Eorex EP3001 1.5mhz, 600ma synchronous step-down converter Datasheet

eorex
EP3001
1.5MHz, 600mA Synchronous Step-down Converter
Features
Description
• High Efficiency: Up to 96%
• 1.5MHz Constant Switching Frequency
• 600mA Output Current at VIN = 3V
• Integrated Main Switch and Synchronous
Rectifier
• No Schottky Diode Required
• 2.5V to 5.5V Input Voltage Range
• Output Voltage as Low as 0.6V
• 100% Duty Cycle in Low Dropout Operation
• Low Quiescent Current: 300µA
• Slope Compensated Current Mode Control for
Excellent Line and Load Transient Response
• Short Circuit Protection
• Thermal Fault Protection, <1uA Shutdown
Current
• Space Saving 5-Pin Thin SOT23 package
The EP3001 is a 1.5MHz, constant frequency,
slope compensated current mode PWM
step-down converter. The device integrates a
main switch and a synchronous rectifier for high
efficiency without an external Schottky diode. It is
ideal for powering portable equipment that runs
from a single cell lithium-Ion (Li+) battery.
The EP3001 can supply 600mA of load current
from a 2.5V to 5.5V input voltage. The output
voltage can be regulated as low as 0.6V. The
EP3001 can also run at 100% duty cycle for low
dropout operation, extending battery life in
portable system. Idle mode operation at light
loads provides very low output ripple voltage for
noise sensitive applications.
The EP3001is offered in a low profile (1mm) 5-pin,
thin SOT package, and is available in an
adjustable version and fixed output voltage of
1.2V, 1.5V and 1.8V.
Applications
• Cellular and Smart Phones
• Microprocessors and DSP Core Supplies
• Wireless and DSL Modems
• PDAs
• MP3 Players
• Digital Still and Video Cameras
• Portable Instruments
Typical Application
Efficiency vs Output Current
100.00%
4
VIN
VIN
C1
4.7μF
SW
L1
2.2μH
3
1
VOUT
GND
80.00%
VOUT
1.2V
70.00%
C1
10μF
EP3001
EN
90.00%
60.00%
50.00%
40.00%
5
30.00%
2
20.00%
10.00%
0.00%
0.1
1
10
100
Figure 1-Basic application circuit with EP3001 fixed output version
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EP3001
Pin Assignment
Adjustable Output Version
Fixed Output Version
Top View
Top View
EN
1
GND
2
SW
3
5
4
FB
VIN
EN
1
GND
2
SW
3
TSOT23-5
5
VOUT
4
VIN
TSOT23-5
* Fixed 1.5V Marking A2YW
* Fixed 1.8V Marking A3YW
* Fixed 1.2V Marking A4YW
Ordering Information
Pin Description
Pin
Name
Function
1
EN
2
3
GND
SW
4
VIN
5
FB/VOUT
Regulator Enable control input. Drive EN above 1.5V to turn on the part.
Drive EN below 0.3V to turn it off. In shutdown, all functions are disabled
drawing <1µA supply current. Do not leave EN floating.
Ground
Power Switch Output. It is the Switch note connection to Inductor. This pin
connects to the drains of the internal P-Ch and N-Ch MOSFET switches.
Supply Input Pin. Must be closely decoupled to GND, Pin 2, with a 2.2µF or
greater ceramic capacitor.
FB(EP3001-Adj):
Feedback Input Pin. Connect FB to the center point of the external resistor
divider. The feedback threshold voltage is 0.6V.
VOUT(EP3001-1.2/EP3001-1.5/EP3001-1.8):
Output Voltage Feedback Pin. An internal resistive divider divides the
output voltage down for comparison to the internal reference voltage.
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EP3001
Thermal Resistance (Note 1)
Package
θJA
θJC
TSOT23-5
220°C/W
110°C/W
Absolute Maximum Rating (Note 2)
Symbol
VIN
VEN,FB
VSW
TOP
TJ
TSTG
TL
Item
Rating
Units
Input Supply Voltage
-0.3 ~ +6
V
EN, FB Voltages
-0.3 ~ VIN
V
-0.3 ~ VIN+0.3
V
P-Channel Switch Source Current(DC)
800
mA
N-Channel Switch Sink Current(DC)
800
mA
Peak SW Sink and Source Current
1.3
A
-40 ~+85
°C
+125
°C
-65 ~ +150
°C
+300
°C
SW Voltages
Operating Temperature Range
Junction Temperature
(Note 3)
Storage Temperature Range
Lead Temperature (Soldering, 10s)
Note 1:Thermal Resistance is specified with approximately 1 square of 1 oz copper.
Note 2:Absolute Maximum Ratings are those values beyond which the life of a device may be
impaired.
Note 3:TJ is calculated from the ambient temperature TA and power dissipation PD according to the
following formula: TJ = TA + (PD) × (220°C/W)
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EP3001
Electrical Characteristics (Note 4)
(VIN=VEN=3.6V, TA=25, unless otherwise noted.)
Symbol
VIN
IS
VFB
∆VFB
IFB
VOUT
Parameter
Input Voltage Range
Input DC Supply Current Active
Mode Shutdown Mode
Regulated Feedback Voltage
Conditions
Output Voltage Load Regulation
IPK
Peak Inductor Current
fOSC
Oscillator Frequency
RPFET
RDS(ON) of P-CH MOSFET
RNFET
RDS(ON) of N-CH MOSFET
ILSW
SW Leakage
VEN
EN Threshold
IEN
EN Leakage Current
5.5
400
1.0
0.6120
V
µA
µA
V
0.5880
TA=0°C≤TA≤85°C
0.5865
0.6000
0.6135
V
TA=-40°C≤TA≤85°C
0.5820
0.6000
0.6180
V
0.04
0.4
%/V
±30
nA
VFB=0.65V
EP3001-1.2,
-40°C≤TA≤ 85°C
EP3001-1.5,
-40°C≤TA≤ 85°C
EP3001-1.8,
-40°C≤TA≤ 85°C
VIN=2.5V to 5.5V
VLOADREG
Units
300
0.1
0.6000
Feedback Input Bias Current
Output Voltage Line Regulation
Max.
2.5
VIN=2.5V to 5.5V
∆ VOUT
Typ.
VFB=0.5V or VOUT=90%
VFB=0V, VIN=4.2V
TA=+25°C
Reference Voltage Line Regulation
Regulated Output Voltage
Min.
1.164
1.200
1.236
V
1.455
1.500
1.546
V
1.746
1.800
1.854
V
0.04
0.40
%
0.5
VIN=3V, VFB=0.5V or
VOUT=90% Duty Cycle
< 35%
VFB=0.6V or
VOUT=100%
ISW=300mA
ISW=-300mA
VEN=0V, VSW=0V or 5V,
VIN=5V
-40°C≤TA ≤ 85°C
%
0.75
1.00
1.25
A
1.2
1.5
1.8
MHz
0.40
0.50
Ω
0.35
0.45
Ω
±0.01
±1
µA
1.0
1.30
V
±0.01
±1
µA
0.3
Note 4:100% production test at +25°C. Specifications over the temperature range are guaranteed by
design and characterization.
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Typical Performance Characteristics
(Test circuitry is as Figure 2, unless otherwise specified.)
Dynamic Supply Current vs Supply Voltage
Output Voltage vs Supply Voltage
400
1.210
380
1.208
360
1.206
340
1.204
320
1.202
300
1.200
280
1.198
260
1.196
240
1.194
220
1.192
200
2
3
4
5
6
1.190
2
Efficiency vs Output Current
100.00%
90.00%
90.00%
80.00%
80.00%
70.00%
70.00%
60.00%
60.00%
50.00%
50.00%
40.00%
40.00%
30.00%
30.00%
20.00%
20.00%
10.00%
0.00%
0.1
10.00%
0.00%
0.1
10
100
1000
Efficiency vs Output Current
100.00%
90.00%
90.00%
80.00%
80.00%
70.00%
70.00%
60.00%
60.00%
50.00%
50.00%
40.00%
40.00%
30.00%
30.00%
20.00%
20.00%
10.00%
0.00%
0.1
10.00%
0.00%
10
100
5
6
1
10
100
1000
Efficiency vs Output Current
100.00%
1
4
Efficiency vs Output Current
100.00%
1
3
1000
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10
100
1000
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Functional Block Diagram
*For Adjustable Output, R1+R2 Is External.
Operation
The EP3001 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs
to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6V. It
operates at a fixed switching frequency, and uses the slope compensated current mode architecture.
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current
limit for excellent load and line responses and protection of the internal main switch (P-Ch MOSFET)
and synchronous rectifier (N-Ch MOSFET). During normal operation, the internal P-Ch MOSFET is
turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and
switched off when the peak inductor current is above the error voltage. The current comparator, ICOMP,
limits the peak inductor current. When the main switch is off, the synchronous rectifier will be turned on
immediately and stay on until either the inductor current starts to reverse, as indicated by the current
reversal comparator, IZERO, or the beginning of the next clock cycle. The OVDET comparator controls
output transient overshoots by turning the main switch off and keeping it off until the fault is no longer
present.
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EP3001
Idle Mode Operation
At very light loads, the EP3001 automatically enters Idle Mode. In the Idle Mode, the inductor current
may reach zero or reverse on each pulse. The PWM control loop will automatically skip pulses to
maintain output regulation. The bottom MOSFET is turned off by the current reversal comparator, IZERO,
and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the
switching regulator.
Dropout Operation
When the input voltage decreases toward the value of the output voltage, the EP3001 allows the main
(Note 5)
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-Ch 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 5: The duty cycle D of a step-down converter is defined as:
V
D = TON × fOSC × 100%≈ OUT × 100%
VIN
where TON is the main switch on time, and fOSC is the oscillator frequency (1.5MHz).
Maximum Load Current
The EP3001 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.
Short-Circuit Protection
A current limit (1A) circuit is equipped in the EP3001, to protect the EP3001 when the output pin is
shorted to GND pin. This current limit will suppress the output current so that the inductor current has
enough time to decay.
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Applications Information
Figure 2-below shows the Basic Application Circuit with EP3001 adjustable versions.
Setting the Output Voltage
Figure 2 above shows the basic application circuit with EP3001 adjustable output version. The external
resistor sets the output voltage according to the following equation:
⎛
⎝
VOUT=0.6V ⎜1 +
R2 ⎞
⎟
R1 ⎠
R2 = 300KΩ for all outputs;
R1 = 300KΩ for VOUT = 1.2V;
R1 = 200KΩ for VOUT = 1.5V;
R1 = 150KΩ for VOUT = 1.8V;
R1 = 95.3KΩ for VOUT = 2.5V;
R1 = 67KΩ for VOUT = 3.3V
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 4.7µF ceramic capacitor
for most applications is sufficient.
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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 high ripple current. The output
ripple VOUT is determined by:
∆VOUT ≤
VOUT × (VIN − VOUT
)
VIN × fOSC × L
⎛
1
⎝
8 × fOSC
× ⎜⎜ ESR +
⎞
⎟
× C3 ⎟⎠
Inductor Selection
For most designs, the EP3001 operates with inductors of 1µH to 4.7µH. Low inductance values are
physically smaller but require faster switching, which results in some efficiency loss. The inductor value
can be derived from the following equation:
L=
VOUT × (VIN − VOUT )
VIN × ΔIL × fOSC
Where ∆IL inductor Ripple Current. Large value inductors lower ripple current and small value inductors
result in high ripple currents. 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 EP3001.
Part #
Sumida
CR43
Sumida
CDRH4D18
Toko
D312C
L (µH)
Max DCR (mΩ)
Rated D.C. Current (A)
1.4
2.2
3.3
4.7
56.2
71.2
86.2
108.7
2.52
1.75
1.44
1.15
1.5
2.2
3.3
4.7
75
110
162
1.32
1.04
0.84
1.5
2.2
3.3
4.7
120
140
180
240
1.29
1.14
0.98
0.79
Jul. 2006
Size W×L×H (mm)
4.5×4.0×3.5
4.7×4.7×2.0
3.6×3.6×1.2
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EP3001
Package Description
5pin TSOT-23 Package Outline Dimensions
DIM
MILLIMETERS
INCHES
MIN.
NOM.
MAX.
MIN.
NOM.
MAX.
A
0.90
−
1.10
0.035
−
0.043
A1
0.01
−
0.13
0.0004
−
0.005
B
0.30
−
0.50
0.012
−
0.020
C
0.09
−
0.20
0.004
−
0.008
D
2.80
−
3.00
0.110
−
0.118
H
2.50
−
3.10
0.098
−
0.122
E
1.50
−
1.70
0.059
−
0.067
e
0.95 REF.
0.037 REF.
e1
1.90 REF.
0.075 REF.
L1
0.20
−
0.55
0.008
−
0.022
L
0.35
−
0.80
0.014
−
0.031
0°
−
10°
Q
0°
10°
−
* Package outline exclusive of mold flash and metal burr.
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