Richtek RT8055GQW, RT8055GSP, RT8055ZQW Schematic [ru]

®

RT8055

3A, 2MHz, Synchronous Step-Down Converter

General Description

The RT8055 is a high efficiency synchronous, step-down DC/DC converter. Its input voltage range is from 2.6V to 5.5V and provides an adjustable regulated output voltage from 0.8V to 5V while delivering up to 3A of output current.

The internal synchronous low on-resistance power switches increase efficiency and eliminate the need for an external Schottky diode. The switching frequency is set by an external resistor. The 100% duty cycle provides low dropout operation extending battery life in portable systems. Current mode operation with external compensation allows the transient response to be optimized over a wide range of loads and output capacitors.

The RT8055 is operated in forced continuous PWM Mode which minimizes ripple voltage and reduces the noise and RF interference.

The RT8055 is available in the WDFN-10L 3x3 and SOP-8 (Exposed Pad) packages.

Features

zHigh Efficiency : Up to 95%

zLow RDS(ON) Internal Switches : 100mΩ

zProgrammable Frequency : 300kHz to 2MHz

zNo Schottky Diode Required

z0.8V Reference Voltage Allows for Low Output Voltage

zForced Continuous Mode Operation

z100% Duty Cycle Operation

zInput Over Voltage Protection

zRoHS Compliant and Halogen Free

Applications

zPortable Instruments

zBattery-Powered Equipment

zNotebook Computers

zDistributed Power Systems

zIP Phones

zDigital Cameras

z3G/3.5GData Card

Ordering Information

RT8055

Package Type

QW : WDFN-10L 3x3 (W-Type)

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

Lead Plating System

G : Green (Halogen Free and Pb Free) 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.

Pin Configurations

(TOP VIEW)

SHDN/RT 1

 

 

10

COMP

GND 2

 

GND

9

FB

LX 3

 

8

VDD

 

 

LX 4

 

 

7

PVDD

PGND 5

 

11 6

PVDD

WDFN-10L 3x3

SHDN/RT

 

 

8

COMP

GND

2

GND

7

FB

LX

3

6

VDD

9

PGND

4

5

PVDD

 

SOP-8 (Exposed Pad)

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8055-05 November 2012

www.richtek.com

 

1

RT8055

Marking Information

RT8055GQW

RT8055GSP

 

 

 

JN= : Product Code

 

 

RT8055GSP : Product Number

 

 

 

RT8055

 

JN=YM

YMDNN : Date Code

 

YMDNN : Date Code

 

 

 

GSPYMDNN

 

 

DNN

 

 

 

 

 

 

 

 

 

 

RT8055ZQW

JN : Product Code

YMDNN : Date Code

JN YM

DNN

Typical Application Circuit

VIN

 

 

 

 

 

 

 

5V

 

 

 

 

 

 

CIN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

22µF

 

 

 

 

 

 

 

 

C1

0.1µF

ROSC

180k

 

 

L1

 

 

PVDD

LX

2µH

 

VOUT

 

 

 

 

3.3V/3A

RT8055

 

 

 

R1

COUT

VDD

 

 

22µF x 2

 

 

75k

 

 

 

 

 

FB

 

R2

 

 

 

 

 

SHDN/RT

COMP

 

24k

 

GND

 

RCOMP

 

 

 

30k

 

 

PGND

 

CCOMP

 

 

 

 

470pF

 

 

Table 1. Recommended Component Selection

VOUT

R1 (kΩ)

R2 (kΩ)

RCOMP (kΩ)

CCOMP (nF)

L1 (μH)

COUT (μF)

3.3

75

24

30

0.47

2.2

22 x 2

 

 

 

 

 

 

 

2.5

51

24

27

0.47

2.2

22 x 2

 

 

 

 

 

 

 

1.8

30

24

22

0.47

2.2

22 x 2

 

 

 

 

 

 

 

1.5

21

24

18

0.47

2.2

22 x 2

 

 

 

 

 

 

 

1.2

12

24

15

0.47

1.0

22 x 2

 

 

 

 

 

 

 

1.0

6

24

13

0.47

1.0

22 x 2

 

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8055-05 November 2012

2

Richtek RT8055GQW, RT8055GSP, RT8055ZQW Schematic

RT8055

Functional Pin Description

Pin No.

 

Pin Name

Pin Function

WDFN-10L 3x3

 

SOP-8

 

 

 

 

 

 

 

Shutdown Control or Frequency Setting Input. Connect a

1

 

1

SHDN/RT

resistor to ground from this pin sets the switching frequency.

 

 

 

 

Force this pin to VDD or GND causes the device to be shut down.

 

 

 

 

Signal Ground. All small-signal components and compensation

2,

 

2,

 

components should be connected to this ground, which in turn

 

GND

connects to PGND at one point. The exposed pad must be

11 (Exposed Pad)

9 (Exposed Pad)

 

 

 

 

soldered to a large PCB and connected to GND for maximum

 

 

 

 

power dissipation.

3, 4

 

3

LX

Internal Power MOSFET Switches Output. Connect this pin to

 

the inductor.

 

 

 

 

5

 

4

PGND

Power Ground. Connect this pin close to the negative terminal of

 

CIN and COUT.

 

 

 

 

6, 7

 

5

PVDD

Power Supply Input. Decouple this pin to PGND with a capacitor.

 

 

 

 

 

8

 

6

VDD

Signal Supply Input. Decouple this pin to GND with a capacitor.

 

Generally, VDD is equal to PVDD.

 

 

 

 

9

 

7

FB

Feedback Pin. This pin receives the feedback voltage from a

 

resistive divider connected across the output.

 

 

 

 

 

 

 

 

Error Amplifier Compensation Point. The current comparator

10

 

8

COMP

threshold increases with this control voltage. Connect external

 

 

 

 

compensation elements to this pin to stabilize the control loop.

Function Block Diagram

 

 

 

 

 

 

 

SHDN/RT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PVDD

 

 

 

SD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ISEN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OSC

 

 

 

Slope

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

COMP

 

 

 

 

 

 

 

 

Comp.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.8V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OC

 

 

 

 

 

 

 

 

 

 

 

 

EA

 

Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FB

 

 

 

Clamp

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Limit

 

 

 

 

 

 

 

 

 

 

 

LX

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Internal -

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Driver

 

 

 

 

 

 

 

 

 

 

 

 

Soft Star

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Control

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0.7V

 

 

 

 

 

Logic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NISEN

 

 

 

 

 

 

PGND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OTP

 

 

 

 

 

 

 

 

 

 

 

POR

 

0.4V

 

 

 

 

 

 

 

 

 

 

N-MOSFET ILIM

 

 

 

 

GND

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VDD

 

 

 

 

 

 

 

 

 

 

 

 

 

VREF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

 

 

 

 

 

 

 

 

is a registered trademark of Richtek Technology Corporation.

DS8055-05 November 2012

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

www.richtek.com

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

RT8055

Absolute Maximum Ratings

(Note 1)

 

 

 

 

 

 

z Supply Input Voltage, VDD, PVDD

----------------------------------------------------------------------------

 

 

 

 

−0.3V to 6.5V

 

z LX Pin Switch Voltage --------------------------------------------------------------------------------------------

 

 

 

 

 

−0.3V to (PVDD + 0.3V)

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

 

 

 

 

 

−5V to 8.5V

 

z Other I/O Pin Voltages -------------------------------------------------------------------------------------------

 

 

 

 

 

−0.3V to 6.5V

 

z LX Pin Switch Current --------------------------------------------------------------------------------------------

 

 

 

 

 

4A

 

 

 

z Power Dissipation, PD @ TA = 25°C

 

 

 

 

 

 

 

 

WDFN-10L 3x3 -----------------------------------------------------------------------------------------------------

 

 

 

 

 

1.667W

 

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

 

 

 

 

 

1.333W

 

z Package Thermal Resistance (Note 2)

 

 

 

 

 

 

 

 

WDFN-10L 3x3, θJA -----------------------------------------------------------------------------------------------

 

 

 

 

 

60°C/W

 

WDFN-10L 3x3, θJC -----------------------------------------------------------------------------------------------

 

 

 

 

 

7.8°C/W

 

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

 

 

 

 

 

75°C/W

 

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

 

 

 

 

 

15°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 Model) --------------------------------------------------------------------------------------

 

 

 

 

 

2kV

 

 

 

Recommended Operating Conditions

(Note 4)

 

 

 

 

 

z Supply Input Voltage ----------------------------------------------------------------------------------------------

 

 

 

 

 

2.6V to 5.5V

 

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

 

 

 

 

 

−40°C to 125°C

 

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

 

 

 

 

 

−40°C to 85°C

 

Electrical Characteristics

 

 

 

 

 

 

 

 

(VDD = 3.3V, TA = 25°C, unless otherwise specified)

 

 

 

 

 

 

Parameter

 

Symbol

 

Test Conditions

Min

Typ

Max

 

Unit

 

 

 

 

 

 

 

 

 

 

 

Input Voltage Range

 

VDD

 

 

 

2.6

--

5.5

 

V

 

 

 

 

 

 

 

 

 

 

 

Feedback Reference Voltage

 

VREF

 

 

 

0.784

0.8

0.816

 

V

Feedback Leakage Current

 

IFB

 

VFB = 3.3V

 

--

--

0.1

 

μA

DC Bias Current

 

 

 

Active , VFB = 0.7V, Not Switching

--

500

--

 

μA

 

 

 

Shutdown

 

--

--

1

 

μA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Output Voltage Line Regulation

 

VLINE

 

VIN = 2.6V to 5.5V

--

0.1

--

 

%/V

Output Voltage Load Regulation

 

VLOAD

 

VIN = 5V, VOUT = 3.3V,

--

0.4

--

 

%

 

 

IOUT = 0A to 3A

 

Error Amplifier

 

gm

 

 

 

--

400

--

 

μA/V

Transconductance

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Current Sense Transresistance

 

RS

 

 

 

--

0.4

--

 

Ω

RT Leakage Current

 

 

 

SHDN/RT = VIN = 5.5V

--

--

1

 

μA

 

 

 

 

 

 

 

 

 

 

 

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

 

www.richtek.com

 

 

 

 

DS8055-05

November 2012

4

RT8055

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

 

 

 

 

 

 

 

 

 

ROSC = 180kΩ

1.44

1.8

2.16

 

Switching Frequency

 

 

 

 

 

MHz

 

Adjustable Switching Frequency

0.3

--

2

 

 

 

 

 

Range

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch On Resistance, High

RDS(ON)_P

ISW = 0.3A

--

100

160

Switch On Resistance, Low

RDS(ON)_N

ISW = 0.3A

--

100

170

Peak Current Limit

ILIM

 

3.5

--

--

A

Under Voltage Lockout

 

VDD Rising @Full Temperature

2.33

2.4

2.57

V

Threshold (Note 5)

 

VDD Falling @Full Temperature

1.98

2.2

2.37

 

 

Shutdown Threshold

VSHDN

VSHDN Rising

--

VIN − 0.85

VIN − 0.4

V

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. Devices are ESD sensitive. Handling precaution is recommended.

Note 4. The device is not guaranteed to function outside its operating conditions. Note 5. Guaranteed by design.

Copyright ©2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8055-05 November 2012

www.richtek.com

 

5

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