Richtek RT8011AGQW, RT8011APQW, RT8011GF, RT8011GQW, RT8011PF Schematic [ru]

2A, 4MHz, Synchronous Step-Down Regulator

RT8011/A

General Description

The RT801 1/A is a high efficiency synchronous, ste p-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 2A of output current.

The internal synchronous low on-resistance power

switches increase efficiency and eliminate the need for
an external Schottky diode. Switching frequency is set
by an external resistor or can be synchronized to an
external clock. 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 opti mized over a wide
range of loads a nd output ca pa citors.

RT801 1/A operation in f orced continuous PWM Mode which

minimizes ripple voltage and reduces the noise and RF
interference.

100% duty cycle in Low Dropout Operation further
maximize battery life.

Ordering Information

RT8011/A

Package Type
F : MSOP-10 (RT8011)
QW : WDFN-10L 3x3 (RT8011)
QW : WDFN-8EL 3x3 (RT8011A)

Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)

Without SYNC and PGOOD Function
With SYNC and PGOOD Function

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.

Features

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High Efficiency : Up to 95%

z

zz

zz

z Low R

zz

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z Programmable Frequency : 300kHz to 4MHz

zz

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z No Schottky Diode Required

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z 0.8V Reference Allows Low Output Voltage

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z Forced Continuous Mode Operation

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z Low Dropout Operation : 100% Duty Cycle

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z Synchronizable Switching Frequency (For RT8011

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Internal Switches : 110m

DS(ON)

ΩΩ

Ω

ΩΩ

Only)

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z Power Good Output Voltage Monitor (For RT8011

zz

Only)

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z RoHS Compliant and 100% Lead (Pb)-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

Pin Configurations

(TOP VIEW)

SHDN/RT

SYNC

GND

LX

PGND

SHDN/RT

SYNC

GND

LX

PGND

1
2
3
4
5

10

9
8
7

WDFN-10L 3x3

2
3
4
5

MSOP-10

COMP
FB
PGOOD
VDD

9

PVDD

10

9
8
7
6

SHDN/RT

GND

LX

PGND

COMP
FB
PGOOD
VDD
PVDD

1
2
3
4

8
7
6
5

WDFN-8EL 3x3

COMP
FB
VDD
PVDD

Marking Information

For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.

DS8011/A-02 March 2011 www.richtek.com

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RT8011/A

Typical Application Circuit

V

IN

2.6V to 5.5V
R

OSC

332k

Figure 1. T ypical Application Circuit for RT8011

V

IN

2.6V to 5.5V

R

OSC

332k

1

SHDN/RT

2

SYNC

3

GND

4

LX

5

PGND

1

SHDN/RT

2

GND

3

LX

4

PGND

RT8011

PGOOD

L1

2.2uH

RT8011A

L1

2.2uH

COMP

FB

VDD

PVDD

COMP

FB

VDD

PVDD

R1

510k

C
1000pF

C
1000pF

R1
510k

C

OUT

22uF

COMP

R2

C

22uF

COMP

R2

22pF

OUT

240k

C1

240k

V

OUT

2.5V/2A

V

OUT

2.5V/2A

R

COMP

R

C

IN

22uF

C

IN

22uF

PGOOD

100k

R

COMP

13k

13k

10

9

8

7
6

8

7
6

5

Figure 2. T ypical Application Circuit f or RT801 1A

Note : Using all Ceramic Capacitors

Table 1

Component Supplier Series Inductance (μH) DCR (mΩ) Current Rating (mA) Dimensions (mm)

TAIYO YUDEN NR 4018 2.2 60 2700 4x4x1.8

Sumida CDRH4D28 2.2 31.3 2040 4.5x4.5x3

GOTREND GTSD53 2.2 29 2410 5x5x2.8

ABC SR0403 2.2 47 2600 4.5x4x3.2

Table 2

Component Supplier Part No. Capacitance (μF) Case Size

TDK C3225X5R0J226M 22 1210
TDK C3225X5R0J226M 22 1210

TDK C2012X5R0J106M 10 0805
Panasonic ECJ4YB0J226M 22 1210
Panasonic ECJ4YB1A226M 22 1210
Panasonic ECJ4YB1A106M 10 1210

TAIYO YUDEN LMK325BJ226ML 22 1210
TAIYO YUDEN JMK316BJ226ML 22 1206
TAIYO YUDEN JMK212BJ106ML 10 0805

DS8011/A-02 March 2011www.richtek.com

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Layout Guide

RT8011/A

CIN must be placed between

and GND as closer as

V

DD

possible

V

IN

PGOOD

R1

C

R2

F

V

OUT

Connect the FB pin directly to feedback resistors. The
resistor divider must be connected between V
GND.

PVDD

VDD

COMP

R

COMP

C

COMP

C

IN

RT8011

6
7
8

FB

9

10

GND

5
4
3
2
1

GND

Output capacitor must
be near RT8011

V

OUT

C

OUT

PGND
LX
GND
SYNC
SHDN/RT

and

OUT

LX should be
connected to
Inductor by wide
and short trace,
keep sensitive
compontents away

L1

from this trace

V

IN

R

OSC

C

F

V

OUT

Figure 3. RT801 1 Layout Guide

CIN must be placed between
V

DD

possible

V

IN

R1

R2

Connect the FB pin directly to feedback resistors. The
resistor divider must be connected between V
GND.

Figure 4. RT801 1A Layout Guide

Functional Pin Description

Pin Number Pin Function

RT8011 RT8011A

1 1 SHDN/RT

2 -- SYNC

3 2 GND

Pin Name

Oscillator Res istor Input. Connec ting a resistor to gro und from this pin s ets
the switching frequency. Forcing this pin t o VDD causes the device to be shut
down.
External Clock Synchronization Input. The oscillation frequency can be
synchronized to an external oscillation app lied to this pin. When tied to VDD,
internal oscillator is selected.
Signal Ground. All small-si gnal components and compensation com ponents
should connect to this ground, which in turn connects to PGND at one point.

and GND as closer as

C

IN

RT8011A

PVDD

VDD

COMP

R

COMP

C

COMP

5

63

7

8

GND

Output capacitor must
be near RT8011A

GND

4

2

1

C

OUT

PGND
LX
GNDFB

SHDN/RT

V

OUT

OUT

and

L1

R

OSC

LX should be
connected to
Inductor by wide
and short trace,
keep sensitive
compontents away
from this trace

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 (−) terminal of CIN and C

OUT

.

6 5 PVDD Po wer Inp ut Sup ply. Decouple this pin to PGND with a capac itor.

7 6 VDD

8 -- PGOOD

9 7 FB

Signal Input Supply. Decouple this pin to GND with a capacitor. Normally V
is equal to PVDD.
Power Good Indicator. Open-drain logic output that is pulled to grou nd when
the output voltage is not within ±12.5% of regulation point.
Feedback Pin. Receives the feedback voltage from a resistive divider
connected across the output.

DD

Error Amplifier Compensation Point. The current comparator threshold

10 8 COMP

increases with this control voltage. Connect external compensation elements
to this pin to stabilize the control loop.

DS8011/A-02 March 2011 www.richtek.com

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RT8011/A

Function Block Diagram

SHDN/RT

SYNC

COMP

FB

0.8V

POR

VDD

EA

Int-SS

SD

Output
Clamp

0.9V

0.7V

0.4V

OSC

Slope
Com

V

REF

RT801 1

Control

Logic

OTP

ISEN

OC

Limit

Driver

NISEN

NMOS I Limit

PVDD

LX

PGND

PGOOD

GND

COMP

FB

0.8V

POR

VDD

EA

Int-SS

SD

Output
Clamp

SHDN/RT

OSC

0.9V

0.7V

0.4V

Slope
Com

V

REF

RT801 1A

Control

Logic

OTP

ISEN

OC

Limit

Driver

NISEN

NMOS I Limit

PVDD

LX

PGND

GND

DS8011/A-02 March 2011www.richtek.com

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Operation

RT8011/A

Main Control Loop

The RT801 1/A is a monolithic, consta nt-frequency , current
mode step-down DC/DC converter. During normal
operation, the internal top power switch (P-Channel
MOSFET) is turned on at the beginning of each clock
cycle. Current in the inductor increases until the peak
inductor current reach the value defined by the voltage on
the COMP pin. The error a mplifier adjusts the voltage on
the COMP pin by comparing the feedback signal from a
resistor divider on the FB pin with an internal 0.8V
reference. When the load current increases, it causes a
reduction in the feedback voltage relative to the reference.
The error amplifier raises the COMP voltage until the
average inductor current matches the new load current.
When the top power MOSFET shuts off, the synchronous
power switch (N-Channel MOSFET) turns on until either
the bottom current limit is rea ched or the beginning of the
next clock cycle.

The operating frequency is set by an external resistor
connected between the RT pin a nd ground. The practical
switching frequency can range from 300kHz to 4MHz.
Power Good comparators will pull the PGOOD output low
if the output voltage comes out of regulation by 12.5%. In
an over-voltage condition, the top power MOSFET is turned
off and the bottom power MOSFET is switched on until
either the over-voltage condition clears or the bottom
MOSFET's current limit is rea ched.

Frequency Synchronization

The internal oscillator of the RT801 1 can be synchronized
to an external clock connected to the SYNC pin. The
frequency of the external clock can be in the range of
300kHz to 4MHz. For this application, the oscillator ti ming
resistor should be chosen to correspond to a frequency
that is about 20% lower than the synchronization
frequency .

The output voltage will then be determined by the input
voltage minus the voltage drop across the internal
P-Channel MOSFET a nd the inductor.

Low Supply Operation

The RT8011/A is designed to operate down to an input
supply voltage of 2.6V. One important consideration at
low input supply voltages is that the R
P-Channel a nd N-Cha nnel power switches increase s. The
user should calculate the power dissipation when the
RT8011/A is used at 100% duty cycle with low input
voltages to ensure that thermal limits are not exceeded.

Slope Compensation and Inductor Peak Current

Slope compensation provides stability in constant
frequency architectures by preventing sub-harmonic
oscillations at duty cycles greater than 50%. It is
accomplished internally by a dding a compensating ra mp
to the inductor current signal. Normally, the maximum
inductor peak current is reduced when slope compensation
is added. In the RT8011/A, however, separated inductor
current signals are used to monitor over current condition.
This keeps the maximum output current relatively constant
regardless of duty cycle.

Short-Circuit Protection

When the output is shorted to ground, the inductor current
decays very slowly during a single switching cycle. A
current runaway detector is used to monitor inductor
current. As current increa sing beyond the control of current
loop, switching cycles will be skipped to prevent current
runaway from occurring.

DS(ON)

of the

Dropout Operation

When the input supply voltage decrea ses toward the output
voltage, the duty cycle increases toward the maximum
on-time. Further reduction of the supply voltage forces
the main switch to remain on for more than one cycle
eventually reaching 100% duty cycle.

DS8011/A-02 March 2011 www.richtek.com

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RT8011/A

Absolute Maximum Ratings (Note 1)

z Supply Input V oltage, V DD, PV DD ----------------------------------------------------------------------------−0.3V to 6V

z LX Pin Switch Voltage-------------------------------------------------------------------------------------------- −0.3V to (PV DD + 0.3V)
z Other I/O Pin Voltages -------------------------------------------------------------------------------------------−0.3V to (VDD + 0.3V)
z LX Pin Switch Current -------------------------------------------------------------------------------------------- 4A
z Power Dissipation, P

MSOP-10------------------------------------------------------------------------------------------------------------ 467mW
W D FN-10L 3x3-----------------------------------------------------------------------------------------------------909mW
WDF N-8EL 3x3 ----------------------------------------------------------------------------------------------------909mW

z Package Thermal Re sistance (Note 2)

MSOP-10, θJA------------------------------------------------------------------------------------------------------214°C/W
W DFN-10L 3x3, θJA-----------------------------------------------------------------------------------------------11 0°C/W
W DFN-8EL 3x3, θJA-----------------------------------------------------------------------------------------------11 0°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 Mode) -------------------------------------------------------------------------------------- 2kV

MM (Ma chine Mode)---------------------------------------------------------------------------------------------- 200V

@ 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 Voltage VFB 0.784 0.8 0.816 V

DC Bias Current

Output Voltage Line Regulation VIN = 2.7V to 5.5V -- 0.04 -- %/V
Output Voltage Load Regulation 0A < I

Error Amp lifi e r
Transconductance

Current Sense Transresistance RT -- 0.4 -- Ω

= 25°C, unless otherwise specified)

A

Parameter Symbol Test Conditions Min Typ Max Unit

Active , VFB = 0.78V, Not Switching -- 460 -- μA
Shutdown -- -- 1 μA

< 2A -- 0.25 - - %

LOAD

g

-- 800 -- μs

m

Power Good Range -- ±12.5 ±15 %
Power Good Pull-Down

Resistance

-- -- 120 Ω

To be continued

DS8011/A-02 March 2011www.richtek.com

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