Richtek RT8259GE, RT8259GJ6, RT8259PE Schematic [ru]

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RT8259

1.2A, 24V, 1.4MHz Step-Down Converter

General Description

The RT8259 is a high voltage buck converter that can support the input voltage range from 4.5V to 24V and the output current can be up to 1.2A. Current Mode operation provides fast transient response and eases loop stabilization.

The chip also provides protection functions such as cycle- by-cycle current limiting and thermal shutdown protection. The RT8259 is available in a SOT-23-6 and TSOT-23-6 packages.

Ordering Information

RT8259

Package Type E : SOT-23-6 J6 : TSOT-23-6

Lead Plating System

G : Green (Halogen Free and Pb Free)

Note :

Richtek products are :

`RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

`Suitable for use in SnPb or Pb-free soldering processes.

Marking Information

For marking information, contact our sales representative directly or through a Richtek distributor located in your area.

Features

zWide Operating Input Voltage Range : 4.5V to 24V

zAdjustable Output Voltage Range : 0.8V to 15V

z1.2A Output Current

z0.3Ω Internal Power MOSFET Switch

zHigh Efficiency up to 92%

z1.4MHz Fixed Switching Frequency

zStable with Low ESR Output Ceramic Capacitors

zThermal Shutdown

zCycle-By-Cycle Over Current Protection

zRoHS Compliant and Halogen Free

Applications

zDistributed Power Systems

zBattery Charger

zPre-Regulator for Linear Regulators

zWLEDDrivers

Pin Configurations

(TOP VIEW)

PHASE VIN EN

6 5 4

2 3

BOOT GND FB

SOT-23-6/TSOT-23-6

Typical Application Circuit

VIN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.5V to 24V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

VIN

 

 

 

 

 

 

 

BOOT

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

C1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CB

L1

 

 

 

3.3V

 

 

 

 

 

 

RT8259

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10µF

 

6

 

 

 

 

 

 

 

10nF

4.7µH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PHASE

 

 

 

 

 

 

 

D1

 

 

 

 

 

 

R1

 

 

Chip Enable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

B230A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN

 

 

 

 

 

 

 

FB

 

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

62k

 

C2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Open =

 

 

GND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R2

 

22µF

Automatic Startup

 

 

 

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

19.6k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DS8259-03 March 2011

www.richtek.com

 

1

RT8259

Table 1. Recommended Component Selection, C2 = 22μF

VOUT (V)

1.2

1.8

2.5

3.3

5

8

10

15

L1 (μH)

2

2

3.6

4.7

6.8

10

10

15

R1 (kΩ)

62

62

62

62

62

68

68

68

R2 (kΩ)

124

49.9

29.4

19.6

12

7.5

5.9

3.9

Functional Pin Description

Pin No.

Pin Name

Pin Function

 

 

 

 

 

Bootstrap. A capacitor is connected between PHASE and BOOT pins to form a floating

1

BOOT

supply across the power switch driver. This capacitor is needed to drive the power switch‘s

 

 

gate above the supply voltage.

 

 

Ground. This pin is the voltage reference for the regulated output voltage. For this reason,

2

GND

care must be taken in its layout. This node should be placed outside of the D1 to C1 ground

 

 

path to prevent switching current spikes from inducing voltage noise into the part.

3

FB

Feedback. An external resistor divider from the output to GND tapped to the FB pin sets the

output voltage. The value of the divider resistors also set loop bandwidth.

 

 

4

EN

Chip Enable (Active High). If the EN pin is open, it will be pulled to high by internal circuit.

 

 

 

5

VIN

Supply Voltage. Bypass VIN to GND with a suitable large capacitor to prevent large voltage

spikes from appearing at the input.

 

 

6

PHASE

Switch Output.

 

 

 

Function Block Diagram

VIN

 

 

 

 

 

X20

-

1µA

 

 

 

 

 

 

 

Current Sense Amp

+

 

 

 

 

 

 

 

 

 

 

 

 

 

25mΩ

 

 

 

Regulator

Ramp

 

 

 

 

 

 

 

Generator

 

 

 

 

 

 

 

 

 

 

 

 

10k

1.1V

-

 

Oscillator

 

 

 

BOOT

 

+

 

 

 

 

 

EN

 

 

1.4MHz

 

S

 

 

3V

Shutdown

Reference

 

 

 

 

Comparator

 

 

Q

Driver

 

 

 

 

 

+

 

 

 

+

R

 

 

 

 

 

- PWM

 

 

FB

 

 

- EA

 

 

PHASE

 

 

 

 

30pF

Comparator

Bootstrap

 

 

 

400k

 

 

 

 

 

 

 

OC Limit Clamp

Control

GND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1pF

 

 

 

 

www.richtek.com

DS8259-03 March 2011

2

 

RT8259

Absolute Maximum Ratings (Note 1)

 

z Supply Voltage, VIN ------------------------------------------------------------------------------------------------

26V

z PHASE Voltage -----------------------------------------------------------------------------------------------------

−0.3V to (VIN + 0.3V)

z BOOT Voltage -------------------------------------------------------------------------------------------------------

VPHASE + 6V

z All Other Pins--------------------------------------------------------------------------------------------------------

0.3V to 6V

z Output Voltage ------------------------------------------------------------------------------------------------------

−0.3V to 15V

z Power Dissipation, PD @ TA = 25°C

 

T/SOT-23-6 -----------------------------------------------------------------------------------------------------------

0.4W

z Package Thermal Resistance (Note 2)

 

T/SOT-23-6, θJA ------------------------------------------------------------------------------------------------------

250°C/W

z Junction Temperature ----------------------------------------------------------------------------------------------

150°C

z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------

260°C

z Storage Temperature Range --------------------------------------------------------------------------------------

−65°C to 150°C

z ESD Susceptibility (Note 3)

 

HBM (Human Body Mode) ----------------------------------------------------------------------------------------

2kV

MM (Machine Mode) -----------------------------------------------------------------------------------------------

200V

Recommended Operating Conditions

(Note 4)

z Supply Voltage, VIN ------------------------------------------------------------------------------------------------

4.5V to 24V

z Output Voltage, VOUT ----------------------------------------------------------------------------------------------

0.8V to 15V

z EN Voltage, VEN -----------------------------------------------------------------------------------------------------

0V to 5.5V

z Junction Temperature Range -------------------------------------------------------------------------------------

−40°C to 125°C

z Ambient Temperature Range -------------------------------------------------------------------------------------

−40°C to 85°C

Electrical Characteristics

(VIN = 12V, TA = 25°C unless otherwise specified)

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

 

Feedback Reference Voltage

VFB

4.5V ≤ VIN ≤ 24V

0.784

0.8

0.816

V

 

Feedback Current

 

 

IFB

VFB = 0.8V

--

0.1

0.3

μA

 

Switch On Resistance

RDS(ON)

 

--

0.3

--

Ω

 

Switch Leakage

 

 

 

VEN = 0V, VPHASE = 0V

--

--

10

μA

 

Current Limit

 

 

ILIM

VBOOT − VPHASE = 4.8V

1.6

2.1

--

A

 

Oscillator Frequency

fSW

 

1.2

1.4

1.6

MHz

 

Maximum Duty Cycle

 

 

--

80

--

%

 

Minimum On-Time

tON

 

--

100

--

ns

 

Under Voltage Lockout

 

Rising

3.9

4.2

4.5

V

 

Threshold

 

 

 

 

 

 

 

 

 

 

 

 

 

Under Voltage Lockout

 

 

--

200

--

mV

 

Threshold Hysteresis

 

 

 

 

 

 

 

 

 

 

EN Input Voltage

 

Logic-High

VIH

 

1.4

--

--

V

 

 

Logic-Low

VIL

 

--

--

0.4

 

EN Pull Up Current

 

VEN = 0V

--

1

--

μA

 

 

 

 

 

 

 

 

To be continued

 

 

 

 

 

 

 

 

 

 

DS8259-03 March

2011

 

 

 

 

www.richtek.com

 

 

 

 

 

 

 

 

3

RT8259

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

Shutdown Current

ISHDN

VEN = 0V

--

25

--

μA

Quiescent Current

IQ

VEN = 2V, VFB = 1V (Not Switching)

--

0.55

1

mA

Thermal Shutdown

TSD

 

--

150

--

°C

Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability.

Note 2. θJA is measured in the natural convection at TA = 25°C on a high effective four layers thermal conductivity test board of JEDEC 51-7 thermal measurement standard.

Note 3. Devices are ESD sensitive. Handling precaution is recommended.

Note 4. The device is not guaranteed to function outside its operating conditions.

www.richtek.com

DS8259-03 March 2011

4

 

Richtek RT8259GE, RT8259GJ6, RT8259PE Schematic

RT8259

Typical Operating Characteristics

Efficiency vs. Load Current

 

100

 

 

 

 

 

 

 

 

VIN = 12V

 

90

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

80

 

 

 

 

 

 

 

 

VIN = 24V

 

 

 

 

 

 

 

 

 

 

 

 

(%)

70

 

 

 

 

 

 

 

 

 

 

 

60

 

 

 

 

 

 

 

 

 

 

 

Efficiency

50

 

 

 

 

 

 

 

 

 

 

 

40

 

 

 

 

 

 

 

 

 

 

 

30

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20

 

 

 

 

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

 

VOUT = 5V

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

Efficiency vs. Load Current

 

100

 

 

 

 

 

 

 

 

 

 

 

 

90

 

 

 

 

 

 

 

 

VIN = 12V

 

80

 

 

 

 

 

 

 

 

VIN = 24V

 

70

 

 

 

 

 

 

 

 

(%)

 

 

 

 

 

 

 

 

 

 

 

60

 

 

 

 

 

 

 

 

 

 

 

Efficiency

 

 

 

 

 

 

 

 

 

 

 

50

 

 

 

 

 

 

 

 

 

 

 

40

 

 

 

 

 

 

 

 

 

 

 

30

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20

 

 

 

 

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

VOUT = 3.3V

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

Load Current (A)

Load Current (A)

Output Voltage vs. Load Current

Output Voltage vs. Temperature

 

3.333

 

 

 

 

 

 

 

 

 

 

 

 

3.38

 

3.328

 

 

 

 

 

 

 

 

 

 

 

 

3.36

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(V)

3.323

 

 

 

 

 

 

 

 

 

 

 

(V)

3.34

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Output Voltage

3.318

 

VIN = 24V

 

 

 

 

 

 

 

Output Voltage

3.32

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.30

3.313

 

VIN = 12V

 

 

 

 

 

 

 

3.28

 

 

 

 

 

 

 

 

 

 

 

 

3.308

 

 

 

 

 

 

 

 

 

 

 

3.26

 

 

 

 

 

 

 

 

 

 

 

 

 

3.303

 

 

 

 

 

 

 

 

 

 

 

 

3.24

 

3.298

 

 

 

 

 

 

 

 

 

 

 

 

3.22

 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

 

 

 

 

 

 

 

VIN = 24V

 

 

 

 

 

 

 

VIN = 12V

 

 

 

 

 

 

 

IOUT = 0A

-50

-25

0

25

50

75

100

125

Load Current (A)

Temperature (°C)

Frequency vs. Input Voltage

Frequency vs. Temperature

 

1.55

 

 

 

 

 

 

 

 

1.55

 

1.50

 

 

 

 

 

 

 

 

1.50

(MHz)

1.45

 

 

 

 

 

 

 

(MHz)

1.45

1.40

 

 

 

 

 

 

 

1.40

 

 

 

 

 

 

 

 

 

Frequency

1.35

 

 

 

 

 

 

 

Frequency

1.35

1.30

 

 

 

 

 

 

 

1.30

1.25

 

 

 

 

 

 

 

1.25

 

 

 

 

 

 

 

 

 

 

1.20

 

 

 

VOUT = 3.3V, IOUT = 0.3A

1.20

 

1.15

 

 

 

1.15

 

 

 

 

 

 

 

 

 

 

4

6.5

9

11.5

14

16.5

19

21.5

24

 

 

 

 

VIN = 12V, VOUT = 3.3V, IOUT = 0.3A

-50

-25

0

25

50

75

100

125

Input Voltage (V)

Temperature (°C)

 

 

DS8259-03 March 2011

www.richtek.com

 

5

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