MPQ4460DQ [MPS]
Industrial Grade, 2.5A, 4MHz, 36V Step-Down Converter;
| 型号： | MPQ4460DQ |
| 厂家： | 
MONOLITHIC POWER SYSTEMS |
| 描述： | Industrial Grade, 2.5A, 4MHz, 36V Step-Down Converter |
| 文件： | 总18页 (文件大小：411K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MPQ4460
Industrial Grade, 2.5A, 4MHz, 36V
Step-Down Converter
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The MPQ4460 is a high frequency step-down
switching regulator with an integrated internal
high-side high voltage power MOSFET. It
provides 2.5A output with current mode control
for fast loop response and easy compensation.
•
•
•
•
•
Guaranteed Industrial Temp Range Limits
120μA Quiescent Current
Wide 3.8V to 36V Operating Input Range
150mΩ Internal Power MOSFET
Up to 4MHz Programmable Switching
Frequency
The wide 3.8V to 36V input range
accommodates
applications, including those in an automotive
input environment. 120µA operational
a
variety of step-down
•
•
•
Ceramic Capacitor Stable
Internal Soft-Start
Internally Set Current Limit without a
Current Sensing Resistor
A
quiescent current allows use in battery-powered
applications.
•
•
•
Up to 95% Efficiency
Output Adjustable from 0.8V to 30V
Available in a 3mm x 3mm QFN10 Package
High power conversion efficiency over a wide
load range is achieved by scaling down the
switching frequency at light load condition to
reduce the switching and gate driving losses.
APPLICATIONS
•
•
•
•
•
High Voltage Power Conversion
Automotive Systems
Industrial Power Systems
Distributed Power Systems
Battery Powered Systems
The frequency foldback helps prevent inductor
current runaway during startup and thermal
shutdown provides reliable, fault tolerant
operation.
By switching at 4MHz, the MPQ4460 is able to
prevent EMI (Electromagnetic Interference)
noise problems, such as those found in AM
radio and ADSL applications.
All MPS parts are lead-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.
The MPQ4460 is available in a small 3mm x
3mm QFN10 package.
TYPICAL APPLICATION
C4
100nF
Efficiency vs
Load Current
100
10
BST
L1
V
=5V
IN
10uH
8,9
3
1,2
5
V
OUT
3.3V
90
80
70
60
50
40
30
SW
FB
V
VIN
IN
C2
22uF
6.3V
C1
10uF
50V
D1
V
=12V
IN
V
=24V
IN
EN
EN
MPQ4460
7
4
COMP
FREQ
C3
220pF
GND
V
=3.3V
C6
NS
OUT
2.0
LOAD CURRENT (A)
6
0
0.5
1.0
1.5
2.5
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
1
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
ORDERING INFORMATION
Part Number*
Package
Top Marking
MPQ4460DQ
QFN10 (3x3)
M7
* For Tape & Reel, add suffix –Z (e.g. MPQ4460DQ–Z);
For Lead Free, add suffix –LF (e.g. MPQ4460DQ–LF–Z)
PACKAGE REFERENCE
TOP VIEW
SW
SW
1
2
3
4
5
10 BST
9
8
7
6
VIN
EN
VIN
COMP
FB
FREQ
GND
EXPOSED PAD
ON BACKSIDE
ABSOLUTE MAXIMUM RATINGS (1)
Supply Voltage (VIN).....................–0.3V to +40V
Switch Voltage (VSW)............ –0.3V to VIN + 0.3V
BST to SW.....................................–0.3V to +6V
All Other Pins.................................–0.3V to +6V
Thermal Resistance (4)
QFN10 (3mm x 3mm).............50...... 12... °C/W
θJA
θJC
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-to-
ambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD(MAX)=(TJ(MAX)-
TA)/ θJA. Exceeding the maximum allowable power dissipation
will cause excessive die temperature, and the regulator will go
into thermal shutdown. Internal thermal shutdown circuitry
protects the device from permanent damage.
(2)
Continuous Power Dissipation (TA = +25°C)
............................................................. 2.5W
Junction Temperature...............................150°C
Lead Temperature ....................................260°C
Storage Temperature.............. –65°C to +150°C
Recommended Operating Conditions (3)
Supply Voltage VIN ...........................3.8V to 36V
Output Voltage VOUT.........................0.8V to 30V
Operating Junct. Temp (TJ)..... –40°C to +125°C
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
2
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
VIN = 12V, VEN = 2.5V, VCOMP = 1.4V, TJ= -40°C to +85°C, unless otherwise noted. Typical values
are at TJ=25°C.
Parameter
Symbol Condition
Min
Typ
Max Units
0.776
0.770
0.8
0.824
0.830
2.0
V
4.5V < VIN < 36V, TJ=25°C
4.5V < VIN < 36V
Feedback Voltage
VFB
Feedback Bias Current
IFB
0.02
150
1
µA
mꢀ
μA
Upper Switch On Resistance(5)
Upper Switch Leakage
RDS(ON) VBST – VSW = 5V
ISW VEN = 0V, VSW = 0V, VIN = 36V
3.5
TJ=25°C
Current Limit
ILIM
GCS
Duty Cycle = 50%
A
2.7
4.5
COMP to Current Sense
Transconductance
6.3
A/V
Error Amp Voltage Gain (5)
Error Amp Transconductance
Error Amp Min Source Current
Error Amp Min Sink Current
VIN UVLO Threshold
200
60
5
V/V
µA/V
µA
µA
V
ICOMP = ±3µA
VFB = 0.7V
VFB = 0.9V
20
100
–5
2.55
3.0
0.35
1.5
2
4
12
120
150
15
100
100
1.5
300
3.45
VIN UVLO Hysteresis
V
Soft-Start Time (5)
0V < VFB < 0.8V
RFREQ = 45kꢀ
0.4
1.55
3.10
ms
MHz
MHz
µA
µA
°C
°C
ns
ns
V
2.45
4.9
18
Oscillator Frequency
fSW
R
FREQ = 18kꢀ
Shutdown Supply Current
Quiescent Supply Current
Thermal Shutdown
IS
IQ
VEN = 0V
No load, VFB = 0.9V
165
Thermal Shutdown Hysteresis
Minimum Off Time (5)
TOFF
TON
Minimum On Time (5)
EN Rising Threshold
EN Threshold Hysteresis
1.2
1.8
mV
Note:
5) Guaranteed by design.
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
3
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin # Name Description
Switch Node. This is the output from the high-side switch. A low forward drop Schottky diode to
ground is required. The diode must be close to the SW pins to reduce switching spikes.
Enable Input. Pulling this pin below the specified threshold shuts the chip down. Pulling it up
above the specified threshold or leaving it floating enables the chip.
Compensation. This node is the output of the error amplifier. Control loop frequency
compensation is applied to this pin.
1, 2
3
SW
EN
4
COMP
Feedback. This is the input to the error amplifier. The output voltage is set by an resistive
divider connected between the output and GND which scales down VOUT equal to the internal
+0.8V reference.
5
FB
Ground. It should be connected as close as possible to the output capacitor to shorten the high
current switch paths.
Switching Frequency Program Input. Connect a resistor from this pin to ground to set the
switching frequency.
6
7
GND
FREQ
Input Supply. This supplies power to all the internal control circuitry, both BS regulators and the
high-side switch. A decoupling capacitor to ground must be placed close to this pin to minimize
switching spikes.
Bootstrap. This is the positive power supply for the internal floating high-side MOSFET driver.
Connect a bypass capacitor between this pin and SW pin.
8, 9
10
VIN
BST
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
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© 2012 MPS. All Rights Reserved.
4
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, C1 = 10µF, C2 = 22µF, L = 10µH and TA = +25°C, unless otherwise noted.
Efficiency vs
Load Current
Oscillating Frequency
vs RFREQ
Efficiency vs
Load Current
100
90
80
70
60
50
40
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
100
90
80
70
60
50
40
0
0.5
1.0
1.5
2.0
2.5
10
100
1000
0
0.5
1.0
1.5
2.0
2.5
LOAD CURRENT (A)
V
V
V
OUT
AC Coupled
20mV/div.
OUT
OUT
AC Coupled
10mV/div.
AC Coupled
10mV/div.
V
V
SW
SW
V
SW
10V/div.
10V/div.
10V/div.
I
L
1A/div.
I
I
L
L
1A/div.
1A/div.
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
5
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, C1 = 10µF, C2 = 22µF, L = 10µH and TA = +25°C, unless otherwise noted.
Startup Shutdown Startup
I
= 0.1A
I
= 0.1A
I
= 1A
OUT
OUT
OUT
V
EN
V
V
EN
EN
5V/div.
5V/div.
5V/div.
V
V
OUT
OUT
V
OUT
2V/div.
2V/div.
2V/div.
V
10V/div.
V
SW
V
SW
SW
10V/div.
10V/div.
I
I
I
L
L
L
1A/div.
1A/div.
1A/div.
1ms/div.
1ms/div.
1ms/div.
Shutdown
Startup
Shutdown
I
= 1A
I
= 2A
OUT
I
= 2A
OUT
OUT
V
V
V
EN
EN
EN
5V/div.
5V/div.
5V/div.
V
V
V
OUT
OUT
OUT
2V/div.
2V/div.
2V/div.
V
V
V
SW
SW
SW
10V/div.
10V/div.
10V/div.
I
I
I
L
L
L
2A/div.
1A/div.
2A/div.
1ms/div.
Short Circuit Entry
Short Circuit Recovery
I
= 0.1A to Short
I
= Short to 0.1A
OUT
OUT
V
V
OUT
OUT
2V/div.
2V/div.
I
I
L
L
1A/div.
1A/div.
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
6
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
OPERATION
The MPQ4460 is
non-synchronous,
a
variable frequency,
PWM Control
step-down switching
At moderate to high output current, the
MPQ4460 operates in a fixed frequency, peak
current control mode to regulate the output
voltage. A PWM cycle is initiated by the internal
clock. The power MOSFET is turned on and
remains on until its current reaches the value
set by the COMP voltage. When the power
switch is off, it remains off for at least 100ns
before the next cycle starts. If, in one PWM
period, the current in the power MOSFET does
not reach the COMP set current value, the
power MOSFET remains on, saving a turn-off
operation.
regulator with an integrated high-side high
voltage power MOSFET. It provides a single
highly efficient solution with current mode
control for fast loop response and easy
compensation. It features a wide input voltage
range, internal soft-start control and precision
current limiting. Its very low operational
quiescent current makes it suitable for battery
powered applications.
V
VIN
IN
+
--
+
--
5V
2.6V
REFERENCE UVLO/
INTERNAL
EN
THERMAL
BST
SW
REGULATORS
SHUTDOWN
SW
--
+
I
SW
1.5ms SS
SS
V
OUT
I
Level
Shift
SW
FB
Gm Error Amp
--
+
COMP
SS
0V8
OSCILLATOR
CLK
V
OUT
FREQ
GND
COMP
Figure 1—Functional Block Diagram
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
7
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
Internal Soft-Start
Error Amplifier
The error amplifier compares the FB pin voltage
with the internal reference (REF) and outputs a
current proportional to the difference between
the two. This output current is then used to
charge the external compensation network to
form the COMP voltage, which is used to
control the power MOSFET current.
The soft-start is implemented to prevent the
converter output voltage from overshooting
during startup. When the chip starts, the
internal circuitry generates a soft-start voltage
(SS) ramping up from 0V to 2.6V. When it is
lower than the internal reference (REF), SS
overrides REF so the error amplifier uses SS as
the reference. When SS is higher than REF,
REF regains control.
During operation, the minimum COMP voltage
is clamped to 0.9V and its maximum is clamped
to 2.0V. COMP is internally pulled down to GND
in shutdown mode. COMP should not be pulled
up beyond 2.6V.
Thermal Shutdown
Thermal shutdown is implemented to prevent
the chip from operating at exceedingly high
temperatures. When the silicon die temperature
is higher than its upper threshold, it shuts down
the whole chip. When the temperature is lower
than its lower threshold, the chip is enabled
again.
Internal Regulator
Most of the internal circuitries are powered from
the 2.6V internal regulator. 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 is
lower than 3.0V, the output decreases.
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. This
UVLO’s rising threshold is 2.2V with a threshold
of 150mV.
Enable Control
The MPQ4460 has a dedicated enable control
pin (EN). With high enough input voltage, the
chip can be enabled and disabled by EN which
has positive logic. Its falling threshold is a
precision 1.2V, and its rising threshold is 1.5V
(300mV higher).
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 is lower than its
regulation, a PMOS pass transistor connected
from VIN to BST is turned on. The charging
current path is from VIN, BST and then to SW.
External circuit should provide enough voltage
headroom to facilitate the charging.
When floating, EN is pulled up to about 3.0V by
an internal 1µA current source so it is enabled.
To pull it down, 1µA current capability is needed.
When EN is pulled down below 1.2V, the chip is
put into the lowest shutdown current mode.
When EN is higher than zero but lower than its
rising threshold, the chip is still in shutdown
mode but the shutdown current increases
slightly.
As long as VIN is sufficiently higher than SW,
the bootstrap capacitor can be charged. When
the power MOSFET is ON, VIN is about equal
to SW so the bootstrap capacitor cannot be
charged. When the external diode is on, the
difference between VIN and SW is largest, thus
making it the best period to charge. When there
is no current in the inductor, SW equals the
output voltage VOUT so the difference between
VIN and VOUT can be used to charge the
bootstrap capacitor.
Under-Voltage Lockout (UVLO)
Under-voltage lockout (UVLO) is implemented
to protect the chip from operating at insufficient
supply voltage. The UVLO rising threshold is
about 3.0V while its falling threshold is a
consistent 2.6V.
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
8
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
At higher duty cycle operation condition, the
Startup and Shutdown
time period available to the bootstrap charging
is less so the bootstrap capacitor may not be
sufficiently charged.
If both VIN and EN are higher than their
appropriate thresholds, the chip starts. The
reference block starts first, generating stable
reference voltage and currents, and then the
internal regulator is enabled. The regulator
provides stable supply for the remaining
circuitries.
In case the internal circuit does not have
sufficient voltage and the bootstrap capacitor is
not charged, extra external circuitry can be
used to ensure the bootstrap voltage is in the
normal operational region. Refer to External
Bootstrap Diode in Application section.
While the internal supply rail is up, an internal
timer holds the power MOSFET OFF for about
50µs to blank the startup glitches. When the
internal soft-start block is enabled, it first holds
its SS output low to ensure the remaining
circuitries are ready and then slowly ramps up.
The DC quiescent current of the floating driver
is about 20µA. Make sure the bleeding current
at the SW node is higher than this value, such
that:
Three events can shut down the chip: EN low,
VIN low and thermal shutdown. In the shutdown
procedure, power MOSFET is turned off first to
avoid any fault triggering. The COMP voltage
and the internal supply rail are then pulled down.
VO
IO
+
> 20μA
(R1+ R2)
Current Comparator and Current Limit
The power MOSFET current is accurately
sensed via a current sense MOSFET. It is then
fed to the high speed current comparator for the
current mode control purpose. The current
comparator takes this sensed current as one of
its inputs. When the power MOSFET is turned
on, the comparator is first blanked till the end of
the turn-on transition to avoid noise issues. The
comparator then compares the power switch
current with the COMP voltage. When the
sensed current is higher than the COMP
voltage, the comparator output is low, turning
off the power MOSFET. The cycle-by-cycle
maximum current of the internal power
MOSFET is internally limited.
Programmable Oscillator
The MPQ4460 oscillating frequency is set by an
external resistor, RFREQ from the FREQ pin to
ground. The relationship between RFREQ and
fS refer to table1 in Application section.
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
9
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
APPLICATION INFORMATION
About 20µA current from high side BS circuitry
can be seen at the output when the MPQ4460
is at no load. In order to absorb this small
COMPONENT SELECTION
Setting the Frequency
The MPQ4460 has an externally adjustable
frequency. The switching frequency (fS) can be
set using a resistor at FREQ pin (RFREQ). The
recommended RFREQ value for various fS see
table1.
amount of current, keep R2 under 40kꢀ.
A
typical value for R2 can be 40.2kꢀ. With this
value, R1 can be determined by:
R1= 50.25 × (VOUT − 0.8)(kΩ)
Table 1—fS vs. RFREQ
For example, for a 3.3V output voltage, R2 is
40.2kꢀ, and R1 is 127kꢀ.
RFREQ (kΩ)
fS (MHz)
Inductor
18
20
4
The inductor is required to supply constant
current to the output load while being driven by
the switched input voltage. A larger value
inductor will result in less ripple current that will
result in lower output ripple voltage. However,
the larger value inductor will have a larger
physical size, higher series resistance, and/or
lower saturation current.
A good rule for determining the inductance to
use is to allow the peak-to-peak ripple current in
the inductor to be approximately 30% of the
maximum switch current limit. Also, make sure
that the peak inductor current is below the
maximum switch current limit. The inductance
value can be calculated by:
3.8
3.5
3.3
3
22.1
24
26.7
30
2.8
2.5
2.2
2
33.2
39
45.3
51
1.8
1.6
1.4
1.2
1
57.6
68
80.6
100
133
200
340
536
⎛
⎜
⎝
⎞
⎟
⎟
⎠
VOUT
VOUT
⎜
L1=
× 1−
fS × ΔIL
V
IN
0.8
0.5
0.3
0.2
Where VOUT is the output voltage, VIN is the input
voltage, fS is the switching frequency, and ΔIL 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:
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to FB pin.
The voltage divider divides the output voltage
down to the feedback voltage by the
ratio:
⎛
⎜
⎝
⎞
⎟
⎟
⎠
VOUT
VOUT
⎜
ILP = ILOAD
+
× 1−
2 × fS × L1
V
IN
Where ILOAD is the load current.
R2
VFB = V
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.
OUT R1+ R2
Thus the output voltage is:
(R1+ R2)
VOUT = VFB
R2
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
10
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
Table 2—Inductor Selection Guide
Dimensions
Part Number
Wurth Electronics
7447789002
Inductance (µH) Max DCR (Ω) Current Rating (A)
L x W x H (mm3)
2.2
3.3
4.7
10
0.019
0.024
0.033
0.035
0.025
0.031
4
7.3x7.3x3.2
7.3x7.3x3.2
7.3x7.3x3.2
10x10x3.8
12x12x6
7447789003
3.42
2.9
7447789004
744066100
3.6
744771115
15
3.75
3.37
744771122
22
12x12x6
TDK
RLF7030T-2R2
RLF7030T-3R3
RLF7030T-4R7
SLF10145T-100
SLF12565T-150M4R2
SLF12565T-220M3R5
Toko
2.2
3.3
4.7
10
0.012
0.02
5.4
4.1
3.4
3
7.3x6.8x3.2
7.3x6.8x3.2
0.031
0.0364
0.0237
0.0316
7.3x6.8x3.2
10.1x10.1x4.5
12.5x12.5x6.5
12.5x12.5x6.5
15
4.2
3.5
22
FDV0630-2R2M
FDV0630-3R3M
FDV0630-4R7M
919AS-100M
919AS-160M
919AS-220M
2.2
3.3
4.7
10
0.021
0.031
5.3
4.3
3.3
4.3
3.3
3
7.7x7x3
7.7x7x3
0.049
7.7x7x3
0.0265
0.0492
0.0776
10.3x10.3x4.5
10.3x10.3x4.5
10.3x10.3x4.5
16
22
Output Rectifier Diode
Input Capacitor
The output rectifier diode supplies the current to
the inductor when the high-side switch is off. To
reduce losses due to the diode forward voltage
and recovery times, use a Schottky diode.
The input current to the step-down converter is
discontinuous, therefore a capacitor is required
to supply the AC current to the step-down
converter while maintaining the DC input
voltage. Use low ESR capacitors for the best
performance. Ceramic capacitors are preferred,
but tantalum or low-ESR electrolytic capacitors
may also suffice.
Choose a diode whose maximum reverse
voltage rating is greater than the maximum
input voltage, and whose current rating is
greater than the maximum load current. Table 3
lists
manufacturers.
example
Schottky
diodes
and
For simplification, choose the input capacitor
with RMS current rating greater than half of the
maximum load current.
Table 3—Diode Selection Guide
Voltage/
Diodes
Current
Rating
Manufacturer
B340A-13-F
CMSH3-40MA
40V, 3A
40V, 3A
Diodes Inc.
Central Semi
MPQ4460 Rev1.21
12/5/2012
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11
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
The input capacitor (C1) can be electrolytic,
Compensation Components
tantalum or ceramic. When using electrolytic or
tantalum capacitors, a small, high quality
ceramic capacitor, i.e. 0.1μF, should be placed
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:
MPQ4460 employs current mode control for
easy compensation and fast transient response.
The system stability and transient response are
controlled through the COMP pin. COMP pin is
the output of the internal error amplifier. A
series capacitor-resistor combination sets a
pole-zero
combination
to
control
the
characteristics of the control system. The DC
gain of the voltage feedback loop is given by:
VFB
⎛
⎜
⎝
⎞
⎟
⎟
⎠
ILOAD
VOUT
VIN
VOUT
AVDC = RLOAD × GCS × AVEA
×
⎜
ΔV
=
×
× 1−
IN
VOUT
fS × C1
V
IN
Where AVEA is the error amplifier voltage gain,
200V/V; GCS is the current sense
transconductance, 3.7A/V; RLOAD is the load
resistor value.
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:
The system has two poles of importance. One
is due to the compensation capacitor (C3), the
output resistor of error amplifier. The other is
due to the output capacitor and the load resistor.
These poles are located at:
⎛
⎜
⎝
⎞
⎟
⎟
⎛
⎜
⎝
⎞
⎟
⎟
⎠
VOUT
VOUT
VIN
1
⎜
⎜
ΔVOUT
=
× 1−
× RESR
+
fS × L
8 × fS × C2
⎠
GEA
fP1
=
Where L is the inductor value and RESR is the
equivalent series resistance (ESR) value of the
output capacitor.
2π× C3× AVEA
1
fP2
=
2π × C2× RLOAD
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:
Where,
GEA
is
the
error
amplifier
transconductance, 60μA/V.
The system has one zero of importance, due to
the compensation capacitor (C3) and the
compensation resistor (R3). This zero is located
at:
⎛
⎞
⎟
⎟
⎠
VOUT
VOUT
⎜
ΔVOUT
=
× 1−
8 × fS2 × L × C2
⎜
⎝
V
IN
1
fZ1
=
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:
2π × C3×R3
The system may have another zero of
importance, if the output capacitor has a large
capacitance and/or a high ESR value. The zero,
due to the ESR and capacitance of the output
capacitor, is located at:
VOUT
VOUT
⎛
⎞
ΔVOUT
=
× ⎜1−
⎟ ×RESR
⎜
⎟
fS ×L
VIN
⎝
⎠
1
The characteristics of the output capacitor also
affect the stability of the regulation system. The
MPQ4460 can be optimized for a wide range of
capacitance and ESR values.
fESR
=
2π × C2× RESR
MPQ4460 Rev1.21
12/5/2012
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12
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
In this case (as shown in Figure 2), a third pole
1. Choose the compensation resistor (R3) to set
the desired crossover frequency. Determine the
R3 value by the following equation:
set by the compensation capacitor (C6) and the
compensation resistor (R3) is used to
compensate the effect of the ESR zero on the
loop gain. This pole is located at:
2π × C2× fC VOUT
R3 =
×
GEA × GCS
VFB
1
fP3
=
2π × C6 × R3
Where fC is the desired crossover frequency.
The goal of compensation design is to shape
the converter transfer function to get a desired
loop gain. The system crossover frequency
where the feedback loop has the unity gain is
important. Lower crossover frequencies result
in slower line and load transient responses,
while higher crossover frequencies could cause
system unstable. A good rule of thumb is to set
the crossover frequency to approximately one-
tenth of the switching frequency. The Table 4
lists the typical values of compensation
components for some standard output voltages
with various output capacitors and inductors.
The values of the compensation components
have been optimized for fast transient
responses and good stability at given conditions.
2. Choose the compensation capacitor (C3) to
achieve the desired phase margin. For
applications with typical inductor values, setting
the compensation zero, fZ1, below one forth of
the crossover frequency provides sufficient
phase margin. Determine the C3 value by the
following equation:
4
C3 >
2π × R3 × fC
3. Determine if the second compensation
capacitor (C6) is required. It is required if the
ESR zero of the output capacitor is located at
less than half of the switching frequency, or the
following relationship is valid:
fS
2
1
<
Table 4—Compensation Values for Typical
Output Voltage/Capacitor Combinations
2π × C2× RESR
If this is the case, then add the second
compensation capacitor (C6) to set the pole fP3
at the location of the ESR zero. Determine the
C6 value by the equation:
VOUT
(V)
C2
(µF)
R3
(kꢀ)
C3
(pF)
L (µH)
C6
1.8
2.5
3.3
5
4.7
47
22
22
22
22
105
54.9
68.1
100
147
100
220
220
150
150
None
C2 × RESR
4.7 - 6.8
6.8 -10
15 - 22
22 - 33
None
None
None
None
C6 =
R3
12
To optimize the compensation components for
conditions not listed in Table 3, the following
procedure can be used.
MPQ4460 Rev1.21
12/5/2012
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13
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
High Frequency Operation
Layout becomes more important when the
device switches at higher frequency. It is
essential to place the input decoupling
capacitor, catch diode and the MPQ4460 (Vin
pin, SW pin and PGND) as close as possible,
with traces that are very short and fairly wide.
This can help to greatly reduce the voltage
spike on SW node, and lower the EMI noise
level as well.
The switching frequency of MPQ4460 can be
programmed up to 4MHz by an external resistor.
Please pay attention to the following if the
switching frequency is above 2MHz.
The minimum on time of MPQ4460 is about
80ns (typ). Pulse skipping operation can be
seen more easily at higher switching frequency
due to the minimum on time. Recommended
operating voltage is 12V or below, and 24V or
below at 2MHz. Refer to Figure 2 below for
detailed information.
Try to run the feedback trace as far from the
inductor and noisy power traces as possible. It
is often a good idea to run the feedback trace
on the side of the PCB opposite of the inductor
with a ground plane separating the two. The
compensation components should be placed
closed to the MPQ4460. Do not place the
compensation components close to or under
high dv/dt SW node, or inside the high di/dt
power loop. If you have to do so, the proper
ground plane must be in place to isolate those.
Switching loss is expected to be increased at
high switching frequency. To help to improve
the thermal conduction, a grid of thermal vias
can be created right under the exposed pad. It
is recommended that they be small
(15mil barrel diameter) so that the hole is
essentially filled up during the plating process,
thus aiding conduction to the other side. Too
large a hole can cause ‘solder wicking’
problems during the reflow soldering process.
The pitch (distance between the centers) of
several such thermal vias in an area is typically
40mil. Please refer to the layout example on
EVQ4460 datasheet.
Recommended VIN (max)
vs Switching Frequency
30
25
20
V
=3.3V
OUT
15
10
5
V
=2.5V
OUT
1500 2000 2500 3000 3500 4000
f (KHz)
s
Figure 2—Recommend Max VIN vs. fs
Since the internal bootstrap circuitry has higher
impedance, which may not be adequate to
charge the bootstrap capacitor during each
(1-D)×Ts charging period, an external bootstrap
charging diode is strongly recommended if the
switching frequency is above 2MHz (see
External Bootstrap Diode section for detailed
implementation information).
With higher switching frequencies, the inductive
reactance (XL) of capacitor comes to dominate,
so that the ESL of input/output capacitor
determines the input/output ripple voltage at
higher switching frequency. As a result of that,
high frequency ceramic capacitor is strongly
recommended as input decoupling capacitor
and output filtering capacitor for such high
frequency operation.
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
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14
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
External Bootstrap Diode
This diode is also recommended for high duty
cycle operation (when VOUT /VIN >65%) or low
VIN (<5Vin) applications.
It is recommended that an external bootstrap
diode be added when the input voltage is no
greater than 5V or the 5V rail is available in the
system. This helps improve the efficiency of the
regulator. The bootstrap diode can be a low
cost one such as IN4148 or BAT54.
At no load or light load, the converter may
operate in pulse skipping mode in order to
maintain the output voltage in regulation. Thus
there is less time to refresh the BS voltage. In
order to have enough gate voltage under such
operating conditions, the difference of VIN –VOUT
should be greater than 3V. For example, if the
VOUT is set to 3.3V, the VIN needs to be higher
than 3.3V+3V=6.3V to maintain enough BS
voltage at no load or light load. To meet this
requirement, EN pin can be used to program
the input UVLO voltage to Vout+3V.
5V
BS
MPQ4460
SW
Figure 3—External Bootstrap Diode
MPQ4460 Rev1.21
12/5/2012
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© 2012 MPS. All Rights Reserved.
15
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS
C4
100nF
10
BST
L1
4.7uH
V
8,9
3
1,2
5
V
IN
OUT
SW
FB
VIN
1.8V
6V - 36V
C2
47uF
6.3V
C1
10uF
50V
D1
EN
EN
MPQ4460
7
4
COMP
FREQ
C3
100pF
GND
C6
NS
6
Figure 4—1.8V Output Typical Application Schematic
C4
100nF
10
BST
L1
15uH
V
8,9
3
1,2
5
V
IN
OUT
SW
FB
VIN
5V
10V - 36V
C2
22uF
6.3V
C1
10uF
50V
D1
EN
EN
MPQ4460
7
4
COMP
FREQ
C3
150pF
GND
C6
NS
6
Figure 5—5V Output Typical Application Schematic
MPQ4460 Rev1.21
12/5/2012
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16
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
PCB LAYOUT GUIDE
2) Bypass ceramic capacitors are suggested
to be put close to the VIN Pin.
PCB layout is very important to achieve stable
operation. It is highly recommended to duplicate
EVB layout for optimum performance.
3) Ensure all feedback connections are short
and direct. Place the feedback resistors
and compensation components as close to
the chip as possible.
If change is necessary, please follow these
guidelines and take Figure 6 for reference.
1) Keep the path of switching current short
and minimize the loop area formed by Input
cap, high-side MOSFET and external
switching diode.
4) Route SW away from sensitive analog
areas such as FB.
5) Connect IN, SW, and especially GND
respectively to a large copper area to cool
the chip to improve thermal performance
and long-term reliability.
C4
L1
BST
V
SW
FB
V
IN
VIN
OUT
D1
R2
C2
C1
R4
R5
EN
EN
MPQ4460
R1
COMP
FREQ
C3
R3
GND
R6
MPQ4460 Typical Application Circuit
L1
R1
SW
C4
D1
R6
C2
C1
Vin
GND
GND
Vo
TOP Layer
Bottom Layer
Figure 6―MPQ4460 Typical Application Circuit and PCB Layout Guide
MPQ4460 Rev1.21
12/5/2012
www.MonolithicPower.com
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© 2012 MPS. All Rights Reserved.
17
MPQ4460 – INDUSTRIAL GRADE 2.5A, 4MHz, 36V STEP-DOWN CONVERTER
PACKAGE INFORMATION
QFN10 (3mm x 3mm)
2.90
3.10
0.30
0.50
1.45
1.75
PIN 1 ID
SEE DETAIL A
PIN 1 ID
MARKING
0.18
10
1
5
0.30
2.25
2.55
2.90
3.10
PIN 1 ID
INDEX AREA
0.50
BSC
6
TOP VIEW
BOTTOM VIEW
PIN 1 ID OPTION A
R0.20 TYP.
PIN 1 ID OPTION B
R0.20 TYP.
0.80
1.00
0.20 REF
0.00
0.05
SIDE VIEW
DETAIL A
NOTE:
2.90
1.70
1) ALL DIMENSIONS ARE IN MILLIMETERS.
0.70
0.25
2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX.
4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VEED-5.
5) DRAWING IS NOT TO SCALE.
2.50
0.50
RECOMMENDED LAND PATTERN
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.
MPQ4460 Rev. 1.21
12/5/2012
www.MonolithicPower.com
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© 2012 MPS. All Rights Reserved.
18
相关型号：
MPQ4462DQ-AEC1-LF-Z
Switching Regulator, Current-mode, 4000kHz Switching Freq-Max, PDSO10, QFN-10
MPS
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