TM
MP1567
1.2A Synchronous Rectified
Step-Down Converter
TM
The Future of Analog IC Technology
DESCRIPTION FEATURES
The MP1567 is a 1.2A, 800KHz DC to DC
" 1.2A Output Current
converter designed for low voltage applications
" Synchronous Rectified
requiring high efficiency. Capable of providing
" Internal 180m&! and 220m&! Power Switches
output voltages as low as 0.9V from a 3.3V
" VIN Range of 2.6V to 6V
supply voltage, the MP1567 eliminates the
" Over 90% Efficiency
need for a 5V rail, providing over 90% efficiency
" Zero Current Shutdown Mode
via synchronous rectification and eliminating
" Under Voltage Lockout Protection
heat issues in confined spaces. Soft-start
" Soft-Start Operation
operation protects internal circuitry from hard
" Thermal Shutdown
turn on issues. Switching at 800KHz reduces
" Internal Current Limit (Source & Sink)
the size of external components and thereby
" Tiny 10-Pin MSOP or QFN Packages
reduces board space.
" Evaluation Boards Available
The MP1567 includes cycle-by-cycle current
APPLICATIONS
limiting and under voltage lockout. Internal
power switches combined with the tiny 10-pin
" SOHO Routers, PCMCIA Cards, Mini PCI
MSOP or QFN packages provide a solution
" Handheld Computers, PDAs
requiring a minimum of space.
" Cell Phones
" Digital Video Cameras
EVALUATION BOARD REFERENCE
" Small LCD Displays
Board Number Dimensions
 MPS and  The Future of Analog IC Technology are Trademarks of Monolithic
EV0033 (MP1567DK) 2.5 X x 2.0 Y x 0.7 Z
Power Systems, Inc.
EV0059 (MP1567DK) 2.5 X x 2.0 Y x 0.4 Z
EV0060 (MP1567DQ) 2.5 X x 2.0 Y x 0.4 Z
TYPICAL APPLICATION
Efficiency vs
INPUT
2.6V to 6V
10nF
Load Current
100
2 1
90
VIN=3.3V
IN BS
80
10 3 VOUT
OFF ON EN SW
1.8V/1.2A
7 70
FB
MP1567
VIN=4V
6 9 60
BP
OPEN IF SS
50
NOT USED
SGND PGND COMP
VIN=5V
40
5 4 8
10nF
30
10nF
20
1nF
VOUT=1.8V
10
0
10 100 1000
LOAD CURRENT (mA)
MP1567_TAC_S01
MP1567_EC01
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EFFICIENCY (%)
TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
PACKAGE REFERENCE
TOP VIEW
TOP VIEW
BS 1 10 EN
BS 1 10 EN
IN 2 9 BP
IN 2 9 BP
SW 3 8 COMP
SW 3 8 COMP
PGND 4 7 FB
PGND 4 7 FB
SGND 5 6 SS
SGND 5 6 SS
EXPOSED PAD
MP1567_PD01_MSOP10
MP1567_PD02_QFN10
ON BACKSIDE
Part Number** Package Temperature
Part Number* Package Temperature
QFN10
MP1567DQ  40�C to +85�C
MP1567DK MSOP10  40�C to +85�C
(3mm x 3mm)
For Tape & Reel, add suffix  Z (eg. MP1567DQ Z)
* For Tape & Reel, add suffix  Z (eg. MP1567DK Z) **
For Lead Free, add suffix  LF (eg. MP1567DK LF Z) For Lead Free, add suffix  LF (eg. MP1567DQ LF Z)
ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance (3) �JA �JC
Input Supply Voltage VIN ............................. 6.5V
MSOP10 ................................ 150 ..... 65... �C/W
SW Voltage VSW...................  0.3V to VIN + 0.3V
QFN10 .................................... 50 ...... 12... �C/W
BS to SW Voltage ......................... 0.3V to +6V
Notes:
Voltage at All Other Pins ............... 0.3V to +6V
1) Exceeding these ratings may damage the device.
Storage Temperature..............  55�C to +150�C
2) The device is not guaranteed to function outside of its
operating conditions.
Recommended Operating Conditions (2)
3) Measured on approximately 1 square of 1 oz copper.
Input Supply Voltage VIN ....................2.6V to 6V
Output Voltage VOUT........................0.9V to 4.5V
Operating Temperature.............  40�C to +85�C
ELECTRICAL CHARACTERISTICS
VIN = 5V, TA = +25�C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
Input Voltage Range VIN 2.6 6 V
Input Undervoltage Lockout 2.2 V
Input Undervoltage Lockout Hysteresis 100 mV
Shutdown Supply Current VEN d" 0.3V 0.5 1.0 �A
Operating Supply Current VEN > 2V, VFB = 1.1V 1.2 1.8 mA
BP Voltage VBP VIN = 2.6 to 6V 2.4 V
EN Input Low Voltage VIL 0.4 V
EN Input High Voltage VHL 1.5 V
EN Hysteresis 100 mV
EN Input Bias Current 1 �A
Oscillator
Switching Frequency fSW 800 KHz
Maximum Duty Cycle DMAX VFB = 0.7V 85 %
Minimum On Time tON 200 ns
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 5V, TA = +25�C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
Error Amplifier
Voltage Gain AVEA 400 V/V
Transconductance GEA 300 �A/V
COMP Maximum Output Current ą30 �A
FB Regulation Voltage VFB 875 905 935 mV
FB Input Bias Current IFB FB = 0.9V  100 nA
Soft-Start
Soft-Start Current ISS 2 �A
Output Switch On-Resistance
VIN = 5V 265 m&!
Switch On Resistance
VIN = 3V 330 m&!
VIN = 5V 220 m&!
Synchronous Rectifier On Resistance
VIN = 3V 270 m&!
Switch Current Limit (Source) 1.5 2.0 A
Synchronous Rectifier Current Limit (Sink) 350 mA
Thermal Shutdown 160 �C
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.3V, VOUT = 1.8V, TA = +25�C, unless otherwise noted.
Current Limit vs.
Load Transient
0.1A to 1A Load Step
Duty Cycle
2.5
VOUT
2.0
50mV/div.
VSS
1V/div.
1.5
VOUT
1.0
1V/div.
ILOAD IIN
0.5
0.5A/div. 0.5A/div.
0
0 20 40 60 80 2ms/div.
MP1567-TPC02 MP1567-TPC03
DUTY CYCLE (%) MP1567-TPC01
Output Short Circuit
IOUT = 1.2A Steady State
VOUT
VSW
1V/div.
2V/div.
VSS
1mV/div.
IINDUCTOR
IINDUCTOR
1A/div.
1A/div.
2ms/div.
MP1567-TPC04 MP1567-TPC05
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CURRENT LIMIT (A)
TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin# Name Function
Power Switch Boost. BS powers the gate of the high-side N-Channel power MOSFET switch.
1 BS
Connect a 10nF or greater capacitor between BS and SW.
Internal Power Input. IN supplies the power to the MP1567 through the internal LDO
2 IN regulator. Bypass IN to PGND with a 10�F or greater capacitor. Connect IN to the input
source voltage.
Output Switching Node. SW is the source of the high-side N-Channel switch and the drain of
3 SW
the low-side N-Channel switch. Connect the output LC filter between SW and the output.
Power Ground. PGND is the source of the N-Channel MOSFET synchronous rectifier.
4 PGND
Connect PGND to SGND as close to the MP1567 as possible.
5 SGND Signal Ground.
Soft-Start Input. Place a capacitor from SS to SGND to set the soft-start period. The MP1567
6 SS sources 2�A from SS to the soft-start capacitor at start up. As the voltage at SS rises, the
feedback threshold voltage increases to limit inrush current at start up.
Feedback Input. FB is the inverting input of the internal error amplifier. Connect a resistive
7 FB
voltage divider from the output voltage to FB to set the output voltage.
Compensation Node. COMP is the output of the error amplifier. Connect a series RC network
8 COMP
to compensate the regulation control loop.
Internal 2.4V Regulator Bypass. Connect a 10nF capacitor between BP and SGND to bypass
9 BP
the internal regulator. Do not apply any load to BP.
On/Off Control Input. Drive EN high to turn on the MP1567; low to turn it off. For automatic
10 EN
startup, connect EN to IN.
OPERATION
The MP1567 measures the output voltage inductor current to decrease. The average
through an external resistive voltage divider and inductor current is controlled by the voltage at
compares that to the internal 0.9V reference to COMP, which in turn, is controlled by the output
generate the error voltage at COMP. The voltage. Thus the output voltage controls the
current-mode regulator uses the voltage at inductor current to satisfy the load.
COMP and compares it to the inductor current
Since the high-side N-Channel MOSFET
to regulate the output voltage. The use of
requires voltage above VIN to drive its gate, a
current-mode regulation improves transient
bootstrap capacitor from SW to BS is required
response and improves control loop stability.
to drive the high-side MOSFET gate. When SW
At the beginning of each cycle, the high-side is driven low (through the low-side MOSFET),
N-Channel MOSFET is turned on, forcing the the BS capacitor is internally charged. The
inductor current to rise. The current at the drain voltage at BS is applied to the high-side
of the high-side MOSFET is internally MOSFET gate to turn it on, and maintains that
measured and converted to a voltage by the voltage until the high-side MOSFET is turned
current sense amplifier. That voltage is off and the low-side MOSFET is turned on, and
compared to the error voltage at COMP. When the cycle repeats. Connect a 10nF or greater
the inductor current raises sufficiently, the PWM capacitor from BS to SW to drive the high-side
comparator turns off the high-side switch and MOSFET gate. Using a larger capacitor does
turns on the low-side switch, forcing the little to improve performance.
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
VIN
2.6V to 6V
IN
CURRENT
SENSE
ENABLE GATE
EN
AMPLIFIER
OFF ON CKT & LDO DRIVE Vdr
+
REGULATOR REGULATOR
--
BS
BP
Vdr
VBP
PWM
2.4V
COMPARATOR
C7
+
L1
SW
-- VOUT
CONTROL
Vdr
LOGIC
800KHz
OSCILLATOR
RAMP
CURRENT
+
LIMIT
COMPARATOR --
VBP
UVLO &
+
THERMAL
--
SHUTDOWN
PGND
SS
C5
--
FB
GM --
ERROR
+
AMPLIFIER
VFB
0.9V
CURRENT
LIMIT
THRESHOLD
SGND COMP
R3
C3
MP1567_BD01
Figure 1 Functional Block Diagram
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
APPLICATION INFORMATION
VOUT - VFB
COMPONENT SELECTION
R2 =
VFB
�# ś#
Internal Low-Dropout Regulator
ś# ź#
ś# ź#
The internal power to the MP1567 is supplied R1
�# #
from the input voltage through an internal 2.4V
Where R2 is the high-side resistor, R1 is the
low-dropout linear regulator, whose output is
low-side resistor, VOUT is the output voltage and
BP. Bypass BP to SGND with a 10nF or greater
VFB is the feedback regulation threshold.
capacitor to insure the MP1567 operates
properly. The internal regulator cannot supply
For R1 = 10k&! and VFB = 0.9V, then
more current than is required to operate the
R2(k&!) = 11.1k&! (VOUT  0.9V)
MP1567, therefore do not apply any external
load to BP.
Selecting the Input Capacitor
The input current to the step-down converter is
Soft-Start
discontinuous, so a capacitor is required to
The MP1567 includes a soft-start timer that
supply the AC current to the step-down
slowly ramps the output voltage at startup to
converter while maintaining the DC input
prevent excessive current at the input. This
voltage. A low ESR capacitor is required to
prevents premature termination of the battery
keep the noise at the IC to a minimum. Ceramic
voltage at startup due to input current overshoot
capacitors are preferred, but tantalum or low
at startup.
ESR electrolytic capacitors will also suffice.
When power is applied to the MP1567 a 2�A
Use an input capacitor with a value greater than
internal current source charges the external
10�F. The capacitor can be electrolytic,
capacitor at SS. As the capacitor charges, the
tantalum or ceramic. However, since it absorbs
voltage at SS will rise. The MP1567 internally
the input switching current it requires an
limits the feedback threshold voltage at FB to
adequate ripple current rating. Use a capacitor
that of the voltage at SS. This forces the output
with a RMS current rating greater than 1/2 of
voltage to rise at the same rate as the voltage
the DC load current.
at SS, forcing the output voltage to ramp
linearly from 0V to the desired regulation
For insuring stable operation, place the input
voltage during soft-start. The soft-start period is
capacitor as close to the IC as possible.
determined by the equation:
Alternately, a smaller high quality 0.1�F
ceramic capacitor may be placed closer to the
tSS = 0.45 � C5
IC with the larger capacitor placed further away.
Where C5 (in nF) is the soft-start capacitor from If using this technique, it is recommended that
SS to GND, and tSS (in ms) is the soft-start the larger capacitor be a tantalum or electrolytic
period. Determine the capacitor required for a type. All ceramic capacitors should be placed
given soft-start period by the equation: close to the MP1567.
C5 = 2.22 � tSS Selecting the Output Capacitor
The output capacitor is required to maintain the
Use values for C5 between 10nF and 22nF to
DC output voltage. Low ESR capacitors are
set the soft-start period (between 4ms and
preferred to keep the output voltage ripple to a
10ms).
minimum. The characteristics of the output
capacitor also affect the stability of the
Setting the Output Voltage
regulation control system. Ceramic, tantalum or
Set the output voltage by selecting the resistive
low ESR electrolytic capacitors are
voltage divider ratio. The voltage divider drops
recommended.
the output voltage to the 0.9V feedback
threshold voltage. Use 10k&! for the low-side
In the case of ceramic capacitors, the
resistor of the voltage divider. Determine the
impedance at the switching frequency is
high side resistor by the equation:
dominated by the capacitance, and so the
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
output voltage ripple is mostly independent of Compensation
the ESR. The output voltage ripple is estimated The system stability is controlled through the
to be: COMP pin. COMP is the output of the internal
transconductance error amplifier. A series
2
�# ś#
fLC
capacitor-resistor combination sets a pole-zero
ś# ź#
VRIPPLE = 1.4 � VIN �
ś# ź#
fSW combination to control the characteristics of the
�# #
control system.
Where VRIPPLE is the output ripple voltage, VIN is
The DC loop gain is:
the input voltage, fLC is the resonant frequency
of the LC filter and fSW is the switching
�# ś#
VFB
ś# ź#
A = A � GCS � RLOAD �
frequency. In the case of tantalum or low-ESR
VDC VEA
ś# ź#
VOUT
�# #
electrolytic capacitors, the ESR dominates the
impedance at the switching frequency, and so
Where AVEA is the transconductance error
the output ripple is calculated as:
amplifier voltage gain, GCS is the current sense
gain (roughly the output current divided by the
VRIPPLE = "I � RESR
voltage at COMP) and RLOAD is the load
Where "I is the inductor ripple current, and
resistance (VOUT/IOUT where IOUT is the output
RESR is the equivalent series resistance of the
load current)
output capacitors.
The system has 2 poles of importance, one is
Choose an output capacitor to satisfy the output
due to the compensation capacitor (C3), and
ripple requirements of the design. A 10�F
the other is due to the load resistance and the
ceramic capacitor is suitable for most
output capacitor (C2). The first is:
applications.
GEA
fP1 =
Selecting the Inductor
2Ą � A � C3
VEA
The inductor is required to supply constant
Where P1 is the first pole and GEA is the error
current to the output load while being driven by
amplifier transconductance (300�A/V). The
the switched input voltage. A larger value
second is:
inductor results in less ripple current that will
results in lower output ripple voltage. However,
1
the larger value inductor has a larger physical fP2 =
2Ą � RLOAD � C2
size, higher series resistance and/or lower
saturation current. Choose an inductor that
The system has one zero of importance, due to
does not saturate under the worst-case load
the compensation capacitor (C3) and the
conditions. A good rule for determining the
compensation resistor (R3). The zero is:
inductance is to allow the peak-to-peak ripple
1
current to be approximately 30% of the
f =
Z1
2Ą � R3 � C3
maximum load current. Make sure that the peak
inductor current (the load current plus half the
If large value capacitors with relatively high
peak-to-peak inductor ripple current) is below
equivalent-series-resistance (ESR) are used,
2A to prevent loss of regulation due to the
the zero due to the capacitance and ESR of the
current limit.
output capacitor can be compensated by a third
Calculate the required inductance value by the pole set by R3 and C4. This pole is:
equation:
1
fP3 =
VOUT � (VIN - VOUT )
2Ą � R3 � C4
L =
VIN � fSW � "I
The system crossover frequency (the frequency
where the loop gain drops to 1, or 0dB) is
important. Set the crossover frequency to
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
75KHz or lower to insure stable operation. R3 � GEA � GCS � VFB
fC =
Lower crossover frequencies result in slower
2Ą � C2 � VOUT
response and worse transient load recovery.
or
Higher crossover frequencies degrade the
phase and/or gain margins and can result in
1.7
fC H"
instability.
C2 � VOUT
Choosing the Compensation Components
Choose the compensation capacitor to set the
The values of the compensation components
zero to one fourth of the crossover frequency.
given in Table 1 yield a stable control loop for
Determine the value by the following equation:
the output voltage and capacitor given.
2 8.5 � 10-6
Table 1 Compensation Values for Typical
C3 = H"
Output Voltage/Capacitor Combinations Ą � R3 � fC R3
if R3 d" 10k&! use the following equation:
VOUT C2 R3 C3 C4
4 � C2 � VOUT
1.8V 4.7�F Ceramic 3.3k&! 2.2nF None
C3 =
2.5V 4.7�F Ceramic 5.1k&! 1.5nF None R32 � GEA � GCS � VFB
3.3V 4.7�F Ceramic 6.8k&! 1.2nF None
Determine if the second compensation
1.8V 10�F Ceramic 7.5k&! 1nF None
capacitor, C4, is required. It is required if the
2.5V 10�F Ceramic 10k&! 820pF None
ESR zero of the output capacitor occurs at less
than four times the crossover frequency, or:
3.3V 10�F Ceramic 10k&! 820pF None
47�F Tantalum
8Ą � C2 � RESR � fC e" 1
1.8V 10k&! 2.2nF 1.5nF
(300m&!)
Where RESR is the equivalent series resistance
47�F Tantalum
2.5V 10k&! 3.3nF 1.5nF
of the output capacitor.
(300m&!)
47�F Tantalum
If this is the case, then add the second
3.3V 10k&! 4.7nF 1.5nF
(300m&!)
compensation capacitor. Determine the value
by the equation:
To optimize the compensation components for
C2 � RESR(MAX)
C4 =
conditions not listed in Table 1, use the
R3
following procedure.
Where RESR(MAX) is the maximum ESR of the
Choose the compensation resistor to set the
output capacitor.
desired crossover frequency. Determine the
value by the following equation: For Example:
Given:
2Ą � C2 � VOUT � fC
R3 =
VOUT = 1.8V
GEA � GCS � VFB
C2 = 10�F Ceramic (ESR = 10m&! max.)
Putting in the known constants and setting the
Calculate:
crossover frequency to the desired 75KHz:
R3 H" 4.36 � 108 (10�F)(1.8V) = 7.85k&!
R3 H" 4.36 � 108 � C2 � VOUT
(Use the nearest standard value of 7.5k&!.)
The value of R3 is limited to 10k&! to prevent
1.9 � 10-14
C3 = = 1.05nF
output overshoot at startup, so if the value
10�F � 1.8V
calculated for R3 is greater than 10k&!, use
(Use 1nF since it is a standard value.)
10k&!. In this case, the actual crossover
8Ą � C2 � RESR � fC = 0.19
frequency is less than the desired 75KHz, and
is calculated by:
which is less than 1, therefore the second
compensation capacitor (C4) is not required.
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
5V
External Boost Diode
For 5V input or output applications, it is
BOOST
recommended that an external boost diode be
DIODE
1
added. This will help improve the regulator
BS
efficiency. The diode can be a low cost diode
10nF
MP1567
such as an IN4148 or BAT54.
3
SW
MP1567_F02
Figure 2 External Boost Diode
TYPICAL APPLICATION CIRCUITS
INPUT
6V
C7
10nF
2 1
IN BS
10
3 VOUT
OFF ON EN SW
1.8V/1.2A
7
FB
MP1567
6 9
BP
OPEN IF SS
NOT USED
SGND PGND COMP
5 4 8
C6
10nF
C5
C3
10nF
1nF
C4
OPEN
MP1567_F03
Figure 3 6V Input Application Circuit
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TM
MP1567  1.2A SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
PACKAGE INFORMATION
MSOP10
0.0197(0.500)TYP
0.004(0.100)
0.008(0.200)
PIN 1
IDENT
SEE DETAIL "A"
.
0.114(2.900) 0.184(4.700)
0.122(3.100) 0.200(5.100)
0.014(0.350)TYP
GATE PLANE 0.010(0.250)
0.014(0.350)TYP
0.114(2.900)
0o-6o
DETAIL "A"
0.122(3.100)
0.017(0.400)
0.025(0.600)
0.030(0.750)
0.032(0.800)
0.038(0.950)
0.044(1.100)
0.002(0.050)
0.008(0.200)REF
0.006(0.150)
NOTE:
1) Control dimension is in inches. Dimension in bracket is millimeters.
QFN10 (3mm x 3mm)
2.250
PAD
PAD
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.
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.
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