_RONis on voltage of internal power MOSFET,

Drain current × R_DS(ON),

The PWM control has the three operation modes

shown below. Since each operation mode has that

characteristic, it is necessary to take account of choosing

the operation mode.

The table on the right shows the comparison of three

operation modes in the same input and output condition.

V_FD1is D1 forward voltage,

V_FD2is D2 forward voltage,

V_FD3is D3 forward voltage,

V_DZ1is DZ1 zener voltage.

Table 10-1. Operation Mode Comparison

When | V_OUT| is 27.5 V or more, add a zener diode or

a regulator. Take care of that power loss.

R_OCP: Current detection resistor between S/OCP pin

and GND pin

P_OW

L

I_LR

P_RD(ON)

P_SW

CCM

Large

Large Small Small Large

CRM Middle Middle Middle Middle Small

When the following have no values, see the values of

Section 2. Electrical Characteristics.

D_{ON_MAX}is maximum on-duty in steady operation, 0.5,

K_{RP_MIN}is 0.4,

DCM

Small

Small Large Large Small

where,

CCM is continuous current mode,

CRM is critical current mode,

DCM is discontinuous current mode,

P_OWis capable output power,

L is inductance value of L2,

I_LRis ripple inductor current,

V_{ST_MAX}is maximum value of V_ST(ON),

V_DC(MAX)is maximum DC input voltage, recommended

value is 400 V,

V_{CC_MIN}is minimum value of VCC Voltage, 10 V,

V_{CC(OVP)_MIN}is minimum value of V_CC(OVP)

,

I_DLIMis less than the value of I_DPEAK× the derating

supposed as 90 %,

P_RDS(ON)is conduction loss on the power MOSFET,

P_SWis switching loss.

f_TYPis typical value of f_OSC(AVG)

f_MINis minimum switching frequency, 23 kHz,

V_{OCP(L)_MIN}is minimum value of V_OCP(L)

V_{OCP(L)_TYP}is typical value of V_OCP(L)

V_{OCP(H)_MIN}is minimum value of V_OCP(H)

V_{OCP(H)_TYP}is typical value of V_OCP(H)

V_{OCP(H)_MAX}is maximum. value of V_OCP(H)

,

V_OCP(STB)is typical value of V_OCP(STB)

DPC is typical value of DPC.

,

CCM

CRM

DCM

I_LH

I_LR

I_LH

I_LR

I_LL

0 A

t_ON

t_OFF

t_ON

t_OFF

t_ONt_OFF

t_D

I_LR

I_LH

1/f_SW

K_RP

=

Figure 10-2. Operation Mode of PWM Control

where,

f_SWis switching frequency, t_ONis on-time, t_OFFis off-time, t_Dis discontinuous current time,

I_LHis upper inductor current, I_LLis lower inductor current, I_LRis ripple inductor current,

⁄

K

_RPis ripple inductor current ratio, I_LRI_LH

.

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10.3.2 Buck Convertor

(B-1) Input and Output Condition

The definition refers to Section 10.3.1.

Lower value is a higher value or more of either V_{ST_MAX}or 2 × V_OUT+ V_FD3+ V_RON

Upper value is V_DC(MAX)or less.

.

V_{DCIN_MIN}

V_{DCIN_MIN}≤ 퐕_{퐃퐂퐈퐍_퐌퐀퐗}< V_DC(MAX)

V_{DCIN_MAX}

V_OUT

(

)

V_{CC_MIN}+ V_DZ1− V_FD3+ V_FD1+ V_FD2< 퐕_퐎퐔퐓< 0.5 × ꢃV_{DCIN_MIN}− V_RON− V_FD3

ꢄ

I_OUT

퐈_퐎퐔퐓< 0.8 × I_DLIM. In addition, I_OUTalso depends on the OCP setting.

Lower value is a higher value or more of either 0 or V_OUT+ V_FD3− ꢃV_FD1+ V_FD2+ V_{CC(OVP)_MIN}ꢄ.

V_DZ1

R_OCP

Upper value is V_OUT+ V_FD3− ꢃV_FD1+ V_FD2+ V_{CC_MIN}

ꢄ

V

Lower value is R_OCP(L)

=

^{ꢅꢆꢇ(ꢈ)_ꢉꢊꢋ}, or more.

I

ꢌꢍꢎꢉ

● Choosing DCM

The on-duty for DCM, D_CCM1, is set in the range of

(B-2) Calculation

There are two calculation ways: L_CALCCalculation,

2 × I_OUT× D_CCM1

≤ D_DCM1< D_CCM1

I_DLIM

and Parameter Calculation assigned L_USER

.

(B-2-1) L_CALCCalculation

The condition of I_OUT: < 0.5 × I_DLIM

The inductance, L_CALC, is given by choosing the

operation mode at V_{DCIN_MIN}. The parameters of both

(B-2-1-1-3) Inductor Current

V_{DCIN_MIN}and V_{DCIN_MAX}are given by L_CALC

.

D_ON1is denoted the on-duty. L_LH1, I_LL1, and I_LR1are

the upper inductor current, the lower inductor current,

and the ripple inductor current, respectively.

(B-2-1-1) Parameters for V_{DCIN_MIN}

(B-2-1-1-1) On-duty in ContinuousOoperation, D_CCM1

● Choosing CCM

V_OUT+ V_FD3

D_ON1= D_CCM1

2 × I_OUT

D_CCM1

=

V_{DCIN_MIN}− V_RON+ V_FD3

I_LH1

=

The condition of D_CCM1: < 0.5

2 − K_RP1

(B-2-1-1-2) Choosing the Operation Mode, and K_RP1

or D_DCM1

I_LR1= K_RP1× I_LH1

I_LL1= I_LH1− I_LR1

● Choosing CRM

D_ON1= D_CCM1

● Choosing CCM

K

_RP1is set in the following range.

I_DLIM− I_OUT

0.4 ≤ K_RP1< 2 ×

< 1

I_DLIM

The condition of I_OUT: < 0.8 × I_DLIM

● Choosing CRM

I_LH1= 2 × I_OUT

I_LR1= I_LH1, I_LL1= 0

The condition of I_OUT: ≤ 0.5 × I_DLIM

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● Choosing DCM

D_ON1= D_DCM1

(B-2-1-1-6) On-time, t_ON1

By D_ON1and f_SW1of the choosing operation mode,

D_ON1

D_CCM1

D_DCM1

t_ON1=

f_SW1

I_LH1= 2 × I_OUT

×

If t_ON1is less than 500 ns, try the procedure 1 in

Section (B-2-1-1-4) to increase it.

I_LR1= I_LH1, I_LL1= 0

(B-2-1-1-4) Upper Temporary Value of R_OCP

R_{OCP(H)_TMP1}

,

(B-2-1-1-7) OCP Threshold Voltage, V_OCP1

V

_OCP1is given below by t_ON1.

V_{OCP(H)_MAX}

● For t_ON1≥ 6µs, V_OCP1= V_{OCP(H)_MIN}

● For t_ON1< 6휇푠,

R_{OCP(H)_TMP1}

=

I_LH1

The temporary range of the current detection resistor,

R_OCP, is given below.

V_OCP1= V_{OCP(L)_MIN}+ DPC × 10^ꢏ3× t_ON1

R_OCP(L)≤ R_OCP< R_{OCP(H)_TMP1}

where, DPC (mV/µs)、t_ON1(µs)

If R_OCPsetting has no range, try the following

procedure 1.

(B-2-1-1-8) Current Detection Resistor, R_OCP

Upper value at V_{DCIN_MIN}of the R_OCPrange is given

below.

● Procedure 1 :

For CCM, reduce K_RP1or I_OUT

For CRM, change to CCM.

For DCM, increase D_DCM1, or change to CRM or CCM.

After these changes, try to calculate again from

Section (B-1) Input and Output Condition.

.

V_OCP1

R_OCP(H)1

=

I_LH1

The range of R_OCPis given below.

R_OCPsetting is set in the previous range.

The switching frequency, f_SW1, and the peak inductor

current at OCP depend on R_OCP. When R_OCPis set low,

f_SW1becomes low, and the peak current becomes large.

R_OCP(L)≤ R_OCP< R_OCP(H)1

If R_OCPsetting has no range, try the procedure 1 in

Section (B-2-1-1-4).

If R_OCPsetting is out of the previous range, try to set it

again, and then try to calculate again from Section

(B-2-1-1-5).

(B-2-1-1-5) Switching Frequency, f_SW1

The f_SW1is given by the following with the I_LH1of the

choosing operation mode and R_OCP

.

The following K is a coefficient.

(B-2-1-1-9) Inductance, L_CALC

f_TYP− f_MIM

By I_LH1, I_LL1, and f_SW1of the choosing operation

mode,

K = ꢁ

ꢂ

0.85 × V_{OCP(L)_TYP}− V_OCP(STB)

(

)

(

)

f

_SW1is given below by using K.

2 × I_OUT× V_OUT+ V_FD3× 1 − D_CCM1

ꢃI_LH1²− I_LL1²ꢄ × f_SW1

L_CALC

=

f_SW1= K × ꢃR_OCP× I_LH1− V_OCP(STB)ꢄ + f_MIM

The value should be the minimum considered a

negative tolerance of inductance and a decline of DC

superposition characteristics.

If L_CACLis less than 100 µH, try the procedure 1 of

Section (B-2-1-1-4) to increase it.

where,

For f_SW1≤ f_MIN, set to f_MIN

For f_SW1≥ f_TYP, set to f_TYP

.

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3) Calculate Switching frequency, f_SW2

f_SW2= K × ꢃR_OCP× I_LH2− V_OCP(STB)ꢄ + f_MIM

where,

(B-2-1-1-10) Drain RMS Current and Inductor RMS

Current : I_DRMS1, I_LRMS1

1

ꢐ

=

(

)

I_DRMS1

ꢑ × I_LH1− I_LL1²+ I_LH1× I_LL1ꢒ × D_ON1

3

For f_SW2< f_MIN, set to f_MIN

For f_TYP< f_SW2, set to f_TYP

.

The conduction loss of R_DS(ON)of power MOSFET is

estimated to be I_DRMS1²× R_DS(ON)

.

When f_SW2is f_MINor f_TYP, calculate I_LH2again by the

following.

1

D_ON1

I_LRMS1= ꢐꢑ × I_LH1− I_LL1²+ I_LH1× I_LL1ꢒ ×

(

)

3

D_CCM1

M2

I_LH2

=

+ I_OUT

4 × I_OUT× f_SW2

This value is equivalent to the rating for inductor.

For f_MIN≤ f_SW2≤ f_TYP, I_LH2is the value of the previous

2).

If I_LH2is I_DLIMor more, try the procedure 1 in Section

(B-2-1-1-4) to decrease it.

(B-2-1-2) Parameters for V_{DCIN_MAX}

(B-2-1-2-1) On-duty in Continuous Operation, D_CCM2

4) Calculate Lower inductor current, I_LL2

I_LL2= 2 × I_OUT− I_LH2

V_OUT+ V_FD3

D_CCM2

=

V_{DCIN_MAX}− V_RON+ V_FD3

5) The operation mode is given by the following.

The condition of D_CCM2: < 0.5

● For I_LL2> 0, CCM

● For I_LL2= 0, CRM

● For I_LL2< 0, DCM

(B-2-1-2-2) Operation Mode Check

1) At first, calculate the following coefficients

R_OCPsetting in Section (B-2-1-1-8) and L_CALC

calculated in Section (B-2-1-1-9) are used.

(B-2-1-2-3) D_ON2, f_SW2, I_LH2, I_LL2of the Operation

Mode Result

f_TYP− f_MIM

These parameters are different in the operation mode

results of Section (B-2-1-2-2)-5).

K = ꢁ

ꢂ

0.85 × V_{OCP(L)_TYP}− V_OCP(STB)

● Resulting in CCM

(

)

(

)

2 × I_OUT× V_OUT+ V_FD3× 1 − D_CCM2

M2 =

D_ON2= D_CCM2

L_CALC

f

_SW2is the value of Section (B-2-1-2-2) - 3).

A = 4 × I_OUT× K × R_OCP

I_LH2is the value of Section (B-2-1-2-2) - 3).

I_LL2is the value of Section (B-2-1-2-2) - 4).

B = 4 × I_OUT× ꢓf_MIM− K

× ꢃI_OUT× R_OCP+ V_OCP(STB)

ꢄ

ꢔ

I_LR2= I_LH2− I_LL2

I_LR2

2

C = −4 × I_OUT× ꢃf_MIM− K × V_OCP(STB)ꢄ − M2

K_RP2

=

I_LH2

2) Calculate Upper inductor current, I_LH2

● Resulting in CRM

D_ON2= D_CCM2

1

2

ꢖ

I_LH2

=

× ꢕ−B + B − 4 × A × Cꢗ

2 × A

f_SW2is the value of Section (B-2-1-2-2) - 3).

I_LH2= 2 × I_OUT

I_LR2= I_LH2, I_LL2= 0

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● Resulting in DCM

2) Set Switching frequency, f_SW2

When f_SWat the intersection of I_{LH2_f}and I_{LH2_DCM}is

in the range of f_MINto f_TYPas shown in Figure 10-3,

f_SW2is set to that value. When f_SWis out of the range

as shown in Figure 10-4, f_SW2is set to the limited

value which is f_MINor f_TYPof the over range side.

1) Draw the graph of the following equations.

By using this, find the values of f_SW2and I_LH2of

DCM.

f_SW2− f_MIN

1

I_{LH2_f}= ꢑ

+ V_OCP(STB)ꢒ ×

K

R_OCP

3) Calculate On-duty, D_ON2

M2

I_{LH2_DCM}= ꢐ

f_SW2

ꢐ

×

D_ON2= D_DCM2= 2 × I_OUT× D_CCM2

M2

I_{LH2_CRM}= 2 × I_OUT

The condition of D_DCM2: < D_CCM2

4) Calculate I_LH2, I_LL2, and I_LR2

I_LH2is the value at the intersection of f_SW2which is

given in the previous 2) and I_{LH2_DCM}. Otherwise, I_LH2

is given below.

I_LH(A)

5

I_{LH2_f}

ILH_f

4

3

2

1

0

I_{LH2_DCM}

ILH_dcm

D_CCM2

I_{LH2_CRM}

ILH_crm

I_LH2= 2 × I_OUT

×

D_DCM2

f_MIN

fmin

f_TYP

fmax

I_LR2= I_LH2, I_LL2= 0

f

_SW(kHz)

20 25 30 35 40 45 50 55 60 65 70

(B-2-1-2-4) I_LH2

If I_LH2is I_DLIMor more, try the procedure 1 in Section

(B-2-1-1-4) to decrease it.

Figure 10-3. I_LH2and f_SW2of DCM Graph in which the

intersection of I_{LH_f}and I_{LH_DCM}is in the Range of f_MIN

to f_TYP.

(B-2-1-2-5) On-time, t_ON2

D_ON2

t_ON2

=

I_LH(A)

5

f_SW2

I_{LH2_f}

ILH_f

If t_ON2is less than 500 ns, try the procedure 1 in

Section (B-2-1-1-4) to increase it.

4

3

2

1

0

I_{LH2_DCM}

ILH_dcm

I_{LH2_CRM}

ILH_crm

(B-2-1-2-6) OCP Threshold Voltage, V_OCP2

f_MIN

fmin

V

_OCP2is given below by t_ON2.

f_TYP

fmax

● For t_ON2≥ 6µs, V_OCP2= V_{OCP(H)_MIN}

● For t_ON2< 6휇푠,

f

_SW(kHz)

20 25 30 35 40 45 50 55 60 65 70

V_OCP2= V_{OCP(L)_MIN}+ DPC × 10^ꢏ3× t_ON2

Figure 10-4.

I_LH2and f_SW2of DCM Graph in which the

intersection of I_{LH_f}and I_{LH_DCM}is out of the Range of

f_MINto f_TYP.

where, DPC (mV/µs)、t_ON1(µs)

In DCM, I_LHvalue at the intersection of I_{LH2_f}and

I_{LH2_DCM}is bigger than that of I_{LH2_CRM}

.

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(B-2-1-2-7) Current Detection Resistor, R_OCP

(B-2-1-2-9) Inductor Current Specification

Upper value at V_{DCIN_MAX}of the R_OCPrange is given

below.

The peak current in OCP operation, I_OCP, is given

below.

V_OCP2

V_{OCP(H)_MAX}

R_OCP(H)2

=

I_OCP

=

I_LH2

R_OCP

Denoting R_OCP(H)as a smaller value of either R_OCP(H)2

for V_{DCIN_MAX}or R_OCP(H)1for V_{DCIN_MIN}in Section

(B-2-1-1-8), the range of R_OCPis given below.

The saturation current of the inductor should be

enough larger than I_OCP

The rating current refers to the equation of RMS in

Section (B-2-1-1-10).

.

R_OCP(L)≤ R_OCP< R_OCP(H)

(B-2-2) Parameter Calculation Assigned L_USER

If R_OCPsetting has no range, try the procedure 1 in

Section (B-2-1-1-4).

If R_OCPsetting is out of the previous range, try to set it

again, and then try to calculate again from Section

(B-2-1-1-5).

Parameter calculation assigned L_USERat V_{DCIN_MIN}and

V_{DCIN_MAX}is similar to the way of Section (B-2-1-2)

Parameters for V_{DCIN_MAX}

Parameters assigned L_USERare given by substituting

the input voltage and L_USERfor V_{DCIN_MAX}and L_CALC

.

If the conditions of calculation aren’t satisfied,

increase L_USERsetting, or decrease I_OUTsetting, and then

try to calculate again.

(B-2-1-2-8) I_DRMS2,I_LRMS2

These are given by substituting I_LH2, I_LL2, D_ON2, and

D_CCM2for I_LH1, I_LL1,D_ON1, and D_CCM1in the equation of

Section (B-2-1-1-10), respectively.

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10.3.3 Inverting Convertor

(I-1) Input and Output Condition

The definition refers to Section 10.3.1. |V_OUT| is the absolute value of V_OUT

.

Lower value is a higher value or more of either V_{ST_MAX}or V_OUT+ V_FD3+ V_RON

Upper value is V_DC(MAX)or less.

.

V_{DCIN_MIN}

V_{DCIN_MIN}≤ 퐕_{퐃퐂퐈퐍_퐌퐀퐗}< V_DC(MAX)

V_{DCIN_MAX}

|V_OUT

(

)

|

V_{CC_MIN}+ V_DZ1− V_FD3+ V_FD1+ V_FD2< 퐕_퐎퐔퐓< V_{DCIN_MIN}− V_RON− V_FD3

|

(

)

퐈_퐎퐔퐓< 0.8 × I_{DLIM_MIN}× 1 − D_CCM1. In addition,I_OUTalso depends on the OCP setting.

where,

I_OUT

V_OUT+ V_FD3

D_CCM1

=

V_{DCIN_MIN}− V_RON+ V_OUT+ V_FD3

Lower value is a higher value or more of either 0 or V_OUT+ V_FD3− ꢃV_FD1+ V_FD2+ V_{CC(OVP)_MIN}ꢄ.

Upper value is V_OUT+ V_FD3− ꢃV_FD1+ V_FD2+ V_{CC_MIN}ꢄ.

V_DZ1

V

^{ꢅꢆꢇ(ꢈ)_ꢉꢊꢋ}, or more.

I

ꢌꢍꢎꢉ

R_OCP

Lower value is R_OCP(L)

=

(I-2) Calculation

There are two calculation ways: L_CALCCalculation,

(I-2-1-1-2) Choosing the Operation Mode, and K_RP1

or D_DCM1

and Parameter Calculation assigned L_USER

.

● Choosing CCM

K

_RP1is set in the following range.

(I-2-1) L_CALCCalculation

I_LAVG1

0.4 ≤ K_RP1< 2 × ꢑ1 −

ꢒ < 1

The inductance, L_CALC, is given by choosing the

operation mode at V_{DCIN_MIN}. The parameters of both

I_DLIM

V_{DCIN_MIN}and V_{DCIN_MAX}are given by L_CALC

.

The condition of I_OUT

:

(I-2-1-1) Parameters for V_{DCIN_MIN}

(

)

< 0.8 × I_DLIM× 1 − D_CCM1

(I-2-1-1-1) On-duty in Continuous Operation, D_CCM1

and Average Inductor Current, I_LAVG1

,

● Choosing CRM

The condition of I_OUT

:

V_OUT+ V_FD3

D_CCM1

=

(

≤ 0.5 × I_DLIM× 1 − D_CCM1

V_{DCIN_MIN}− V_RON+ V_OUT+ V_FD3

● Choosing DCM

On-duty, D_DCM1, is set in the following range.

The condition of D_CCM1: < 0.5

I_OUT

2 × I_LAVG1× D_CCM1

≤ D_DCM1< D_CCM1

I_DLIM

I_LAVG1

=

1 − D_CCM1

The condition of I_OUT

:

(

)

< 0.5 × I_DLIM× 1 − D_CCM1

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R_OCPsetting is set in the previous range.

The switching frequency, f_SW1, and the peak inductor

current at OCP depend on R_OCP. When R_OCPis set low,

f_SW1becomes low, and the peak current becomes

large.

(I-2-1-1-3) Inductor Current

D_ON1is denoted the on-duty. L_LH1, I_LL1, and I_LR1are

the upper inductor current, the lower inductor current,

and the ripple inductor current, respectively.

● Choosing CCM

D_ON1= D_CCM1

2 × I_LAVG1

(I-2-1-1-5) Switching Frequency, f_SW1

The f_SW1is given by the following with the I_LH1of the

choosing operation mode and R_OCP

.

I_LH1

=

The following K is a coefficient.

2 − K_RP1

f_TYP− f_MIM

I_LR1= K_RP1× I_LH1

I_LL1= I_LH1− I_LR1

● Choosing CRM

D_ON1= D_CCM1

K = ꢁ

ꢂ

0.85 × V_{OCP(L)_TYP}− V_OCP(STB)

f_SW1is given below by using K.

f_SW1= K × ꢃR_OCP× I_LH1− V_OCP(STB)ꢄ + f_MIM

where,

For f_SW1≤ f_MIN, set to f_MIN

.

I_LH1= 2 × I_LAVG1

I_LR1= I_LH1, I_LL1= 0

● Choosing DCM

D_ON1= D_DCM1

For f_SW1≥ f_TYP, set to f_TYP

.

(I-2-1-1-6) On-time, t_ON1

By D_ON1and f_SW1of the choosing operation mode,

D_ON1

t_ON1

=

f_SW1

D_CCM1

D_DCM1

I_LH1= 2 × I_LAVG1

×

If t_ON1is less than 500 ns, try the procedure 1 in

Section (I-2-1-1-4) to increase it.

I_LR1= I_LH1, I_LL1= 0

(I-2-1-1-7) OCP Threshold Voltage, V_OCP1

(I-2-1-1-4) Upper Temporary Value of R_OCP

R_{OCP(H)_TMP1}

,

V

_OCP1is given below by t_ON1.

● For t_ON1≥ 6µs, V_OCP1= V_{OCP(H)_MIN}

● For t_ON1< 6휇푠,

V_{OCP(H)_MAX}

R_{OCP(H)_TMP1}

=

I_LH1

V_OCP1= V_{OCP(L)_MIN}+ DPC × 10^ꢏ3× t_ON1

The temporary range of the current detection resistor,

R_OCP, is given below.

where, DPC (mV/µs)、t_ON1(µs)

R_OCP(L)≤ R_OCP< R_{OCP(H)_TMP1}

(I-2-1-1-8) Current Detection Resistor, R_OCP

If R_OCPsetting has no range, try the following

procedure 1.

Upper value at V_{DCIN_MIN}of the R_OCPrange is given

below.

● Procedure 1 :

For CCM, reduce K_RP1or I_OUT

For CRM, change to CCM.

V_OCP1

.

R_OCP(H)1

=

I_LH1

For DCM, increase D_DCM1, or change to CRM or CCM.

After these changes, try to calculate again from

Section (I-1) Input and Output Condition.

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The range of R_OCPis given below.

R_OCP(L)≤ R_OCP< R_OCP(H)1

(I-2-1-2-2) Operation Mode Check

1) At first, calculate the following coefficients

R_OCPsetting in Section (I-2-1-1-8) and L_CALC

calculated in Section (I-2-1-1-9) are used.

If R_OCPsetting has no range, try the procedure 1 in

Section (I-2-1-1-4).

If R_OCPsetting is out of the previous range, try to set it

again, and then try to calculate again from Section

(I-2-1-1-5).

f_TYP− f_MIM

K = ꢁ

ꢂ

0.85 × V_{OCP(L)_TYP}− V_OCP(STB)

(

)

(

)

2 × I_LAVG2× V_OUT+ V_FD3× 1 − D_CCM2

M2 =

L_CALC

(I-2-1-1-9) Inductance, L_CALC

By I_LH1, I_LL1, and f_SW1of the choosing operation

mode,

A = 4 × I_AVG2× K × R_OCP

B = 4 × I_AVG2× ꢓf_MIM− K

(

)

2 × I_OUT× V_OUT+ V_FD3

L_CALC

=

× ꢃI_AVG2× R_OCP+ V_OCP(STB)

ꢄ

ꢔ

ꢃI_LH1²− I_LL1²ꢄ × f_SW1

2

C = −4 × I_AVG2× ꢃf_MIM− K × V_OCP(STB)ꢄ − M2

The value should be the minimum considered a

negative tolerance of inductance and a decline of DC

superposition characteristics.

2) Calculate Upper inductor current, I_LH2

If L_CACLis less than 100 µH, try the procedure 1 of

Section (I-2-1-1-4) to increase it.

1

2

ꢖ

I_LH2

=

× ꢕ−B + B − 4 × A × Cꢗ

2 × A

(I-2-1-1-10) Drain RMS Current and Inductor RMS

Current : I_DRMS1, I_LRMS1

3) Calculate Switching frequency, f_SW2

f_SW2= K × ꢃR_OCP× I_LH2− V_OCP(STB)ꢄ + f_MIM

where,

1

2

ꢐ

(

)

I_DRMS1

=

ꢑ × I_LH1− I_LL1+ I_LH1× I_LL1ꢒ × D_ON1

3

For f_SW2< f_MIN, set to f_MIN

For f_TYP< f_SW2, set to f_TYP

.

The conduction loss of R_DS(ON)of power MOSFET is

estimated to be I_DRMS1²× R_DS(ON)

.

When f_SW2is f_MINor f_TYP, calculate I_LH2again by the

following.

1

D_ON1

I_LRMS1= ꢐꢑ × I_LH1− I_LL1²+ I_LH1× I_LL1ꢒ ×

(

)

3

D_CCM1

M2

I_LH2

=

+ I_LAVG2

This value is equivalent to the rating for inductor.

4 × I_LAVG2× f_SW2

(I-2-1-2) Parameters for V_{DCIN_MAX}

For f_MIN≤ f_SW2≤ f_TYP, I_LH2is the value of the previous

2).

If I_LH2is I_DLIMor more, try the procedure 1 in Section

(I-2-1-1-4) to decrease it.

(I-2-1-2-1) On-duty in Continuous Operation, D_CCM2

and Average Inductor Current, I_LAVG2

,

4) Calculate Lower inductor current, I_LL2

V_OUT+ V_FD3

D_CCM2

=

V_{DCIN_MAX}− V_RON+ V_OUT+ V_FD3

I_LL2= 2 × I_LAVG2− I_LH2

The condition of D_CCM2: < 0.5

I_OUT

I_LAVG2

=

1 − D_CCM2

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5) The operation mode is given by the following.

I_LH(A)

5

● For I_LL2> 0, CCM

● For I_LL2= 0, CRM

● For I_LL2< 0, DCM

I_{LH2_f}

ILH_f

4

3

2

1

0

I_{LH2_DCM}

ILH_dcm

(I-2-1-2-3) D_ON2, f_SW2, I_LH2, I_LL2of the Operation

Mode Result

I_{LH2_CRM}

ILH_crm

f_MIN

fmin

These parameters are different in the operation mode

results of Section (I-2-1-2-2)-5).

f_TYP

fmax

● Resulting in CCM

f

_SW(kHz)

20 25 30 35 40 45 50 55 60 65 70

D_ON2= D_CCM2

Figure 10-5 I_LH2and f_SW2of DCM Graph in which the

intersection of I_{LH_f}and I_{LH_DCM}is in the range of f_MINto

f_TYP.

fSW2 is the value of Section (I-2-1-2-2)-3).

ILH2 is the value of Section (I-2-1-2-2)-3)

ILL2 is the value of Section (I-2-1-2-2)-4)

I_LR2= I_LH2− I_LL2

I_LH(A)

5

I_{LH2_f}

ILH_f

4

3

2

1

0

I_{LH2_DCM}

ILH_dcm

I_LR2

I_{LH2_CRM}

ILH_crm

K_RP2

=

I_LH2

f_MIN

fmin

● Resulting in CRM

f_TYP

fmax

f

_SW(kHz)

20 25 30 35 40 45 50 55 60 65 70

D_ON2= D_CCM2

f_SW2is the value of Section (I-2-1-2-2)-3).

I_LH2= 2 × I_LAVG2

Figure 10-6.

I_LH2and f_SW2of DCM Graph in which the

Intersection of I_{LH_f}and I_{LH_DCM}is out of the Range of

f_MINto f_TYP.

I_LR2= I_LH2, I_LL2= 0

● Resulting in DCM

In DCM, I_LHvalue at the intersection of I_{LH2_f}and

I_{LH2_DCM}is bigger than that of I_{LH2_CRM}

.

2) Set Switching frequency, f_SW2

1) Draw the graph of the following equations.

By using this, find the values of f_SW2and I_LH2of

DCM.

When f_SWat the intersection of I_{LH2_f}and I_{LH2_DCM}is

in the range of f_MINto f_TYPas shown in Figure 10-5,

f_SW2is set to that value. When f_SWis out of the range

as shown in Figure 10-6, f_SW2is set to the limited

value which is f_MINor f_TYPof the over range side.

f_SW2− f_MIN

1

I_{LH2_f}= ꢑ

+ V_OCP(STB)ꢒ ×

K

R_OCP

3) Calculate On-duty, D_ON2

f_SW2

ꢐ

M2

D_ON2= D_DCM2= 2 × I_LAVG2× D_CCM2

×

M2

I_{LH2_DCM}= ꢐ

f_SW2

The condition of D_DCM2: < D_CCM2

I_{LH2_CRM}= 2 × I_LAVG2

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4) Calculate I_LH2, I_LL2, and I_LR2

(I-2-1-2-8) I_DRMS2, I_LRMS2

I_LH2is the value at the intersection of f_SW2which is

given in the previous 2) and I_{LH2_DCM}. Otherwise, I_LH2

is given below.

These are given by substituting I_LH2, I_LL2, D_ON2, and

D_CCM2for I_LH1, I_LL1,D_ON1, and D_CCM1in the equation of

Section (I-2-1-1-10), respectively.

D_CCM2

I_LH2= 2 × I_LAVG2

×

(I-2-1-2-9) Inductor Current Specification

D_DCM2

The peak current in OCP operation, I_OCP, is given

below.

I_LR2= I_LH2, I_LL2= 0

V_{OCP(H)_MAX}

(I-2-1-2-4) I_LH2

I_OCP

=

R_OCP

If I_LH2is I_DLIMor more, try the procedure 1 in Section

(I-2-1-1-4) to decrease it.

The saturation current of the inductor should be

enough larger than I_OCP

The rating current refers to the equation of RMS in

Section (I-2-1-1-10).

.

(I-2-1-2-5) On-time, t_ON2

D_ON2

t_ON2

=

f_SW2

(I-2-2) Parameter Calculation Assigned L_USER

Parameter calculation assigned L_USERat V_{DCIN_MIN}and

V_{DCIN_MAX}is similar to the way of Section (I-2-1-2)

If t_ON2is less than 500 ns, try the procedure 1 in

Section (I-2-1-1-4) to increase it.

Parameters for VDCIN_{_MAX}

Parameters assigned L_USERare given by substituting

the input voltage and L_USERfor V_{DCIN_MAX}and L_CALC

.

(I-2-1-2-6) OCP threshold voltage, V_OCP2

.

If the conditions of calculation aren’t satisfied,

increase L_USERsetting, or decrease I_OUTsetting, and then

try to calculate again.

V

_OCP2is given below by t_ON2.

● For t_ON2≥ 6µs, V_OCP2= V_{OCP(H)_MIN}

● For t_ON2< 6휇푠,

V_OCP2= V_{OCP(L)_MIN}+ DPC × 10^ꢏ3× t_ON2

where, DPC (mV/µs)、t_ON1(µs)

(I-2-1-2-7) Current Detection Resistor, R_OCP

Upper value at V_{DCIN_MAX}of the R_OCPrange is given

below.

V_OCP2

R_OCP(H)2

=

I_LH2

Denoting R_OCP(H)as a smaller value of either R_OCP(H)2

for V_{DCIN_MAX}or R_OCP(H)1for V_{DCIN_MIN}in Section

(I-2-1-1-8), the range of R_OCPis given below.

R_OCP(L)≤ R_OCP< R_OCP(H)

If R_OCPsetting has no range, try the procedure 1 in

Section (I-2-1-1-4).

If R_OCPsetting is out of the previous range, try to set it

again, and then try to calculate again from Section

(I-2-1-1-5).

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STR5A450 Series

4) VCC Trace Layout

10.4 PCB Trace Layout

This is the trace for supplying power to the IC, and

thus it should be as small loop as possible. If C4 and

the IC are distant from each other, placing a

capacitor such as film capacitor C_f(about 0.1 μF to

1.0 μF) close to the VCC pin and the GND pin is

recommended.

Since the PCB circuit trace design and the component

layout significantly affects operation, EMI noise, and

power dissipation, the high frequency PCB trace should

be low impedance with small loop and wide trace.

In addition, the ground traces affect radiated EMI

noise, and wide, short traces should be taken into

account.

5) FB Trace Layout

The divided voltage by R2+R3 and R1 of output

voltage is input to the FB pin.

Figure 10-7 and Figure 10-8 show the circuit design

example.

To increase the detection accuracy, R3 and R1

should be connected to the bottom of C3 and the

GND pin, respectively. The trace between R1, R2

and the FB pin should be as short as possible.

1) Main Circuit Trace Layout

This is the main trace containing switching currents,

and thus it should be as wide trace and small loop as

possible.

2) Freewheeling Loop Layout

6) Thermal Considerations

This is the trace for the current of freewheeling

diode, D3, and thus it should be as wide trace and

small loop as possible.

Since the internal power MOSFET has a positive

thermal coefficient of R_DS(ON), consider it in thermal

design.

Since the copper area under the IC and the GND pin

trace act as a heatsink, its traces should be as wide as

possible.

3) Control Ground Trace Layout

Since the operation of IC may be affected from the

large current of the main trace that flows in control

ground trace, the control ground trace should be

separated from main trace and connected at single

point grounding.

(4) Loop of the power supply should be small

(7) Trace of D/ST pin should be

wide for heat release

D1

(6) Components connected

D/ST

VCC

GND

to FB pin should be

connected as close to

FB pin as possible.

4

3

2

1

5

6

7

8

C3

C4

C2

D/ST

R1

D2

FB

R2

R3

L1

V_OUT

R_OCP

S/OCP

(＋)

U1

D3

R4

C5

C1

(－)

(5)R_OCPshould be

(3)Control GND trace should be

connected at a single point as

close to R_OCPas possible.

(2) Freewheeling Loop trace

should be wide trace and

small loop

(1) Main trace should be wide

trace and small loop

connected as close to

S/OCP pin as possible.

Figure 10-7 Peripheral circuit example around the IC for Buck converter

STR5A450-DSE Rev.1.1

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STR5A450 Series

(4) Loop of the power supply should be small

(7) Trace of D/ST pin should be

wide for heat release

D1

(6) Components connected

to FB pin should be

connected as close to

FB pin as possible.

D/ST

VCC

GND

4

5

6

7

8

C3

C4

C2

3

2

1

R1

D2

FB

R2

R3

V_OUT

R_OCP

D3

S/OCP

(－)

U1

C5

C1

R4

L1

(＋)

(5)R_OCPshould be

(3)Control GND trace should be

connected at a single point as

close to R_OCPas possible.

(2) Freewheeling Loop trace

should be wide trace and

small loop

(1) Main trace should be wide

trace and small loop

connected as close to

S/OCP pin as possible.

Figure 10-8 Peripheral circuit example around the IC for Inverting converter

STR5A450-DSE Rev.1.1

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STR5A450 Series

11. Reference Design of Power Supply

11.1 Buck Converter

As an example, the following show the power supply specification, the circuit schematic, the bill of materials, and the

transformer specification.

● Power supply specification

IC

STR5A453D

Input voltage

AC 85 V to AC 265 V

Maximum output power 15 W (max.)

Output voltage

Output current

15 V

1 A

● Circuit schematic

U1

D6

D/ST

VCC

GND

4

3

2

1

5

6

7

8

C5

C4

C6

R2

R3

L2

R4

FB

CN1

CN2

D7

F1

L1

S/OCP

1

(+)

(-)

D2

D3

D1

D4

R1

C1

C2

R5

D5

ZD1

C11

C8 C9

3

TC_STR5A450_5_R3

● Bill of materials

Symbol

Part type

Ratings⁽¹⁾

Recommended Sanken Parts

F1

C1

C2

C4

C5

C6

C8, C9

C11

Fuse

Film capacitor

250 V, 2 A

275 V, 0.1 μF

400 V, 56 μF

50 V, 470 pF

50 V, 10 μF

50 V, 2.2 μF

25 V, 470 μF

2 kV, 22 pF

600 V, 1 A

Electrolytic capacitor

Ceramic capacitor

Electrolytic capacitor

Ceramic capacitor

Electrolytic capacitor

Ceramic capacitor

Diode

(2)

D1, D2, D3, D4

D5

D6

D7

ZD1

L1

Fast recovery diode

Zener diode

600 V, 3 A

90 V, 1 A

600 V, 0.5 A

V_Z= 18.8 V (min.)

10 mH

RL4A

SJPB-D9

AG01A

SJPZ-E20

(2)

CM inductor

L2

Inductor

180 μH

R1

R2

R3

R4

R5

U1

Resistor

AC/DC convertor IC

0.33 Ω, 1 W

10 kΩ, 1/8 W

47 kΩ, 1/8 W

4.7 kΩ, 1/8 W

6.8 kΩ, 1/4 W

650 V/1.9 Ω

(2)

STR5A453D

⁽¹⁾Unless otherwise specified, the voltage rating of capacitor is 50 V or less and the power rating of resistor is 1/8 W or less.

⁽²⁾It is necessary to be adjusted based on actual operation in the application.

STR5A450-DSE Rev.1.1

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STR5A450 Series

11.2 Inverting Converter

As an example, the following show the power supply specification, the circuit schematic, the bill of materials, and the

transformer specification.

● Power supply specification

IC

STR5A453D

Input voltage

AC 85 V to AC 265 V

Maximum output power 15 W (max.)

Output voltage

Output current

– 15 V

1 A

● Circuit schematic

U1

D6

D/ST

VCC

GND

4

3

2

1

5

6

7

8

C5

C6

C4

R2

C11

R3

R4

FB

CN1

CN2

D7

F1

L1

S/OCP

1

(-)

(+)

D2

D1

D4

R1

D5

C1

C8 C9

C2

R5

ZD1

L2

D3

3

TC_STR5A450_6_R3

● Bill of materials

Symbol

Part type

Ratings⁽¹⁾

Recommended Sanken Parts

F1

C1

C2

C4

C5

C6

C8, C9

C11

Fuse

Film capacitor

250 V, 2 A

275 V, 0.1 μF

400 V, 56 μF

50 V, 470 pF

50 V, 10 μF

50 V, 2.2 μF

25 V, 470 μF

2 kV, 22 pF

600 V, 1 A

Electrolytic capacitor

Ceramic capacitor

Electrolytic capacitor

Ceramic capacitor

Electrolytic capacitor

Ceramic capacitor

Diode

(2)

D1, D2, D3, D4

D5

D6

D7

ZD1

L1

Fast recovery diode

Zener diode

600 V, 3 A

90 V, 1 A

600 V, 0.5 A

V_Z= 18.8 V (min.)

10 mH

RL4A

SJPB-D9

AG01A

SJPZ-E20

(2)

CM inductor

L2

Inductor

180 μH

R1

R2

R3

R4

R5

U1

Resistor

AC/DC convertor IC

0.33 Ω, 1 W

10 kΩ, 1/8 W

47 kΩ, 1/8 W

4.7 kΩ, 1/8 W

6.8 kΩ, 1/4 W

650 V/1.9 Ω

(2)

STR5A453D

⁽¹⁾Unless otherwise specified, the voltage rating of capacitor is 50 V or less and the power rating of resistor is 1/8 W or less.

⁽²⁾It is necessary to be adjusted based on actual operation in the application.

STR5A450-DSE Rev.1.1

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SANKEN ELECTRIC CO.,LTD.

http://www.sanken-ele.co.jp/en

31

STR5A450 Series

Important Notes

● All data, illustrations, graphs, tables and any other information included in this document as to Sanken’s products listed herein (the

“Sanken Products”) are current as of the date this document is issued. All contents in this document are subject to any change

without notice due to improvement of the Sanken Products, etc. Please make sure to confirm with a Sanken sales representative

that the contents set forth in this document reflect the latest revisions before use.

● The Sanken Products are intended for use as components of general purpose electronic equipment or apparatus (such as home

appliances, office equipment, telecommunication equipment, measuring equipment, etc.). Prior to use of the Sanken Products,

please put your signature, or affix your name and seal, on the specification documents of the Sanken Products and return them to

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equipment and its control systems, traffic signal control systems or equipment, disaster/crime alarm systems, various safety

devices, etc.), you must contact a Sanken sales representative to discuss the suitability of such use and put your signature, or affix

your name and seal, on the specification documents of the Sanken Products and return them to Sanken, prior to the use of the

Sanken Products. The Sanken Products are not intended for use in any applications that require extremely high reliability such as:

aerospace equipment; nuclear power control systems; and medical equipment or systems, whose failure or malfunction may result

in death or serious injury to people, i.e., medical devices in Class III or a higher class as defined by relevant laws of Japan

(collectively, the “Specific Applications”). Sanken assumes no liability or responsibility whatsoever for any and all damages and

losses that may be suffered by you, users or any third party, resulting from the use of the Sanken Products in the Specific

Applications or in manner not in compliance with the instructions set forth herein.

● In the event of using the Sanken Products by either (i) combining other products or materials therewith or (ii) physically,

chemically or otherwise processing or treating the same, you must duly consider all possible risks that may result from all such

uses in advance and proceed therewith at your own responsibility.

● Although Sanken is making efforts to enhance the quality and reliability of its products, it is impossible to completely avoid the

occurrence of any failure or defect in semiconductor products at a certain rate. You must take, at your own responsibility,

preventative measures including using a sufficient safety design and confirming safety of any equipment or systems in/for which

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injury or death, fire accident or social harm which may result from any failure or malfunction of the Sanken Products. Please refer

to the relevant specification documents and Sanken’s official website in relation to derating.

● No anti-radioactive ray design has been adopted for the Sanken Products.

● No contents in this document can be transcribed or copied without Sanken’s prior written consent.

● The circuit constant, operation examples, circuit examples, pattern layout examples, design examples, recommended examples, all

information and evaluation results based thereon, etc., described in this document are presented for the sole purpose of reference of

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suffered by you, users or any third party, or any possible infringement of any and all property rights including intellectual property

rights and any other rights of you, users or any third party, resulting from the foregoing.

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● In the event of using the Sanken Products, you must use the same after carefully examining all applicable environmental laws and

regulations that regulate the inclusion or use of any particular controlled substances, including, but not limited to, the EU RoHS

Directive, so as to be in strict compliance with such applicable laws and regulations.

● You must not use the Sanken Products or the Technical Information for the purpose of any military applications or use, including

but not limited to the development of weapons of mass destruction. In the event of exporting the Sanken Products or the Technical

Information, or providing them for non-residents, you must comply with all applicable export control laws and regulations in each

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● Sanken assumes no responsibility for any troubles, which may occur during the transportation of the Sanken Products including

the falling thereof, out of Sanken’s distribution network.

● Although Sanken has prepared this document with its due care to pursue the accuracy thereof, Sanken does not warrant that it is

error free and Sanken assumes no liability whatsoever for any and all damages and losses which may be suffered by you resulting

from any possible errors or omissions in connection with the contents included herein.

● Please refer to the relevant specification documents in relation to particular precautions when using the Sanken Products, and refer

to our official website in relation to general instructions and directions for using the Sanken Products.

● All rights and title in and to any specific trademark or tradename belong to Sanken or such original right holder(s).

DSGN-CEZ-16002

STR5A450-DSE Rev.1.1

Oct. 19, 2016

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http://www.sanken-ele.co.jp/en

32


型号：	STR5A450
厂家：	SANKEN ELECTRIC
描述：	For Non-Isolated Off-Line PWM Controllers with Integrated Power MOSFET
文件：	总32页 (文件大小：900K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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