Richtek RT8068AZQW, RT8068AZSP Schematic [ru]

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®

RT8068A

3A, 1MHz, Synchronous Step-Down Converter

General Description

The RT8068A is a high efficiency synchronous, step-down DC/DC converter. It's input voltage range from 2.7V to 5.5V that provides an adjustable regulated output voltage from 0.6V to VIN 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 fixed internally at 1MHz. The 100% duty cycle provides low dropout operation, hence extending battery life in portable systems. Current mode operation with internal compensation allows the transient response to be optimized over a wide range of loads and output capacitors. The RT8068A is available in WDFN-10L 3x3 and SOP-8 (Exposed Pad) packages.

Ordering Information

RT8068A

Package Type

QW : WDFN-10L 3x3 (W-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.

Marking Information

RT8068AZQW

13 : Product Code

13 YM YMDNN : Date Code

DNN

RT8068AZSP

RT8068AZSP : Product Code

RT8068A YMDNN : Date Code

ZSPYMDNN

Features

High Efficiency : Up to 95%

Low RDS(ON) Internal Switches : 69mΩ/49mΩ at VIN = 5V

Fixed Frequency : 1MHz

No Schottky Diode Required

Internal Compensation

0.6V Reference Allows Low Output Voltage

Low Dropout Operation : 100% Duty Cycle

OCP, UVP, OVP, OTP

RoHS Compliant and Halogen Free

Applications

Portable Instruments

Battery Powered Equipment

Notebook Computers

Distrib uted Power Systems

IP Phones

Digital Cameras

Pin Configurations

(TOP VIEW)

LX

1

 

10

PVIN

LX

2

GND

9

PVIN

LX

3

8

SVIN

PGOOD 4

 

7

NC

EN 5

11

6

FB

WDFN-10L 3x3

LX

 

 

8

PVIN

LX

2

GND

7

PVIN

PGOOD

3

9

6

SVIN

EN

4

 

5

FB

SOP-8 (Exposed Pad)

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8068A-05 June 2015

www.richtek.com

 

1

RT8068A

Typical Application Circuit

 

 

RT8068A

L

 

PGOOD

R1

PGOOD

LX

 

VOUT

 

 

 

 

COUT

 

100k

 

 

 

CFF

V

 

PVIN

 

RFB1

IN

CIN

 

 

 

 

SVIN

FB

 

 

 

10µF

 

 

 

C1

 

 

 

 

 

 

RFB2

 

 

 

1µF

 

 

 

 

 

 

 

Chip Enable

 

EN

GND

 

 

 

 

 

 

Table 1. Recommended Component Selection

VOUT (V)

RFB1 (k )

RFB2 (k )

CFF (pF)

L ( H)

COUT ( F)

3.3

229.5

51

22

2

22 x 2

 

 

 

 

 

 

2.5

161.5

51

22

2

22 x 2

 

 

 

 

 

 

1.8

102

51

22

1.5

22 x 2

 

 

 

 

 

 

1.5

76.5

51

22

1.5

22 x 2

 

 

 

 

 

 

1.2

51

51

22

1.5

22 x 2

 

 

 

 

 

 

1.0

34

51

22

1.5

22 x 2

 

 

 

 

 

 

Functional Pin Description

Pin No.

Pin

Pin Function

 

 

SOP-8

 

WDFN-10L

Name

 

(Exposed Pad)

 

 

 

 

 

 

1, 2, 3

1, 2

LX

Switch Node. Connect this pin to the inductor.

 

 

 

 

 

 

 

 

Power Good Indicator. This pin is an open drain logic output that is

4

3

PGOOD

pulled to ground when the output voltage is less than 90% of the

 

 

 

target output voltage. Hysteresis = 5%.

 

5

4

EN

Enable Control. Pull high to turn on. Do not float.

 

 

 

 

 

 

6

5

FB

Feedback Pin. This pin receives the feedback

voltage from a

resistive voltage divider connected across the output.

 

 

 

7

--

NC

No Internal Connection.

 

 

 

 

 

8

6

SVIN

Signal Input Pin. Decouple this pin to GND with at least 1 F ceramic

cap.

 

 

 

 

 

9,10

7,8

PVIN

Power Input Pin. Decouple this pin to GND with

at least 4.7 F

ceramic cap.

 

 

 

 

 

11

9

GND

Ground. The exposed pad must be soldered to a large PCB and

(Exposed Pad)

(Exposed Pad)

connected to GND for maximum power dissipation.

 

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8068A-05 June 2015

2

 

Richtek RT8068AZQW, RT8068AZSP Schematic

RT8068A

Function Block Diagram

 

 

EN

 

 

 

 

 

EN

 

ISEN

PVIN

 

 

 

 

 

 

 

 

 

PGOOD

PGOOD

OSC

Slope

 

 

 

 

Com

 

 

 

 

 

 

 

 

VREF

 

 

 

 

 

0.6V

 

 

 

 

 

EA

Output

 

OC

 

FB

Clamp

 

Limit

 

 

 

 

 

 

Int-SS

 

 

 

Driver

 

 

0.72V

 

Control

LX

 

 

OV

 

 

 

 

Logic

 

 

 

 

 

 

 

 

0.54V

 

 

 

 

 

 

PGOOD

 

NISEN

 

 

 

 

Zero Current

 

 

0.4V

UV

 

 

 

 

 

 

 

POR

 

 

OTP

100

 

 

 

 

 

 

 

 

 

 

SVIN

 

 

 

 

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8068A-05 June 2015

www.richtek.com

 

3

RT8068A

Absolute Maximum Ratings (Note 1)

Supply Input Voltage, PVIN, SVIN-------------------------------------------------------------------------------------

−0.3V to 6.5V

LX Pin

 

DC -----------------------------------------------------------------------------------------------------------------------------

−0.3V to 6.8V

< 20ns -----------------------------------------------------------------------------------------------------------------------

−2.5V to 9V

Other I/O Pin Voltage -----------------------------------------------------------------------------------------------------

−0.3V to 6.5V

Power Dissipation, PD @ TA = 25°C

 

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

1.429W

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

1.333W

Package Thermal Resistance (Note 2)

 

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

70°C/W

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

8.2°C/W

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

75°C/W

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

15°C/W

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

260°C

Junction Temperature -----------------------------------------------------------------------------------------------------

150°C

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

−65°C to 150°C

ESD Susceptibility (Note 3)

 

HBM (Human Body Model) ----------------------------------------------------------------------------------------------

2kV

MM (Machine Model) -----------------------------------------------------------------------------------------------------

200V

Recommended Operating Conditions

(Note 4)

 

 

 

 

Supply Input Voltage, PVIN, SVIN

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

 

 

 

 

2.7V to 5.5V

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

 

 

 

 

 

−40°C to 125°C

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

 

 

 

 

 

−40°C to 85°C

Electrical Characteristics

 

 

 

 

 

 

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

 

 

 

 

 

 

Parameter

 

Symbol

Test Conditions

Min

Typ

Max

Unit

Feedback Reference Voltage

 

VREF

 

 

0.594

0.6

0.606

V

 

 

 

 

 

 

 

 

 

Feedback Leakage Current

 

IFB

 

 

--

0.1

0.4

A

 

 

 

Active , VFB = 0.7V, Not

--

110

140

 

DC Bias Current

 

 

Switching

 

A

 

 

 

 

 

 

 

 

 

Shutdown

 

--

--

1

 

Output Voltage Line Regulation

 

 

VIN = 2.7V to 5.5V

--

0.3

--

%/V

 

 

IOUT = 0A

 

 

 

 

 

 

 

 

 

Output Voltage Load Regulation

 

 

IOUT = 0A to 3A

1

--

1

%

Switch Leakage Current

 

 

 

 

--

--

1

A

 

 

 

 

 

 

 

 

 

Switching Frequency

 

 

 

 

0.8

1

1.2

MHz

 

 

 

 

 

 

 

 

 

Switch On Resistance, High

 

RDS(ON)_P

VIN = 5V

 

--

69

--

m

Switch On Resistance, Low

 

RDS(ON)_N

VIN = 5V

 

--

49

--

m

P-MOSFET Current Limit

 

ILIM

 

 

4

--

--

A

 

 

 

 

 

 

 

 

 

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS8068A-05 June 2015

4

 

RT8068A

Parameter

Symbol

Test Conditions

Min

Typ

Max

Unit

Under Voltage Lockout

VUVLO

VIN Rising

2.2

2.4

2.6

V

Threshold

 

VIN Falling

2

2.2

2.4

 

 

 

 

 

 

 

 

 

 

 

EN Input

Logic-High

VIH

 

1.6

--

--

V

Threshold Voltage

Logic-Low

VIL

 

--

--

0.4

 

 

 

 

 

 

 

 

 

 

EN Pull Low Resistance

 

 

--

500

--

k

Over Temperature Protection

TSD

 

--

150

--

C

Over Temperature Protection

 

 

--

20

--

C

Hysteresis

 

 

 

 

 

 

 

 

 

 

Soft-Start Time

 

tSS

 

500

--

--

s

VOUT Discharge Resistance

 

 

--

100

--

 

VOUT Over Voltage Protection

 

 

115

120

130

%

(Latch-Off, Delay Time = 10 s)

 

 

 

 

 

 

 

 

VOUT Under Voltage Lock Out

 

 

57

66

75

%

(Latch-Off)

 

 

 

 

 

 

 

 

 

 

Power Good

 

 

Measured FB, With Respect to

85

90

--

%

 

 

VREF

 

 

 

 

 

 

 

Power Good Hysteresis

 

 

--

5

--

%

 

 

 

 

 

 

 

 

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.

Copyright ©2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS8068A-05 June 2015

www.richtek.com

 

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