The Future of Analog IC Technology MP1584
DESCRIPTION 3A, 1.5MHz, 28V
Step-Down Converter
The MP1584 is a high frequency step-down
switching regulator with an integrated internal FEATURES
high-side high voltage power MOSFET. It
provides 3A output with current mode control for Wide 4.5V to 28V Operating Input Range
fast loop response and easy compensation. Programmable Switching Frequency from
The wide 4.5V to 28V input range accommodates 100kHz to 1.5MHz
a variety of step-down applications, including High-Efficiency Pulse Skipping Mode for
those in an automotive input environment. A
100A operational quiescent current allows use in Light Load
battery-powered applications. Ceramic Capacitor Stable
Internal Soft-Start
High power conversion efficiency over a wide Internally Set Current Limit without a
load range is achieved by scaling down the
switching frequency at light load condition to Current Sensing Resistor
reduce the switching and gate driving losses. Available in SOIC8E Package.
The frequency foldback helps prevent inductor APPLICATIONS
current runaway during startup and thermal
shutdown provides reliable, fault tolerant High Voltage Power Conversion
operation. Automotive Systems
Industrial Power Systems
By switching at 1.5MHz, the MP1584 is able to Distributed Power Systems
prevent EMI (Electromagnetic Interference) noise Battery Powered Systems
problems, such as those found in AM radio and
ADSL applications. "MPS" and "The Future of Analog IC Technology" are Registered Trademarks of
Monolithic Power Systems, Inc.
The MP1584 is available in a thermally enhanced
SOIC8E package.
TYPICAL APPLICATION Efficiency Curve
C4 (fSW=500kHz)
100nF
100
8 90 VIN=12V
VIN 7 VIN BST SW 1 VOUT 80
3.3V
EFFICIENCY (%) 70
D1 60 VIN=24V
C3
EN 2 EN FB 4 220pF 50
MP1584 C6 40
NS
6 FREQ COMP 3 30
GND 20
5
10
0
0.01 0.1 1 10
OUTPUT CURRENT (A)
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
ORDERING INFORMATION
Part Number* Package Top Marking Free Air Temperature (TA)
MP1584EN SOIC8E MP1584EN 20C to +85C
* For Tape & Reel, add suffix Z (e.g. MP1584ENZ);
For RoHS Compliant Packaging, add suffix LF. (e.g. MP1584ENLFZ)
PACKAGE REFERENCE
TOP VIEW
SW 1 8 BST
EN 2 7 VIN
COMP 3 6 FREQ
FB 4 5 GND
ABSOLUTE MAXIMUM RATINGS (1) Operating Junct. Temp (TJ) .....20C to +125C
Supply Voltage (VIN).....................0.3V to +30V Thermal Resistance (4) JA JC
Switch Voltage (VSW)............ 0.3V to VIN + 0.3V
BST to SW .....................................0.3V to +6V SOIC8E .................................. 50 ...... 10... C/W
All Other Pins .................................0.3V to +6V
Continuous Power Dissipation (TA = Notes:
+25C)(2) 1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
............................................................. 2.5W
maximum junction temperature TJ(MAX), the junction-to-
Junction Temperature ...............................150C ambient thermal resistance JA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
Lead Temperature ....................................260C any ambient temperature is calculated by PD(MAX)=(TJ(MAX)-
TA)/ JA. Exceeding the maximum allowable power dissipation
Storage Temperature.............. 65C to +150C will cause excessive die temperature, and the regulator will go
into thermal shutdown. Internal thermal shutdown circuitry
Recommended Operating Conditions (3) protects the device from permanent damage.
3) The device is not guaranteed to function outside of its
Supply Voltage VIN ........................... 4.5V to 28V operating conditions.
Output Voltage VOUT.........................0.8V to 25V 4) Measured on JESD51-7, 4-layer PCB.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
VIN = 12V, VEN = 2.5V, VCOMP = 1.4V, TA= +25C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
0.8 0.824 V
Feedback Voltage VFB 4.5V < VIN < 28V 0.776 150 m
Upper Switch On Resistance RDS(ON) VBST VSW = 5V 4.0 1 A
Upper Switch Leakage VEN = 0V, VSW = 0V, VIN = 28V 4.7 A
Current Limit
COMP to Current Sense GCS 9 A/V
Transconductance
Error Amp Voltage Gain (5) 200 V/V
Error Amp Transconductance 60
Error Amp Min Source current ICOMP = 3A 40 5 80 A/V
Error Amp Min Sink current 5
VIN UVLO Threshold VFB = 0.7V 3.0 A
VIN UVLO Hysteresis 0.35
Soft-Start Time (5) VFB = 0.9V 1.5 A
Oscillator Frequency 900
Shutdown Supply Current 2.7 12 3.3 V
Quiescent Supply Current 100
Thermal Shutdown 150 V
15
0V < VFB < 0.8V 100 ms
RFREQ = 100k 100
VEN = 0V 1.5 kHz
No load, VFB = 0.9V 300
20 A
125 A
C
Thermal Shutdown Hysteresis C
Minimum Off Time (5)
Minimum On Time (5) ns
EN Up Threshold ns
EN Hysteresis 1.35 1.65 V
mV
Note:
5) Guaranteed by design.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
PIN FUNCTIONS
SOIC Name Description
Pin #
1 SW 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.
2 EN 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.
3 COMP Compensation. This node is the output of the error amplifier. Control loop frequency
compensation is applied to this pin.
Feedback. This is the input to the error amplifier. The output voltage is set by a resistive divider
4 FB connected between the output and GND which scales down VOUT equal to the internal +0.8V
reference.
5 GND Ground. It should be connected as close as possible to the output capacitor to shorten the high
Exposed current switch paths. Connect exposed pad to GND plane for optimal thermal performance.
Pad
6 FREQ Switching Frequency Program Input. Connect a resistor from this pin to ground to set the
switching frequency.
Input Supply. This supplies power to all the internal control circuitry, both BS regulators and the
7 VIN high-side switch. A decoupling capacitor to ground must be placed close to this pin to minimize
switching spikes.
8 BST 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.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT=5V, C1 = 10F, C2 = 22F, L1= 10H, TA = +25C, unless otherwise noted.
Oscillating Frequency
vs. Rfreq
1600
OSCILLATING FREQUENCY (kHZ)
1400
1200
1000
800
600
400
200
0
10 100 1000 10000
Steady State Steady State Steady State
IOUT=0.1A, fSW=500kHz IOUT=1A, fSW=500kHz IOUT=2A, fSW=500kHz
VOUT VOUT VOUT
AC Coupled AC Coupled AC Coupled
10mV/div. 10mV/div. 10mV/div.
VSW VSW VSW
10V/div. 10V/div. 10V/div.
IL IL IL
1A/div. 1A/div. 2A/div.
1 v. 2 v. 2 v.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 12V, C1 = 10F, C2 = 22F, L1 = 10H, fSW=500kHz, and TA = +25C, unless otherwise noted.
Startup Shutdown Startup
IOUT = 0.1A IOUT = 0.1A IOUT = 1A
VEN VEN VEN
5V/div. 5V/div. 5V/div.
VOUT VOUT VOUT
2V/div. 2V/div. 2V/div.
VSW VSW VSW
10V/div. 10V/div. 10V/div.
IL IL IL
1A/div. 1A/div. 1A/div.
5ms/div. 1ms/div. 5ms/div.
Shutdown Startup Shutdown
IOUT = 1A IOUT = 2A IOUT = 2A
VEN VEN VEN
5V/div. 5V/div. 5V/div.
VOUT VOUT VOUT
2V/div. 2V/div. 2V/div.
VSW VSW VSW
10V/div. 10V/div. 10V/div.
IL IL IL
1A/div. 2A/div. 2A/div.
5ms/div.
Short Circuit Entry Short Circuit Recovery
IOUT = 0.1A to Short IOUT = Short to 0.1A
VOUT VOUT
2V/div. 2V/div.
IL IL
1A/div. 1A/div.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
BLOCK DIAGRAM
VIN VIN
+
5V +-- --
2.6V
EN REFERENCE UVLO/ INTERNAL BST
THERMAL REGULATORS SW
SHUTDOWN
VOUT
SW
ISW --
VOUT 1.5ms SS SS +
Level ISW
FB Shift
Gm Error Amp
-- COMP
SS OSCILLATOR CLK
0V8 +
COMP GND FREQ
Figure 1--Functional Block Diagram
OPERATION PWM Control
At moderate to high output current, the MP1584
The MP1584 is a variable frequency, operates in a fixed frequency, peak current
non-synchronous, step-down switching control mode to regulate the output voltage. A
regulator with an integrated high-side high PWM cycle is initiated by the internal clock. The
voltage power MOSFET. It provides a highly power MOSFET is turned on and remains on
efficient solution with current mode control for until its current reaches the value set by the
fast loop response and easy compensation. It COMP voltage. When the power switch is off, it
features a wide input voltage range, internal remains off for at least 100ns before the next
soft-start control and precision current limiting. cycle starts. If, in one PWM period, the current
Its very low operational quiescent current in the power MOSFET does not reach the
makes it suitable for battery powered COMP set current value, the power MOSFET
applications. remains on, saving a turn-off operation.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
Error Amplifier Internal Soft-Start
The error amplifier compares the FB pin voltage The soft-start is implemented to prevent the
with the internal reference (REF) and outputs a converter output voltage from overshooting
current proportional to the difference between during startup. When the chip starts, the
the two. This output current is then used to internal circuitry generates a soft-start voltage
charge the external compensation network to (SS) ramping up from 0V to 2.6V. When it is
form the COMP voltage, which is used to lower than the internal reference (REF), SS
control the power MOSFET current. overrides REF so the error amplifier uses SS as
the reference. When SS is higher than REF,
During operation, the minimum COMP voltage REF regains control.
is clamped to 0.9V and its maximum is clamped
to 2.0V. COMP is internally pulled down to GND Thermal Shutdown
in shutdown mode. COMP should not be pulled Thermal shutdown is implemented to prevent
up beyond 2.6V. the chip from operating at exceedingly high
temperatures. When the silicon die temperature
Internal Regulator is higher than its upper threshold, it shuts down
Most of the internal circuitries are powered from the whole chip. When the temperature is lower
the 2.6V internal regulator. This regulator takes than its lower threshold, the chip is enabled
the VIN input and operates in the full VIN range. again.
When VIN is greater than 3.0V, the output of
the regulator is in full regulation. When VIN is Floating Driver and Bootstrap Charging
lower than 3.0V, the output decreases. The floating power MOSFET driver is powered
by an external bootstrap capacitor. This floating
Enable Control driver has its own UVLO protection. This
The MP1584 has a dedicated enable control pin UVLO's rising threshold is 2.2V with a threshold
(EN). With high enough input voltage, the chip of 150mV.
can be enabled and disabled by EN which has
positive logic. Its falling threshold is a precision The bootstrap capacitor is charged and
1.2V, and its rising threshold is 1.5V (300mV regulated to about 5V by the dedicated internal
higher). bootstrap regulator. When the voltage between
the BST and SW nodes is lower than its
When floating, EN is pulled up to about 3.0V by regulation, a PMOS pass transistor connected
an internal 1A current source so it is enabled. from VIN to BST is turned on. The charging
To pull it down, 1A current capability is current path is from VIN, BST and then to SW.
needed. External circuit should provide enough voltage
headroom to facilitate the charging.
When EN is pulled down below 1.2V, the chip is
put into the lowest shutdown current mode. As long as VIN is sufficiently higher than SW,
When EN is higher than zero but lower than its the bootstrap capacitor can be charged. When
rising threshold, the chip is still in shutdown the power MOSFET is ON, VIN is about equal
mode but the shutdown current increases to SW so the bootstrap capacitor cannot be
slightly. charged. When the external diode is on, the
difference between VIN and SW is largest, thus
Under-Voltage Lockout (UVLO) making it the best period to charge. When there
is no current in the inductor, SW equals the
Under-voltage lockout (UVLO) is implemented output voltage VOUT so the difference between
to protect the chip from operating at insufficient VIN and VOUT can be used to charge the
supply voltage. The UVLO rising threshold is bootstrap capacitor.
about 3.0V while its falling threshold is a
consistent 2.6V.
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MP1584 3A, 1.5MHz, 28V 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 If both VIN and EN are higher than their
sufficiently charged. appropriate thresholds, the chip starts. The
reference block starts first, generating stable
In case the internal circuit does not have reference voltage and currents, and then the
sufficient voltage and the bootstrap capacitor is internal regulator is enabled. The regulator
not charged, extra external circuitry can be provides stable supply for the remaining
used to ensure the bootstrap voltage is in the circuitries.
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
The DC quiescent current of the floating driver 50s to blank the startup glitches. When the
is about 20A. Make sure the bleeding current internal soft-start block is enabled, it first holds
at the SW node is higher than this value, such its SS output low to ensure the remaining
that: circuitries are ready and then slowly ramps up.
IO VO 20A Three events can shut down the chip: EN low,
(R1 R2) VIN low and thermal shutdown. In the shutdown
procedure, power MOSFET is turned off first to
Current Comparator and Current Limit avoid any fault triggering. The COMP voltage
The power MOSFET current is accurately and the internal supply rail are then pulled
sensed via a current sense MOSFET. It is then down.
fed to the high speed current comparator for the
current mode control purpose. The current Programmable Oscillator
comparator takes this sensed current as one of
its inputs. When the power MOSFET is turned The MP1584 oscillating frequency is set by an
on, the comparator is first blanked till the end of
the turn-on transition to avoid noise issues. The external resistor, Rfreq from the FREQ pin to
comparator then compares the power switch ground. The value of Rfreq can be calculated
current with the COMP voltage. When the from:
sensed current is higher than the COMP
voltage, the comparator output is low, turning 180000
off the power MOSFET. The cycle-by-cycle fs (kHz) 1.1
maximum current of the internal power Rfreq(k)
MOSFET is internally limited.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
APPLICATION INFORMATION A good rule for determining the inductance to
use is to allow the peak-to-peak ripple current in
COMPONENT SELECTION the inductor to be approximately 30% of the
maximum switch current limit. Also, make sure
Setting the Output Voltage that the peak inductor current is below the
maximum switch current limit. The inductance
The output voltage is set using a resistive value can be calculated by:
voltage divider from the output voltage to FB pin.
The voltage divider divides the output voltage
down to the feedback voltage by the
ratio:
VFB VOUT R2 L1 VOUT 1 VOUT
R1 R2 fS IL VIN
Thus the output voltage is: Where VOUT is the output voltage, VIN is the input
voltage, fS is the switching frequency, and IL is
VOUT VFB (R1 R2) the peak-to-peak inductor ripple current.
R2
About 20A current from high side BS circuitry Choose an inductor that will not saturate under
can be seen at the output when the MP1584 is the maximum inductor peak current. The peak
at no load. In order to absorb this small amount inductor current can be calculated by:
of current, keep R2 under 40K. A typical
value for R2 can be 40.2k. With this value, R1 ILP ILOAD 2 VOUT L1 1 VOUT
can be determined by: fS VIN
R1 50.25 (VOUT 0.8)(k) Where ILOAD is the load current.
For example, for a 3.3V output voltage, R2 is Table 1 lists a number of suitable inductors
40.2k, and R1 is 127k. from various manufacturers. The choice of
which style inductor to use mainly depends on
Inductor the price vs. size requirements and any EMI
The inductor is required to supply constant requirement.
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.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
Table 1--Inductor Selection Guide
Part Number Inductance (H) Max DCR () Current Rating (A) Dimensions
Wurth Electronics L x W x H (mm3)
3.3 0.024 3.42
7447789003 7.3x7.3x3.2
744066100 10 0.035 3.6 10x10x3.8
744771115 12x12x6
744771122 15 0.025 3.75 12x12x6
TDK
RLF7030T-3R3 22 0.031 3.37 7.3x6.8x3.2
RLF7030T-4R7 7.3x6.8x3.2
SLF10145T-100 3.3 0.02 4.1 10.1x10.1x4.5
SLF12565T-220M3R5 12.5x12.5x6.5
Toko 4.7 0.031 3.4
FDV0630-3R3M 7.7x7x3
FDV0630-4R7M 10 0.0364 3 7.7x7x3
919AS-100M 10.3x10.3x4.5
919AS-160M 22 0.0316 3.5 10.3x10.3x4.5
919AS-220M 10.3x10.3x4.5
3.3 0.031 4.3
4.7 0.049 3.3
10 0.0265 4.3
16 0.0492 3.3
22 0.0776 3
Output Rectifier Diode Input Capacitor
The output rectifier diode supplies the current to The input current to the step-down converter is
the inductor when the high-side switch is off. To discontinuous, therefore a capacitor is required to
reduce losses due to the diode forward voltage supply the AC current to the step-down converter
and recovery times, use a Schottky diode. while maintaining the DC input voltage. Use low
ESR capacitors for the best performance. Ceramic
Choose a diode whose maximum reverse capacitors are preferred, but tantalum or low-ESR
voltage rating is greater than the maximum electrolytic capacitors may also suffice.
input voltage, and whose current rating is
greater than the maximum load current. Table 2 For simplification, choose the input capacitor
lists example Schottky diodes and with RMS current rating greater than half of the
manufacturers. maximum load current.
Table 2--Diode Selection Guide
Diodes Voltage/ Manufacturer
Current
B340A-13-F Rating Diodes Inc.
CMSH3-40MA Central Semi
40V, 3A
40V, 3A
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
The input capacitor (C1) can be electrolytic, Compensation Components
tantalum or ceramic. When using electrolytic or MP1584 employs current mode control for easy
tantalum capacitors, a small, high quality compensation and fast transient response. The
ceramic capacitor, i.e. 0.1F, should be placed system stability and transient response are
as close to the IC as possible. When using controlled through the COMP pin. COMP pin is
ceramic capacitors, make sure that they have the output of the internal error amplifier. A
enough capacitance to provide sufficient charge series capacitor-resistor combination sets a
to prevent excessive voltage ripple at input. The pole-zero combination to control the
input voltage ripple caused by capacitance can characteristics of the control system. The DC
be estimated by: gain of the voltage feedback loop is given by:
VIN ILOAD VOUT 1 VOUT A VDC RLOAD GCS A VEA VFB
fS C1 VIN VIN VOUT
Output Capacitor Where AVEA is the error amplifier voltage gain,
The output capacitor (C2) is required to 200V/V; GCS is the current sense
maintain the DC output voltage. Ceramic, transconductance, 9A/V; RLOAD is the load
tantalum, or low ESR electrolytic capacitors are resistor value.
recommended. Low ESR capacitors are
preferred to keep the output voltage ripple low. The system has two poles of importance. One
The output voltage ripple can be estimated by: is due to the compensation capacitor (C3), the
output resistor of error amplifier. The other is
VOUT VOUT 1 VOUT RESR 8 1 C2 due to the output capacitor and the load resistor.
fS L VIN fS These poles are located at:
Where L is the inductor value and RESR is the fP1 GEA
equivalent series resistance (ESR) value of the 2 C3 A VEA
output capacitor.
fP2 1
In the case of ceramic capacitors, the 2 C2 RLOAD
impedance at the switching frequency is
dominated by the capacitance. The output Where, GEA is the error amplifier
voltage ripple is mainly caused by the transconductance, 60A/V.
capacitance. For simplification, the output
voltage ripple can be estimated by: The system has one zero of importance, due to
the compensation capacitor (C3) and the
VOUT VOUT 1 VOUT compensation resistor (R3). This zero is located
fS2 L VIN at:
8 C2 1
2 C3 R3
In the case of tantalum or electrolytic capacitors, fZ1
the ESR dominates the impedance at the
switching frequency. For simplification, the The system may have another zero of
output ripple can be approximated to: importance, if the output capacitor has a large
capacitance and/or a high ESR value. The zero,
VOUT VOUT 1 VOUT RESR due to the ESR and capacitance of the output
fS L VIN capacitor, is located at:
The characteristics of the output capacitor also fESR 1
affect the stability of the regulation system. The 2 C2 RESR
MP1584 can be optimized for a wide range of
capacitance and ESR values.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
In this case (as shown in Figure 2), a third pole 1. Choose the compensation resistor (R3) to set
set by the compensation capacitor (C6) and the the desired crossover frequency. Determine the
compensation resistor (R3) is used to R3 value by the following equation:
compensate the effect of the ESR zero on the
loop gain. This pole is located at: R3 2 C2 fC VOUT
GEA GCS VFB
fP3 1
2 C6 R3 Where fC is the desired crossover frequency.
The goal of compensation design is to shape 2. Choose the compensation capacitor (C3) to
the converter transfer function to get a desired achieve the desired phase margin. For
loop gain. The system crossover frequency applications with typical inductor values, setting
where the feedback loop has the unity gain is the compensation zero, fZ1, below one forth of
important. Lower crossover frequencies result the crossover frequency provides sufficient
in slower line and load transient responses, phase margin. Determine the C3 value by the
while higher crossover frequencies could cause following equation:
system unstable. A good rule of thumb is to set
the crossover frequency to approximately one- C3 4 fC
tenth of the switching frequency. The Table 3 2 R3
lists the typical values of compensation
components for some standard output voltages 3. Determine if the second compensation
with various output capacitors and inductors. capacitor (C6) is required. It is required if the
The values of the compensation components ESR zero of the output capacitor is located at
have been optimized for fast transient less than half of the switching frequency, or the
responses and good stability at given conditions. following relationship is valid:
Table 3--Compensation Values for Typical 1 fS
Output Voltage/Capacitor Combinations 2 C2 RESR 2
VOUT L (H) C2 R3 C3 C6 If this is the case, then add the second
(V) (F) (k) (pF) compensation capacitor (C6) to set the pole fP3
at the location of the ESR zero. Determine the
1.8 4.7 47 105 100 None C6 value by the equation:
2.5 4.7 - 6.8 22 54.9 220 None C6 C2 RESR
R3
3.3 6.8 -10 22 68.1 220 None
5 15 - 22 22 100 150 None
12 22 - 33 22 147 150 None
To optimize the compensation components for
conditions not listed in Table 3, the following
procedure can be used.
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
High Frequency Operation External Bootstrap Diode
The switching frequency of MP1584 can be It is recommended that an external bootstrap
programmed up to 1.5MHz with an external diode be added when the input voltage is no
resistor. greater than 5V or the 5V rail is available in the
system. This helps improve the efficiency of the
With higher switching frequencies, the inductive regulator. The bootstrap diode can be a low
reactance (XL) of capacitor comes to dominate, cost one such as IN4148 or BAT54.
so that the ESL of input/output capacitor
determines the input/output ripple voltage at 5V
higher switching frequency. As a result of that,
high frequency ceramic capacitor is strongly BS
recommended as input decoupling capacitor
and output filtering capacitor for such high MP1584
frequency operation.
SW
Layout becomes more important when the
device switches at higher frequency. It is Figure 2--External Bootstrap Diode
essential to place the input decoupling
capacitor, catch diode and the MP1584 (Vin pin, This diode is also recommended for high duty
SW pin and PGND) as close as possible, with cycle operation (when VOUT /VIN >65%) or low
traces that are very short and fairly wide. This VIN (<5Vin) applications.
can help to greatly reduce the voltage spike on
SW node, and lower the EMI noise level as well. At no load or light load, the converter may
operate in pulse skipping mode in order to
Try to run the feedback trace as far from the maintain the output voltage in regulation. Thus
inductor and noisy power traces as possible. It there is less time to refresh the BS voltage. In
is often a good idea to run the feedback trace order to have enough gate voltage under such
on the side of the PCB opposite of the inductor operating conditions, the difference of VIN VOUT
with a ground plane separating the two. The should be greater than 3V. For example, if the
compensation components should be placed VOUT is set to 3.3V, the VIN needs to be higher
closed to the MP1584. Do not place the than 3.3V+3V=6.3V to maintain enough BS
compensation components close to or under voltage at no load or light load. To meet this
high dv/dt SW node, or inside the high di/dt requirement, EN pin can be used to program
power loop. If you have to do so, the proper the input UVLO voltage to Vout+3V.
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.
MP1584 Rev. 1.0 www.MonolithicPower.com 14
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MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS
C4
100nF
VIN 7 VIN 8 SW 1 VOUT
4.5V - 28V BST 1.8V
EN 2 EN MP1584 FB 4 D1
C3
6 FREQ COMP 3 100pF
GND C6
5 NS
Figure 3--1.8V Output Typical Application Schematic
C4
100nF
8
VIN 7 VIN BST SW 1 VOUT
8V - 28V 5V
EN D1
2 EN MP1584 FB 4
6 FREQ COMP 3
GND C3
5 150pF
C6
NS
Figure 4--5V Output Typical Application Schematic
MP1584 Rev. 1.0 www.MonolithicPower.com 15
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2011 MPS. All Rights Reserved.
MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
PCB LAYOUT GUIDE 3) Ensure all feedback connections are short
and direct. Place the feedback resistors and
PCB layout is very important to achieve stable compensation components as close to the
operation. It is highly recommended to duplicate chip as possible.
EVB layout for optimum performance.
Route SW away from sensitive analog areas
4) such as FB.
If change is necessary, please follow these
guidelines and take Figure 5 for reference. Connect IN, SW, and especially GND
respectively to a large copper area to cool
5) the chip to improve thermal performance and
1) Keep the path of switching current short and long-term reliability.
minimize the loop area formed by Input cap,
high-side MOSFET and external switching
diode.
2) Bypass ceramic capacitors are suggested to
be put close to the VIN Pin.
C4
VIN BST L1
VIN SW VOUT
C1 R5 D1 C2
EN EN MP1584 FB R1
R4 R2
FREQ COMP
GND C3
R6 R3
MP1584 Typical Application Circuit
Top Layer Bottom Layer
Figure 5MP1584 Typical Application Circuit and PCB Layout Guide
MP1584 Rev. 1.0 www.MonolithicPower.com 16
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2011 MPS. All Rights Reserved.
MP1584 3A, 1.5MHz, 28V STEP-DOWN CONVERTER
PACKAGE INFORMATION
SOIC8E (EXPOSED PAD)
0.189(4.80) 0.124(3.15)
0.197(5.00) 0.136(3.45)
8 5
PIN 1 ID 0.150(3.80) 0.228(5.80) 0.089(2.26)
0.157(4.00) 0.244(6.20) 0.101(2.56)
1 4
TOP VIEW BOTTOM VIEW
0.051(1.30) SEE DETAIL "A" 0.0075(0.19)
0.067(1.70) 0.0098(0.25)
SEATING PLANE SIDE VIEW
0.013(0.33) 0.000(0.00)
0.020(0.51) 0.006(0.15)
0.050(1.27)
BSC
FRONT VIEW 0.010(0.25) x 45o
0.020(0.50)
GAUGE PLANE
0.010(0.25) BSC
0.024(0.61) 0.050(1.27) 0.016(0.41)
0.063(1.60) 0.050(1.27)
0o-8o
DETAIL "A"
0.103(2.62) 0.213(5.40)
0.138(3.51) NOTE:
RECOMMENDED LAND PATTERN 1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN
BRACKET IS IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
PROTRUSIONS OR GATE BURRS.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH
OR PROTRUSIONS.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.004" INCHES MAX.
5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION BA.
6) DRAWING IS NOT TO SCALE.
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.
MP1584 Rev. 1.0 www.MonolithicPower.com 17
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2011 MPS. All Rights Reserved.
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