Richtek RT7266ZSP Schematic [ru]

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®

RT7266

3A, 18V, 700kHz ACOTTM Synchronous Step-Down

Converter

General Description

The RT7266 is an adaptive on-time ACOTTM mode synchronous buck converter. The adaptive on-timeACOTTM mode control provides a very fast transient response with few external components. The low impedance internal MOSFET can support high efficiency operation with wide input voltage range from 4.5V to 18V . The proprietary circuit of the RT7266 enables to support all ceramic capacitors. The output voltage can be adjustable between 0.8V and 8V. The soft-start is adjustable by an external capacitor.

Ordering Information

RT7266

Package Type

SP : SOP-8 (Exposed Pad-Option 2)

Lead Plating System

Z : ECO (Ecological Element with 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.

Features

zACOTTM Mode Enables Fast Transient Response

z4.5V to 18V Input Voltage Range

z3A Output Current

z60mΩ Internal Low Site N-MOSFET

zAdaptive On-Time Control

zFast Transient Response

zSupport All Ceramic Capacitors

zUp to 95% Efficiency

z700kHz Switching Frequency

zAdjustable Output Voltage from 0.8V to 8V

zAdjustable Soft-Start

zCycle-by-Cycle Current Limit

zInput Under Voltage Lockout

zThermal Shutdown Protection

zRoHS Compliant and Halogen Free

Applications

zIndustrial and Commercial Low Power Systems

zComputer Peripherals

zLCD Monitors and TVs

zGreen Electronics/Appliances

zPoint of Load Regulation for High-Performance DSPs, FPGAs, and ASICs

Marking Information

Pin Configurations

 

 

RT7266

RT7266ZSP : Product Number

 

(TOP VIEW)

 

YMDNN : Date Code

 

 

 

 

 

 

ZSPYMDNN

 

 

 

 

 

EN

 

8

VIN

 

 

 

 

 

FB

2

7

BOOT

 

 

PVCC

GND

 

SW

 

 

3

6

 

 

SS

9

 

GND

 

 

4

5

SOP-8 (Exposed Pad)

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS7266-02 September 2012

www.richtek.com

 

1

RT7266

Typical Application Circuit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8

RT7266

6

 

1.4µH

 

 

 

 

 

 

 

 

 

 

 

VOUT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIN

SW

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.05V/3A

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C1

 

 

 

 

 

 

C2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C6

 

 

 

 

 

 

 

 

 

 

 

C7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

10µF x 2

 

 

 

 

 

 

0.1µF

 

 

7

 

0.1µF

C3

 

 

R1

 

 

 

 

 

22µF x 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8.25k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Chip

Enable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

EN

BOOT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5, 9 (Exposed Pad)

GND

FB

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

R2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SS

PVCC

 

 

VPVCC

 

 

 

 

 

22.1k

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C5

 

 

 

 

C4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3.9nF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1µF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1. Suggested Component Values

VOUT (V)

R1 (kΩ)

R2 (kΩ)

C3 (pF)

L1 (μH)

C7 (μF)

1

6.81

22.1

--

1.4

22 to 68

 

 

 

 

 

 

1.05

8.25

22.1

--

1.4

22 to 68

 

 

 

 

 

 

1.2

12.7

22.1

--

1.4

22 to 68

 

 

 

 

 

 

1.8

30.1

22.1

5 to 22

2

22 to 68

 

 

 

 

 

 

2.5

49.9

22.1

5 to 22

2

22 to 68

 

 

 

 

 

 

3.3

73.2

22.1

5 to 22

2

22 to 68

 

 

 

 

 

 

5

124

22.1

5 to 22

3.3

22 to 68

 

 

 

 

 

 

7

180

22.1

5 to 22

3.3

22 to 68

 

 

 

 

 

 

Functional Pin Description

Pin No.

Pin Name

 

Pin Function

 

 

 

 

Enable Input. A logic-high enables the converter; a logic-low forces the RT7266

 

1

EN

into shutdown mode reducing the supply current to less than 10μA. Attach this

 

 

 

pin to VIN with a 100kΩ pull up resistor for automatic start-up.

 

 

 

 

Feedback Input. It is used to regulate the output of the converter to a set value

 

2

FB

via an external resistive voltage divider. The feedback reference voltage is

 

 

 

0.765V typically.

 

 

 

3

PVCC

Internal Regulator

Output. Connect a 1μF capacitor to GND to stabilize

 

output voltage.

 

 

 

 

 

 

 

 

 

 

Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor

 

4

SS

from SS to GND to set the soft-start period. A 3.9nF capacitor sets the soft-start

 

 

 

period to 1.5ms.

 

 

 

5, 9 (Exposed pad)

GND

Ground. The Exposed pad should be soldered to a large PCB and connected to

 

GND for maximum thermal dissipation.

 

 

 

 

 

 

6

SW

Switch Node. Connect this pin to an external L-C filter.

 

 

 

 

 

 

 

7

BOOT

Bootstrap for High Side Gate Driver. Connect a 0.1μF or

greater ceramic

 

capacitor from BOOT to SW pins.

 

 

 

 

 

 

8

VIN

Supply Input. The input voltage range is from 4.5V to 18V. Must bypass with a

 

suitable large ( ≥10μF x 2) ceramic capacitor.

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

 

 

DS7266-02

September 2012

2

 

 

 

 

 

Richtek RT7266ZSP Schematic

RT7266

Function Block Diagram

VIN

 

 

 

 

 

 

 

PVCC

Reg

 

 

 

 

 

BOOT

 

 

 

 

 

 

UGATE

 

 

OC

Control

Driver

 

SW

 

 

 

 

 

 

LGATE

GND

SS

Soft-Start

 

 

 

 

 

FB

On-Time

+

 

 

 

EN

EN

 

 

-

Comparator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VREF

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS7266-02 September 2012

www.richtek.com

3

RT7266

Absolute Maximum Ratings

(Note 1)

 

 

 

 

 

 

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

 

 

 

 

 

−0.3V to 20V

 

z Switch Voltage, SW -----------------------------------------------------------------------------------------------

 

 

 

 

 

−0.8V to (VIN + 0.3V)

< 10ns-----------------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

−5V to 25V

 

z BOOT to SW --------------------------------------------------------------------------------------------------------

 

 

 

 

 

 

−0.3V to 6V

 

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

 

 

 

 

 

 

−0.3V to 6V

 

z Power Dissipation, PD @ TA = 25°C

 

 

 

 

 

 

 

 

SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------

 

 

 

 

 

1.333W

 

z Package Thermal Resistance

(Note 2)

 

 

 

 

 

 

 

 

SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------

 

 

 

 

 

75°C/W

 

SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------

 

 

 

 

 

15°C/W

 

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

 

 

 

 

 

150°C

 

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

 

 

 

 

260°C

 

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

 

 

 

 

 

−65°C to 150°C

Recommended Operating Conditions

(Note 3)

 

 

 

 

 

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

 

 

 

 

 

4.5V to 18V

 

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

Supply Current

 

 

 

 

 

 

 

 

 

 

Shutdown Current

ISHDN

 

VEN = 0V

 

--

1

10

 

μA

Quiescent Current

IQ

 

VEN = 3V, VFB = 1V

--

0.7

--

 

mA

Logic Threshold

 

 

 

 

 

 

 

 

 

 

EN Voltage

 

Logic-High

 

 

 

 

2

--

5.5

 

V

 

 

 

 

 

 

 

 

 

 

 

Logic-Low

 

 

 

 

--

--

0.4

 

 

 

 

 

 

 

 

 

VREF Voltage and Discharge Resistance

 

 

 

 

 

 

 

 

Feedback Reference Voltage

VREF

 

4.5V ≤ VIN ≤ 18V

0.753

0.765

0.777

 

V

Feedback Input Current

IFB

 

VFB = 0.8V

 

−0.1

0

0.1

 

μA

VPVCC Output

 

 

 

 

 

 

 

 

 

 

VPVCC Output Voltage

VPVCC

 

6V ≤ VIN ≤ 18V, 0 < IPVCC < 5mA

4.7

5.1

5.5

 

V

Line Regulation

 

 

 

6V ≤ VIN ≤ 18V, IPVCC = 5mA

--

--

20

 

mV

Load Regulation

 

 

 

0 < IPVCC < 5mA

--

--

60

 

mV

Output Current

 

IPVCC

 

VIN = 6V, VPVCC = 4V

--

110

--

 

mA

RDS(ON)

 

 

 

 

 

 

 

 

 

 

Switch On

 

High Side

RDS(ON)_H

 

 

 

--

90

--

 

Resistance

 

Low Side

RDS(ON)_L

 

 

 

--

60

--

 

 

 

 

 

 

 

Current Limit

 

 

 

 

 

 

 

 

 

 

Current limit

 

ILIM

 

 

 

3.5

4.1

5.7

 

A

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

 

 

 

 

 

DS7266-02

September 2012

4

 

 

 

 

 

 

 

 

 

 

 

RT7266

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

Thermal Shutdown

 

 

 

 

 

 

Thermal Shutdown Threshold

TSD

 

--

150

--

°C

Thermal Shutdown

TSD

 

--

20

--

Hysteresis

 

 

On-Time Timer Control

 

 

 

 

 

 

On-Time

tON

VIN = 12V, VOUT = 1.05V

--

145

--

ns

Minimum On-Time

tON(MIN)

 

--

60

--

ns

Minimum Off-Time

tOFF(MIN)

 

--

230

--

ns

Soft-Start

 

 

 

 

 

 

SS Charge Current

 

VSS = 0V

1.4

2

2.6

μA

SS Discharge Current

 

VSS = 0.5V

0.05

0.1

--

mA

UVLO

 

 

 

 

 

 

UVLO Threshold

 

VIN Rising to Wake up VPVCC

3.55

3.85

4.15

V

Hysteresis

 

 

--

0.3

--

 

 

 

Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 may affect device reliability.

Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package.

Note 3. The device is not guaranteed to function outside its operating conditions.

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS7266-02 September 2012

www.richtek.com

 

5

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