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 constantfrequency. 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. Itcan run 100% duty cycle for low dropout application. The output voltage of ELM600xB is adjustable from theFB 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

SymbolVinVsw
VenVfbIsw

Power dissipation

Pd

Operating temperature range
Storage temperature range

TopTstg

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

UnitVVVVAmW°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
1/ 7

ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com■Selection guide

ELM600xB-x
SymbolaPackageb

Product version

cTaping 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)

6544656445612331213321Pin No.
123456Exposed Pad

Pin name
NC
EN
VIN
SW
GND
FBNC

Pin description
No connected.
Enable control input
Main supply
Power switch output
GroundVoltage feedback
No connected.

TSOT-25(TOP VIEW)
Pin No. Pin namePin description
1EN
Enable control input
2
GND Ground
3SW
Power switch output
4VIN
Main supply
5FB
Voltage feedback

Rev.1.02/ 7

ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com■Standard circuit ( Adjustable Output Voltage )L=2.2�H

C1=4.7�F

C5C6R1C3R2C4C2=10�F

R3

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

M1

PWM
LogicSW

PWM
Comparator

Error
amplifierOscillator

LG

M2

ClockDCC

Zero-current
comparator

+-+

FB

UG+

0.6V+

EN

Shut down
control

GND

Rev.1.0
3/ 7

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
SymbolTest condition
Min.
Typ.
Max. Unit
Supply voltage
Vin2.55.5V
Output voltage line regulation∆Vout/∆Vin Vin=2.5V to 5.5V
-33%/V
Output voltage load regulation
Vlr-33%
Reference voltage
For adjustable Vout
0.588 0.600 0.612
VVref
Output range (adjustable voltage)
Vin=2.5V to 5.5V
-3+3%
Vout
Shutdown current
Is
Ven=0V
0.1
1.0µA
Ven=Vin, Vfb=Vref×1.1110Quiescent current
IqµA
No switching
SW leakage current
Ileak
Ven=0V, Vsw=0V or Vin-11µA
RdsonP Isw=100mA
250mΩ
PMOSFET on resistance
NMOSFET on resistanceRdsonN Isw=-100mA
200mΩ
Duty cycle=100%
PMOSFET current limit
IPcl
2ACurrent 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
VEN low level input voltage
Venl-40°C ≤ Top ≤ +85°C
0.4
VEN input current
Ien
Ven=0V to Vin-11µA■MarkingDFN6-2x2
Marka~fContent
Assembly lot No. :0 ~ 9 and A ~ ZTSOT-25
Marka~eContent
Assembly lot No. :0 ~ 9 and A ~ Z

Rev.1.04/ 7

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 definedas:
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 forsuperior 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 theerror 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 mainswitch 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.1.05/ 7

ELM600xB 1A 1.5MHz high efficiency synchronous PWM step down DC/DC converter
http://www.elm-tech.com■Typical characteristics

Iout-Efficiency

Iout-VoutVin=5V, Vout=1.8V

100

1.88901.86801.8470Eefficiency (%)

Vout (V)

1.90

1.82

1.80

1.78

1.76

60

����

50

����4030

1.74

20

1.72
1.70
0.1

1000.1110100

1000

10000

Vin=5V

1101001000

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/divVin
5V/divVen
5V/divVen
5V/divVout
1V/divVout
1V/divIsw
1A/divIsw
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

6/ 7200μs/div

Rev.1.0Ven
5V/divVin
5V/divVout
1V/divVen
5V/divIsw
1A/divVout
1V/divVen
5V/div

Startup

Vin=5.0V, Vout=1.8V, Iload=1A

Vout
1V/divVin
5V/divShutdown

Vin=5.0V, Vout=1.8V, Iload=1A

Ven
ELM600xB 1A 1.5MHz high efficiency synchronous
5V/divIsw PWM step down DC/DC converter

Isw
1A/div

1A/divVout
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/div10μs/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~shortVout
1V/divIsw
2A/divIsw
2A/div

200μs/div

200μs/div

Rev.1.07/ 7