EP3003

EP3003
Revision History
Revision 0.1 (Apr. 2006)
- First release.
Revision 0.2 (Feb. 2008)..
- Modify ordering infomation.(page 2)
Revision 0.3 (Apr. 2008)..
- Update currently version “not supported burst mode＂ information.
- Modify Typical Performance Characteristics without burst mode (page 5)
Rev.03
1
EP3003
2-CH, 600mA Synchronous Step-down Converter
DESCRIPTION
FEATURES
The EP3003 is a dual channel, 1.5MHz constant
‧ High Efficiency: Up to 96%
frequency, slope compensated current mode PWM
‧ 1.5MHz Constant Switching Frequency
step-down converter. The EP3003 can supply
‧ 600mA Output Current
600mA of load current from a 2.5V to 5.5V input
‧ Integrated Main Switch and Synchronous
voltage. Each output voltage is adjustable from
Rectifier
0.6V to 5V. It is ideal for powering portable
‧ High Switch Current: 1A on Each Channel
equipment that runs from a single cell lithium-Ion
‧ 2.5V to 5.5V Input Voltage Range
(Li+) battery. Internal synchronous 0.35Ω, 1A
‧ Output Voltage as Low as 0.6V
power switches provide high efficiency without the
‧ 100% Duty Cycle in Dropout
need for external Schottky diodes. The EP3003
‧ Low Quiescent Current: 50µA
can also run at 100% duty cycle for low dropout
‧ Slope Compensated Current Mode Control for
operation, extending battery life in portable
Excellent Line and Load Transient Response
system. Pulse Skipping Mode operation at light
‧ Can be synchronized to an external oscillator
loads provides very low output ripple voltage for
‧ Short Circuit Protection
noise sensitive applications.
‧ Power-on Reset Output
APPLICATIONS
‧ Cellular and Smart Phones
‧ Microprocessors and DSP Core Supplies
‧ Thermal Fault Protection
‧ <1uA Shutdown Current
‧ Small Thermally Enhanced 10-Pin MSOP and
3mm × 3mm DFN Packages
‧ Wireless and DSL Modems
‧ PDAs
‧ Portable Instruments / Media Players
‧ Digital Cameras
‧ PC Cards
Typical Application
Figure 1. Basic Application Circuit for 2.5V and 1.8V Output Voltages
Rev.03
2
EP3003
Package/Order Information
MSOP:
DFN:
Ordering Information
Absolute Maximum Rating (Note1)
Input Supply Voltage........ ...................... -0.3V to +6V
RUN, VFB Voltages ................. ..... -0.3V to VIN+0.3V
SW Voltages............................…....-0.3V to VIN+0.3V
MODE/SYNC Voltages....................-0.3V to VIN+0.3V
/POR Voltages..................... ....…... ...... -0.3V to +6V
P-Channel Switch Source Current (DC).….......800mA
N-Channel Switch Sink Current (DC).....……....800mA
Operating Temperature Range............ -40°C to +85°C
Junction Temperature……….............................+125°C
Storage Temperature Range (MSOP) -65°C to +150°C
Storage Temperature Range (DFN) .. -65°C to +125°C
Lead Temperature (Soldering, 10s) ............…..+300°C
Note 1. Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Rev.03
3
EP3003
Electrical Characteristics (Note 2) :
(VIN =VRUN= 3.6V, TA = 25°C, unless otherwise noted.)
Parameter
Conditions
Input Voltage Range
MIN
TYP
2.5
MAX
unit
5.5
V
Input DC Supply Current
Active Mode
VFB=0.5V
600
800
µA
Shutdown Mode
RUN=0V, VIN=5.5V, MODE/SYNC=0V
0.1
1.0
µA
Regulated Feedback
Voltage
TA = +25°C
0.588
0.600
0.612
V
TA= 0°C ≦ TA ≦ 85°C
0.586
0.600
0.613
V
TA= -40°C ≦ TA ≦ 85°C
0.582
0.600
0.618
V
30
nA
0.5
%/V
VFB Input Bias Current
Reference Voltage
0.3
VIN = 2.5V to 5.5V
Line Regulation
Power-On Reset
Threshold:
(POR)
VFBX Ramping Up, MODE/SYNC = 0V
8.5
%
VFBX Ramping Down, MODE/SYNC =
-8.5
%
0V
Power-On Reset On-Resistance
100
Power-On Reset Delay
Output
Voltage
Load
200
Ω
270K
Cycles
0.5
%
Regulation
Peak Inductor Current
VIN=3V, VFB=0.5V
0.75
1.00
1.25
A
1.2
1.5
1.8
MHz
Duty Cycle < 35%
Oscillator Frequency
VFBX =0.6V
Synchronization
1.5
MHz
Frequency
RDS(ON)
SW Leakage
Top Switch On-Resistance
0.35
0.45
Ω
Bottom Switch On-Resistance
0.30
0.45
Ω
VRUN = 0V, VFBX= 0V,
0.01
1
µA
1.0
1.50
V
±0.01
±1
µA
VIN = 5V
RUN Threshold
-40°C ≦ TA ≦ 85°C
RUN Leakage Current
0.3
Note 2. 100% production test at +25°C. Specifications over the temperature range are guaranteed by design
and characterization.
Rev.03
4
EP3003
Typical Performance Characteristics (TBD)
Rev.03
5
EP3003
Functional Block Diagram
Rev.03
6
EP3003
Pin Description
PIN
NAME
FUNCTION
1
VFB1
Output Voltage Feedback Pin. An internal resistive divider divides the output voltage
down for comparison to the internal reference voltage. Nominal voltage for this pin is
0.6V.
2
RUN1
Regulator 1 Enable control input. Forcing this pin to VIN enables regulator 1, while
forcing it to GND causes regulator 1 to shut down. In shutdown, all functions are
disabled drawing <1µA supply current. Do not leave RUN floating.
3
VIN
4
SW1
Main Power Supply. Must be closely decoupled to GND with a ceramic capacitor.
Regulator 1 Power Switch Output. Switch Node Connection to the
Inductor. This pin swings from VIN to GND.
5
GND
6
Mode/Sync
Ground
Combination of Mode Selection and Oscillator Synchronization. This pin controls the
operation of the device. When tied to VIN or GND, Burst Mode operation or pulse
skipping mode is selected, respectively. Do not float this pin. The oscillation frequency
can be synchronized to an external oscillator applied to this pin and pulse skipping mode
is automatically selected. ( Current version “Burst Mode” is not supported )
7
SW2
Regulator 2 Power Switch Output. Switch Node Connection to the Inductor. This pin
swings from VIN to GND.
8
/POR
Power-On Reset. This common-drain logic output is pulled to GND when the output
voltage is not within ±8.5% of regulation and goes high after 175ms when both channels
are within regulation.
9
RUN2
Regulator 2 Enable control input. Forcing this pin to VIN enables regulator 2, while
forcing it to GND causes regulator 2 to shut down.
10
VFB2
11
Power
Connect to the (–) terminal of COUT, and (–) terminal of CIN. Must be soldered to
Ground
electrical ground on PCB.
Output Voltage Feedback Pin for Regulator 2. See VFB1 section.
Rev.03
7
EP3003
OPERATION
The EP3003 uses current mode architecture with frequency set at 1.5MHz and can be synchronized to
an external oscillator. Both channels share the same clock and run in-phase. To suit a variety of
applications, the selectable Mode pin allows the user to trade-off noise for efficiency.
Output voltage is set by an external divider returned to the VFB pins. An error amplifier compares the
divided output voltage with a reference voltage of 0.6V and adjusts the peak inductor current accordingly.
Over voltage and under voltage comparators will pull the POR output low if the output voltage is not
within ±8.5%. The POR output will go high after 270K clock cycles of achieving regulation. During normal
operation, the top power switch (P-channel MOSFET) is turned on at the beginning of a clock cycle when
the VFB voltage is below the reference voltage.
The current into the inductor and the load increases until the current limit is reached. The switch turns off
and energy stored in the inductor flows through the bottom switch (N-channel MOSFET) into the load
until the next clock cycle.
The peak inductor current is controlled by the internally compensated ITH voltage, which is the output of
the error amplifier. This amplifier compares the VFB pin to the 0.6V reference. When the load current
increases, the VFB voltage decreases slightly below the reference. This decrease causes the error
amplifier to increase the ITH voltage until the average inductor current matches the new load current.
The main control loop is shut down by pulling the RUN pin to ground.
Low Current Control
Pulse skipping mode is available to control the operation of the EP3003 at low currents.
For lower ripple noise at low currents, the pulse skipping mode can be used. In this mode, the EP3003
continues to switch at a constant frequency down to very low currents, where it will begin skipping pulses.
Rev.03
8
EP3003
Dropout Operation
The EP3003 allows the main switch to remain on for more than one switching cycle and increases the
duty cycle until it reaches 100%. The output voltage then is the input voltage minus the voltage drop
across the main switch and the inductor. At low input supply voltage, the RDS(ON) of the P Channel
MOSFET increases, and the efficiency of the converter decreases. Caution must be exercised to ensure
the heat dissipated not to exceed the maximum junction temperature of the IC.
Note 3. The duty cycle D of a step-down converter is defined as:
D = TON x fOSC x 100% ≈ VOUT/VIN x 100%
where TON is the main switch on time, and fOSC is the oscillator frequency (1.5MHz).
Maximum Load Current
The EP3003 will operate with input supply voltage as low as 2.5V, however, the maximum load current
decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope
compensation signal reduces the peak inductor current as a function of the duty cycle to prevent
sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the
duty cycle decreases.
APPLICATIONS INFORMATION
A general application circuit for EP3003 is shown in Figure 1, which is the baseline for some calculation
mentioned below. All external component selection for EP3003 application design will be illustrated as
the following.
Setting the Output Voltage
The external resistor sets the output voltage according to the following equation:
R2 ⎞
⎛
V out = 0 . 6V ⎜ 1 +
⎟
R1 ⎠
⎝
R1 = 150KΩ; R2 = 300KΩ for VOUT = 1.8V;
R3 = 100KΩ; R4 = 330KΩ for VOUT = 2.5V.
Rev.03
9
EP3003
Inductor Selection
For most designs, the EP3003 operates with inductors of 1µH to 4.7µH. Low inductance values are
physically smaller but require faster switching, which results in some efficiency loss. Large value
inductors lower ripple current and small value inductors result in high ripple currents. The inductor value
can be derived from the following equation:
L=
VOUT × (VIN − VOUT )
VIN × ∆I L × f OSC
where
∆I L is
inductor Ripple Current. Choose inductor ripple current approximately 35% of the
maximum load current 600mA, or 210mA.
For output voltages above 2.0V, when light-load efficiency is important, the minimum recommended
inductor is 2.2µH. For optimum voltage-positioning load transients, choose an inductor with DC series
resistance in the 50mΩ to 150mΩ range. For higher efficiency at heavy loads (above 200mA), or minimal
load regulation (but some transient overshoot), the resistance should be kept below 100mΩ. The DC
current rating of the inductor should be at least equal to the maximum load current plus half the ripple
current to prevent core saturation (600mA+105mA). Table 1 lists some typical surface mount inductors
that meet target applications for the EP3003.
Part #
L (µH)
Max DCR (m.)
Rated D.C. Current (A)
Sumida
1.4
56.2
2.52
CR43
2.2
71.2
1.75
3.3
86.2
1.44
4.7
108.7
1.15
Sumida
1.5
CDRH4D18
2.2
75
1.32
3.3
110
1.04
4.7
162
0.84
Toko
1.5
120
1.29
D312C
2.2
140
1.14
3.3
180
0.98
4.7
240
0.79
Rev.03
Size WxLxH (mm)
4.5x4.0x3.5
4.7x4.7x2.0
3.6x3.6x1.2
10
EP3003
Input Capacitor Selection
The input capacitor reduces the surge current drawn from the input and switching noise from the device.
The input capacitor impedance at the switching frequency shall be less than input source impedance to
prevent high frequency switching current passing to the input. A low ESR input capacitor sized for
maximum RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly
recommended because of their low ESR and small temperature coefficients. A 10µF ceramic capacitor
for most applications is sufficient.
Output Capacitor Selection
The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop
stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors
with X5R or X7R dielectrics are recommended due to their low ESR and minimization of large
temperature and voltage coefficients. The output ripple
∆VOUT ≤
∆VOUT
is determined by:
⎞
VOUT × (VIN − VOUT ) ⎛
1
⎟
× ⎜⎜ ESR +
VIN × f OSC × L
8 × f OSC × C 3 ⎟⎠
⎝
Rev.03
11
EP3003
Package Description
DFN:
Rev.03
12
EP3003
MSOP:
Rev.03
13