Download

RT8003
600mA, 2MHz, High-Efficiency Synchronous Buck PWM
Converter
General Description
Features
The RT8003 is a high-efficiency synchronous buck PWM
converter with integrated P-Channel and N-Channel power
MOSFET switches. Capable of delivering 600mA output
current over a wide input voltage range of 2.4V to 5.5V,
the RT8003 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, COUT capacitor and
inductor.
l
l
l
l
l
l
l
l
The RT8003 integrates two low RDS(ON) 230mΩ and 180mΩ
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 RT8003
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.
l
Ordering Information
l
RT8003
l
l
l
l
l
l
Applications
Package Type
QV : VDFN-10L 3x3 (V-Type)
l
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
l
Note :
Richtek products are :
l
l
Battery-Powered Equipments
Low Power CPU and DSP Supplies
Digital Cameras and Hard Disks
Protable Instruments and Notebook Computers
Celluar Phones, PDAs, and Handheld PCs
USB-Based DSL Modems and Other Network Interface
Cards
Pin Configurations
RoHS compliant and compatible with the current require-
(TOP VIEW)
ments of IPC/JEDEC J-STD-020.
}
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS8003-08 March 2011
LX
VDD
NC
NC
EN
1
10
2
9
3
GND
4
5
8
7
11
9
}
l
2.4V to 5.5V Input Voltage Range
Adjustable Output from 0.5V to VIN
Guaranteed 600mA Output Current
Accurate Reference : 0.5V (±1.5%)
Up to 90% Conversion Efficiency
Typical Quiescent Current : 200µA
Integrated Low RDS(ON) High- and Low Side Power
MOSFET Switches : 230mΩ and 180mΩ
Current Mode PWM Operation
Fixed Frequency : 2MHz
100% Maximum Duty Cycle for Lowest Dropout
Internal Soft-Start
No Schottky Diode Required
Over Temperature and Over Current Protection
Small 10-Lead VDFN 3x3 Package
RoHS Compliant and 100% Lead (Pb)-Free
GND
GND
GND
COMP
FB
VDFN-10L 3x3
www.richtek.com
1
RT8003
Typical Application Circuit
V IN
2.4V to 4.2V
C IN
1uF
Chip Enable
2
VDD
5
7
C COMP
10nF
LX
EN
1
L OUT
2.2uH
RT8003
R1
10k
6
COMP
FB
GND
8, 9, 10,
Exposed Pad (11)
R2
7.15k
V OUT
1.2V/600mA
C OUT
1uF
Recommended component selection for Typical Application Circuit.
VOUT (V)
V IN (V)
CIN (µF)
COUT (µF)
LOUT (µH)
R1 (kΩ)
R2 (kΩ)
CCOMP (nF)
0.5
2.4 to 3.3
1
1/2.2
2.2/1
10
Open
10
1
2.4 to 3.6
1
1/2.2
2.2/1
10
10
10
1.2
2.4 to 4.2
1
1/2.2
2.2/1
10
7.15
10
1.8
2.4 to 5.5
1
1/2.2
2.2/1
10
3.83
10
2.5
3.3 to 5.5
1
1/2.2
2.2/1
10
2.49
10
3.3
4.2 to 5.5
1
1/2.2
2.2/1
10
1.78
10
Suggested Inductors
Component
Series
Supplier
ABC
SR0302
Sumida
CDRH2D14
TDK
VLP4612
Inductance
ESR
Current Rating
Dimensions
(µH)
(mΩ)
(mA)
(mm)
1
60
2100
2.2
90
1650
2.2
94
1000
1
110
1500
2.5
170
1100
3x2.8x2.5
3.2x3.2x1.55
4.6x3.4x1.2
Suggested Capacitors For CIN and COUT
Component Supplier
TDK
Panasonic
TAIYO YUDEN
www.richtek.com
2
Part No.
Capacitance (uF)
Case Size
C1608X5R1A105M
1
0603
C1608X5R1A225M
2.2
0603
ECJ1VB0J105M
1
0603
ECJ1VB0J225M
2.2
0603
JMK107BJ105M
1
0603
JMK107BJ225M
2.2
0603
DS8003-08 March 2011
RT8003
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
LX
Internal Power MOSFET Switches Output. Connect this pin to the inductor.
2
VDD
Power Input Supply. Input voltage which supplies current to the output pin. Connect
this pin with a low-ESR capacitor to GND
3, 4
NC
No Internal Connection
5
EN
Chip Enable (Active High). Logic low shuts down the converter. Floating this pin is
forbidden.
6
FB
Switcher Feedback Voltage. This pin is the inverting input of the error amplifier. FB
senses the switcher output through an external resistor divider network. FB
regulation voltage is 0.5V.
7
COMP
Compensation Input. This pin is the output of the internal error amplifier. Connect
an external capacitor to compensate the regulator controlled loop.
GND
Ties the pin directly to the cathode terminal of CIN and C OUT and ground plane with
the lowest impedance. Signal and Common Ground (The exposed pad must be
soldered to a large PCB and connected to GND for maximum power dissipation).
The GND pad area should be as large as possible and using many vias to conduct
the heat into the buried GND plate of PCB layer. All small-signal, compensation and
feedback components should connect to this pin.
8, 9, 10, 11
(Exposed Pad)
Function Block Diagram
EN
Shutdown
Control
VDD
Slope
Compensation
Oscillator
Current Limit
Detector
-
PWM
Comparator
COMP
VREF
FB
+
Error
Amplifier
-
+
Over
Temperature
Detector
Control
Logic
Current
Sense
Driver
LX
Zero
Detector
GND
DS8003-08 March 2011
www.richtek.com
3
RT8003
Absolute Maximum Ratings
(Note 1)
Supply Voltage ---------------------------------------------------------------------------------------------------−0.3V to 6V
LX Voltage --------------------------------------------------------------------------------------------------------- −0.3V to (VDD + 0.3V)
l Power Dissipation, PD @ TA = 25°C
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
l
l
(Note 4)
Recommended Operating Conditions
l
l
l
l
Supply Voltage ---------------------------------------------------------------------------------------------------2.4V to 5.5V
Enable Input Voltage, VEN -------------------------------------------------------------------------------------0V to 5.5V
Ambient Temperature Range ---------------------------------------------------------------------------------- −40°C to 85°C
Junction Temperature Range ----------------------------------------------------------------------------------0°C to 125°C
Electrical Characteristics
(VDD = 3.3V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Supply Current
Quiescent Current
IQ
VEN = 3.3V, VFB = VREF + 0.15V,
IOUT = 0mA
90
200
400
µA
Shutdown Current
I SHDN
VEN = 0V
--
0.01
1
µA
V REF
0.4925
0.5
0.5075
V
Switching Frequency Range
f OSC
1.7
2.0
2.3
MHz
Maximum Duty Cycle
DC
100
--
--
%
Reference
Reference Voltage
Oscillator
VDD = VOUT
Output Voltage
Line R egulation
VDD = 2.4V to 5.5V, ILOAD = 100mA
--
--
+1.5
%
Load Regulation
10mA < ILOAD < 600mA
--
--
+1.5
%
Power Switches
RDS(ON) of P-Channel MOSFET
RP_FET
VDD = 3.3V, IL X = 300mA
100
230
600
mΩ
RDS(ON) of N-Channel MOSFET
RN_FET
VDD = 3.3V, IL X = −300mA
100
180
600
mΩ
Current Limit
ILIMIT
VDD = 3.3V, V FB = V REF - 0.15V
1.6
2
2.4
A
To be continued
www.richtek.com
4
DS8003-08 March 2011
RT8003
Parameter
Symbol
Test Conditions
Min
Typ
Max
--
--
0.4
1.5
--
--
Unit
Logic Input
EN Threshold
Logic-Low Voltage VIL
VDD = 2.4V to 5.5V, Shutdown
Logic-High Voltage VIH
VDD = 2.4V to 5.5V, Enable
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. θJA is measured in the natural convection at TA = 25°C on a high effective thermal conductivity test board of
JEDEC 51-7 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
DS8003-08 March 2011
www.richtek.com
5
RT8003
Typical Operating Characteristics
Output Voltage Deviation vs. Output Current
Output Voltage Deviation vs. Temperature
0.40%
0.4
0.00%
0
Output Voltage Deviation (%)
Output Voltage Deviation (%)
0.10%
0.1
-0.10%
-0.1
-0.20%
-0.2
-0.30%
-0.3
-0.40%
-0.4
-0.50%
-0.5
-0.60%
-0.6
-0.70%
-0.7
0.20%
0.2
0.00%
0
-0.20%
-0.2
-0.40%
-0.4
-0.60%
-0.6
-0.80%
-0.8
-1.00%
-1.0
-1.20%
-1.2
-1.40%
-1.4
-1.60%
-1.6
-1.80%
-1.8
0
100
200
300
400
500
600
700
800
-50
-25
0
Output Current (mA)
100%
100
Efficiency vs. Output Current
100
125
150
90%
90
80
80%
80%
80
70%
70
70%
70
60%
60
50%
50
40%
40
30%
30
60%
60
50%
50
40%
40
30%
30
20%
20
20%
20
10%
10
10%
10
0%
0
0%
0
10
100
1000
VIN = 3.3V, VOUT = 1.2V, IOUT = 200mA
-50
-25
0
25
50
75
100
125
150
Temperature (°C)
Output Current (mA)
Frequency vs. Input Voltage
Frequency vs. Temperature
2.15
2.05
2.1
2.00
Frequency (MHz)1
Frequency (MHz)
75
Efficiency vs. Temperature
100%
100
VIN = 3.3V, VOUT = 1.2V
1
50
Temperature (°C)
Efficiency (%)
Efficiency (%)
90%
90
25
2.05
2
1.95
1.95
1.90
1.85
1.80
1.9
1.85
1.75
2.5
3
3.5
4
4.5
Input Voltage(V)
www.richtek.com
6
5
5.5
-50
-25
0
25
50
75
100
125
Temperature
DS8003-08 March 2011
RT8003
Quiescent Current vs. Input Voltage
300
Quiescent Current vs. Temperature
250
VFB = 0.65V
Quiescent Current (μA)
Quiescent Current (μA)
250
200
150
100
50
VIN = 3.3V, VFB = 0.65V
200
150
100
50
0
0
2.5
3
3.5
4
4.5
5
-50
5.5
-25
0
Input Voltage(V)
VREF vs. Temperature
75
100
125
5
5.5
VREF vs. Input Voltage
0.52
0.515
0.515
0.51
0.51
0.505
V REF (V)
V REF (V)
50
Temperature (°C)
0.52
0.5
0.495
0.49
0.505
0.5
0.495
0.49
0.485
0.485
0.48
-50
-25
0
25
50
75
100
125
0.48
2.5
Temperature (°C)
3
3.5
4
4.5
Input Voltage (V)
Current Limit vs. Input Voltage
Load Transient Response
3
VIN = 3.3V, VOUT = 1.2V
IOUT = 50mA to 600mA
2.5
Current Limit (A)
25
2
Output
Voltage
(50mV/Div)
Load
Current
(200mA/Div)
1.5
1
0.5
0
2.5
3
3.5
4
4.5
Input Voltage (V)
DS8003-08 March 2011
5
5.5
Time (250μs/Div)
www.richtek.com
7
RT8003
Steady State
Steady State
VIN = 3.3V, VOUT = 1.2V, IOUT = 0mA, COUT = 1uF
Output
Voltage
VIN = 3.3V, VOUT = 1.2V, IOUT = 600mA, COUT = 1uF
Output
Voltage
(10mV/Div)
(10mV/Div)
(1V/Div)
VLX
VLX
(1V/Div)
Time (25μs/Div)
Time (250ns/Div)
Soft Start Function
Output
Voltage
VEN
Input
Current
(500mV/Div)
(2V/Div)
(200mA/Div)
VIN = 3.3V, VOUT = 1.2V, IOUT = 600mA
Time (500μs/Div)
www.richtek.com
8
DS8003-08 March 2011
RT8003
Application Information
RT8003 is a Pulse-Width-Modulated (PWM) step-down
DC/DC converter. Capable of delivering 600mA output
current over a wide input voltage range from 2.4V to 5.5V.
The RT8003 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.
PSM Operation
Consequently, the converter will enter pulse-skipping mode
(PSM) during extreme light load condition or when
modulation index (VOUT /VIN) is extreme low. This could
reduce switching loss and further increase power
conversion efficiency.
Over Current Protection
Chip Enable/Disable and Soft-Start
Four operational modes are available: PWM, PSM, LowDrop-Out and shut down modes. Pulling EN pin lower than
0.4V shuts down the RT8003 and reduces its quiescent
current to 1µA. Pulling EN pin higher than 1.5V enables
the RT8003 and initiates the soft-start cycle. RT8003 has
internal soft-start that can reduce the Inrush Current during
the rising of Output Voltage.
The RT8003 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. But it will shut down when the VOUT trip the UV
protection.
Output Voltage Setting and Feedback Network
PWM Operation
During normal operation, the RT8003 regulates output
voltage by switching at a constant frequency transferring
the power to the load in each cycle by PWM. The RT8003
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 PMOSFET. 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
The output voltage can be set from VREF to VIN by a voltage
divider as: the internal VREF is 0.5V with 1.5% accuracy.
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
turns off and allows the converter entering discontinuous
conduction mode when the inductor current decreases to
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 1µF is recommend. The capacitor must conform to
the RMS current requirement. The maximum RMS ripple
current is calculated as :
zero. The zero current detection on threshold is about
80mA.This reduces conduction loss and increase power
IRMS = IOUT(MAX)
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 v oltage drop across the N-MOSFET
synchronous rectifier when it turns on. The N-MOSFET
conversion efficiency at light load condition.
DS8003-08 March 2011
VOUT (VIN - VOUT)
VIN
www.richtek.com
9
RT8003
L1
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:
∆VOUT = ∆IC (ESR +
VOUT
LX
VIN
R4
C1
VDD
RT8003
EN
R1
FB
C3
COMP
C2
GND
R2
1
)
8 x COUT x fOSC
Where f OSC = operating frequency, COUT = output
capacitance and ∆IC = ∆IL = ripple current in the inductor.
Figure 1
The ceramic capacitor with low ESR value provides the
low output ripple and low size profile. Connect a 1µF/2.2µF
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 RT8003.
1. For the main current paths as indicated in bold lines in
Figure 1, keep their traces short and wide.
2. Put the input capacitor as close as possible to the device
pins (VDD and GND).
Figure 2. Top Layer
3. 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.
4. Connect feedback network behind the output capacitors.
Keep the loop area small. Place the feedback components
near the RT8003.
5.Connect all analog grounds to a command node and
then connect the command node to the power ground
behind the output capacitors.
6. An example of 2-layer PCB layout is shown in Figure 2
to Figure 3 for reference.
www.richtek.com
10
Figure 3. Bottom Layer
DS8003-08 March 2011
RT8003
Outline Dimension
D2
D
L
E
E2
SEE DETAIL A
1
e
b
2
1
2
1
A
A1
A3
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
L
0.500
0.350
0.020
0.450
0.014
0.018
V-Type 10L DFN 3x3 Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
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.
DS8003-08 March 2011
www.richtek.com
11