ELM604PA 1.4MHz, 800mA dual PWM step-down converter
http://www.elm-tech.com■General description

ELM604PA consists of dual high efficiency PWM step-down DC/DC converters operated with current
mode and constant frequency. For each converter the integration of a main switch and a synchronous rectifier eliminates the use of an external Schottky diode. ELM604PA is ideal for the application of portableelectronic devices with a single cell Lithium-ion (Li+) battery. Each converter can supply 800mA of load current
from a 2.5V to 6V input voltage. The output voltage can be regulated as low as 0.6V. It can also run at 100%duty cycle for low dropout applications.

■Features■Application• Current mode operation• Thermal shutdown protection• Short circuit protection• Constant frequency operation : Typ.1.4MHz• Output current: 800mA(on each channel)• Low output voltage: 0.6V• High efficiency: Max.95%• Shutdown current: Typ.0.1µA• Supply voltage: 2.5V to 6.0V
• Full duty ratio: 0 to 100% (in dropout)• Package: TDFN10-3x3• PDAs• MP3 players• Portable instruments• Cellular and smart phones• Digital still and video cameras• Microprocessors and DSP core supplies■Maximum absolute ratings
Parameter
VIN1/VIN2 power supply voltage
Apply voltage to SW1/SW2
Apply voltage to FB1/FB2Apply voltage to EN1/EN2
Operating temperature range
Storage temperature range

SymbolVinVsw
VfbVenTopTstg

Limit-0.3 to +6.5
-0.3 to Vin+0.3-0.3 to Vin1/Vin2-0.3 to Vin1/Vin2-40 to +85-65 to +150

Caution:Permanent damage to the device may occur when ratings above maximum absolute ones are used.

UnitVVVV°C°C■Selection guide

ELM604PA-N
Symbolabc

Package
Product version
Taping direction

ELM604PA - N↑↑ ↑ab c

P: TDFN10-3x3
A
N: Refer to PKG file

* Taping direction is one way.

Rev.1.2
1/6

ELM604PA 1.4MHz, 800mA dual PWM step-down converter
http://www.elm-tech.com■Pin configuration
TDFN10-3x3(TOP VIEW)TDFN10-3x3(BOTTOM VIEW)

11101010101122999922338888334477774455666655Pin No.
12345678910Pin name
EN1FB1VIN2
GND2SW2EN2FB2
VIN1
GND1
SW1Cin122�FR5Pin description
Channel 1 enable control input
Channel 1 voltage feedback
Channel 2 supply input
Channel 2 ground pin
Channel 2 power switch output
Channel 2 enable control input
Channel 2 voltage feedback
Channel 1 supply input
Channel 1 ground pin
Channel 1 power switch output■Standard circuit
8361
L14.7�H1052
R11M�

R2499k�L24.7�H
C2

C1
Cout110�FCin222�FR679

Cout210�F4* Passive components not specified values in the above figure are optional.

Rev.1.2
2/6

ELM604PA 1.4MHz, 800mA dual PWM step-down converter
http://www.elm-tech.com■Block diagram

Vin1/Vin2
Slope Comp

Shut down
control

Current sense
amplifier+EN1/EN2

M1

Reference+

FB1/EB2+0.6V

PWM
Logic

PWM
Comparator

Error
amplifierSW1/SW2
M2

ClockDCC
Zero-current
comparator+-Oscillator

GND1/GND2■Electrical characteristics
Parameter
Supply voltage
Feedback current
Regulated feedback voltage
Reference voltage line regulation
Output voltage line regulation
Output voltage load regulation
Shutdown current
Quiescent current
SW leakage current
PMOSFET on resistance
NMOSFET on resistancePMOSFET current limit
Oscillator frequency
Thermal shutdown thresholdEN high level input voltage
EN low level input voltage
EN input current

Vin=3.6V, Typical values are at Top=25°C, unless otherwise noted.
Test condition
Min.
Typ.
Max. Unit
2.5
6.0
V-30.00.5
30.0
nA-40°C ≤ Top ≤ +85°C
0.582 0.600 0.618
VVin=2.5V to 6V
0.04
0.40 %/V
Vin=2.5V to 6V
0.04
0.40 %/V
0.5%
Ven=0V, Vin=6V
0.01
1.00
µA
Ven=Vin, Vfb=0.65V
Iq
200
µA
No switching
Ven=0V, Vfb=0.65V
Ileak
-1
1µA
Vsw=0V or 6V
RdsonP Isw=100mA
0.35
Ω
RdsonN Isw=-100mA
0.24Ω
Duty cycle=100%
IPcl
0.8
1.1
1.5
A
Current pulse width<1ms
Fosc
1.12
1.40
1.68 MHz
Ts
145°C
Venh
-40°C ≤ Top ≤ +85°C-1.1VVenl-40°C ≤ Top ≤ +85°C
0.3
VIen
Ven=0V to Vin-1
1µA
Symbol
Vin
Ifb
Vfb
∆Vfb
∆VoutVlrIs

Rev.1.2
3/6

ELM604PA 1.4MHz, 800mA dual PWM step-down converter
http://www.elm-tech.com■Application notes

ELM604PA has dual independent constant frequency current mode PWM step-down converters.
ELM604PA is optimized for low voltage, Li-ion battery powered applications where high efficiency andsmall size are critical. ELM604PA uses external resistor dividers to set two output voltages indepe
ndently from 0.6V to 6V. The device integrates both main switches and synchronous rectifiers, which provides high efficiency and eliminates the need for an external Schottky diode. ELM604PA can achieve 100% duty cycle. The duty cycle D of each 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 (1.4MHz), 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. Each channel switches at a constant frequency (1.4MHz) and regulates the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the induct
or peak current based on the feedback error voltage. During normal operation, the main switch is tur
ned 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 the next cycle starts.
2) Dropout operation
Each channel of the ELM604PA 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
ELM604PA 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 feedback voltage reaches 0.6V.
4) Maximum load current
ELM604PA 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.

■MarkingTDFN10-3x3
Marka to p

Content
Assembly lot No.:
0 to 9 & A to Z
Rev.1.24/6

ELM604PA 1.4MHz, 800mA dual PWM step-down converter
http://www.elm-tech.com■Typical characteristics• Vout=1.8V : Unless otherwise noted• V=1.8V
Cin1=22µF, Cout1=10µF, C1=1000pF, L1=4.7µH, R1=100kΩ, R2=50kΩ, Top=25°C
Ven=2V, Vin=5V, No load

Vout (V)100

Vin=5V

8060

210402120000.1

11010001000

2Iout (mA)

Vout-Iout

1.94Time (ms)

6Ven (V)EFFICIENCY (%)

Start Response

EFFICIENCY-Iout

8

Vout-Vin

2.4

Vout (V)

Vout (V)2.0

1.8
Vin=5V

Iout=1mA

1.6100mA

1.2

0.8

0.4

1101001000

Iout (mA)

034Vin (V)

5Vin=5V, Iout=10mA�600mA

Vin=5V, Iout=100mA�600mA

Vout (V)

2.5

22

1.5

1.5

1

1000.5

11.5

2

2.5

Time (ms)3

3.5

Iout (A)Vout (V)2

Load Transient Response

Load Transient Response
2.5

1004

0.5

1

1.5

2

2.5

Time (ms)3

3.5

Iout (A)

1.74

Rev.1.2
5/6

ELM604PA 1.4MHz, 800mA dual PWM step-down converter
http://www.elm-tech.com• Vout=3.3V : Unless otherwise noted•Cin2=22µF,
V=3.3V Cout2=10µF, C2=1000pF, L2=4.7µH, R3=150kΩ, R4=33kΩ, Top=25°C
100

Vin=5V80Ven=2V, Vin=5V, No load

4
Vout (V)60

2040

2120000.1

11010001000

2Iout (mA)

Vout-Iout

3.35

4Time (ms)

6Ven (V)EFFICIENCY (%)

Start Response

EFFICIENCY-Iout

8Vout-Vin

3.5
3.0

3.3

3.25

Vout (V)

Vout (V)2.5

Vin=5V

Iout=1mA

2.0100mA

1.5

1.0

3.2

0.5
1101001000

Iout (mA)

0Vin=5V, Iout=10mA�600mA

Vout (V)
01

1.5

2

2.5

Time (ms)33.5

5

Vin=5V, Iout=100mA�600mA

3.5

3

2.5

10.5

4

1Iout (A)Vout (V)303Vin (V)

4

3.5

2.5

2

Load Transient Response

Load Transient Response
41004

0.5

11.52

2.5

Time (ms)3

3.5

Iout (A)

3.15

4Rev.1.2
6/6