SGM61412 [SGMICRO]
1.2MHz, 1.2A, 42V Synchronous Buck Converter;
| 型号： | SGM61412 |
| 厂家： | 
Shengbang Microelectronics Co, Ltd |
| 描述： | 1.2MHz, 1.2A, 42V Synchronous Buck Converter |
| 文件： | 总21页 (文件大小：1094K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SGM61412
1.2MHz, 1.2A, 42V
Synchronous Buck Converter
GENERAL DESCRIPTION
FEATURES
The SGM61412 is a high frequency, synchronous Buck
converter with integrated switches. It can deliver up to
1.2A to the output over a wide input voltage range of
4.5V to 42V. It is suitable for various industrial
applications with high input voltage or for power
conditioning from unregulated sources. Moreover, the
low 55µA quiescent current and ultra-low shutdown
current of only 1.2µA make it a suitable choice for
battery-powered applications.
● Wide 4.5V to 42V Input Voltage Range
● Current Output up to 1.2A
● 1.2MHz Switching Frequency
● 0.83V Internal Reference
● SGM61412A:PSM and PWM Mode
● SGM61412B: PFM and PWM Mode
● Low Quiescent Current: 55μA (TYP)
● Ultra-Low Shutdown Current: 1.2μA (TYP)
● 0.83V to 20V Adjustable Output Voltage
● Internal Compensation and Soft-Start
● Precision Enable Function with UVLO Setting
● Monotonic Startup with Pre-biased Output
● Thermal Shutdown Protection
SGM61412 features high efficiency over a wide load
range achieved by scaling down the switching frequency
at light load condition 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 due to the
peak-current mode controller. Switching at 1.2MHz, the
SGM61412 can prevent EMI noise problems, such as
the ones found in AM radio, ADSL and PLC applications.
● Available in a Green TSOT-23-6 Package
● -40℃ to +125℃ Operating Temperature Range
APPLICATIONS
High Voltage Power Conversions
Industrial Power Systems
Protection features include current limit and short-circuit
protection, thermal shutdown with auto recovery and
output over-voltage protection. Frequency fold-back helps
prevent inductor current runaway during startup.
Distributed Power Systems
Battery Powered Systems
Power Meters
The SGM61412 is available in a Green TSOT-23-6
package. It operates over a wide ambient temperature
range of -40℃ to +125℃.
TYPICAL APPLICATION
VIN
3
6
VIN
BOOT
C2
0.1μF
CBOOT
0.1μF
CIN
10μF
L
SGM61412
1
VOUT
5V
2
4
SW
FB
GND
4.7μH to 10μH
COUT
22μF
C1
R1
49.9kΩ
56pF
5
EN
R2
10kΩ
Figure 1. Typical Application Circuit
SG Micro Corp
MAY 2022–REV. A. 2
www.sg-micro.com
1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
PACKAGE/ORDERING INFORMATION
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
DESCRIPTION
ORDERING
NUMBER
PACKAGE
MARKING
PACKING
OPTION
MODEL
SGM61412A
SGM61412B
TSOT-23-6
TSOT-23-6
SGM61412AXTN6G/TR
SGM61412BXTN6G/TR
CN1XX
CN2XX
Tape and Reel, 3000
Tape and Reel, 3000
-40℃ to +125℃
-40℃ to +125℃
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.
OVERSTRESS CAUTION
ABSOLUTE MAXIMUM RATINGS
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.
VIN to GND........................................................ -0.3V to 45V
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
TSOT-23-6, θJA ........................................................ 132℃/W
Junction Temperature.................................................+150℃
Storage Temperature Range.......................-65℃ to +150℃
Lead Temperature (Soldering, 10s)............................+260℃
ESD Susceptibility
ESD SENSITIVITY CAUTION
This integrated circuit can be damaged if ESD protections are
not considered carefully. SGMICRO recommends that all
integrated circuits be handled with appropriate precautions.
Failureto observe proper handlingand installation procedures
can cause damage. ESD damage can range from subtle
performance degradation tocomplete device failure. Precision
integrated circuits may be more susceptible to damage
because even small parametric changes could cause the
device not to meet the published specifications.
HBM.............................................................................2000V
CDM ............................................................................1000V
RECOMMENDED OPERATING CONDITIONS
Supply Input Voltage Range................................4.5V to 42V
Operating Junction Temperature Range......-40℃ to +125℃
Operating Ambient Temperature Range......-40℃ to +125℃
DISCLAIMER
SG Micro Corp reserves the right to make any change in
circuit design, or specifications without prior notice.
SG Micro Corp
www.sg-micro.com
MAY 2022
2
1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
PIN CONFIGURATION
(TOP VIEW)
GND
SW
1
2
3
6
5
4
BOOT
EN
VIN
FB
TSOT-23-6
PIN DESCRIPTION
PIN
1
NAME
GND
SW
FUNCTION
Ground Pin. It is the reference for input and the regulated output voltages. Special layout
considerations are required.
Switching Node Output. Switching node of the internal power converter and should be
connect to the output inductor and bootstrap capacitor. This node should be kept small on
the PCB to minimize capacitive coupling, noise coupling and radiation.
2
Power Supply Input Pin. This pin is connected to the input supply voltage and powers the
internal control circuitry. VIN voltage is monitored by a UVLO lockout comparator. VIN is
also connected to the drain of the converter high-side 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.
3
VIN
Feedback Input. Feedback pin for programming the output voltage. The SGM61412
regulates the FB pin to 0.83V. Connect the midpoint of the feedback resistor divider.
4
5
FB
EN
Active High Enable Input. Internal pull-up current source. Pull below 0.9V to disable the
device. Float to enable. Adjust the input under-voltage lockout with a resistor divider.
Bootstrap Input. Bootstrap pin is used to provide a drive voltage, higher than the input
voltage, to the high-side power switch. Place a 0.1µF Boost capacitor (CBOOT) as close as
possible to the IC between this pin and SW pin.
6
BOOT
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
ELECTRICAL CHARACTERISTICS
(VIN = 24V, TJ = -40℃ to +125℃, typical values are at TJ = +25℃, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
4.5
TYP
MAX
42
UNITS
V
Supply Input Voltage
VIN
Under-Voltage Lockout Threshold
Under-Voltage Lockout Threshold Hysteresis
Shutdown
VUVLO
4.00
4.25
320
1.2
4.50
V
VUVLO_HYS
mV
VEN/UV = 0V
2.0
85
µA
VEN/UV = 2V, Non-switching, VIN ≤ 36V
SGM61412A
VEN/UV = 2V, Non-switching, VIN ≤ 36V
SGM61412B
55
VIN Quiescent Current
Sleep Mode
IQ
1.95
2.8
mA
Feedback Reference Voltage
Feedback Pin Input Current
Minimum High-side Switch On-Time
Minimum High-side Switch Off-Time
Switching Frequency
VFB
IFB
0.805
0.830
0.1
0.855
1
V
µA
ns
VFB = 1V
ILOAD = 1A
ILOAD = 1A
tON_MIN
tOFF_MIN
fSW
100
120
1.2
ns
0.85
1.6
1.55
1
MHz
ISW_H
ISW_L
ILIM
VSW = 42V
VSW = 0V
0.1
Switch Leakage Current
µA
0.1
1
High-side NMOS Current Limit
High-side NMOS On-Resistance
Low-side NMOS On-Resistance
EN Input High Voltage
2.0
2.4
410
230
1.4
1.0
A
mΩ
mΩ
V
TJ = +25℃
ILOAD = 0.1A
ILOAD = 0.1A
VEN Rising
VEN Falling
230
130
1.3
RDSON
VIH
VIL
1.2
0.8
EN Input Low Voltage
0.9
V
EN Threshold, Hysteresis
VEN_HYS
400
0.1
mV
VEN = 42V
VEN = 0V
1
Enable Leakage Current
IEN
μA
-1
-0.4
155
30
Thermal Shutdown
TSHDN
THYS
℃
℃
Thermal Shutdown Hysteresis
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
TYPICAL PERFORMANCE CHARACTERISTICS
TA = +25℃, VIN = 24V, VOUT = 5V, L = 6.8μH and COUT = 22μF, unless otherwise noted.
Efficiency vs. Load Current
Efficiency vs. Load Current
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
VOUT = 3.3V
L = 4.7μH
DCR = 26mΩ
VIN = 12V
VOUT = 5V
L = 6.8μH
DCR = 17.6mΩ
VIN = 12V
V
V
IN = 24V
IN = 36V
V
V
IN = 24V
IN = 36V
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Load Current (A)
Load Current (A)
Efficiency vs. Load Current
Load Regulation
100
90
80
70
60
50
40
30
20
10
0
1.0
0.8
VOUT = 5V
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
VOUT = 12V
L = 10μH
DCR = 26.5mΩ
VIN = 15V
VIN = 12V
V
V
IN = 24V
IN = 36V
V
V
IN = 24V
IN = 36V
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Load Current (A)
Load Current (A)
Line Regulation
Quiescent Current vs. Temperature
2.0
1.5
80
70
60
50
40
30
20
10
0
VOUT = 5V
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
IOUT = 0A
I
I
I
OUT = 10mA
OUT = 0.6A
OUT = 1.2A
42
5
10
15
20
25
30
35
40
-40 -25 -10
5
20 35 50 65 80 95 110 125
Input Voltage (V)
Junction Temperature (℃)
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 24V, VOUT = 5V, L = 6.8μH and COUT = 22μF, unless otherwise noted.
Switching Frequency vs. Temperature
Switch Leakage vs. Temperature
1.20
1.19
1.18
1.17
1.16
1.15
1.14
1.13
1.12
1.11
1.10
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
ISW_H
ISW_L
20 35 50 65 80 95 110 125
-40 -25 -10
5
20 35 50 65 80 95 110 125
-40 -25 -10
-40 -25 -10
-40 -25 -10
5
Junction Temperature (℃)
Junction Temperature (℃)
Shutdown Current vs. Temperature
EN Voltage vs. Temperature
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
Rising
Falling
-40 -25 -10
5
20 35 50 65 80 95 110 125
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
Junction Temperature (℃)
Reference Voltage vs. Temperature
RDSON vs. Temperature
0.850
0.845
0.840
0.835
0.830
0.825
0.820
0.815
0.810
400
350
300
250
200
150
100
50
High-side Switch
Low-side Switch
0
-40 -25 -10
5
20 35 50 65 80 95 110 125
5
20 35 50 65 80 95 110 125
Junction Temperature (℃)
Junction Temperature (℃)
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 24V, VOUT = 5V, L = 6.8μH and COUT = 22μF, unless otherwise noted.
Output Voltage Ripple
Output Voltage Ripple
AC Coupled
VOUT
AC Coupled
VOUT
VIN
VSW
IL
VIN
VSW
IL
VIN = 24V, VOUT = 5V, IOUT = 0A
VIN = 24V, VOUT = 5V, IOUT = 1A
Time (5ms/div)
Time (1μs/div)
Enable Startup
Enable Startup
VOUT
VOUT
VEN
VSW
VEN
VSW
IL
IL
VIN = 24V, VOUT = 5V, IOUT = 0A
VIN = 24V, VOUT = 5V, IOUT = 1A
Time (1ms/div)
Time (1ms/div)
VIN Startup
VIN Startup
VOUT
VIN
VOUT
VIN
VSW
VSW
IL
IL
VIN = 24V, VOUT = 5V, IOUT = 0A
VIN = 24V, VOUT = 5V, IOUT = 1A
Time (1ms/div)
Time (1ms/div)
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 24V, VOUT = 5V, L = 6.8μH and COUT = 22μF, unless otherwise noted.
Enable Shutdown
Enable Shutdown
VOUT
VOUT
VEN
VEN
VSW
VSW
IL
IL
VIN = 24V, VOUT = 5V, IOUT = 0A
VIN = 24V, VOUT = 5V, IOUT = 1A
Time (200ms/div)
Time (50μs/div)
VIN Shutdown
VIN Shutdown
VOUT
VIN
VOUT
VIN
VSW
VSW
IL
IL
VIN = 24V, VOUT = 5V, IOUT = 0A
VIN = 24V, VOUT = 5V, IOUT = 1A
Time (20ms/div)
Time (10ms/div)
Short-Circuit Recovery
Short-Circuit Entry
VOUT
VOUT
VIN
VIN
VSW
VSW
IL
IL
VIN = 24V, VOUT = 5V, IOUT = 1A
VIN = 24V, VOUT = 5V, IOUT = 1A
Time (1ms/div)
Time (100μs/div)
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
TA = +25℃, VIN = 24V, VOUT = 5V, L = 6.8μH and COUT = 22μF, unless otherwise noted.
Pre-biased Startup
Load Transient Response
VOUT
AC Coupled
VOUT
VEN
VSW
IOUT
IL
VIN = 24V, VOUT = 5V, IOUT = 0A
VIN = 24V, VOUT = 5V, IOUT = 200mA-1A, SR = 2.5A/μs
Time (1ms/div)
Time (100μs/div)
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
FUNCTIONAL BLOCK DIAGRAM
EN
VIN
Thermal
UVLO
Shutrdown
OV Comparator
-
Shutdown
Logic
+
+
-
Boot Charge
Current
Sense
Minimum Clamp
Pulse Skip
Boot UVLO
BOOT
-
FB
Error Amplifier
+
+
HS MOSFET
Current
Comparator
SW
Power Stage
and
Dead Time
Control
VIN
30kΩ
0.83V
Voltage
2pF
Logic
Regulator
Reference
2.2nF
Slope
Compensation
Soft-Start
Current
Sense
Overload
Recovery
Maximum
Clamp
LS MOSFET
Current Limit
Oscillator
GND
Figure 2. Block Diagram
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
DETAILED DESCRIPTION
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
Overview
The SGM61412 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 and shutdown currents. It also
features a power-save mode in which operating
frequency is adaptively reduced under light load
condition to reduce switching and gate losses and keep
high efficiency. At no load and with switching stopped,
the total operating current is approximately 55μA. If the
device is disabled, the total consumption is typically
1.2μA.
charging to the desired VOUT
.
Peak-Current Mode (PWM Control)
Figure 2 shows the functional block diagram and Figure
3 shows the switching node operating waveforms of the
SGM61412. Switching node voltage is generated by
controlling the duty cycles of the complementary
high-side and low-side switches. The high-side duty
cycle 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. When high-side switch
is turned on, the SW pin voltage sharply rises towards
VIN, and the inductor current (IL) starts ramping up with
(VIN - VOUT)/L slope. When high-side switch is turned off,
the low-side switch is turned on after a very short dead
time to avoid shoot-through, and IL ramps down with
-VOUT/L slope. In ideal case, the output voltage is
proportional to the input voltage and duty cycle (D =
Figure 2 shows the functional block diagram of the
SGM61412. The two integrated MOSFET switches of
the power stage are both over-current protected and
can provide up to 1.2A of continuous current for the
load. Current limit 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.
V
OUT/VIN) if component parasitics are ignored.
The SGM61412 employs fixed-frequency, peak-current
mode control in continuous conduction mode (CCM)
(when inductor minimum current is above zero). In light
load condition (when the inductor current reaches zero)
the SGM61412 will enter discontinuous conduction
mode (DCM) 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-save mode).
The device is designed for safe monotonic start-up
even if the output is pre-biased.
VSW
D = tON/tSW
VIN
If the junction temperature exceeds a maximum
threshold (TSHDN, typically +155℃), 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 30℃.
tON
tOFF
t
0
tSW
IL
ILPK
IOUT
The SGM61412 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 SGM61412 will continue to provide its
maximum output current and will not shut down. In such
a case, the junction temperature may rise rapidly and
trigger thermal shutdown.
ΔIL
t
0
Figure 3. Converter Switching Waveforms in CCM
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
DETAILED DESCRIPTION (continued)
In CCM, SGM61412 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
dead time.
The resulting PFM frequency mainly depends on the
load current. The lighter the load, the slower the output
voltage drops, and the lower switching frequency.
Lower switching frequency reduces the switching and
gate drive losses, and improves the efficiency
significantly. The PFM is left and PWM mode entered in
case the output current rise for the internal VCOMP to rise
above the internal threshold.
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 is turned on and
connected VIN and BOOT pins internally, otherwise it
will be turned off. The power supply for the floating
driver has its own UVLO protection. The rising UVLO
threshold is about 4.25V and with 320mV hysteresis;
the falling threshold is about 3.93V. In case of UVLO,
the reference voltage of the controller is reset to zero
and after recovery a new soft-start process will start.
The internally compensated voltage feedback loop
allows for simpler design, fewer external components,
and stable operation with almost any combination of
output capacitors.
Power-Save Mode (SGM61412A Only)
The SGM61412A/B operate in PWM mode to provide
lower ripple at heavy load. The SGM61412A operates
in power-save mode (PSM) at light load to boost light
load efficiency by reducing switching and gate drive
losses. When the inductor peak-current is low and the
internal VCOMP falls to the internal threshold, the device
will enter PSM. After entering PSM for a delay time,
some modules are shut down to minimum quiescent
current. The high-side MOSFET will not switch until the
output voltage falls for the internal VCOMP to rise above
the internal threshold. Since the integrated current
comparator catches the inductor peak-current only, the
average load current entering PSM varies with the
applications and external output filters.
Minimum High-side On/Off-Time and
Frequency Fold-Back
The shortest duration for the high-side switch on-time
(tON_MIN) is 100ns (TYP). For the off-time (tOFF_MIN) the
minimum value is 120ns (TYP). The duty cycle (or
equivalently the VOUT/VIN ratio) range in CCM operation
is limited by tON_MIN and tOFF_MIN depending on the
switching frequency. Note that at 1.2MHz the total cycle
time is tSW = 833ns.
Pulse Frequency Mode (SGM61412B Only)
As the load current decreases, the SGM61412B enters
pulse frequency mode (PFM). When the inductor
peak-current is low and the internal VCOMP falls to the
internal threshold, the device will enter PFM. During
PFM, when output feedback voltage VFB falls below
0.83V typically, the device starts a PFM current pulse.
The high-side MOSFET switch is turned on, and the
inductor current ramps up. As the inductor peak-current
rise for the current sense voltage VSENSE reaches the
internal threshold, the switch is turned off and the
low-side MOSFET switch is turned on until the inductor
current becomes zero. The converter effectively
delivers a current to the output capacitor and the load.
The minimum and maximum duty cycles without
frequency fold-back are given by Equations 1 and 2:
DMIN = tON_MIN × fSW
(1)
(2)
DMAX = 1 - tOFF_MIN × fSW
For any given output voltage, the highest input voltage
without frequency fold-back can be calculated from:
VOUT
V
=
IN_MAX
(3)
fSW ×tON_MIN
The minimum VIN is estimated by:
VOUT
V
=
IN_MIN
(4)
1 - fSW ×tOFF_MIN
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MAY 2022
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
DETAILED DESCRIPTION (continued)
Many applications will profit from the employment of an
enable divider RENT and RENB (see Figure 4) to build an
accurate system UVLO level for the converter. System
UVLO can be used for supplies operating from utility
power as well as battery power. This feature can be
used for power supply sequencing which is required for
proper power up of the system voltage rails. It can also
be used as protection, such as preventing supply
battery from depletion. Control of the enable input by
logic signals may also be used for sequencing or
protection.
Input Voltage
The SGM61412 can operate efficiently for inputs as
high as 42V. For CCM operation keeps duty cycle
between 12% and 88%.
Output Voltage
The output voltage can be bucked to as low as the
0.83V reference voltage (VREF). As explained before,
when the output voltage is set to 0.83V and there is no
voltage divider, a minimum small load will be needed.
An 80kΩ resistor to ground will prevent the output
voltage floating up.
VIN
Soft-Start
The integrated soft-start circuit in SGM61412 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.
SGM61412
RENT
EN
RENB
Figure 4. System UVLO by Enable Divider
Enable
EN pin turns the SGM61412 operation in on or off
condition. If an applied voltage is less than 0.9V, the
device will shut down. If the voltage is more than 1.3V,
the device will start the regulator. The simplest way to
enable the device is to connect the EN pin to VIN pin
via a resistor. This enables the SGM61412 to start up
automatically when VIN is within the operating range.
Thermal Shutdown
Thermal protection is designed to protect the die
against overheating damage. If the junction
temperature exceeds +155℃, the switching stops and
the device shuts down. Automatic recovery with an
internal soft-start will begin when the junction
temperature drops below the +125℃ falling threshold.
SG Micro Corp
www.sg-micro.com
MAY 2022
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
TYPICAL APPLICATION CIRCUITS
VIN
3
6
2
VIN
BOOT
C2
0.1μF
CBOOT
0.1μF
CIN
10μF
L
SGM61412
1
VOUT
SW
FB
GND
5V/1.2A
6.8μH
COUT
22μF
C1
R1
56pF
49.9kΩ
5
4
EN
R2
10kΩ
Figure 5. 5V Output Typical Application Circuit for Power Meters
VIN
3
6
VIN
BOOT
C2
CBOOT
CIN
0.1μF
0.1μF
10μF
L
SGM61412
1
VOUT
12V/1.2A
2
4
SW
FB
GND
10μH
COUT
22μF
C1
R1
52.3kΩ
56pF
5
EN
R2
3.9kΩ
Figure 6. 12V Output Typical Application Circuit for Power Meters
SG Micro Corp
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MAY 2022
14
1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
APPLICATION INFORMATION
External Components
The following guides can be used to select external components.
fSW (MHz)
VOUT (V)
R1 (kΩ)
30
R2 (kΩ)
10
L (µH)
4.7
CBOOT (µF)
0.1
CIN (µF)
10
COUT (µF)
3.3
5
22
22
22
1.2
49.9
52.3
10
6.8
0.1
10
12
3.9
10
0.1
10
0.4. Choosing a higher K value reduces the selected
inductance, but a too high K factor may result in
insufficient slope compensation. The inductance is
selected based on the desired peak-to-peak ripple
current (ΔIL) for CCM. Equation 7 shows that ∆IL is
inversely proportional to fSW × L and is increased at the
maximum input voltage (VIN_MAX). Therefore by
accepting larger ∆IL values, smaller inductances can be
chosen but the cost is higher output voltage ripple and
increased core losses.
Output Voltage Programming
Output voltage can be set with a resistor divider
feedback network between output and FB pin as shown
in Figure 5 and Figure 6. Usually, a design is started by
selecting lower resistor R1 and calculating R2 with the
following equation:
R
1
VOUT = VREF
×
1 +
(5)
R2
where VREF = 0.83V.
Inductor peak-current should never exceed the
saturation even in transients to avoid over-current
protection. Also inductor RMS rating should always be
larger than operating RMS current even at maximum
ambient temperature.
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.
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
(0.83V) 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 5μA ~ 6μA from BOOT into the SW pin, which can
slowly charge the output capacitor and pull VOUT up to
VIN. Therefore a minimum load of at least 10μA must be
always present on VOUT (for example, an 80kΩ resistor:
0.83V/10.4μA = 80kΩ).
VOUT ×(V
- VOUT
)
IN_MAX
∆IL =
(6)
(7)
VIN_MAX ×L× fSW
V
- VOUT
VOUT
IN_MAX
LMIN
=
×
IOUT ×KIND
VIN_MAX × fSW
where KIND = ΔIL/IOUT (DC Current, MAX).
Note that it is generally desired to choose a smaller
inductance value for faster transient response, smaller
size, and lower DCR. On the other hand, if the
inductance is too small, current ripple will increase
which can trigger over-current protection. The larger
the ripple of inductance current is, the larger the ripple
of output voltage of output capacitor is. 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 for 12V input voltage is
calculated to be 5.1µH. The nearest standard value
would be a 6.8µH ferrite inductor with a 2A RMS
current rating and 2.5A saturation current that are well
above the designed converter output current RMS and
DC respectively.
Inductor Selection
Higher operating frequency allows the designer to
choose smaller inductor and capacitor values; however,
the switching and gate losses are increased. On the
other hand, at lower frequencies the current ripple (∆IL)
is higher, which results in higher light load losses. Use
Equation 6 to calculate the required inductance (LMIN).
K is the ratio of the inductor peak-to-peak ripple (∆IL) to
the maximum operating DC current (IOUT). The
recommended selection range for K is between 0.2 and
SG Micro Corp
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MAY 2022
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1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
APPLICATION INFORMATION (continued)
∆IL
KIND ×IOUT
8× fSW ×COUT 8× fSW ×COUT
Bootstrap Capacitor Selection
∆VOUT_C
=
=
(9)
A 0.1μF ceramic capacitor with 16V or higher voltage
rating must be connected between the BOOT-SW pin
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. X7R or X5R dielectric types
are recommended.
These AC components are not in phase and the total
peak-to-peak ripple is less than ΔVOUT_ESR + ΔVOUT_C
.
Transient performance specification usually limits
output capacitance if the system requires tight voltage
regulation in presence of large current steps and/or fast
slew rate. The output capacitor must provide the
increased load current or absorb the excess inductor
current (when the load current steps down) until the
control loop can re-adjust the current of the inductor to
the new load level. The control loop of regulator usually
requires 8 or more clock cycles to adjust the inductance
current to the new load level. The output capacitance
must be as large as possible to provide a current
difference of 8 clock cycles to keep the output voltage
within the specified range. Equation 10 shows the
minimum output capacitance required to specify output
overshoot/undershoot.
Input Capacitor Selection
The input capacitor also provides the high frequency
switching transient currents. So, choosing a low-ESR
and small size capacitor with high self-resonance
frequency and sufficient RMS rating is necessary.
Typically, 10μF high quality ceramic capacitor (X5R,
X7R or better) with voltage rating twice the maximum
input voltage is recommended for decoupling capacitor.
If the source is away from the device (> 5cm), some
bulk capacitances are also needed to damp the voltage
spikes caused by the wiring or PCB trace parasitic
inductances. The value for this capacitor is not critical
but must be rated to handle the maximum input voltage
including ripple.
8×(IOH −IOL
)
1
2
COUT
>
×
(10)
fSW × ∆VOUT_SHOOT
where:
In this example, one 10μF/50V/X7R capacitor and a
0.1μF ceramic capacitor placed right beside the device
VIN and GND pins for very high-frequency filtering are
used.
IOL = Low level of the output current step during load
transient.
IOH = High level of the output current during load
transient.
Output Capacitor Selection
VOUT_SHOOT = Target output voltage over/undershoot.
This device is designed to be used with external LC
filters. The minimum required capacitance to keep cost
and size down and bandwidth high. The main parts for
designing the output capacitance are output voltage
ripple, loop stability and the voltage over/undershoot
during load current transients. So, COUT should be
chosen carefully. The output voltage ripple is determined
of two factors. One is caused by the inductor current
ripple going through the ESR of the output capacitors:
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 62.5mΩ and Equation 9 requires COUT > 1.67μF.
The target over/undershoot range of 5V output is
ΔVOUT_SHOOT = 5% × VOUT = 250mV. From Equation 10,
COUT > 16μF. So, in summary, the most stringent
criteria for the output capacitor is transient constrain of
COUT > 16μF. For the derating margin, one 22μF, 10V,
X7R ceramic capacitor with 10mΩ ESR is used.
ΔVOUT_ESR = ΔIL × ESR = KIND × IOUT × ESR (8)
The other part is caused by the inductor current ripple
charging and discharging the output capacitors:
SG Micro Corp
www.sg-micro.com
MAY 2022
16
1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
APPLICATION INFORMATION (continued)
Layout Guide
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 7. Suggested PCB
VIN
3
6
2
VIN
BOOT
C2
0.1μF
CBOOT
CIN
10μF
0.1μF
L
SGM61412
1
VOUT
5V
SW
FB
GND
4.7μH to 10μH
COUT
22μF
C1
R1
56pF
49.9kΩ
5
4
EN
R2
10kΩ
Figure 8. Typical Application Circuit
SG Micro Corp
www.sg-micro.com
MAY 2022
17
1.2MHz, 1.2A, 42V
SGM61412
Synchronous Buck Converter
REVISION HISTORY
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
MAY 2022 ‒ REV.A.1 to REV.A.2
Page
Updated Detailed Description and Application Information sections.......................................................................................................... 11 to 17
AUGUST 2021 ‒ REV.A to REV.A.1
Page
Added the SGM61412B section.........................................................................................................................................................................All
Changes from Original (APRIL 2021) to REV.A
Page
Changed from product preview to production data.............................................................................................................................................All
SG Micro Corp
www.sg-micro.com
MAY 2022
18
PACKAGE INFORMATION
PACKAGE OUTLINE DIMENSIONS
TSOT-23-6
0.69
0.95
D
e
2.59
E1
E
0.99
b
RECOMMENDED LAND PATTERN (Unit: mm)
L
A
θ
0.25
A1
c
A2
Dimensions
In Millimeters
Dimensions
In Inches
Symbol
MIN
MAX
MIN
MAX
0.043
0.004
0.039
0.020
0.008
0.116
0.065
0.116
A
A1
A2
b
1.000
0.100
0.900
0.500
0.200
2.950
1.650
2.950
0.000
0.700
0.300
0.080
2.850
1.550
2.650
0.000
0.028
0.012
0.003
0.112
0.061
0.104
c
D
E
E1
e
0.950 BSC
0.037 BSC
L
0.300
0°
0.600
8°
0.012
0°
0.024
8°
θ
SG Micro Corp
www.sg-micro.com
TX00038.001
PACKAGE INFORMATION
TAPE AND REEL INFORMATION
REEL DIMENSIONS
TAPE DIMENSIONS
P2
P0
W
Q2
Q4
Q2
Q4
Q2
Q4
Q1
Q3
Q1
Q3
Q1
Q3
B0
Reel Diameter
P1
A0
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 Width
Reel
Diameter
A0
B0
K0
P0
P1
P2
W
Pin1
Package Type
W1
(mm)
(mm) (mm) (mm) (mm) (mm) (mm) (mm) Quadrant
TSOT-23-6
7″
9.5
3.20
3.10
1.10
4.0
4.0
2.0
8.0
Q3
SG Micro Corp
TX10000.000
www.sg-micro.com
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)
Reel Type
Pizza/Carton
7″ (Option)
7″
368
442
227
410
224
224
8
18
SG Micro Corp
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TX20000.000
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