MPQ2451
Industrial/Automotive-Grade
36V, 2MHz, 0.6A Step-Down Converter
AEC-Q100 Qualified
The Future of Analog IC Technology
FEATURES
DESCRIPTION
The MPQ2451 is a high frequency, step-down,
switching regulator with an integrated highvoltage high-side power MOSFET. It efficiently
provides up to a 0.6A output with current-mode
control for fast loop response.
The wide 3.3V-to-36V input range accommodates
a variety of automotive step-down applications,
and the 3μA shutdown-mode quiescent current
allows use in battery-powered applications.
The MPQ2451 achieves high power-conversion
efficiency over a wide load range by scaling
down the switching frequency under light-load
condition to reduce the switching and gate
driving losses.
Guaranteed Industrial/Automotive Temp.
Range Limits
130μA Operating Quiescent Current
Wide 3.3V-to-36V Operating Input Range
500mΩ Internal Power MOSFET
2MHz Fixed Switching Frequency
Internally Compensated
Stable with Ceramic Output Capacitors
Internal Soft-Start
Precision Current Limit Without Current
Sensing Resistor
>90% Efficiency
Output Adjustable from 0.8V to 0.9·VIN,
Fixed 5V & 3.3V Output
Frequency fold-back prevents inductor current
runaway during start-up. Thermal shutdown
provides reliable, fault-tolerant operation.
6-Lead SOT23, TSOT23 and QFN Packages
Available in AEC-Q100 Grade 1
APPLICATIONS
The MPQ2451 is available in a cost-effective
SOT23-6L, TSOT23-6L and QFN-6L packages.
High-Voltage Power Conversion
Automotive Systems
Industrial Power Systems
Distributed Power Systems
Battery-Powered Systems
All MPS parts are lead-free, halogen free, and adhere to the RoHS directive. For
MPS green status, please visit MPS website under Quality Assurance.
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks
of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
Efficiency
BST
SW
6
D1
MPQ2451
GND
VIN
VIN
5
C1
3
C3
33pF
FB
EN
L1
4
Control
95
VOUT
5V/0.6A
VIN=8V
VIN=24V
85
VIN=12V
80
75
VIN=36V
70
65
60
55
50
MPQ2451 Rev 1.2
8/4/2017
VOUT=5V
90
EFFICIENCY (%)
1
C4
100nF
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT(A)
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0.6
1
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
ORDERING INFORMATION
Part Number
MPQ2451DT*
MPQ2451DT-AEC1
MPQ2451DG**
MPQ2451DG-AEC1
MPQ2451DJ-AEC1
Package
Top Marking
SOT23-6L***
See Below
QFN-6L
See Below
TSOT23-6L
See Below
* For Tape & Reel, add suffix –Z (e.g. MPQ2451DT–Z).
For RoHS Compliant packaging, add suffix –LF (e.g. MPQ2451DT–LF–Z)
** For Tape & Reel, add suffix -Z (e.g. MPQ2451DG-Z)
For RoHS Compliant packaging, add suffix -LF (e.g. MPQ2451DG-LF-Z)
*** SOT23-6L is not recommended for new designs
Part Number
MPQ2451GT-5*
MPQ2451GT-5-AEC1
MPQ2451GT-33**
MPQ2451GT-33-AEC1
MPQ2451GG-5
MPQ2451GG-5-AEC1
MPQ2451GG-33
MPQ2451GG-33-AEC1
Package
Top Marking
See Below
SOT23-6L***
See Below
See Below
QFN-6L
See Below
* For Tape & Reel, add suffix –Z (e.g. MPQ2451GT-5-Z)
** For Tape & Reel, add suffix -Z (e.g. MPQ2451GT-33-Z)
*** SOT23-6L is not recommended for new designs
TOP MARKING
V7: product code of MPQ2451DT and MPQ2451DT-AEC1
Y: year code
W: week code
MPQ2451 Rev 1.2
8/4/2017
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2
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TOP MARKING
AML: product code of MPQ2451DJ-AEC1
Y: year code
TOP MARKING
V7: product code of MPQ2451DG and MPQ2451DG-AEC1
Y: year code
LLL: lot number
TOP MARKING
AGE: product code of MPQ2451GT-5 and MPQ2451GT-5-AEC1
Y: year code
TOP MARKING
AGF: product code of MPQ2451GT-33 and MPQ2451GT-33-AEC1
Y: year code
MPQ2451 Rev 1.2
8/4/2017
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3
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TOP MARKING
BP: product code of MPQ2451GG-5 and MPQ2451GG-5-AEC1
Y: year code
LLL: lot number
TOP MARKING
BQ: product code of MPQ2451GG-33 and MPQ2451GG-33-AEC1
Y: year code
LLL: lot number
MPQ2451 Rev 1.2
8/4/2017
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4
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
PACKAGE REFERENCE
TOP VIEW
BST
1
6
SW
GND
2
5
VIN
FB
3
4
EN
SOT23-6L, TSOT23-6L
MPQ2451 Rev 1.2
8/4/2017
QFN-6L
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5
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage (VIN)......................-0.3V to +40V
Switch Voltage (VSW)............ -0.3V to (VIN+0.3V)
BST to SW ..................................... -0.3 to +5.0V
All Other Pins .............................. –0.3V to +5.0V
(2)
Continuous Power Dissipation (TA = 25°C)
TSOT23-6L .............................................. 0.57W
SOT23-6L ................................................ 0.57W
QFN-6L .................................................... 1.56W
Junction Temperature ...............................150°C
Lead Temperature ....................................260°C
Storage Temperature ............... -65°C to +150°C
Recommended Operating Conditions
(3)
Supply Voltage VIN ........................... 3.3V to 36V
Output Voltage VOUT ................... 0.8V to 0.9·VIN
Maximum Junction Temp. (TJ) ............... +125°C
MPQ2451 Rev 1.2
8/4/2017
Thermal Resistance
(4)
θJA
θJC
TSOT23-6L ............................ 220 .... 110 .. °C/W
SOT23-6L .............................. 220 .... 110 .. °C/W
QFN-6L ................................... 80 ...... 16 ... °C/W
Notes:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient 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.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
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6
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
ELECTRICAL CHARACTERISTICS
VIN = 12V, VEN = 2V, TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TJ = 25°C.
Parameter
Symbol
Feedback Voltage
Condition
4.0V < VIN < 36V
3.3V < VIN < 4.0V
VFB
MPQ2451-5
Output Voltage
VOUT
MPQ2451-33
Min
0.774
0.766
Typ
0.794
0.794
Max
0.814
0.822
6V < VIN < 36V
4.8
5
5.2
6V < VIN < 36V,
TJ= 25°C
4.85
5
5.15
3.3V < VIN < 36V
3.168
3.3
3.432
3.3V < VIN < 36V,
TJ= 25°C
3.2
3.3
3.4
0.05
1.0
Feedback Bias Current
Upper Switch On
Resistance
RDS(ON)
Upper Switch Leakage
Current Limit
ILIM
COMP to Current
Sense
Transconductance
GCS
VBST-VSW=5V
TJ= 25°C
500
VEN = 0V, VSW = 0V
0.5
0.65
VIN UVLO Up Threshold
VIN UVLO Hysteresis
Soft-Start Time
Oscillator Frequency
Minimum Switch On
Time
Shutdown Supply
Current
Quiescent Supply
Current
Thermal Shutdown
Enable High Threshold
Enable Threshold
Hysteresis
MPQ2451 Rev 1.2
8/4/2017
FB from 0 to 0.794V
1.4
IS
VEN < 0.3V
IQ
No load, VFB=0.9,
no switching
VIH
Low-to-High
1.35
V
V
μA
mΩ
2
μA
A
3
A/V
0.4
0.5
2
3.29
V
1
2.6
V
ms
MHz
100
tON
V
1
2.7
fSW
Units
ns
3
30
μA
130
200
µA
1.8
°C
V
150
1.5
400
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mV
7
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
PIN FUNCTIONS
SOT23-6L
TSOT23-6L
Pin #
QFN-6L
Pin #
Name
1
6
BST
Bootstrap. Positive power supply for the internal floating high-side
MOSFET driver. Connect a bypass capacitor between this pin and SW
pin.
2
5
GND
Ground. Connect the output capacitor as close to this pin as possible.
Avoid routing near high-current switch paths.
3
4
FB
4
3
EN
5
2
VIN
6
1
SW
MPQ2451 Rev 1.2
8/4/2017
Description
Feedback. Input to the error amplifier. Connected to an external resistive
divider between output and GND; compared against the internal 0.8V
reference to set the regulation voltage.
Enable Input. Pull this pin below the specified threshold to shut the chip
down. Pull it above the specified threshold to enable the chip. Float this
pin to disable the chip.
Input Supply. Supplies power to all internal control circuitry; both BS
regulators and the high side switch. Requires a decoupling capacitor to
ground close to this pin to reduce switching spikes.
Switch Node. Output of the high-side switch. Requires a low VF Schottky
diode to ground close to this pin to reduce switching spikes.
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8
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TYPICAL CHARACTERISTICS
IQ vs. Temp
VIN=7V, MPQ2451-5
VIN=12V, MPQ2451-5
5.02
4.98
4.94
20
50
130
120
110
20
50
80
VOUT vs. Temp
MPQ2451-5
VIN=12V, MPQ2451-33
3.50
2.1
2.0
-10
20
50
80
3.26
3.18
ILIMIT vs. Temp
SWITCHING FREQUENCY ( MHz )
1.3
1.2
1.1
1.0
-10
MPQ2451 Rev 1.2
8/4/2017
20
50
50
1.0
-10
20
50
80 110 140
80
110 140
80
110 140
VIN=12V, MPQ2451-33
140
130
120
110
100
-40
-10
20
50
80
110 140
FSW vs. Temp
MPQ2451-33
0.9
-40
20
1.1
150
3.34
-10
1.2
IQ vs. Temp
3.42
3.10
-40
110 140
1.3
0.9
-40
110 140
IQ CURRENT ( A )
2.2
1.9
-40
CURRENT LIMIT ( A )
-10
FSW vs. Temp
2.3
1.4
MPQ2451-5
1.4
140
100
-40
80 110 140
OUTPUT VOLTAGE ( V )
2.4
-10
ILIMIT vs. Temp
CURRENT LIMIT ( A )
5.06
4.90
-40
ΣΩΙΤΧΗΙΝΓ ΦΡΕΘΥΕΝ
ΧΨ ( ΜΗζ )
150
IQ CURRENT ( A )
OUTPUT VOLTAGE ( V )
5.10
VOUT vs. Temp
80
110 140
2.4
MPQ2451-33
2.3
2.2
2.1
2.0
1.9
-40
-10
20
50
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9
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TYPICAL CHARACTERISTICS (continued)
MPQ2451 Rev 1.2
8/4/2017
www.MonolithicPower.com
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© 2017 MPS. All Rights Reserved.
10
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, C1 = 4.7µF, C2 = 10µF, L = 3.3µH and TA= 25°C, unless otherwise noted.
100
100
5.000
90
90
4.992
80
80
4.984
70
70
4.976
60
60
4.968
50
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
50
6
12
18
24
30
36
4.960
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Efficiency
Efficiency
VOUT=2.5V
90
4.992
85
VIN=6V
VIN=12V
75
4.976
70
4.968
4.960
6
MPQ2451 Rev 1.2
8/4/2017
18
24
30
36
VIN=12V
80
75
VIN=24V
70
65
65
12
VIN=8V
85
80
4.984
VOUT=3.3V
90
EFFICIENCY (%)
5.000
60
60
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT(A)
0.6
0
0.1 0.2 0.3 0.4 0.5
OUTPUT CURRENT(A)
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0.6
11
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, C1 = 4.7µF, C2 = 10µF, L = 3.3µH and TA = 25°C, unless otherwise noted.
Steady State
Steady State
VOUT
Startup Through EN
VIN=12V,VOUT=5V,IOUT=0.6A
VIN=12V,VOUT=5V,IOUT=0.1A
VIN=12V,VOUT=5V,IOUT=0.1A
VOUT
(AC coupled)
10mV/div.
(AC coupled)
10mV/div.
VSW
10V/div.
IL
500mA/div.
VSW
10V/div.
VEN
2V/div.
VSW
10V/div.
IL
500mA/div.
IL
500mA/div.
400ns/div.
400ns/div.
Shutdown Through EN
Startup Through EN
VEN
2V/div.
VSW
10V/div.
IL
500mA/div.
Shutdown Through EN
VIN=12V,VOUT=5V,IOUT=0.1A
VIN=12V,VOUT=5V,IOUT=0.6A
VOUT
5V/div.
VOUT
5V/div.
VIN=12V,VOUT=5V,IOUT=0.6A
VOUT
5V/div.
VEN
2V/div.
VOUT
5V/div.
VEN
2V/div.
VSW
10V/div.
VSW
10V/div.
IL
500mA/div.
IL
500mA/div.
.
2ms/div.
Short Circuit Entry
Short Circuit Recovery
IOUT=0A to Short
IOUT= Short to 0A
VOUT
2V/div.
VOUT
2V/div.
IL
500mA/div
IL
500mA/div
MPQ2451 Rev 1.2
8/4/2017
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12
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
FUNCTIONAL BLOCK DIAGRAM
VIN
INTERNAL
REGULATOR
REFERENCE
UVLO
EN
BST
ISW
0.5ms SS
+
SS
LOGIC
ISW
SW
FB
SS
0.8V
--
COMP
+
OSCILATOR
2MHz
GND
Figure 1: Functional Block Diagram
MPQ2451 Rev 1.2
8/4/2017
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13
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
OPERATION
The MPQ2451 is a 2MHz, non-synchronous,
step-down switching regulator with an integrated
high-side high voltage power MOSFET. It
provides an internally-compensated, highlyefficient output of up to 0.6A with current mode
control. It also features wide input voltage range,
internal soft-start control, and a precision current
limit. Its very low operational quiescent current
makes
it
suitable
for
battery-powered
applications.
PWM Control
At moderate-to-high output current, the
MPQ2451 operates in a fixed-frequency peakcurrent–control mode to regulate the output
voltage. A PWM cycle—initiated by the internal
clock—turns the power MOSFET on, and the
MOSFET remains on until its current reaches the
value set by COMP voltage. When the PWM
signal goes low, the power switch turns off and
remains off for at least 100ns before the next
cycle starts.
If the current in the power MOSFET does not
reach COMP set current value within one PWM
cycle, the power MOSFET remains on to avoid a
turn-off operation.
Pulse-Skipping Mode
Under light-load conditions, the MPQ2451 goes
into pulse-skipping mode to improve efficiency.
Pulse-skipping triggers when the COMP voltage
drops below the internal sleep threshold, which
generates a PAUSE command to block the turnon clock pulse so the power MOSFET does not
turn ON; this procedure reduces gate driving and
switching losses. This PAUSE command causes
the whole chip to enter sleep mode, reducing the
quiescent current to further improve the light load
efficiency.
When the COMP voltage exceeds the sleep
threshold, the PAUSE signal resets and the chip
resumes normal PWM operation. Whenever the
PAUSE changes state from low to high, the PWM
signal immediately goes HIGH and turns on the
power MOSFET.
MPQ2451 Rev 1.2
8/4/2017
Error Amplifier
The error amplifier is composed of an internal opamp with an RC feedback network connected
between its output node (internal COMP node)
and its negative input node (FB). When the FB
voltage drops below the internal reference
voltage (VREF), the op-amp drives the COMP
output high, causing a higher switch peak current
output and delivering more energy to the output.
Conversely, when the FB voltage rises above
VREF, the switch peak current output drops.
When using the FB pin, connect to the tap of a
voltage divider that is connected between VOUT
and GND composed of R1 and R2; R1 also serves
to control the gain of the error amplifier in
addition to the internal compensation RC network.
Internal Regulator
The 2.6V internal regulator powers most of the
internal circuitry. This regulator takes the VIN
input and operates in the full VIN range. When
VIN is greater than 3.0V, the output of the
regulator is in full regulation. When VIN drops
below 3.0V, the output degrades.
Enable Control
The MPQ2451 has a dedicated enable control
pin, EN. When VIN rises above threshold, the EN
pin can enable or disable the chip for HIGH
effective logic. Its falling threshold is 1.2V, and its
rising threshold is about 1.6V. When floated, the
EN pin is internally pulled down to GND to
disable the.
When the EN voltage is pulled to 0V, the chip
enters the lowest shutdown current mode. When
the EN voltage rises above 0V but lower than
rising threshold, the chip remains in shutdown
mode with a slightly higher shutdown current.
Under Voltage Lockout (UVLO)
VIN under-voltage lockout (UVLO) protects the
chip from operating at an insufficient supply
voltage. The UVLO rising threshold is
approximately 2.9V while its falling threshold is
2.6V.
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14
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
Internal Soft-start
A reference-type soft-start (SS) prevents the
converter-output voltage from overshooting
during startup. When the chip starts, the internal
circuitry generates a soft-start voltage (VSS) that
ramps up from 0V over the SS time. When VSS is
less than VREF, VSS overrides VREF as the error
amplifier reference.
The maximum VSS is approximately the same as
VFB; i.e. if VFB falls, the maximum of VSS falls. This
accommodates short-circuit recovery; when the
short-circuit is removed, VSS ramps up to prevent
output voltage overshoot.
Thermal Shutdown
Thermal shutdown prevents thermal runaway.
When the silicon die temperature exceeds its
upper threshold, the entire chip shuts down.
When the temperature drops below its lower
threshold, the chip is enabled again.
Floating Driver and Bootstrap Charging
The floating power MOSFET driver is powered by
an external bootstrap capacitor. This floating
driver has its own UVLO protection with a rising
threshold of about 2.4V and a falling threshold of
about 300mV. During this UVLO, VSS resets to
zero. When the UVLO is removed, the controller
enters soft-start.
The bootstrap capacitor is charged and regulated
to about 5V by the dedicated internal bootstrap
regulator. When the voltage between the BST
and SW nodes falls below its regulation, a PMOS
pass transistor connected from VIN to BST turns
on. The charging current path goes from VIN, BST
and then to SW. The external circuit must provide
enough voltage headroom to facilitate the
charging.
If VIN is sufficiently higher than VSW, the bootstrap
capacitor will charge. When the power MOSFET
is ON, VIN is equal to VSW so the bootstrap
capacitor does not charge. Optimal charging
occurs when the difference between VIN and VSW
reaches its apex when the external freewheeling
diode is on. When there is no current in the
inductor, SW equals VOUT so the difference
between VIN and VOUT can charge the bootstrap
capacitor.
voltage and time to charge the bootstrap
capacitor, add an extra external circuit to ensure
the bootstrap voltage in normal operation region.
The floating driver’s UVLO is not communicated
to the controller.
Make sure the bleed-through current at SW node
is at least higher than the floating driver’s DC
quiescent current of about 20µA.
Current Comparator and Current Limit
A current-sense MOSFET senses the power
MOSFET current. This value is input to the highspeed current comparator for current-mode
control. When the power MOSFET turns on, the
comparator is first blanked to limit noise, and
then compares the power switch current against
the COMP voltage. When the sensed value
exceeds the COMP voltage, the comparator
output goes low to turn off the power MOSFET.
The maximum current of the internal power
MOSFET is internally limited cycle-by-cycle.
Startup and Shutdown
If both VIN and VEN exceed their respective
thresholds, the chip starts. The reference block
first starts to generate a stable reference voltage
and current, and then the internal regulator starts
to provide a stable supply for the rest circuit.
While the internal supply rail is up, an internal
timer turns the power MOSFET off for about 50µs
to blank startup noise. When the internal softstart block is enabled, it first holds its SS output
low to ensure the rest of the circuit is ready
before ramping up.
Three events shut down the chip: EN low, VIN low,
thermal shutdown. In shutdown procedure, the
signaling path is blocked first to avoid any fault
triggering. The COMP voltage and the internal
supply rail are then pulled low. The floating driver
is not subject to this shutdown command but its
charging path is disabled.
At a higher duty cycle, the bootstrap capacitor
may not be charged sufficiently because of a
shorter charging period. If there is insufficient
MPQ2451 Rev 1.2
8/4/2017
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15
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
APPLICATION INFORMATION
COMPONENT SELECTION
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to the
FB pin. The voltage divider sets VOUT and VFB
using the following equation:
VFB VOUT
R2
R1 R2
Thus the output voltage is:
VOUT VFB
(R1 R2)
R2
The feedback resistor R1 also sets the
feedback loop bandwidth with the internal
compensation capacitor.
Choose R1 around 124kΩ for optimal transient
response. R2 is then given by:
R2
R1
VOUT
1
0.8V
Table 1: Resistor Selection vs. Output Voltage
Setting
VOUT
R1
R2
0.8V
124kΩ (1%)
NS
1.2V
124kΩ (1%)
249kΩ (1%)
3.3V
124kΩ (1%)
40.2kΩ (1%)
5V
124kΩ (1%)
23.7kΩ (1%)
MPQ2451 Rev 1.2
8/4/2017
Inductor
The inductor supplies constant current to the
output load while being driven by the switched
input voltage. A larger-value inductor will result
in less ripple current and lower output ripple
voltage. However, the larger-value inductor is
typically physically larger, has a higher series
resistance, or has a lower saturation current.
To determine the inductance, allow the peak-topeak ripple current in the inductor to be
approximately 30% of the maximum load
current. Also, chose a peak inductor current
below the maximum switch current limit. The
inductance value can be calculated by:
L1
VOUT
V
1 OUT
fS ∆IL
VIN
Where VOUT is the output voltage, VIN is the input
voltage, fS is the switching frequency, and ∆IL is
the peak-to-peak inductor ripple current.
Choose an inductor that will not saturate under
the maximum inductor peak current. The peak
inductor current can be calculated by:
ILP ILOAD
VOUT
V
1 OUT
2 fS L1
VIN
Where ILOAD is the load current.
Table 2 lists a number of suitable inductors
from various manufacturers. The choice of
which style inductor to use mainly depends on
the price vs. size requirements and any EMI
requirement.
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MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
Table 2: Inductor Selection Guide
Inductance (µH)
Max DCR (Ω)
Current Rating (A)
Dimensions
L x W x H (mm3)
7440430022
2.2
0.028
2.5
4.8x4.8x2.8
744043003
3.3
0.035
2.15
4.8x4.8x2.8
7447785004
4.7
0.078
2.4
5.9x6.2x3.2
D63CB-#A916CY-2R0M
2.0
0.019
2.36
6.2x6.3x3.0
D62CB-#A916CY-3R3M
3.3
0.026
2.17
6.2x6.3x3.0
D62CB-#A916CY-4R7M
4.7
0.032
2.1
6.2x6.3x3.0
2.2
0.04
3.2
5.2x5.0x2.2
3.3
0.06
2.5
5.2x5.0x2.2
4.7
0.081
2.0
5.2x5.0x2.2
2.2
0.031
2.8
5.2x5.2x2.5
3.3
0.038
2.21
5.2x5.2x2.5
4.7
0.047
1.83
5.2x5.2x2.5
Part Number
Wurth Electronics
TOKO
TDK
LTF5022T-2R2N3R2
LTF5022T-3R3N2R5
LTF5022T-4R7N2R0
COOPER BUSSMANN
SD25-2R2
SD25-3R3
SD25-4R7
The input capacitor (C1) can be electrolytic,
tantalum or ceramic. When using electrolytic or
tantalum capacitors, add a small, high quality
ceramic capacitor—for example, a 0.1μF—as
close to the IC as possible. When using ceramic
capacitors, make sure that they have enough
capacitance to provide sufficient charge to
prevent excessive voltage ripple at input. The
input voltage ripple caused by capacitance can
be estimated by:
VIN
ILOAD
V
V
OUT 1 OUT
fS C1 VIN
VIN
Output Capacitor
The output capacitor (C2) is required to maintain
the DC output voltage. Ceramic, tantalum, or low
ESR electrolytic capacitors are recommended.
Low ESR capacitors are preferred to keep the
output voltage ripple low. The output voltage
ripple can be estimated by:
VOUT
VOUT
V
1 OUT
fS L
VIN
1
R ESR
8 f S C2
Where L is the inductor value and RESR is the
equivalent series resistance (ESR) value of the
output capacitor.
In the case of ceramic capacitors, the impedance
at the switching frequency is dominated by the
capacitance. The output voltage ripple is mainly
caused by the capacitance. For simplification, the
output voltage ripple can be estimated by:
∆VOUT
V
1 OUT
V
L C2
IN
VOUT
8 fS
2
In the case of tantalum or electrolytic capacitors,
the ESR dominates the impedance at the
switching frequency. For simplification, the output
ripple can be approximated to:
∆VOUT
VOUT
V
1 OUT
f S L
VIN
R ESR
The characteristics of the output capacitor also
affect the stability of the regulation system.
MPQ2451 Rev 1.2
8/4/2017
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MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
Compensation Components
The goal of compensation design is to shape the
converter transfer function to get a desired loop
gain. Lower crossover frequencies result in
slower line and load transient responses, while
higher crossover frequencies can cause system
instability. Generally, set the crossover frequency
to equal approximately one-tenth of the switching
frequency. If using an electrolytic capacitor,
select a loop bandwidth is no higher than 1/4 of
the ESR zero frequency (fESR), where fESR is
given by:
fESR
1
2 C2 R ESR
The Table 3 lists the typical values of
compensation components of some standard
output voltages with various output capacitors
(ceramic) and inductors. The values of the
compensation components have been optimized
for fast transient responses and good stability
under the given conditions.
Table 3: Compensation Values for Typical
VOUT (V)
L (µH)
C2 (µF) R2 (kΩ) C3 (pF)
1.2
2.2
10
249
22
2.5
2.2
10
57.6
22
3.3
2.2
10
40.2
33
5
3.3
10
23.7
33
12
6.2
10
8.87
47
Note:
With the compensation, the control loop has the bandwidth at about
1/10 switching frequency and the phase margin higher than 45
degree.
MPQ2451 Rev 1.2
8/4/2017
External Bootstrap Diode
An external bootstrap diode may enhance the
efficiency of the regulator. Connect an external
BST diode from 5V to the BST pin if:
There is a 5V rail available to the system;
VIN ≤ 5V;
3.3V < VOUT < 5V;
This diode is also recommended for high-duty–
cycle (VOUT/VIN > 65%) applications.
A low-cost bootstrap diode, such as IN4148 or
BAT54, is suitable for such applications.
5V
BS
MPQ2451
SW
Figure 2: External Bootstrap Diode
At no load or light load, the converter may
operate in pulse-skipping mode in order to
regulate the output voltage and leave less time to
refresh the BST voltage. To ensure sufficient
gate voltage, select (VIN - VOUT) > 3V. For
example, if VOUT is 3.3V, VIN needs to be higher
than 3.3V+3V=6.3V at no load or light load. To
meet this requirement, the EN pin can be used to
program the input UVLO voltage to VOUT+3V.
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18
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
greater switching
frequencies.
PCB Layout
PCB layout requires high-frequency noise
considerations to limit voltage spikes on the SW
node and to limit EMI noise. Keep the path of the
input decoupling capacitor, catch diode, the VIN
pin, SW pin, and PGND as short as possible
using short and wide traces, with the passive
components as close to the device as possible.
losses
at
high
switching
Add a grid of thermal vias under the exposed pad
to improve thermal conductivity. Use small vias
(15mil barrel diameter) so that the hole fills
during the plating process, and to avoid solder
wicking during the reflow process associated with
larger vias. Use a pitch (distance between the
centers) of approximately 40mil between the
thermal vias. Please refer to the layout example
on EVQ2451 datasheet.
Run the feedback trace far from the inductor and
noisy power traces: if possible, run the feedback
trace on the opposite side of the PCB from the
inductor, separated by a ground plane. Expect
TYPICAL APPLICATION CIRCUITS (SOT23-6L)
H
Figure 3: Low Input Voltage With Boost Diode Application Schematic
1
BST
SW
6
MPQ2451
2 GND
VIN
C4
100nF
5
VIN
18-36V
VOUT
12V
D1
C1
3
C3
47pF
FB
EN
4
Control
Figure 4: 12V Output Typical Application Schematic
MPQ2451 Rev 1.2
8/4/2017
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19
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
VIN
5.6V to 36V
2
VIN U1
R1
100k
0603
GND
BST
MPQ2451-5
SW
3
EN
D2
6
EN
GND
5
5V
1
D1
B140
SMA
VOUT
OUT 4
GND
Figure 5: Fixed 5V Output Typical Application Schematic
VIN
3.6V to 36V
GND
EN
2
BST
VIN U1
R1
100k
0603
D2
6
MPQ2451-33
SW
3
EN
GND
5
3.3V
1
D1
B140
SMA
VOUT
OUT 4
GND
Figure 6: Fixed 3.3V Output Typical Application Schematic
MPQ2451 Rev 1.2
8/4/2017
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20
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
PACKAGE INFORMATION
SOT23-6L
MPQ2451 Rev 1.2
8/4/2017
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21
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
QFN6 (2mmx2mm)
PIN 1 ID
MARKING
1.90
2.10
0.30
0.40
0.20
0.30
1.90
2.10
PIN 1 ID
INDEX AREA
0.65
0.85
PIN 1 ID
SEE DETAIL A
1
6
1.25
1.45
0.65
BSC
3
4
TOP VIEW
BOTTOM VIEW
0.80
1.00
0.20 REF
PIN 1 ID OPTION A
0.30x45º TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.00
0.05
SIDE VIEW
DETAIL A
1.90
0.70
0.70
0.25
1.40
0.65
RECOMMENDED LAND PATTERN
MPQ2451 Rev 1.2
8/4/2017
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22
MPQ2451―INDUSTRIAL-GRADE 36V, 2MHz, 0.6A, STEP-DOWN CONVERTER, AEC-Q100 QUALIFIED
TSOT23-6L
NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third
party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not
assume any legal responsibility for any said applications.
MPQ2451 Rev 1.2
8/4/2017
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23
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