RT8005
1A, 2MHz, High-Efficiency Synchronous Buck PWM Converter
General Description
The RT8005 is a high-efficiency synchronous buck PWM
converter with integrated P-Channel and N-Channel power
MOSFET switches. Capable of delivering 1A output current
over a wide input voltage range of 2.4V to 5.5V, the RT8005
is ideally suited for portable applications powered by a
single Li-Ion battery or by 3-cell NiMH/NiCd batteries. The
device operates at 2MHz PWM switching fixed frequency,
can use smaller CIN, C
The RT8005 integrates two low R
capacitor and inductor.
OUT
230mΩ and 180mΩ
DS(ON)
of high and low side switching MOSFETs to reduce board
space, as only resistors and capacitors along with one
inductor are required externally for operation. The RT8005
has adjustable output range down to 0.5V. The other
features include internal soft-start, chip enable, over
temperature and over current protections. It is available in
a space-saving VDFN-10L 3x3 package.
Ordering Information
RT8005
Package Type
QV : VDFN-10L 3x3 (V-Type)
Lead Plating System
P : Pb Free
G : Green (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.
Features
l 2.4V to 5.5V Input Voltage Range
l Adjustable Output from 0.5V to V
l Guaranteed 1A Output Current
l Accurate Reference : 0.5V (± 1.5%)
l Up to 90% Conversion Efficiency
l Typical Quiescent Current : 200µA
l Integrated Low R
High and Low Side Power
DS(ON)
IN
MOSFET Switches : 230mΩ and 180mΩ
l Current Mode PWM Operation
l Fixed Frequency : 2MHz
l 100% Maximum Duty Cycle for Lowest Dropout
l Internal Soft-Start
l No Schottky Diode Required
l Over Temperature and Over Current Protection
l Small 10-Lead VDFN 3x3 Package
l RoHS Compliant and 100% Lead (Pb)-Free
Applications
l Battery-Powered Equipments
l Low Power CPU and DSP Supplies
l Digital Cameras and Hard Disks
l Protable Instruments and Notebook Computers
l Celluar Phones, PDAs, and Handheld PCs
l USB-Based DSL Modems and Other Network Interface
Cards
Pin Configurations
(TOP VIEW)
PGND
10
9
PGND
8
GND
7
COMP
9
11
FB
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
1
LX
2
PVDD
3
PVDD
4
VDD
5
EN
VDFN-10L 3x3
GND
area.
DS8005-10 March 2011 www.richtek.com
1
RT8005
Typical Application Circuit
V
2.4V to 5.5V
Recommended component selection for Typical Application Circuit.
V
OUT
(V)
VIN (V) CIN (uF) C
0.5 2.4 to 5.5
IN
2,3
PVDD
PGND
OUT
2.2µH
1
LX
6
FBCOMP
9, 10
(uH) R1 (kΩ) R2 (kΩ) C
Chip Enable
C
2.2µF
C
COMP
10nF
OUT
IN
5
EN
7
GND
(uF) L
4
VDD
RT8005
8,
11 (Exposed Pad)
2.2 2.2/4.7 2.2 10 Open 10
L
OUT
R1
10k
R2
7.15k
V
1.2V/1A
C
OUT
2.2µF
OUT
COMP
(nF)
1 2.4 to 5.5
1.2 2.4 to 5.5
1.8 2.4 to 5.5
2.5 3.3 to 5.5
3.3 4.2 to 5.5
2.2 2.2/4.7 2.2 10 10 10
2.2 2.2/4.7 2.2 10 7.15 10
2.2 2.2/4.7 2.2 10 3.83 10
2.2 2.2/4.7 2.2 10 2.49 10
2.2 2.2/4.7 2.2 10 1.78 10
Suggested Inductors
Component
Supplier
Series Inductance
(µH)
DCR
(mΩ)
Current Rating
(mA)
Dimensions
(mm)
ABC SR0403 2.2 47 2600 4.5x4x3.2
Sumida CDRH3D16
2.2 59 1750 4x4x1.8
GOTREND GTSD53 2.2 29 2410 5x5x2.8
Suggested Capacitors For CIN and C
Component Supplier
Part No. Capacitance (uF) Case Size
OUT
TDK C1608X5R1A225M 2.2 0603
Panasonic ECJ1VB0J225M 2.2 0603
TAIYO YUDEN JMK107BJ225M 2.2 0603
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Functional Pin Description
ormally VDD is
Floating this pin is
Switcher Feedback Voltage. This pin is the inverting input of the error amplifier.
h an external resistor divider network. FB
Compensation Input. This pin is the output of the internal error amplifier. Connect
signal components, compensation components and the
exposed pad on the bottom side of the IC should connect to this ground, which in
The exposed pad must be soldered to a
Pin No. Pin Name
1 LX Internal Power MOSFET Switches Output. Connect this pin to the inductor.
2, 3 PVDD Power Input Supply. Decouple this pin to PGND with a capacitor.
4 VDD
5 EN
Signal Input Supply. Decouple this pin to GND with a capacitor. N
equal to PVDD.
Chip Enable (Active High). Logic low shuts down the converter.
forbidden.
RT8005
Pin Function
6 FB
FB senses the switcher output throug
regulation voltage is 0.5V.
7 COMP
an external capacitor to compensate the regulator controlled loop.
Signal Ground. All small-
8,
Exposed Pad (11)
GND
turn connects to PGND at one point.
large PCB and connected to GND for maximum power dissipation.
9, 10 PGND Power Ground. Connect this pin close to the terminal of CIN and C
Function Block Diagram
EN
Slope
Compensation
+
Error
Amplifier
-
COMP
FB
Shutdown
Control
Oscillator
V
REF
Current Limit
Detector
-
PWM
Comparator
+
VDD
Over
Temperature
Detector
Control
Logic
Zero
Detector
Current
Sense
Driver
PVDD
OUT
.
LX
GND
DS8005-10 March 2011 www.richtek.com
PGND
3
RT8005
Absolute Maximum Ratings (Note 1)
l Supply Voltage, PVDD and VDD ------------------------------------------------------------------------------−0.3V to 6V
l EN, FB Voltage---------------------------------------------------------------------------------------------------−0.3V to V
l PGND to GND----------------------------------------------------------------------------------------------------−0.3V to 0.3V
l LX Voltage---------------------------------------------------------------------------------------------------------−0.3V to (V
l Power Dissipation, P
@ T
D
= 25°C
A
VDFN-10L 3x3----------------------------------------------------------------------------------------------------1.923W
l Package Thermal Resistance (Note 2)
VDFN-10L 3x3, θJA-----------------------------------------------------------------------------------------------52°C/W
l Junction Temperature-------------------------------------------------------------------------------------------150°C
l Lead Temperature (Soldering, 10 sec.)----------------------------------------------------------------------260°C
l Storage Temperature Range----------------------------------------------------------------------------------- −65°C to 150°C
l ESD Susceptibility (Note 3)
HBM (Human Body Mode)-------------------------------------------------------------------------------------2kV
MM (Machine Mode)--------------------------------------------------------------------------------------------200V
Recommended Operating Conditions (Note 4)
l Supply Voltage, PVDD and VDD------------------------------------------------------------------------------2.4V to 5.5V
l Enable Input Voltage,
l Ambient Temperature Range----------------------------------------------------------------------------------−40°C to 85°C
l Junction Temperature Range----------------------------------------------------------------------------------−40°C to 125°C
-------------------------------------------------------------------------------------0V to V
VEN
DD
DD
DD
+ 0.3V)
Electrical Characteristics
(V
= 3.3V, T
DD
Supply Current
Quiescent Current
Shutdown Current
Reference
Reference Voltage
Oscillator
Switching Frequency Range
Maximum Duty Cycle DC
Output Voltage
Line Regulation
Load Regulation
Power Switches
R
DS(ON)
R
DS(ON)
Current Limit
= 25°C, unless otherwise specified)
A
Parameter Symbol
IQ
I
SHDN
V
f
OSC
of P-MOSFET R
of N-MOSFET R
I
LIMIT
REF
P_FET
N_FET
V
Test Conditions Min Typ Max Unit
V
V
EN
I
OUT
EN
= 3.3V, V
= 0mA
= 0V
FB
= V
+ 0.15V,
REF
-- 200 400 µA
-- 0.01
0.4925 0.5 0.5075 V
1.7 2.0 2.3 MHz
V
PVDD
V
DD
10mA < I
V
PVDD
V
PVDD
PVDD
= V
= 2.4V to 5.5V, I
OUT
LOAD
LOAD
< 600mA
= 3.3V, ILX = 300mA
= 3.3V, I
= 3.3V, V
= −300mA
LX
= V
FB
= 100mA
- 0.15V
REF
100
-- -- +1.5 %
-- -- +1.5 %
-- 230 -- mΩ
-- 180 --
-- 1.8 -- A
-- -- %
1 µA
mΩ
To be continued
DS8005-10 March 2011www.richtek.com
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RT8005
Parameter Symbol Test Conditions Min Typ Max Unit
Logic Input
Logic-Low VIL VDD = 2.4V to 5.5V, Shutdown -- -- 0.4
EN Threshold Voltage
Logic-High VIH VDD = 2.4V to 5.5V, Enable 1.5
-- --
V
Protection
Thermal Shutdown Temperature TSD -- 180
-- °C
Thermal Shutdown Hysteresis ∆TSD -- 20 -- °C
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θ
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
is measured in the natural convection at T
JA
JEDEC 51-7 thermal measurement standard.
= 25°C on a high effective thermal conductivity test board of
A
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RT8005
Typical Operating Characteristics
Output Voltage Deviation (%) 1
Line Regulation Deviation
0.4%
0.4
V
= 1.2V
OUT
I
= 50mA
I
OUT
OUT
= 500mA
I
OUT
0.2%
0.2
0.0%
0
-0.2%
-0.2
-0.4%
-0.4
-0.6%
-0.6
2 2.5 3 3.5 4 4.5 5 5.5
Input Voltage (V)
Current Limit vs. Input Voltage
2.2
V
= 1.2V
OUT
2
1.8
1.6
1.4
Current Limit (A)
1.2
1
2 2.5 3 3.5 4 4.5 5 5.5
Input Voltage (V)
= 1000mA
-0.002
-0.004
Output Voltage Deviation (%) 1
-0.006
Load Regulation Deviation
0.004
0.4
0.002
0.2
0
0
VIN = 5V
-0.2
VIN = 3.3V
-0.4
-0.6
0 100200300400500600700800900100
Load Regulation (mA)
Efficiency vs. Output Current
100
V
= 1.2V
OUT
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
1 10 100 1000
VIN = 3.3V
VIN = 5V
Output Current (mA)
1000
0
Frequency vs. Input Voltage
2.15
2.1
2.05
2
1.95
Frequency(MHz) 1
1.9
1.85
2.5 3 3.5 4 4.5 5 5.5
Input Voltage(V)
2.1
2.05
2
1.95
1.9
Frequency(MHz) 1
1.85
1.8
-50 -25 0 25 50 75 100 125
Frequency vs. Temperature
Temperature (°C)
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RT8005
)
)
Quiescent Current vs. Input Voltage
300
VEN = 3.3V, VFB = 0.65V
275
250
225
200
Quiescent Current (μA
175
150
2 2.5 3 3.5 4 4.5 5 5.5
Input Voltage(V)
V
vs. Input Voltage
0.51
0.505
REF
Quiesce nt Current vs. Tem perature
220
VEN = 3.3V, VFB = 0.65V
210
200
190
180
170
Quiescent Current (μA
160
150
-50 -25 0 25 50 75 100 125
Temperature (°C)
V
vs. Tem perature
0.502
0.5
0.498
REF
0.5
(V)
REF
V
0.495
0.49
0.485
V
(500mV/Div)
OUT
V
EN
(2V/Div)
22.533.544.5 55.5
Input Voltage (V)
Soft-Start Function
VIN = 3.3V
V
= 1.2V
OUT
I
= 0mA
OUT
0.496
(V)
0.494
REF
V
0.492
0.49
0.488
0.486
V
(500mV/Div)
OUT
V
EN
(2V/Div)
-50 -25 0 25 50 75 100 125
Temperature (°C)
Soft-Start Function
VIN = 3.3V
V
= 1.2V
OUT
I
= 1A
OUT
I
(50mA/Div)
IN
(500mA/Div)
Time (500μs/Div)
I
IN
Time (500μs/Div)
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RT8005
V
OUT
(2mV/Div)
V
(1V/Div)
I
(500mA/Div)
Output
Voltage
VIN = 3.3V, V
LX
LX
VIN = 3.3V, V
I
OUT
Steady State
= 1.2V, I
OUT
Time (100μs/Div)
OUT
= 0mA
Load Transient Response
= 1.2V
= 100mA to 1A
OUT
(100mV/Div)
V
OUT
(2mV/Div)
V
(2V/Div)
I
(1A/Div)
VIN = 3.3V, V
LX
LX
Steady State
= 1.2V, I
OUT
Time (250ns/Div)
OUT
= 1A
Load
Current
(500mA/Div)
Time (100μs/Div)
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Application Information
RT8005
RT8005 is a pulse-width-modulated (PWM) step-down DC/
DC converter. Capable of delivering 1A output current over
a wide input voltage range from 2.4V to 5.5V. The RT8005
is ideally suited for portable electronic devices that are
powered from 1-cell Li-ion battery or from other power
sources within the range such as cellular phones, PDAs
and handy terminals.
Chip Enable/Disable and Soft-Start
Four operational modes are available: PWM, PSM, Low-
Drop-Out and shut-down modes. Pulling EN pin lower than
0.4V shuts down the RT8005 and reduces its quiescent
current to 1µA. Pulling EN pin higher than 1.5V enables
the RT8005 and initiates the soft-start cycle. RT8005 has
internal soft-start that can reduce the Inrush Current during
the rising of Output Voltage.
PWM Operation
During normal operation, the RT8005 regulates output
voltage by switching at a constant frequency transferring
the power to the load in each cycle by PWM. The RT8005
uses a slope-compensated, current mode PWM controller
capable of achieving 100% duty cycle. At each rising edge
of the internal oscillator, the Control Logic cell sends a
PWM ON signal to the Driver cell to turn on internal P-
MOSFET. This allows current to ramp up through the
inductor to the load, and stores energy in a magnetic field.
The switch remains on until either the current-limit is
tripped or the PWM comparator signals for the output in
regulation. After the switch is turned off, the inductor
releases the magnetic energy and forces current through
the N-MOSFET synchronous rectifier to the output-filter
capacitor and load. The output-filter capacitor stores charge
when the inductor current is above the average output
current and releases charge when the inductor current is
below the average current to smooth the output voltage
across the load. A Zero Detector monitors inductor current
by sensing voltage drop across the N-MOSFET
synchronous rectifier when it turns on. The N-MOSFET
turns off and allows the converter entering discontinuous
conduction mode when the inductor current decreases to
zero. The zero current detection on threshold is about
80mA.This reduces conduction loss and increase power
conversion efficiency at light load condition.
PSM Operation
Consequently, the converter will enter pulse-skipping mode
(PSM) during extreme light load condition or when
modulation index (V
OUT/VIN
) is extreme low. This could
reduce switching loss and further increase power
conversion efficiency.
Over Current Protection
The RT8005 continuously monitors the inductor current
by sensing the voltage across the P-MOSFET when it
turns on. When the inductor current is higher than current
limit threshold (1.8A typical), OCP activates and forces
the P-MOSFET turning off to limit inductor current cycle
by cycle.
Output Voltage Setting and Feedback Network
The output voltage can be set from V
divider as: the internal V
is 0.5V with 1.5% accuracy.
REF
to VIN by a voltage
REF
In practical application, keep R1 = 10kΩ respectively and
choose appropriate R2 according to the required output
voltage.
Inductor Selection
The output inductor is suggested as the table of suggested
inductors for optimal performance. Make sure that the
inductor will not saturate over the operation conditions
including temperature range, input voltage range, and
maximum output current. If possible, choose an inductor
with rated current higher than 2A so that it will not saturate
even under short circuit condition.
Input Capacitor Selection
The input capacitor can filter the input peak current and
noise at input voltage source. The capacitor with low ESR
(effective series resistance) provides the small drop voltage
to stabilize the input voltage during the transient loading.
For input capacitor selection, the ceramic capacitors larger
than 2.2µF is recommend. The capacitor must conform to
the RMS current requirement. The maximum RMS ripple
current is calculated as :
OUTINOUT
OUT(MAX)RMS
I I =
IN
V
) V- (V V
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9
RT8005
Output Capacitor Selection
The capacitor’ s ESR determines the output ripple voltage
and the initial voltage drop following a high slew-rate
transient’ s edge. Typically, if the ESR requirement is
satisfied, the capacitance is adequate to filtering. The
output ripple voltage can be calculated as :
COUT +∆=∆
(ESR I V
1
)
f x C x 8
OSCOUT
1
6
7
9, 10
L1
R4
C4
R2
R1
C1
V
OUT
4
5
8
PVDD
VDD
EN
GND
RT8005
COMP
LX
FB
PGND
V
IN
R5
2, 3
R3
C3
V
IN
C2
Where f
capacitance and ∆IC = ∆I
= operating frequency, C
OSC
= ripple current in the inductor.
L
= output
OUT
The ceramic capacitor with low ESR value provides the
low output ripple and low size profile. Connect a
2.2µF/4.7µF ceramic capacitor at output terminal for good
performance and place the input and output capacitors as
close as possible to the device.
Layout Considerations
Follow the PCB layout guidelines for optimal performance
of RT8005.
} For the main current paths as indicated in bold lines in
Figure 1, keep their traces short and wide.
} Put the input capacitor as close as possible to the device
pins (PVDD and PGND).
} LX node is with high frequency voltage swing and should
be kept small area. Keep analog components away from
LX node to prevent stray capacitive noise pick-up.
Figure 1
Figure 2. Top Layer
} Connect feedback network behind the output capacitors.
Keep the loop area small. Place the feedback components
near the RT8005.
} Connect all analog grounds to a command node and
then connect the command node to the power ground
behind the output capacitors.
} An example of 2-layer PCB layout is shown in Figure 2
to Figure 3 for reference.
10
Figure 3. Bottom Layer
DS8005-10 March 2011www.richtek.com
Outline Dimension
RT8005
D
E
A
A3
A1
D2
L
E2
SEE DETAIL A
1
e
b
2
1 1
2
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min Max Min Max
A 0.800 1.000 0.031 0.039
A1 0.000 0.050 0.000 0.002
A3 0.175 0.250 0.007 0.010
b 0.180 0.300 0.007 0.012
D 2.950 3.050 0.116 0.120
D2 2.300 2.650 0.091 0.104
E 2.950 3.050 0.116 0.120
E2 1.500 1.750 0.059 0.069
e 0.500 0.020
L 0.350 0.450
Richtek Technology Corporation
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
0.014 0.018
V-Type 10L DFN 3x3 Package
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 95, Minchiuan Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
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