SGM61410
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
GENERAL DESCRIPTION
FEATURES
The SGM61410 is a high frequency, synchronous
step-down converter with integrated switches. It can
deliver up to 600mA to the output over a wide input
voltage range of 5V to 45V. It is suitable for various
industrial or automotive applications with high input
voltage or for power conditioning from unregulated
sources. Moreover, the low 14µA quiescent current and
ultra-low shutdown current of only 0.6µA make it a
suitable choice for battery-powered applications.
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SGM61410 features high efficiency over a wide load
range achieved by scaling down the switching
frequency at light loads to reduce switching and gate
driving losses. Other features include, internal
compensation, internal monotonic soft-start even with
pre-biased output and fast loop response thanks to the
peak-current mode controller. Switching at 1.2MHz, the
SGM61410 can prevent EMI noise problems, such as
the ones found in AM radio, ADSL and PLC applications.
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Protection features include current limiting and short
circuit protection, thermal shutdown with auto recovery
and output over-voltage protection. Frequency foldback helps prevent inductor current runaway during
startup.
Wide 5V to 45V Operating Input Voltage Range
0.8V Internal Reference
Low Quiescent Current: 14μA (TYP)
0.6μA (TYP) Shutdown Current
Current Output up to 600mA
1.2MHz Switching Frequency
Internal Compensation and Soft-Start
Simple design and Minimal External Components
Up to 95% Efficiency at 12V/400mA
0.8V to 20V Adjustable Output Voltage
Current Limit and Short-Circuit Protection
Output Over-Voltage Protection and Thermal
Shutdown
Power-Save Mode and PWM Mode Operation
Monotonic Startup with Pre-biased Output
90% Maximum Duty Cycle
Available in a Green SOT-23-6 Package
-40℃ to +125℃ Operating Temperature Range
APPLICATIONS
High Voltage Power Conversions
Automotive Systems
Industrial Power Systems
Distributed Power Systems
Battery Powered Systems
Power Meters
SGM61410 is available in a Green SOT-23-6 package.
It operates over a wide ambient temperature range of
-40℃ to +125℃.
TYPICAL APPLICATION
VIN
1
2
CIN
10μF
5
EN
4
2
VIN
EN
BOOT
SGM61410
GND
1
SW 6
FB
3
CBOOT
0.47μF
L
10μH to 33μH
C1
330pF
COUT
22μF
VOUT
5V
R1
52.5kΩ
R2
10kΩ
Figure 1. Typical Application Circuit
SG Micro Corp
www.sg-micro.com
JUNE 2019 – REV. A
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
PACKAGE/ORDERING INFORMATION
MODEL
PACKAGE
DESCRIPTION
SPECIFIED
TEMPERATURE
RANGE
ORDERING
NUMBER
PACKAGE
MARKING
PACKING
OPTION
SGM61410
SOT-23-6
-40℃ to +125℃
SGM61410XN6G/TR
MPEXX
Tape and Reel, 3000
MARKING INFORMATION
NOTE: XX = Date Code.
YYY X X
Date Code - Week
Date Code - Year
Serial Number
Green (RoHS & HSF): SG Micro Corp defines "Green" to mean Pb-Free (RoHS compatible) and free of halogen substances. If
you have additional comments or questions, please contact your SGMICRO representative directly.
ABSOLUTE MAXIMUM RATINGS
VIN to GND ........................................................ -0.3V to 50V
EN to GND ................................................-0.3V to VIN + 0.3V
FB to GND ........................................................ -0.3V to 5.5V
SW to GND ...............................................-0.3V to VIN + 0.3V
BOOT to SW ..................................................... -0.3V to 5.5V
Package Thermal Resistance
SOT-23-6, θJA .......................................................... 170℃/W
Junction Temperature .................................................+150℃
Storage Temperature Range........................ -65℃ to +150℃
Lead Temperature (Soldering, 10s) ............................+260℃
ESD Susceptibility
HBM ............................................................................. 2000V
CDM ............................................................................ 1000V
ESD SENSITIVITY CAUTION
This integrated circuit can be damaged if ESD precautions
are not taken when handling. SGMICRO recommends that all
integrated circuits be handled with appropriate precautions.
Failure to observe proper handling and installation procedures
can cause damage. ESD damage can range from subtle
performance degradation to complete device failure. Precision
integrated circuits may be more susceptible to damage
because very small parametric changes could cause the
device not to meet its published specifications.
DISCLAIMER
SG Micro Corp reserves the right to make any change in
circuit design, or specifications without prior notice.
RECOMMENDED OPERATING CONDITIONS
Supply Input Voltage Range ...................................5V to 45V
Operating Junction Temperature Range ...... -40℃ to +125℃
Operating Ambient Temperature Range ...... -40℃ to +125℃
OVERSTRESS CAUTION
Stresses beyond those listed in Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to
absolute maximum rating conditions for extended periods
may affect reliability. Functional operation of the device at any
conditions beyond those indicated in the Recommended
Operating Conditions section is not implied.
SG Micro Corp
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JUNE 2019
2
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
PIN CONFIGURATION
(TOP VIEW)
BOOT
1
6
SW
GND
2
5
VIN
FB
3
4
EN
SOT-23-6
PIN DESCRIPTION
PIN
NAME
FUNCTION
1
BOOT
Bootstrap pin is used to provide a drive voltage, higher than the input voltage, to the topside
power switch. Place a 0.47µF boost capacitor (CBOOT) as close as possible to the IC between
this pin and SW pin. Do not place a resistor in series with this pin.
2
GND
Ground pin is the reference for input and the regulated output voltages. Requires special
layout considerations.
3
FB
Feedback pin for programming the output voltage. The SGM61410 regulates the FB pin to
0.8V. Connect the feedback resistor divider tap to this pin. If the FB voltage exceeds 110% of
0.8V, over-voltage protection (OVP) will stop all PWM switching.
4
EN
5
VIN
6
SW
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Enable pin should not be left open and it should not be driven above VIN + 0.3V. Device will
operate when the EN pin is high and shut down when the EN pin is low. EN can be tied to
VIN pin if the shutdown feature is not required or to a logic input for controlling shutdown.
VIN pin is connected to the input supply voltage and powers the internal control circuitry. This
voltage is monitored by a UVLO lockout comparator. VIN is also connected to the drain of the
converter top switch. Due to power switching, this pin has high di/dt transition edges and
must be decoupled to the GND by input capacitors as close as possible to the GND pin to
minimize the parasitic inductances.
Switching node pin is the output of the internal power converter and should be connect to the
output inductor. Bootstrap capacitor also connects to this pin. This node should be kept small
on the PCB to minimize capacitive coupling, noise coupling and radiation.
JUNE 2019
3
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
ELECTRICAL CHARACTERISTICS
(VIN = 18V, TJ = -40℃ to +125℃, typical values are at TJ = +25℃, unless otherwise noted.)
PARAMETER
Supply Input Voltage
SYMBOL
CONDITIONS
MIN
VIN
5
Under-Voltage Lockout Threshold
VUVLO
4.45
Under-Voltage Lockout Threshold
Hysteresis
VUVLO_HYS
VIN Quiescent Current
Shutdown
Sleep Mode
IQ
TYP
MAX
UNITS
45
V
4.7
4.95
V
370
mV
VEN = 0V
0.6
1.2
VEN = 2V, Not Switching, VIN ≤ 36V
14
20
Feedback Reference Voltage
VFB
VIN = 6V
0.800
0.823
V
Feedback Pin Input Current
IFB
VFB = 1V
0.1
1
µA
ILOAD = 600mA
100
Minimum High-side Switch On-Time
tON_MIN
Minimum High-side Switch Off-Time
tOFF_MIN
Switching Frequency
Switch Leakage Current
Top Power NMOS Current Limit
Top Power NMOS On-Resistance
Bottom Power NMOS On-Resistance
ISW_L
ILIM
RDSON
EN Input High Voltage
VIH
EN Input Low Voltage
VIL
ns
100
fSW
ISW_H
0.777
µA
0.85
VSW = 45V
VSW = 0V
TJ = +25℃
0.9
ILOAD = 0.1A
ILOAD = 0.1A
ns
1.2
1.5
MHz
0.1
1
µA
0.1
1
µA
1.2
1.5
A
700
mΩ
300
mΩ
1.2
V
0.5
EN Threshold, Hysteresis
VEN_HYS
120
Enable Leakage Current
IEN
0.1
1
Output Over-Voltage Threshold
VOUT_OV
V
mV
OVP Rising
0.84
0.89
0.95
OVP Falling
0.80
0.85
0.90
μA
V
Thermal Shutdown
TSHDN
150
℃
Thermal Shutdown Hysteresis
THYS
20
℃
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JUNE 2019
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1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
TYPICAL PERFORMANCE CHARACTERISTICS
TA = +25℃, VIN = 18V, L = 22μH and COUT = 10μF, unless otherwise noted.
Steady State
Steady State
5V/div
5V/div
VIN
VIN
5V/div
5V/div
VSW
VOUT
VIN = 12V, VOUT = 5V, IOUT = 100mA
500mA/div
IL
VOUT
IL
VIN = 12V, VOUT = 5V, IOUT = 600mA
Time (1μs/div)
Time (1μs/div)
Steady State
Steady State
VSW
VOUT
IL
VIN = 18V, VOUT = 12V, IOUT = 600mA
Time (1μs/div)
Time (1μs/div)
Power Up
Power Down
VSW
VIN = 18V, VOUT = 12V, IOUT = 600mA
Time (500μs /div)
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IL
VIN = 18V, VOUT = 12V, IOUT = 600mA
1A/div
IL
VSW
VOUT
5V/div
1A/div
VOUT
5V/div 20V/div
5V/div 20V/div 5V/div
VEN
VEN
500mA/div
VIN = 18V, VOUT = 12V, IOUT = 100mA
VIN
5V/div
IL
5V/div 500mA/div
VSW
VOUT
10V/div 10V/div
10V/div 10V/div
VIN
5V/div 500mA/div
5V/div
VSW
Time (200μs/div)
JUNE 2019
5
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 18V, L = 22μH and COUT = 10μF, unless otherwise noted.
Power Up
Power Down
VOUT
VIN = 24V, VOUT = 5V, IOUT = 600mA
500mA/div
IL
VSW
VOUT
IL
VIN = 24V, VOUT = 5V, IOUT = 600mA
Time (500μs/div)
Time (200μs/div)
Short Circuit Entry
Short Circuit Recovery
VSW
VOUT
VIN = 18V, VOUT = 5V
VIN
VSW
VOUT
IL
VIN = 18V, VOUT = 5V
Time (100μs/div)
500mA/div
IL
10V/div 20V/div 5V/div
10V/div 20V/div 5V/div 500mA/div
VIN
5V/div 20V/div 5V/div 500mA/div
5V/div 20V/div 5V/div
VEN
VSW
VEN
Time (800μs/div)
Load Transient Response
20V/div 20V/div
VIN
VSW
IOUT
VOUT = 5V, IOUT = 50mA to 600mA
200mV/div 500mA/div
VOUT
Time (1ms/div)
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JUNE 2019
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1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 18V, L = 22μH and COUT = 10μF, unless otherwise noted.
Efficiency vs. Load Current
100
90
90
80
80
70
70
Efficiency (%)
Efficiency (%)
Efficiency vs. Load Current
100
60
50
40
30
VIN = 12V
VIN = 15V
VIN = 18V
20
10
VOUT = 3.3V
0
0
100
200
300
400
500
60
50
40
30
VIN = 12V
VIN = 18V
VIN = 24V
VIN = 36V
20
10
VOUT = 5V
0
600
0
100
Load Current (mA)
200
Efficiency vs. Load Current
400
500
600
Load Regulation
100
5.045
90
VOUT = 5V
5.040
80
Output Voltage (V)
70
Efficiency (%)
300
Load Current (mA)
60
50
40
30
VIN = 15V
VIN = 18V
VIN = 24V
VIN = 36V
20
10
VOUT = 12V
0
0
100
5.035
5.030
5.025
VIN = 12V
VIN = 18V
VIN = 24V
VIN = 36V
5.020
5.015
200
300
400
500
600
0
100
Load Current (mA)
200
300
400
500
600
Load Current (mA)
Line Regulation
Shutdown Current and Quiescent Current
5.045
100
VOUT = 5V
ISLEEP
Input Current (μA)
Output Voltage (V)
5.040
5.035
5.030
5.025
IOUT = 100mA
IOUT = 300mA
IOUT = 600mA
5.020
5.015
5
14
23
32
Input Voltage (V)
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41
10
ISHUTDOWN
1
VOUT = 5V
0.1
50
0
5
10
15
20
25
30
35
40
45
50
Input Voltage (V)
JUNE 2019
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1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 18V, L = 22μH and COUT = 10μF, unless otherwise noted.
Switching Frequency vs. Temperature
1.20
5.0
1.18
Switching Frequency (MHz)
Output Voltage (V)
Dropout Curve
5.5
4.5
4.0
IOUT = 10mA
IOUT = 100mA
IOUT = 300mA
IOUT = 600mA
3.5
VOUT = 5V
3.0
4.7
5.1
1.16
1.14
1.12
1.10
5.5
5.9
6.3
6.7
7.1
7.5
-40 -25 -10
Input Voltage (V)
Switch Leakage vs. Temperature
Quiescent Current vs. Temperature
20
0.10
0.08
0.06
0.04
ISW_BOTTOM
Quiescent Current (μA)
0.12
Switch Leakage (μA)
20 35 50 65 80 95 110 125
Junction Temperature (℃)
0.14
0.02
ISW_TOP
0.00
-40 -25 -10
5
16
12
8
4
0
20 35 50 65 80 95 110 125
-40 -25 -10
Junction Temperature (℃)
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
Shutdown Current vs. Temperature
EN Voltage vs. Temperature
1
1.2
Rising
1
0.8
EN Voltage (V)
Shutdown Current (μA)
5
0.6
0.4
0.2
0.8
Falling
0.6
0.4
0.2
0
0
-40 -25 -10
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
SG Micro Corp
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-40 -25 -10
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
JUNE 2019
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1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 18V, L = 22μH and COUT = 10μF, unless otherwise noted.
Reference Voltage vs. Temperature
Output Over-Voltage Protection vs. Temperature
0.9
Output Over-Voltage Protection (V)
Reference Voltage (V)
0.820
0.810
0.800
0.790
0.780
0.89
OVPH
0.88
0.87
0.86
OVPL
0.85
0.84
-40 -25 -10
5
20 35 50 65 80 95 110 125
-40 -25 -10
Junction Temperature (℃)
20 35 50 65 80 95 110 125
Junction Temperature (℃)
RDSON vs. Temperature
Under-Voltage Lockout vs. Temperature
1200
4.9
Top Switch
800
600
400
200
Bottom Switch
0
Under-Voltage Lockout (V)
4.8
1000
RDSON (mΩ)
5
Rising
4.7
4.6
4.5
4.4
Falling
4.3
4.2
4.1
-40 -25 -10
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
-40 -25 -10
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
Temperature Derating
120
Rated Power (%)
100
80
60
40
20
0
-55 -35 -15
5
25
45
65
85 105 125 145
Ambient Temperature (℃)
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JUNE 2019
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1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
FUNCTIONAL BLOCK DIAGRAM
EN
VIN
Thermal
Hiccup
-
Shutdown
Logic
+
FB
Reference
Boot Charge
Current
Sense
BOOT
Boot UVLO
Error Amplifier
HS_FET
Current
Comparator
+
0.8V
EN Comparator
Minimum Clamp
Pulse Skip
-
+
UVLO
OV Comparator
Power Stage
and
Dead Time
Control
Logic
Voltage
Reference
SW
VIN
Regulator
Slope
Compensation
Soft-Start
Overload
Protection
Oscillator
Current
Sense
LS_FET
Current Limit
GND
Figure 2. Functional Block Diagram
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SGM61410
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
DETAILED DESCRIPTION
Figure 2 shows the simplified block diagram of the
SGM61410. The two integrated MOSFET switches of
the power stage are both overcurrent protected and can
provide up to 600mA of continuous current for the load.
Current limiting of the switches also prevents inductor
current runaway. The converter switches are optimized
for high efficiency at low duty cycle.
At the beginning of each switching cycle, the high-side
switch is turned on. This is the time that feedback
voltage (VFB) is below the reference voltage (VREF) and
power must be delivered to the output. After the
on-period, the high-side switch is turned off and the
low-side switch is turned on until the end of switching
cycle. For reliable operation and preventing shoot
through, a short dead time is always inserted between
gate pulses of the converter complimentary switches.
During dead time, both switch gates are kept off.
The device is designed for safe monotonic start-up
even if the output is pre-biased.
If the junction temperature exceeds a maximum
threshold (TSHDN, typically +150℃), thermal shutdown
protection will happen and switching will stop. The
device will automatically recover with soft-start when
the junction temperature drops back well below the trip
point. This hysteresis is typically 20℃.
The SGM61410 has current limit on both the high-side
and low-side MOSFET switches. When current limit is
activated frequency fold-back is also activated. This
occurs in the case of output overload or short circuit.
Note that SGM61410 will continue to provide its
maximum output current and will not shut down or
hiccup. In such a case, the junction temperature may
rise rapidly and trigger thermal shutdown.
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Peak-Current Mode (PWM Control)
Figure 2 shows the functional block diagram and Figure
3 shows the switching node operating waveforms of the
SGM61410. Switching node voltage is generated by
controlling the duty cycles of the complementary
high-side and low-side switches. The duty cycle of the
high-side switch is used as control parameter of the
buck converter to regulate output voltage and is defined
as: D = tON/tSW , where tON is the high-side switch
on-time and tSW is the switching period. During
high-side switch on-time, the SW pin voltage swings up
to approximately VIN, and the inductor current, IL,
linearly rises with a slope of (VIN - VOUT)/L. When control
logic turns off the high-side switch, the low-side switch
will turn on after a small dead time. During off-time,
inductor current discharges through the low-side switch
with a slope of (-VOUT/L). In ideal case, where losses
are ignored, D is proportional to the output voltage and
inversely proportional to the input voltage: D = VOUT/VIN.
The SGM61410 employs fixed-frequency peak-current
mode control in continuous conduction mode (when
inductor minimum current is above zero). In light load
conditions (when the inductor current reaches zero) the
SGM61410 will enter discontinuous conduction mode
and the control mode will change to shift frequency,
peak-current mode to reduce the switching frequency
and the associated switching and gate driving losses
(power saving mode).
VSW
SW Voltage
The SGM61410 is an internally compensated wide
input range current mode controlled synchronous
step-down converter. It is designed for high reliability
and is particularly suitable for power conditioning from
unregulated sources or battery-powered applications
that need low sleep/shutdown currents. It also features
a power-save mode in which operating frequency is
adaptively reduced at light load conditions to reduce
switching and gate losses and keep high efficiency. At
no load and with switching stopped, the total operating
current is approximately 14μA. If the device is disabled,
the total consumption is typically less than 0.6μA.
During initial power up of the device (soft-start), current
limit and frequency fold-back are activated to prevent
inductor current runaway while the output capacitor is
charging to the desired VOUT.
D = tON/tSW
VIN
tON
tOFF
t
0
tSW
IL
Inductor Current
Overview
ILPK
IOUT
0
ΔIL
t
Figure 3. SW Node and Inductor Current Waveforms in
Continuous Conduction Mode (CCM)
JUNE 2019
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SGM61410
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
DETAILED DESCRIPTION (continued)
Continuous Conduction Mode (CCM)
In continuous conduction mode, SGM61410 operates
at fixed-frequency using peak-current mode control
scheme. The controller has an outer voltage feedback
loop to get accurate DC voltage regulation. The output
of the outer loop is fed to an inner peak current control
loop as reference command that adjusts the peak
current of the inductor. The inductor peak-current is
sensed from the high-side switch and is compared to
the peak-current reference to control the duty cycle. In
other words, as soon as the inductor current reaches
the reference peak current determined by voltage loop,
the high-side switch is turned off and the low side
switch is turned on after deadtime.
The voltage feedback loop is internally compensated,
which allows for fewer external components, simpler
design, and stable operation with almost any
combination of output capacitors.
Power-Save Mode
When the load is reduced, the inductor minimum (valley)
current eventually reaches zero level (boundary
condition). Synchronous rectifier (low-side switch)
current is always sensed and when it reaches zero, the
controller turns off the low-side switch and does not let
the low-side switch sink current. This prevents inductor
current from going below zero (negative). This results
in discontinuous conduction mode (DCM) operation in
which inductor current remains zero until next switching
cycle. Both switches are off during this period and do
not act as complementary switches. This off-time will
extend (that means lower frequency) until output
voltage falls below reference voltage again and triggers
a new switching cycle. With a new cycle, the high-side
switch is turned on again for almost the same tON time
as CCM. Therefore, the output capacitors take almost
the same charge in each cycle and with lighter loads it
will take longer off-times until output capacitor voltage
falls below reference. The extended off-times mean
lower switching frequency that is called frequency
foldback and significantly reduces the switching losses,
but usually increases the output ripple a little bit.
Note that the on-time of synchronous rectifier switch
should always be long enough to fully charge the
bootstrap capacitor and prevent bootstrap under
voltage lockout due to insufficient voltage for the
high-side switch gate driver.
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Floating Driver and Bootstrap Charging
UVLO Protection
The high-side MOSFET driver is powered by a floating
supply provided by an external bootstrap capacitor. The
bootstrap capacitor is charged and regulated to about
5V by the dedicated internal bootstrap regulator. When
the voltage between BOOT and SW nodes is below
regulation, a PMOS pass transistor turns on and
connects VIN and BOOT pins internally, otherwise it will
turn off. The power supply for the floating driver has its
own UVLO protection. The rising UVLO threshold is
about 4.75V and with 350mV hysteresis, the falling
threshold is about 4.4V. In case of UVLO, the reference
voltage of the controller is reset to zero and after
recovery a new soft-start process will start.
Output Over-Voltage Protection (OVP)
The SGM61410 contains an over-voltage comparator
that monitors the FB pin voltage. The over-voltage
threshold is approximately 110% of nominal FB voltage.
When the voltage at the FB pin exceeds the
over-voltage threshold (VOUT_OV), PWM switching will
be stopped and both high-side and low-side switches
will be turned off. If the over-voltage fault is removed,
the regulator will automatically recover.
The error amplifier is normally able to maintain
regulation since the synchronous output stage has
excellent sink and source capability. However it is not
able to regulate output when the FB pin is disconnected
or when the output is shorted to a higher supply like
input supply. Also when VOUT is set to its minimum
(0.8V) usually there is no voltage divider and VOUT is
directly connected to FB through a resistor (R1 in the
divider) and there is no resistor to ground (no R2). In
such case and with no load an internal current source
of 5~6μA from BOOT into the SW pin, can slowly
charge the output capacitor and pull VOUT up, toward
VIN. Therefore a minimum load of at least 10μA must be
always present on VOUT (for example an 80kΩ resistor:
0.8V/10μA = 80kΩ).
If the FB pin is disconnected, a tiny internal current
source will force the voltage at the FB pin to rise above
VOUT_OV that triggers over voltage protection and
disables the regulator to protect the loads from a
significant over-voltage. Also, if by accident a higher
external voltage is shorted to the output, VFB will rise
above the over-voltage threshold and trigger an OVP
event to protect the low-side switch.
JUNE 2019
12
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
DETAILED DESCRIPTION (continued)
Minimum High-side On/Off-Time and
Frequency Fold-Back
Minimum high-side switch on-time (tON_MIN) is the
smallest duration that the high-side switch can be
turned on. The tON_MIN is typically 100ns. Minimum
high-side switch off-time (tOFF_MIN), is the smallest
duration that the high-side switch can be turned off. The
tOFF_MIN is typically 100ns. In CCM operation, tON_MIN
and tOFF_MIN limit the voltage conversion ratio without
switching frequency fold-back. Note that at 1.2MHz the
total cycle time is tSW = 833ns.
The minimum and maximum duty cycles without
frequency fold-back are given by:
DMIN = tON_MIN × fSW
(1)
and
DMAX = 1 - tOFF_MIN × fSW
(2)
Given a required output voltage, the maximum VIN
without frequency fold-back is given by:
VIN_MAX =
VOUT
fSW × t ON_MIN
(3)
and the minimum VIN without frequency fold-back can
be calculated by:
VIN_MIN =
VOUT
1 - fSW × t OFF_MIN
(4)
Input Voltage
The SGM61410 can operate efficiently for inputs as high
as 45V. For CCM operation (continuous conduction
mode) keep duty cycle between 12% and 88%.
Output Voltage
The output voltage can be stepped down to as low as
the 0.8V reference voltage (VREF). As explained before,
when the output voltage is set to 0.8V and there is not a
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voltage divider, a minimum small load will be needed.
An 80kΩ resistor to ground will prevent the output
voltage floating up.
Soft-Start
The integrated soft-start circuit in SGM61410 limits the
input inrush current right after power up or enabling the
device. Soft-start is implemented by slowly ramping up
the reference voltage that in turn slowly ramps up the
output voltage to its target regulation value.
Enable
EN pin turns the SGM61410 operation on or off. An
applied voltage of less than 0.5V shuts down the device,
and a voltage of more than 1.2V is required to start the
regulator. The EN pin is an input and must not be left
open. The simplest way to enable the device is to
connect the EN pin to VIN. This allows for self-startup
of the SGM61410 when VIN is within the operating
range.
An external logic signal can be used to drive the EN
input for power savings, power supply sequencing
and/or protection. If the EN pin is driven by an external
logic signal a 100kΩ resistor in series with the input is
recommended.
Note: Voltage on the EN pin should never exceed VIN +
0.3V. Do not drive the EN pin with a logic level if VIN is
not present. This can damage the EN pin and the
device.
Thermal Shutdown
The SGM61410 provides an internal thermal shutdown
to protect the device when the junction temperature
exceeds +150 ℃ . Both switches stop switching in
thermal shutdown. Once the die temperature falls
below +130 ℃ , the device reinitiates the power up
sequence by the internal soft-start.
JUNE 2019
13
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
TYPICAL APPLICATION CIRCUITS
VIN
5
CIN
10μF
4
2
VIN
BOOT
SGM61410
EN
SW
FB
GND
1
6
CBOOT
0.47μF
L
22μH
3
R1
52.5kΩ
COUT
22μF
VOUT
5V/0.2A
R2
10kΩ
Figure 4. 5V Output Typical Application Circuit for Power Meters
VIN
5
CIN
10μF
4
2
VIN
BOOT
SGM61410
EN
GND
SW
FB
1
6
CBOOT
0.47μF
L
47μH
3
R1
140kΩ
COUT
47μF
VOUT
12V/0.6A
R2
10kΩ
Figure 5. 12V Output Typical Application Circuit for Power Meters
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JUNE 2019
14
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
APPLICATION INFORMATION AND DESIGN GUIDLINES
External Components
The following guidelines can be used to select external components.
fSW (MHz)
VOUT (V)
R1 (kΩ)
R2 (kΩ)
L (µH)
CBOOT (µF)
CIN (µF)
COUT (µF)
3.3
31.2
10
10
0.47
10
10
5
52.5
10
22
0.47
10
22
12
140
10
47
0.47
10
47
1.2
Output Voltage Programming
Output voltage can be set with a resistor divider
feedback network between output and FB pin as shown
in Figure 4 and Figure 5. Usually, a design is started by
selecting lower resistor R1 and calculating R2 with the
following equation:
R
VOUT = VREF × 1 + 1
R
2
(5)
where VREF = 0.8V.
To keep operating quiescent current small and prevent
voltage errors due to leakage currents, it is
recommended to choose R1 in the range of 10kΩ to
100kΩ.
If the output has no load other than the FB divider,
make sure the divider draws at least 10μA from VOUT or
an internal current source (5~6μA) from BOOT to SW
will slowly charge the output capacitor beyond the
desired voltage.
Inductor Selection
The critical parameters for selecting the inductor are
the inductance (L), saturation current (Isat) and the
maximum RMS current (Irms,max). The inductance is
selected based on the desired peak-to-peak ripple
current ΔIL that is given in Equation 6 for CCM. Since
the ripple current increases with the input voltage, the
maximum input voltage is usually considered to
calculate the minimum inductance LMIN that is given in
Equation 7. KIND is a design parameter that represents
the ratio of inductor ripple current to its maximum
operating dc current. Lower KIND means higher
inductance value that needs a larger size and higher
KIND results in more ripple and loss in the core. Typically,
a reasonable value for KIND is around 20%~40%.
Inductor peak current should never exceed the
saturation even in transients to avoid over current
protection. Also inductor RMS rating should always be
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larger than operating RMS current even at maximum
ambient temperature.
∆IL =
=
LMIN
VOUT × (VIN_MAX - VOUT )
VIN_MAX × L × fSW
VIN_MAX - VOUT
IOUT × K IND
×
VOUT
VIN_MAX × fSW
(6)
(7)
where KIND = ΔIL/IOUT (max DC current).
Note that lower inductance is usually preferred in a
switching power supply, because it usually corresponds
to faster transient response and bandwidth, smaller
DCR, and reduced size for a more compact design. On
the other hand, if the inductance is too small, current
ripple will increase which can trigger over current
protection. Larger inductor current ripple also implies
larger output voltage ripple with the same output
capacitors. For peak-current mode control, it is
recommended to choose large current ripple, because
controller comparator performs better with higher signal
to noise ratio. So, for this design example, KIND = 0.4 is
chosen, and the minimum inductor value is calculated
to be 16.3µH. The nearest standard value would be a
22µH ferrite inductor with a 1A RMS current rating and
1.5A saturation current that are well above the
designed converter output current RMS and DC
respectively.
Bootstrap Capacitor Selection
The SGM61410 requires a small external bootstrap
capacitor, CBOOT, between the BOOT and SW pins to
provide the gate drive supply voltage for the high-side
MOSFET. The bootstrap capacitor is refreshed when
the high-side MOSFET is off and the low-side switch
conducts. An X7R or X5R 0.47µF ceramic capacitor
with a voltage rating of 16V or higher is recommended
for stable operating performance over temperature and
voltage variations.
JUNE 2019
15
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
APPLICATION INFORMATION AND DESIGN GUIDELINES (continued)
Input Capacitor Selection
The SGM61410 requires high frequency input
decoupling capacitor(s). The recommended high
frequency decoupling capacitor value is 10μF X5R or
X7R or higher. It is recommended to choose the voltage
rating of the capacitor(s) at least twice the maximum
input voltage to avoid derating of the ceramic
capacitors with DC voltage. Some bulk capacitance
may be needed, especially if the SGM61410 is not
located within 5cm distance from the input voltage
source for input stability.
Bulk capacitors have high ESR and can provide the
damping needed to prevent input voltage spiking due to
the wiring inductance of the input. The value for this
capacitor is not critical but must be rated to handle the
maximum input voltage including ripple.
For this design, one 10μF, X7R, 50V is used for the
input decoupling capacitor. The Equivalent Series
Resistance (ESR) is approximately 10mΩ, and the
current rating is 1A. To improve high frequency filtering
a small parallel 0.1μF capacitor may be placed as close
as possible to the device pins.
Output Capacitor Selection
The device is designed to be used with a wide variety of
LC filters. It is generally desired to use as little output
capacitance as possible to keep cost and size down
and bandwidth high. The output capacitor(s), COUT,
should be chosen carefully since it directly affects the
steady state output voltage ripple, loop stability and the
voltage over/undershoot during load current transients.
The output voltage ripple is essentially composed of
two parts. One is caused by the inductor current ripple
going through the Equivalent Series Resistance (ESR)
of the output capacitors:
ΔVOUT_ESR = ΔIL × ESR = KIND × IOUT × ESR
(8)
DVOUT_C =
KIND × IOUT
DIL
(9)
=
8 × fSW × COUT 8 × fSW × COUT
The two components in the voltage ripple are not in
phase, so the actual peak-to-peak ripple is smaller than
the sum of the two peaks.
Output capacitance is usually limited by transient
performance specifications if the system requires tight
voltage regulation in presence of large current steps
and/or fast slew rate. When a large load step happens,
output capacitors provide the required charge before
the inductor current can slew up to the appropriate level.
The regulator’s control loop usually needs 8 or more
clock cycles to regulate the inductor current equal to
the new load level. The output capacitance must be
large enough to supply the current difference for 8 clock
cycles to maintain the output voltage within the
specified range. Equation 10 shows the minimum
output capacitance needed for specified output
over/undershoot.
COUT >
8 × (IOH − IOL )
1
×
2 fSW × ∆VOUT_SHOOT
(10)
where IOL = Low level of the output current step during
load transient, IOH = High level of the output current
during load transient, VOUT_SHOOT = Target output
voltage over/undershoot.
For this design example, the target output ripple is
30mV. Assuming ΔVOUT_ESR = ΔVOUT_C = 30mV, and
choosing KIND = 0.4, Equation 8 requires ESR to be less
than 125mΩ and Equation 9 requires COUT > 0.91μF.
The target over/undershoot range of this design is
ΔVOUT_SHOOT = 5% × VOUT = 250mV. From Equation 10,
COUT > 8.3μF. So, in summary, the most stringent
criteria for the output capacitor is transient constrain of
COUT > 8.3μF. For the derating margin, one 22μF, 10V,
X7R ceramic capacitor with 10mΩ ESR is used.
The other part is caused by the inductor current ripple
charging and discharging the output capacitors:
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JUNE 2019
16
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
SGM61410
APPLICATION INFORMATION AND DESIGN GUIDELINES (continued)
Layout Guideline
Careful layout is always important to ensure good performance and stable operation to any kind of switching
regulator. Place the capacitors close to the device, use the GND pin of the device as the center of star-connection to
other grounds, and minimize the trace area of the SW node. With smaller transient current loops, lower parasitic
ringing will be achieved.
Figure 6. Suggested PCB
VIN
1
2
CIN
10μF
5
EN
4
2
VIN
EN
BOOT
SGM61410
GND
1
SW 6
FB
3
CBOOT
0.47μF
L
10μH to 33μH
C 1*
330pF
* NOTE: An optional feed-forward capacitor can be used across R1 (as shown) to improve
transient performance and reduce the over/undershoot peaks during load steps.
COUT
22μF
VOUT
5V
R1
52.5kΩ
R2
10kΩ
Figure 7. Typical Application Circuit
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JUNE 2019
17
SGM61410
1.2MHz, 600mA, 45V
Synchronous Step-Down Converter
REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Original (JUNE 2019) to REV.A
Page
Changed from product preview to production data ............................................................................................................................................. All
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JUNE 2019
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PACKAGE INFORMATION
PACKAGE OUTLINE DIMENSIONS
SOT-23-6
D
e1
e
2.59
E
E1
0.99
b
0.95
0.69
RECOMMENDED LAND PATTERN (Unit: mm)
L
A
A1
θ
A2
Symbol
Dimensions
In Millimeters
MIN
MAX
c
0.2
Dimensions
In Inches
MIN
MAX
A
1.050
1.250
0.041
0.049
A1
0.000
0.100
0.000
0.004
A2
1.050
1.150
0.041
0.045
b
0.300
0.500
0.012
0.020
c
0.100
0.200
0.004
0.008
D
2.820
3.020
0.111
0.119
E
1.500
1.700
0.059
0.067
E1
2.650
2.950
0.104
0.116
e
0.950 BSC
0.037 BSC
e1
1.900 BSC
0.075 BSC
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L
0.300
0.600
0.012
0.024
θ
0°
8°
0°
8°
TX00034.000
PACKAGE INFORMATION
TAPE AND REEL INFORMATION
REEL DIMENSIONS
TAPE DIMENSIONS
P2
W
P0
Q1
Q2
Q1
Q2
Q1
Q2
Q3
Q4
Q3
Q4
Q3
Q4
B0
Reel Diameter
A0
P1
K0
Reel Width (W1)
DIRECTION OF FEED
NOTE: The picture is only for reference. Please make the object as the standard.
KEY PARAMETER LIST OF TAPE AND REEL
Reel
Diameter
Reel Width
W1
(mm)
A0
(mm)
B0
(mm)
K0
(mm)
P0
(mm)
P1
(mm)
P2
(mm)
W
(mm)
Pin1
Quadrant
SOT-23-6
7″
9.5
3.17
3.23
1.37
4.0
4.0
2.0
8.0
Q3
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TX10000.000
DD0001
Package Type
PACKAGE INFORMATION
CARTON BOX DIMENSIONS
NOTE: The picture is only for reference. Please make the object as the standard.
KEY PARAMETER LIST OF CARTON BOX
Length
(mm)
Width
(mm)
Height
(mm)
Pizza/Carton
7″ (Option)
368
227
224
8
7″
442
410
224
18
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DD0002
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