Richtek RT8055GQW, RT8055GSP, RT8055ZQW Schematic [ru]

®

3A, 2MHz, Synchronous Step-Down Converter

RT8055

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 a n 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 exter

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 loa ds and output ca pacitors.

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

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

nal Schottky diode. The switching frequency is

Features

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High Efficiency : Up to 95%

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z Low R

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z Programmable Frequency : 300kHz to 2MHz

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z No Schottky Diode Required

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z 0.8V Reference Voltage Allows for Low Output

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Internal Switches : 100m

DS(ON)

ΩΩ

Ω

ΩΩ

Voltage

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z Forced Continuous Mode Operation

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z 100% Duty Cycle Operation

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z Input Over Voltage Protection

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z RoHS Compliant and Halogen Free

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Applications

z Portable Instruments
z Battery-Powered Equipment
z Notebook Computers
z Distributed Power Systems
z IP Phones
z Digital Camera s
z 3G/3.5G Data 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 require-

ments of IPC/JEDEC J-STD-020.

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

Pin Configurations

(TOP VIEW)

SHDN/RT

SHDN/RT

GND

PGND

1
2

GND

3

LX

4

LX

5

PGND

WDFN-10L 3x3

2

GND

3

LX

4

SOP-8 (Exposed Pad)

GND

11

10

COMP

9

FB

8

VDD

7

PVDD

6

PVDD

8

COMP

7

FB

6

9

VDD

5

PVDD

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DS8055-05 November 2012 www.richtek.com

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RT8055

Marking Information

RT8055GQW RT8055GSP

JN= : Product Code

JN=YM

YMDNN : Date Code

DNN

RT8055ZQW

JN : Product Code

JN YM

YMDNN : Date Code

DNN

Typical Application Circuit

V

IN

5V

C

IN

22µF

C1

0.1µF

R
180k

OSC

PVDD

RT8055

VDD

SHDN/RT
GND

PGND

COMP

RT8055
GSPYMDNN

L1

2µH

LX

FB

R
30k

COMP

C

COMP

470pF

RT8055GSP : Product Number
YMDNN : Date Code

V

OUT

3.3V/3A

OUT

R1
75k

R2
24k

C
22µF x 2

Table 1. Recommended Component Selection

V

R1 (kΩ) R2 (kΩ) R

OUT

COMP

(kΩ) C

(nF) L1 (μH) C

COMP

OUT

(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

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Functional Pin Description

RT8055

Pin No.

WDFN-10L 3x3 SOP-8

1 1 SHDN/RT

2,

11 (Exposed Pad)

9 (Expos ed Pad)

2,

3, 4 3 LX

5 4 PGND

6, 7 5 PVDD Powe r Supp ly Input. D eco upl e this pin to P G ND with a cap aci tor .

8 6 VDD

9 7 FB

10 8 COMP

Pin Name Pin Function

Shutdown Control or Frequency Setting Input. Connect a
resistor to ground from this pin sets the switching frequency.
Force t hi s pin to V

or GND caus es the dev ice to be shu t dow n.

DD

Signal Ground. All small-signal components and compensation
com pon ent s sh ou ld b e co nn ect ed t o th is g ro und , wh ich in t urn

GND

connects to PGND at one point. The exposed pad must be
soldered to a large PCB and connected to GND for maximum
power dissipation.
Internal Power MOSFET Switches Output. Connect this pin to
the inductor.
Powe r Ground. Conne ct this pin cl ose to the neg ativ e termin al of
C

and C

IN

OUT

.

Signal Supply Input. Dec ouple this pin to GND with a capac itor.
Generally, V

is equal to PVDD.

DD

Feedback Pin. This pin receives the feedback voltage from a
resistive d ivider connected acr oss the output.
Error Amplifier Compensation Point. The current comparator
threshold increases with this control voltage. Connect external
compens ation elem ents to this pin to stabilize the control loop.

Function Block Diagram

SD

COMP

0.8V

FB

EA

Internal ­Soft Star

POR

VDD

SHDN/RT

Output
Clamp

0.7V

0.4V

OSC

Slope

Comp.

Control

Logic

OTP

VREF

ISEN

OC

Limit

Driver

NISEN

N-MOSFET I

PVDD

LX

PGND

LIM

GND

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DS8055-05 November 2012 www.richtek.com

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RT8055

Absolute Maximum Ratings (Note 1)

z Supply Input V oltage, V DD, PV DD ----------------------------------------------------------------------------−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, P

W D FN-10L 3x3-----------------------------------------------------------------------------------------------------1.667W

SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------1.333W

z Package Thermal Re sistance (Note 2)

W DFN-10L 3x3, θJA-----------------------------------------------------------------------------------------------6 0 °C/W

WDFN-10L 3x3, θJC-----------------------------------------------------------------------------------------------7.8°C/W
SOP-8 (Exposed Pad), θJA-------------------------------------------------------------------------------------7 5 °C/W
SOP-8 (Exposed Pad), θJC-------------------------------------------------------------------------------------1 5 °C/W

z Junction T emperature---------------------------------------------------------------------------------------------150°C
z Lead Temperature (Soldering, 10 sec.)-----------------------------------------------------------------------260°C
z Storage T emperature Range ------------------------------------------------------------------------------------−65°C to 150°C
z ESD Susceptibility (Note 3)

HBM (Human Body Model)--------------------------------------------------------------------------------------2kV

@ TA = 25°C

D

Recommended Operating Conditions (Note 4)

z Supply Input V oltage----------------------------------------------------------------------------------------------2.6V to 5.5V
z Junction T emperature Range------------------------------------------------------------------------------------
z Ambient T emperature Range------------------------------------------------------------------------------------

−40°C to 125°C

−40°C to 85°C

Electrical Characteristics

(V

= 3.3V, T

DD

Input Voltage Range VDD 2.6 -- 5.5 V
Feedback Reference Voltage V
Feedback Leakage Current IFB V

DC Bias Current

Output Voltage Line Regulation ΔV
Output Voltage Load Regulation ΔV
Error Amplifier

Transconductance

= 25°C, unless otherwise specified)

A

Parameter Symbol Test Conditions Min Typ Max Unit

0.784 0.8 0.816 V

REF

= 3.3V -- -- 0.1 μA

FB

Active , VFB = 0.7V, Not Switchin g -- 500 - - μA
Shutdown -- -- 1 μA

VIN = 2.6V to 5.5V -- 0.1 -- %/V

LINE

LOAD

= 5V, V

V

IN

I

= 0A to 3A

OUT

= 3.3V,

OUT

-- 0.4 -- %

gm -- 400 -- μA/V

Current Sense Transresistance RS -- 0.4 -- Ω
RT Leakage Current SHDN/RT = VIN = 5.5V -- -- 1 μA

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Parameter Symbol Test Conditions Min Typ Max Unit

Switch ing Frequency

RT8055

R

= 180kΩ 1.44 1.8 2.16

OSC

Adjustable Switching Frequency
Range

0.3 -- 2

MHz

Switch On Resistance, High R
Switch On Resistance, Low R
Peak Current Limit I

Under Voltage Lockout
Threshold (Note 5)

Shutdown Threshold 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. θ

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.

is measured at T

JA

measured at the exposed pad of the package.

DS(ON)_P ISW
DS(ON)_N ISW

3.5 -- -- A

LIM

V
V

V

SHDN

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

A

= 0.3A -- 100 160 mΩ
= 0.3A -- 100 170 mΩ

Rising @Full Temperature 2.33 2.4 2.57

DD

Falling @Full Temperature 1.98 2.2 2.37

DD

Rising -- VIN − 0.85 VIN − 0. 4 V

SHDN

V

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