elm600 series

ELM600xB 1A 1.5MHz
high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com
■General description
ELM600xB is a high efficiency step down DC/DC converter operated with current mode and constant
frequency. The internal switch and synchronous rectifier are integrated for high efficiency. External Schottky
diodes are not required. The supply current is only 100μA during operation and drops to less than 1μA in
shutdown. ELM600xB can supply 1A of load current from 2.5V to 5.5V supply voltage.
The switching frequency is set at 1.5MHz, allowing the use of small surface mount inductors and capacitors. It
can run 100% duty cycle for low dropout application. The output voltage of ELM600xB is adjustable from the
FB pin.
■Features
■Application
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Current mode operation
Thermal shutdown protection and short circuit protection
Constant frequency
: Typ.1.5MHz
Output current
: 1A
High efficiency
: Max.95%
Shutdown current
: Max.1µA(Ven=0V, Vin=5.5V)
Supply voltage
: 2.5V to 5.5V
Low quiescent current
: Typ.110µA(Outgoing stopped)
Full duty ratio
: 0 to 100% (in dropout)
Package
: DFN6-2x2, TSOT-25
Cellular phone
PDA and smart phone
MP3 player
Digital camera
Wireless and DSL card
Microcomputer and DSP power supply
Portable machine
■Maximum absolute ratings
Parameter
VIN power supply voltage
Apply voltage to SW
Apply voltage to EN
Apply voltage to FB
SW peak current
Power dissipation
Operating temperature range
Storage temperature range
Symbol
Vin
Vsw
Ven
Vfb
Isw
Limit
-0.3 to +6.0
GND-0.3 to Vin+0.3
GND-0.3 to Vin+0.3
GND-0.3 to Vin+0.3
3.0 (*2)
1000 (DFN6-2x2) (*3)
600 (TSOT-25) (*3)
-40 to +85
-65 to +150
Pd
Top
Tstg
Unit
V
V
V
V
A
mW
°C
°C
Caution:
* 1. Permanent damage to the device may occur when ratings above maximum absolute ones are used.
* 2. Output current must not exceed power dissipation specified in maximum absolute ratings.
* 3. Mounted on glass epoxy board (FR-4). (76.2mm×114.3mm×1.6mm : based on EIJ/JEDEC standard size), 2layers,
Cu thickness 35μm, Cu area : top side 20%, back side 100%.
Rev.1.0
7 - 1
ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com
■Selection guide
ELM600xB-x
Symbol
a
Package
b
Product version
c
Taping direction
* Taping direction is one way.
G: DFN6-2x2
L: TSOT-25
B
N: DFN6-2x2(Refer to PKG file)
S: TSOT-25(Refer to PKG file)
ELM600 x B - x
↑↑ ↑
ab c
■Pin configuration
DFN6-2x2(TOP VIEW)
DFN6-2x2(BOTTOM VIEW)
6
5
4
46
5
64
4
5
6
1
2
3
31
2
13
3
2
1
Pin No.
1
2
3
4
5
6
Exposed Pad
Pin name
NC
EN
VIN
SW
GND
FB
NC
Pin description
No connected.
Enable control input
Main supply
Power switch output
Ground
Voltage feedback
No connected.
TSOT-25(TOP VIEW)
Pin No. Pin name
1
EN
2
GND
3
SW
4
VIN
5
FB
Pin description
Enable control input
Ground
Power switch output
Main supply
Voltage feedback
Rev.1.0
7 - 2
ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com
■Standard circuit ( Adjustable Output Voltage )
Vin
L=2.2µH
●
VIN
●
C1=
4.7µF
C5
SW
Vout
●
●
GND
EN
●
●
C6
C4
R2
R3
C2=
10µF
●
ELM600xB
●
C3
R1
FB
●
●
Vin
Vout=Vfb × (1+R1/R2)
with R1 = 300k for typical application, and C3 should be in
the range between 10pF and 47pF for component selection.
■Block diagram
VIN
Slope Comp
Current
Sense
Amplifier
Reference
UG
+
_
0.6V
FB
+
_
PWM
Logic
SW
PWM
Comparator
Error
Amplifier
Oscillator
M1
LG
M2
Clock
DCC
Zero-current
Comparator
+
_
EN
Shut down
control
GND
Rev.1.0
7 - 3
ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com
■Electrical characteristics
Vin=5V, Vout=1.8V, L=2.2µH, Cout=10µF, Top=25°C, unless otherwise specified
Parameter
Symbol
Test condition
Min.
Typ.
Max. Unit
Supply voltage
Vin
2.5
5.5
V
Output voltage line regulation
∆Vout/∆Vin Vin=2.5V to 5.5V
-3
3
%/V
Output voltage load regulation
Vlr
-3
3
%
Reference voltage
For adjustable Vout
0.588 0.600 0.612
V
Vref
Output range (adjustable voltage)
Vin=2.5V to 5.5V
-3
+3
%
Vout
Shutdown current
Is
Ven=0V
0.1
1.0
µA
Ven=Vin, Vfb=Vref×1.1
110
Quiescent current
Iq
µA
No switching
SW leakage current
Ileak
Ven=0V, Vsw=0V or Vin
-1
1
µA
RdsonP Isw=100mA
250
mΩ
PMOSFET on resistance
NMOSFET on resistance
RdsonN Isw=-100mA
200
mΩ
Duty cycle=100%
PMOSFET current limit
IPcl
2
A
Current pulse width<1ms
Oscillator frequency
Fosc
1.2
1.5
1.8 MHz
Thermal shutdown threshold
160
°C
Ts
EN high level input voltage
Venh
-40°C ≤ Top ≤ +85°C
1.5
V
EN low level input voltage
Venl
-40°C ≤ Top ≤ +85°C
0.4
V
EN input current
Ien
Ven=0V to Vin
-1
1
µA
■Marking
DFN6-2x2
Mark
a~f
Content
Assembly lot No. :
0 ~ 9 and A ~ Z
TSOT-25
Mark
a~e
Content
Assembly lot No. :
0 ~ 9 and A ~ Z
Rev.1.0
7 - 4
ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com
■Application notes
ELM600xB is constant frequency current mode PWM step down converter. ELM600xB is optimized for low
voltage, Li-ion battery, powered applications where high efficiency and small size are critical. The device integrates both a main switch and a synchronous rectifier, which provides high efficiency and eliminates an external
Schottky diode. ELM600xB can achieve 100% duty cycle. The duty cycle D of a step down converter is defined
as:
D = Ton × Fosc × 100% ≈ (Vout/Vin) × 100%
Where Ton is the main switch on time, Fosc is the oscillator frequency (1.5MHz), Vout is the output voltage
and Vin is the input voltage.
1) Current mode PWM control
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for
superior load and line response and protection of the internal main switch and synchronous rectifier. ELM600xB
switches at a constant frequency (1.5MHz) and regulates the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback
error voltage. During normal operation, the main switch 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. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on
until either the next cycle starts or the inductor current drops to zero. The device skips pulses to improve efficiency at light load.
2) Dropout operation
ELM600xB allows the main switch to remain on for more than one switching cycle and increases the duty cycle while the input voltage is dropping close to the output voltage. When the duty cycle reaches 100%, the main
switch is held on continuously to deliver current to the output up to the P MOSFET current limit. The output
voltage then is the input voltage minus the voltage drop across the main switch and the inductor.
3) Short circuit protection
ELM600xB has short circuit protection. When the output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the P MOSFET current limit. The frequency will
return to the normal values once the short circuit condition is removed and the Vout reaches regulated voltage.
4) Maximum load current
ELM600xB can operate down to 2.5V input voltage; 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.
Rev.1.0
7 - 5
ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com
■Typical characteristics
Iout-Efficiency
Iout-Vout
Vin=5V, Vout=1.8V
100
1.88
90
1.86
80
1.84
70
Eefficiency (%)
Vout (V)
1.90
1.82
1.80
1.78
1.76
60
����
50
����
40
30
1.74
20
1.72
1.70
0.1
10
0
0.1
1
10
100
1000
10000
Vin=5V
1
10
100
1000
10000
Iout (mA)
Iout (mA)
Shutdown
Startup
Vin=5.0V, Vout=1.8V, Iload=1A
Vin=5.0V, Vout=1.8V, Iload=1A
Vin
5V/div
Vin
5V/div
Ven
5V/div
Ven
5V/div
Vout
1V/div
Vout
1V/div
Isw
1A/div
Isw
1A/div
10μs/div
200μs/div
Load Transient
Output Ripple
Vin=5.0V, Vout=1.8V, Iload=0.05A~1A
Vin=5.0V, Vout=1.8V, Iload=1A
Vout
50mV/div
Vout
10mV/div
Isw
1A/div
1L
1A/div
500ns/div
Short Protection/Current limit
Vin=5.0V, Vout=1.8V, Iload=0A~short
7 - 6
200μs/div
Rev.1.0
Ven
5V/div
Vin
5V/div
Vout
1V/div
Ven
5V/div
Isw
1A/div
Vout
1V/div
Ven
5V/div
Startup
Vin=5.0V, Vout=1.8V, Iload=1A
Vout
1V/div
Vin
5V/div
Shutdown
Vin=5.0V, Vout=1.8V, Iload=1A
Ven
ELM600xB 1A 1.5MHz high efficiency synchronous
5V/div
Isw PWM step down DC/DC converter
Isw
1A/div
1A/div
Vout
1V/div
200μs/div
Isw
1A/div
Vin=5.0V, Vout=1.8V, Iload=0.05A~1A
10μs/div
Load Transient
Output Ripple
Vin=5.0V, Vout=1.8V, Iload=0.05A~1A
Vin=5.0V, Vout=1.8V, Iload=1A
Vout
10mV/div
Vout
50mV/div
Isw
1A/div
Vout
10mV/div
1L
Vout
1A/div
50mV/div
200μs/div
500ns/div
1L
1A/div
Short Protection/Current limit
Vin=5.0V, Vout=1.8V, Iload=0A~short
500ns/div
Vout
1V/div
10μs/div
Load Transient
Output Ripple
Vin=5.0V, Vout=1.8V, Iload=1A
200μs/div
Isw
1A/div
http://www.elm-tech.com
200μs/div
Short Protection/Current limit
Vin=5.0V, Vout=1.8V, Iload=0A~short
Vout
1V/div
Isw
2A/div
Isw
2A/div
200μs/div
200μs/div
Rev.1.0
7 - 7
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