Richtek RT8068AZQW, RT8068AZSP Schematic [ru]

3A, 1MHz, Synchronous Step-Down Converter

RT8068A

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 V

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 require-

ments of IPC/JEDEC J-STD-020.

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

Marking Information

RT8068AZQW

13 : Product Code

13 YM

DNN

YMDNN : Date Code

Features



High Efficiency : Up to 95%





 Low R



Internal Switches : 69m

DS(ON)

ΩΩ

Ω/49m

ΩΩ

= 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)

GND

PVIN

SVIN

PVIN

SVIN

PGOOD

WDFN-10L 3x3

PGOOD

SOP-8 (Exposed Pad)

ΩΩ

Ω at V

ΩΩ

RT8068AZSP

RT8068AZSP : Product Code

RT8068A

YMDNN : Date Code

ZSPYMDNN

DS8068A-05 June 2015 www.richtek.com

RT8068A

Typical Application Circuit

PGOOD

Chip Enable

R1 100k

10µF

RT8068A

PGOOD

PVIN

1µF

SVIN

GND

OUT

FB1

FB2

Table 1. Recommended Component Selection

(V) R

OUT

(k) R

FB1

(k) C

FB2

(pF) L (H) C

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

OUT

(F)

Functional Pin Description

Pin No.

WDFN-10L

SOP-8

(Exposed Pad)

1, 2, 3 1, 2 LX Switch Node. Connect this pin to the induc tor.

4 3 PGOOD

5 4 EN Enable Contro l. P ull high to turn on. Do not fl oat.

6 5 FB

7 -- NC No Internal Connection.

8 6 SVIN

9,10 7,8 PVI N

(Exposed Pad)

Name

GND

Pin Function

Power Good Indicator. This pin is an open drain logic output that is pulled to ground when the output voltage is less than 90 % of the target output voltage. Hysteresis = 5%.

Feedback Pin. Th is pin receives the feedback voltage from a resistive voltage divider connected ac ross the output.

Signal Input Pin. Decouple th is pin to GND wit h a t least 1F ceramic cap. Power Input Pin. Decouple this pin to GND with at least 4.7F ceramic cap. Ground. The exposed pa d must be soldered t o a large PCB and connected to GND for maximum power dissipation.

DS8068A-05 June 2015www.richtek.com

Function Block Diagram

RT8068A

PGOOD

REF

0.6V

POR

SVIN

Int-SS

Output Clamp

0.72V

0.54V

0.4V

OSC

PGOOD

Slope

Com

Control

Logic

OTP

ISEN

Limit

PVIN

Driver

NISEN

Zero Current

100

DS8068A-05 June 2015 www.richtek.com

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, P

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

@ TA = 25°C

Recommended Operating Conditions

 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

(Note 4)

Electrical Characteristics

(VIN = 3.3V, T

Feedback Reference Voltage V

Feedback Leakage Current IFB -- 0.1 0.4 A

DC Bias Current

Output Voltage Line Regulation

Output Voltage Load Regulation I Switch Leakage Current -- -- 1 A

Switching Frequency 0.8 1 1.2 MHz

Switch On Resistance, High R

Switch On Resistance, Low R

P-MOSFET Current Limit I

= 25°C, unless otherwise specified)

Parameter Symbol Test Conditions Min Typ Max Unit

0.594 0.6 0.606 V

REF

Active , V Switching

= 0.7V, Not

-- 110 140

A

Shutdown -- -- 1

= 2.7V to 5.5V

= 0A

OUT

= 0A to 3A 1 -- 1 %

OUT

DS(ON)_P

DS(ON)_N

LIM

VIN = 5V -- 69 -- m

VIN = 5V -- 49 -- m

4 -- -- A

-- 0.3 -- %/V

DS8068A-05 June 2015www.richtek.com

Parameter Symbol Test Conditions Min Typ Max Unit

Under Voltage Lockout

Threshold

UVLO

RT8068A

Rising 2.2 2.4 2.6

VIN Falling 2 2.2 2.4

EN Input

Threshold Voltage

Logic-High V

Logic-Low VIL -- -- 0.4

1.6 -- --

EN Pull Low Resistance -- 500 -- k

Over Temperature Protection TSD -- 150 -- C

Over Temperature Protection

Hysteresis

-- 20 -- C

Soft-Start Time tSS 500 -- -- s

Discharge Resistance -- 100 -- 

OUT

Over Voltage Protection

OUT

(Latch-Off, Delay Time = 10s)

Under Voltage Lock Out

OUT

(Latch-Off)

Power Good

115 120 130 %

57 66 75 %

Measured FB, With Respect to

REF

85 90 -- %

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. θ

Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.

is measured at T

measured at the exposed pad of the package.

= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is

DS8068A-05 June 2015 www.richtek.com

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