ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■General description

ELM613xDC is a fully integrated high efficiency synchronous step-down converter which requires minimum
number of external components. It offers very compact solution with up to 4A continuous output current overa wide input range. ELM613xDC employs proprietary Constant On-Time (COT) control scheme providing
superior transient response and maintaining constant switching frequency under the continuous conduction
mode operation. The internal ramp compensation network allows stable operation with ultra-low equivalent
series resistance (ESR) output ceramic capacitors without using external compensation network. An error
amplifier in the control loop provides excellent line and load regulation. ELM613xDC integrates extensive
protection functions include: UVLO, OCP and thermal shutdown. Input under- voltage lockout is internally set as 3.8V.
The unique ultrasonic pulse-skipping mode (ELM613UDC) maintains the switching frequency above 25kHz,
which eliminates noise in audio applications. Other features include pulse skipping mode (ELM613NDC),
which maximizes efficiency in light-load applications, and forced PWM mode(ELM613ADC) which operates
in constant frequency PWM mode regardless of load current.

■Features■Application• Stable operation with output low ESR ceramic capacitors• Laptop computer• Externally adjustable built-in soft start (Typ.2ms)• Tablet PC• Fast PWM Constant On Time (COT) control scheme• Networking systems
with superior transient performance• Personal video recorders• Accurate EN threshold for the external programmable Vin UVLO
• Flat panel television and monitors• Low quiescent current• Distributed power systems• Thermal shutdown with auto recovery• Hiccup mode 8 times then latch-off over current protection• Input voltage range: 4.0V to 30.0V• Feedback voltage accuracy: 0.8V±2%• Continuous output current: Max.4A(5A Peak)• Duty cycle (low dropout operation): Max.100%• Switching frequency: Typ.500kHz• 2 Types of light load mode and a forced PWM mode control schemes
ELM613UDC : Ultrasonic pulse skip mode (25kHz min)
ELM613NDC : Pulse skip mode
ELM613ADC : Forced PWM mode
• Integrated high side and low side switches: Typ.40mΩ/40mΩ• Package: SOP-8(with Exposed Pad)

■Standard circuit

Ren1
100K

5

Cin1
22�F

Cin2
0.1�F

Cvcc
1�F

Cen
0.1�F
Option

BST

3

SW

4

80%

L

6.8�H
Cout1
22�F

EN

FB
SS GND
PGND
Css
EP
Option

7

90%
Cbst
0.1�F

2 VCC

8

Ren2
Option

VIN

Cout2

22�F

R1

1

Cff

Efficiency(%)

4V to 30V

Cbuck
100�F
OptionEfficiency-Iout

100%

70%
12Vin5Vo
24Vin5Vo
12Vin9Vo
24Vin9Vo
Ultra Sonic Mode 12Vin5Vo
Ultra Sonic Mode 24Vin5Vo
Ultra Sonic Mode 12Vin9Vo
Ultra Sonic Mode 24Vin9Vo
FPWM Mode 12Vin5Vo
FPWM Mode 24Vin5Vo

60%

50%
40%
30%
20%

R2

10%

0%

0.01

0.1

1

10

Iout (A)Rev.1.8
1 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Selection guide
ELM613xDC-N
SymbolaLight load operationbcd

Package
Product version
Taping direction

U: Ultra-sonic mode
N: PFM mode
A: Forced PWM mode
D: SOP-8 (with Exposed Pad)C
N: Please refer to page 14

ELM613 x DC - N
↑↑↑ ↑
abc d

* Taping direction is one way.

■Maximum absolute ratings (1)Parameter
VIN supply voltage
EN to GND
SW to GNDPGND to GND
BST to SW
All other pins to GND
Junction temperature
Thermal resistance (3), (4)Power dissipation (3), (4)Storage temperature range

Symbol
Vin
Ven
Vsw
Vpgnd
Vbst
Vall
Tj
θja
Pd
Tstg

Limit
+36
+36
-0.3 to Vin+0.3-0.3 to +0.3
-0.3 to +6.0
-0.3 to +6.0
+150
51
2.45
-65 to +150

Unit
V
V
V
V
V
V
°C
°C/W
W
°C

Limit
+4.0 to +30.0
0.8 to Vin-40 to +125

Unit
V
V
°C

■Recommend operating conditions (2)Parameter
Supply voltage
Output voltage
Operating temperature

Symbol
Vin
Vout
Top

Note:
(1) Stress exceeding those listed “Maximum absolute ratings” may damage the device.
(2) The device is not guaranteed to function outside of the recommended operating conditions.
(3) Measured on JESD51-7, 4-Layer PCB.
(4) The maximum allowable power dissipation is a function of the maximum junction temperature Tj_max, the junction
to ambient thermal resistance θJA, and the ambient temperature Ta. The maximum allowable continuous power dissipation at any ambient temperature is calculated by Pd_max= (Tj_max-Ta)/θja. Exceeding the maximum allowable
power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal
thermal shutdown circuitry protects the device from permanent damage.

Rev.1.8
2 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Pin configuration
SOP-8(TOP VIEW)

Exposed pad on backside
Pin No.

Pin name

1

FB

2

VCC

3

BST

4

SW

5

VIN

6

GND

7

SS

8

EN

EP

PGND

Pin description
Feedback Input. Connect FB to the center of the external resistor divider from theoutput to the AGND to set the output voltage.
Internal 5V LDO output. The driver and control circuits are powered from this voltage.
Decouple with a minimum 1µF ceramic capacitor to PGND as close to the pin as possible.
High-Side Driver Bootstrap Supply. Connect a 0.1µF capacitor between SW and BST
for proper operation.
Output pin of internal power switches. Connect this pin to the inductor and bootstrap
capacitor.
Supply voltage. VIN pin supplies power for internal MOSFET and regulator.
ELM613xDC operates from a +4V to +30V input rail. Bypass VIN to PGND witha 22µF or greater low ESR ceramic capacitor. If the voltage spike on VIN pin exceeds
36V, additional 100µF electrolytic capacitor is recommended.
System analog ground.
Output Soft-Start Pin. This pin allows user control of output voltage ramp rate during
start-up. An internal 10μA pull-up current from VCC on this pin allows a capacitor toprogram output voltage slew rate. This pin is pulled to ground with an internal 200Ω
MOSFET during shutdown and fault conditions.
The device is shut down when this pin is low and active when this pin is high. The
hysteretic threshold voltage is 1.3V going up and 1.2V going down. An external resistor
divider from VIN can be used to program a VIN threshold below which the device will
shut down. Connect EN to VIN through a 100k resistor for automatic startup.
Exposed pad is connected to the low side MOSFET Power Ground. Connect EP to alarge-area contiguous copper ground plane for effective power dissipation.

Rev.1.8
3 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Block diagram
VCC

EN

VCCREGSS

Softstrat

VIN

ULVO

Bootstrap
Regulator

BG

+
+

Vref

Error
Amplifier

+
+

Ren

PWM
On Time

PWM
Comparator

BST
HS
Driver

M1

Control
Logic

SW
VCC
LS
Driver

M2

PGND

FB

+
-

Zero - Current
Comparator+-

Valley - Current
Comparator

Fault
Logic

GND

+

90%Vref+-

110%Vref■Electrical characteristics
Parameter
Input voltage range
Shutdown current
Input under voltage lockout threshold
Input under voltage lockout hysteresis
Supply current
Feedback regulation voltage
Feedback current
Internal soft-start time
Switching frequency

Top=+25°C, Vin=+12V, Vout=5V and Ven=2V, unless otherwise noted.

SymbolConditions
Vin
Is
Ven=0V, Vin=12V
Vuvlo Vin increasing
Vth_hys
Icc
Vfb=0.84V
VfbrefIfb
Vfb=0.8V
Tss
Iout=1A
Fsw

Minimum off time
Toff
Maximum duty cycle (5)Dmax
HS main switch on resistance
Ron_hsHS switch leakage current
Ileak_H
Low side(LS) switch valley current limit Ivalley
LS switch zero-cross current limit
Izx
LS switch on resistanceRon_lsLS switch leakage current
Ileak_ls
EN on threshold
Ven_onEN off threshold
Ven_off
EN internal pull down resistor
Ren
Vcc linear regulator
Vreg
Thermal shutdown
Tsd1
Thermal shutdown hysteresis
Tsd2

Min. Typ.
4
1
3.80
430
130
784 800-100
2500
Ultrasonic mode ELM613UDC Iout=0A 25
30
120
Vfb=0.76V
100
40
Vin=12V, Ven=Vsw=0V
4.5
6.5
80
40
Vin=Vsw=12V, Ven=0V
Ven ramp up
1.2
1.3
Ven ramp down
1.1
1.2
700 10000<Ivcc<10mA
4.7
5.0
160
30

Max. Unit
30
V
8
µA
4.05
V
mV
µA
816 mV+100 nA
msec
kHz

1
8.5
1
1.4
1.3
1300
5.3

ns
%
mΩ
µA
A
mA
mΩ
µA
V
V
kΩ
V
°C
°C

Note(5):
When the input voltage approaches the output voltage, ELM613xDC will extend the on-time and force the main highside switch remaining on for multiple cycles (>10 µsec). High side switch is only turned off momentarily, and low sideswitch is forced on shortly (typical 120ns) to refresh the BST capacitor. High side switch will resume on after the BST
refresh.

Rev.1.8
4 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Typical characteristics• Vin=12V, Vout=3.3V/5V, L=4.7µH/6.8µH, Cbuck=100µF, Cin1=22µF, Cin2=0.1µF,
Cout=22µF×2,
Ta=+25°C,
unlessnoted.
Performance waveforms
are testedon the otherwise
evaluation boardof the Design Example section.
VIN=12V, VOUT =3.3V/5V, L=3.3µH/4.7µH, TJ=+25°C, unless otherwise noted.

Steady State Test

Steady State Test (Ultra-sonic mode)
VIN
10V/div
VOUT
50mV/div

Steady State Test

VIN=12V
Ultra Sonic Modef>25kHzSW
5V/divIL
1A/div

VOUT=3.3V

IOUT=0A

80us/div

Steady State Test

Steady State Test (Ultra-sonic mode)
VIN
10V/div
VOUT
50mV/div

Steady State Test

VIN=12V
Ultra Sonic Modef>25kHzSW
5V/divIL
1A/div

VOUT=5V

IOUT=0A
40us/div

Load Transient Response

Load Transient Response

Load Transient Response

Rev.1.8
5 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com• Vin=12V, Vout=3.3V/5V, L=4.7µH/6.8µH, Cbuck=100µF, Cin1=22µF, Cin2=0.1µF,
Performance waveforms
are testedon the evaluation
boardof the Design Example section.
Cout=22µF×2,
Ta=+25°C,
unlessotherwise
noted.
VIN=12V, VOUT =3.3V/5V, L=3.3µH/4.7µH, TJ=+25°C, unless otherwise noted.

VIN power on

VIN power on

VIN power on

VIN power off

VIN power on

VIN power off

VIN power off

VIN power off

Short Protection
VIN
10V/div
VOUT
2V/div

VIN=12V
VOUT=5V
IOUT=0A~shortSW
5V/divIL
5A/div

4ms/div

Rev.1.8
6 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com• Vin=12V, Vout=3.3V/5V, L=4.7µH/6.8µH, Cbuck=100µF, Cin1=22µF, Cin2=0.1µF,
Performance waveforms
are testedon the evaluation
boardof the Design Example section.
Cout=22µF×2,
Ta=+25°C,
unlessotherwise
noted.
VIN=12V, VOUT =3.3V/5V, L=3.3µH/4.7µH, TJ=+25°C, unless otherwise noted.

EN power on

EN power off

Short Protection
VIN
20V/div
VOUT
2V/div

VIN=24V
VOUT=5V
IOUT=0A~shortSW
10V/div
IL
5A/div

EN power on

EN power on

EN power off

EN power off

4ms/div

EN power on

EN power off

Rev.1.8
7 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Operation

ELM613xDC is a fully integrated synchronous step-down converter employing constant on-time (COT) control
scheme to achieve superior transient performance. Its proprietary internal ramp compensation offers stable
operation with lower ESR ceramic output capacitors without using external complex compensation networks.
1. Constant on-time control
The constant on-time control (COT) operates by comparing the feedback voltage Vfb with the reference voltage. When FB droops below the reference, the control circuit turns on HS switch immediately for a pre-determined period of time (on-time) to ramp up the inductor current. When this on-time times out, the LS switch isthen turned on to ramp down the inductor current. The LS switch is turned off when inductor current reaches
zero Izx (or triggers negative current limit) or HS switch is turned on again for the next cycle. This operation repeats itself if FB droops below reference again.
ELM613xDC uses a proprietary algorithm to calculate the on-time based on input voltage, output voltage andload current to achieve nearly constant switching frequency over entire continuous conduction load current
range. The on-time can be estimated as:
Vout
Ton =
× 2µs
Vin
Due to its immediate response on FB voltage droop and simplified loop compensation, The ELM613xDC offers superior transient response compare to traditional fixed frequency PWM control converters.
2. Light load operation
In medium and heavy load condition, ELM613xDC operates in PWM mode with typical switching frequencyof 500kHz. When load current reduces, ELM613NDC naturally transitions from PWM mode to PFM mode
where the pulse width remains the calculated on-time but the switching frequency reduces to accommodate thelow output current. The lower the output current, the lower the switching frequency. Once the switching frequency drops to low enough, the devices enter sleep mode to cut down its quiescent current to maintain high efficiency in light load.
The critical load current at the boundary of PWM mode and PFM mode is related to the inductor ripple current,
which depends on the inductor value, input voltage and output voltage. Typically this critical load current levelis estimated as:
1 (Vin - Vout ) × Vout
Icrit =
2 L × Fsw × Vin
When switching frequency drops below 20kHz in very light load condition, the switching noise can be heard
by the human ears. ELM613UDC offers a unique pulse-skipping mode with a minimum switching frequency of
25kHz. This ultrasonic pulse-skipping mode reduces audio-frequency modulation of the power supply that may
occur at very light loads. The transition to fixed-frequency PWM operation is automatic and occurs at the same
point as in pulse-skipping Mode. Ultrasonic pulse skipping occurs if no switching has taken place within thelast 30µs. Low side switch turns on for a short period to induce a negative current in the inductor to discharge
the output. High side turns on if the output drops below the regulation point. The ELM613ADC in forced
PWM mode performs PWM mode control with a fixed oscillation frequency of 500kHz regardless of the load.
Therefore, the ELM613ADC emphasizes easy noise suppression, low output ripple voltage and high output
voltage accuracy, and high speed response to load fluctuations, rather than high efficiency under light load.
Rev.1.88 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com

3. 100% Duty cycle low dropout operation

When input voltage approaches the output voltage, ELM613xDC will extend the on-time toward the maximum
on-time to satisfy the duty cycle requirement to regulate the output voltage. If the input further drops to equal or
lower than the output level, ELM613xDC forces the main high side (HS) switch to remain on for more than one
cycle, eventually reaching 100% duty cycle. The 100% duty cycle operation allows the converter to effectively
pass through the input voltage directly to output with minimum voltage drops on the HS switch and the inductor.
In the low dropout operation mode, ELM613xDC turns on HS switch for multiple switching cycles until it turns
off HS switch momentarily and turns on low side (LS) switch (typical 120ns) to refresh the BST supply voltage.
The LS switch is turned off after the BST refresh pulse, then the HS switch resumes on for multiple switchingcycles which gives the effective 100% duty cycle. The refresh BST pulse is needed to charge the BST capacitor
and ensure the HS switch driver circuit proper operation.
4. Enable
ELM613xDC offers an accurate enable threshold of EN pin, which is typically 1.3V rise and 1.2V fall.
ELM613xDC is enabled by pulling up the EN pin above 1.3V and ELM613xDC is disabled by pulling down the
EN pin below 1.2V.
When using the EN pin threshold voltage to program the input startup voltage level, the following equation
shall be used:
Ren1 + Ren2 // 1M
Vin-shutdown = 1.2V ×
Ren2 // 1M
Where the 1MegΩ is the internal pull down resistor on EN pin.
When EN is pulled high, ELMx613DC will start up if VIN is higher than UVLO threshold. When EN is pulled
low, ELM613xDC will go into shutdown. Tie EN pin to VIN if the shutdown feature is not used.
5. Soft start
ELM613xDC has built-in soft start of 2 msec. During the soft start period, output voltage is ramped up linearly
to the regulation level, independent of the load current and output capacitor value. SS pin allows user control of
output voltage ramp rate during start-up. An internal 10μA pull-up current from VCC on this pin allows a capacitor to program output voltage slew rate. The soft start time with different capacitor is below:
Tss =0.8V × Css
× 1000,10µA

here Css > 0.025µF

6. Current limit and hiccup mode
ELM613xDC has built-in cycle-by-cycle current limit protection to prevent inductor current from runningaway in any fault conditions. ELM613xDC continuously monitors the inductor valley current during its
operation. Once the valley current exceeds the limit level, ELM613xDC will turn on LS and wait for the
inductor current to drop down to a pre-determined level before the HS can be turned on again. If this current
limit condition is repeated for a sustained long period of time, ELM613xDC will enter hiccup mode, where itstop switching for a pre-determined period of time before automatically re-try to start up again. It always starts
up with soft-start to limit inrush current and avoid output overshoot.
When ELM613xDC enters valley current limit mode, the peak current is also limit due to the fixed on-time of
the HS, and this peak current can be estimated as:
Vin - Vout
Ipeak = Ivalley + Ton ×
L
Rev.1.8
9 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Application information
1. Setting the output voltage

External feedback resistors are used to set the output voltage. 1% resistors are recommended to maintain output voltage accuracy. Refer to typical application circuit on page1, the top feedback resistor R1 has some impact
on the loop stability, R1 recommended range is between 10kΩ~150kΩ. For any chosen R1, the bottom feedback
resistor R2 can be calculated as:
R1
R2 =
Vout
-1
0.8
2. Inductor
The inductor is necessary to supply constant current to the output load while being driven by the switched input voltage. A larger-value inductor will result in less ripple current that will result in lower output ripple voltage. However, a larger-value inductor will have a larger physical footprint, higher series resistance, and/or lower
saturation current. A good rule for determining the inductance value is to design the peak-to-peak ripple current
in the inductor to be in the range of 30% to 40% of the maximum output current, and that the peak inductor current is below the maximum switch current limit. The inductance value can be calculated by:
Vout
Vout
L=
× (1 )
Fsw × ∆IL
Vin
Where ΔIL is the peak-to-peak inductor ripple current.
To avoid overheating and poor efficiency, an inductor must be chosen with an RMS current rating that isgreater than the maximum expected output load of the application. In addition, the saturation current (typicallylabeled ISAT) rating of the inductor must be higher than the maximum load current plus 1/2 of in inductor ripple
current.
The peak inductor current can be calculated by:
Vout
Vout
ILP = Iout +×(1)2Fsw × L
Vin
3. Input capacitor
The input current to the step-down converter is discontinuous and therefore requires a capacitor to supply the
AC current to the step-down converter while maintaining the DC input voltage. Ceramic capacitors are recommended for best performance and should be placed as close to the VIN pin as possible. Capacitors with X5R
and X7R ceramic dielectrics are recommended because they are fairly stable with temperature fluctuations. The
capacitors must also have a ripple current rating greater than the maximum input ripple current of the converter.
The input ripple current can be estimated as follows:
Icin = Iout ×

√

Vout
Vout
)
×(1VinVin

The worst-case condition occurs at Vin = 2*Vout, where:
Iout
Icin =
2
For simplification, choose the input capacitor with an RMS current rating greater than half of the maximum
load current. The input capacitance value determines the input voltage ripple of the converter. If there is an input
Rev.1.8
10 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com
voltage ripple requirement in the system, choose the input capacitor that meets the specification. The input voltage ripple can be estimated as follows:
Vout
Vout
Iout
∆Vin =
××(1)Fsw × Cin Vin
Vin
Under worst-case conditions where Vin = 2*Vout:
1
Iout∆Vin = ×
4 Fsw × Cin
4. Output capacitor
The output capacitor has two essential functions. Along with the inductor, it filters the square wave generated
by the ELM613xDC to produce the DC output. In this role it determines the output ripple, thus low impedanceat the switching frequency is important. The second function is to store energy in order to satisfy transient loads
and stabilize the ELM613xDC’s control loop. X5R or X7R type ceramic capacitors have very low equivalent
series resistance (ESR) and provide low output ripple and good transient response. Transient performance canbe improved with a higher value output capacitor and the addition of a feed-forward capacitor placed between
Vout and FB. Increasing the output capacitance will also decrease the output voltage ripple. A lower value of
output capacitor can be used to save space and cost but transient performance will suffer and may cause loop instability. When choosing a capacitor, special attention should be given to the data sheet to calculate the effective
capacitance under the relevant operating conditions of voltage bias and temperature. A physically larger capacitor or one with a higher voltage rating may be required.
5. PCB Layout instruction(1) The high current paths (PGND, VIN, and SW) should be placed very close to the device with short, direct
and wide traces.
(2) Put the input capacitors as close to the VIN and PGND pins as possible.
(3) Put the decoupling capacitor as close to the VCC and PGND pins as possible. If necessary to use VIA, place
3 or more VIAs to reduce the parasitic inductance of the VIA.
(4) Keep the switching node SW short and away from the feedback network.
(5) The external feedback resistors should be placed next to the FB pin, which is a high-impedance node.
(6) Keep the BST voltage path (BST, Cbst and SW) as short as possible.
(7) Keep the VIN and PGND pads connected with large copper and use at least two layers for VIN and PGND
trace to achieve better thermal performance. Also, add several Vias with 10mil_drill/18mil_copper_widthclose to the VIN and PGND pads to help on thermal dissipation.
(8) Four-layer layout is strongly recommended to achieve better thermal performance.

Rev.1.8
11 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Application schematic
4V to 30V

5

Cbuck
100�F
Option

Ren1
100K

Cin1
22�F

Cin2
0.1�F
Cvcc
1�F

Ren2
Option

BST

3

Cbst
0.1�F

2 VCC

SW
8

Cen
0.1�F
Option

VIN

7

4

6.8�H
Cout1
22�F

EN

SS GND

Css
Option

L

FB
PGND
EP

Cout2
22�F

R1

1

Cff

R2

Application schematic BOM list
Value

Ref

1
1
1

Cin1
22µF
Ceramic capacitor, 50V, X5R
Cin2
0.1µF
Ceramic capacitor, 50V, X5R
Cbuck 100µF (Option, see Pin configuration item-5) Electrolytic capacitor, 50V

2

Cout

22µF

Ceramic capacitor, 16V, X5R

1206

1
1

Cbst
Cvcc

0.1µF
1µF

Ceramic capacitor, 10V, X5R
Ceramic capacitor, 10V, X5R

0603
0603

1

Css

(Option, see Operation item-5)

Ceramic capacitor, 10V, X5R

0603

1

Cen

Ceramic capacitor, 50V, X5R

0603

1

L

0.1μF(Option, for delayed EN)
6.8µH
Vout=5.0V

Inductor, Isat>6A

SMD

1

R1

Resistor, ±1%

0603

1

R2

1

Cff

1

Ren1

100KΩ

1
1

Ren2
Power IC

(Option, see Operation item-4)
ELM613xDC

Vout=3.3V

Description

Package(size inch)

Qty

1206
0603
8×12(mm)

Vout=5.0V

4.7µH
120KΩ

Vout=3.3V

120KΩ

Vout=5.0V
Vout=3.3V
Vout=5.0V
Vout=3.3V

22.6KΩ
38.3KΩ

Resistor, ±1%0603

10~47pf
10~47pf

Ceramic capacitor, 10V

0603

Resistor, ±5%0603

Resistor, ±5%
Step-down DC/DC converter

0603
SOP-8

Rev.1.8
12 / 14

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Marking

Mark
MT3905

Content
Product ID: ELM613NDC

MT3905U
MT3905A
a to eProduct ID: ELM613UDC
Product ID: ELM613ADC
Assembly lot No.

■SOP-8 Outline dimensions
L

D

e

A1

b

Symbol
A
A1
DA
E1
A1
D1
D
E2
E1
E
D1
L
E2
b
E
e

SYMBOLSLMILLIMETERS
MIN.
MAX.
1.35MILLIMETERS1.75
0.00
0.15
MIN.
MAX.
4.7
5.1
1.35
1.75
3.7
4.1
0.00
0.15
2.90
3.50
4.7
5.1
2.00
2.50
3.7
4.1
5.80
6.20
2.90
3.50
0.40
1.27
2.00
2.50
0.31
0.51
5.80
6.20
1.16
1.37

A

E

E2

E1

D1

INCHES
MIN.
0.053 INCHES
0.000
MIN.
0.185
0.053
0.145
0.000
0.114
0.185
0.080
0.145
0.228
0.114
0.016
0.080
0.012
0.228
0.046

MAX.
0.069
0.006
MIN.
0.200
0.069
0.161
0.006
0.138
0.200
0.098
0.161
0.244
0.138
0.050
0.098
0.020
0.244
0.054

0.40

1.27

b

0.31

0.51

0.012

0.020

e

1.16

1.37

0.046

0.054

13 / 14

0.016

0.050

Rev.1.8

ELM613xDC 4A, 30V, 500kHz, synchronous step-down DC/DC converter
http://www.elm-tech.com■Reel & carrier tape dimension• Orientation / Carrier tape information

B

A

A

A

B

B

C
C

C

D
Feeding direction

2.

D

D

Feeding direction
Feeding direction

Reel Information:

2. Reel Information:• Reel information
2. Reel Information:• Dimension
detailsDetails:
3. Dimension
3.

3. Dimension Details:
Dimension Details:
PKG Type

A

B

C

D

E

F

Q'ty/Reel

PKG Type 4.0 mm A
SOP8EP
1.5 mm B 12.0 mm C 8.0 mm D 13 inches E 13.0 mm F
2,500Q'ty/Reel
PKG Type
A
B
C
D
E
F
Q'ty/Reel
SOP8EP
4.0 mm
1.5 mm
12.0 mm
8.0 mm13 inches
13.0 mm2,500
SOP8EP
4.0 mm
1.5 mm
12.0 mm
8.0 mm13 inches
13.0 mm2,500

Rev.1.8
14 / 14