TM

MP1412
2A, 23V, 380KHz
Step-Down Converter
TM
The Future of Analog IC Technology

DESCRIPTION FEATURES
The MP1412 is a monolithic step down switch • 2A Output Current
mode converter with a built in internal power • 0.18Ω Internal Power MOSFET Switch
MOSFET. It achieves 2A continuous output • Stable with Low ESR Output Ceramic
current over a wide input supply range with Capacitors
excellent load and line regulation. • Up to 95% Efficiency
Current mode operation provides fast transient • 23µA Shutdown Mode
response and eases loop stabilization. • Fixed 380KHz Frequency
• Thermal Shutdown
Fault condition protection includes cycle-by-cycle
• Cycle-by-Cycle Over Current Protection
current limiting and thermal shutdown. In
shutdown mode the regulator draws 23µA of • Wide 4.75V to 23V Operating Input Range
supply current. Programmable soft-start • Output Adjustable from 0.92V to 16V
minimizes the inrush supply current and the • Programmable Under Voltage Lockout
output overshoot at initial startup. • Available in an MSOP10 with Exposed Pad
Package
The MP1412 requires a minimum number of
readily available standard external components. APPLICATIONS
EVALUATION BOARD REFERENCE • Distributed Power Systems
• Battery Charger
Board Number Dimensions
• DSL Modems
EV1412DH-00A 2.3”X x 1.4”Y x 0.4”Z • Pre-Regulator for Linear Regulators
“MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic
Power Systems, Inc.

TYPICAL APPLICATION
INPUT
Efficiency vs
4.75V - 23V C5
Output Current
10nF 95
4 2
90
IN BS 5.0V
OPEN = AUTOMATIC 9 5 VOUT
EFFICIENCY (%)

EN SW 85 3.3V
STARTUP D1 3.3V/2A
MP1412 B220A 80
2.5V
10 7
SS FB
GND COMP 75
6 8
70
C3
C4 3.9nF
10nF C6 65
OPEN
60
0 0.5 1.0 1.5 2.0 2.5
MP1412_TAC_S01
OUTPUT CURRENT (A)
MP1412_EC01

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 TM

MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

PACKAGE REFERENCE ABSOLUTE MAXIMUM RATINGS (1)

Supply Voltage (VIN) .................................... 24V
Switch Node Voltage (VSW).......................... 25V
Bootstrap Voltage (VBS) ....................... VSW + 6V
TOP VIEW Feedback Voltage (VFB) ................. –0.3V to +6V
Enable/UVLO Voltage (VEN)........... –0.3V to +6V
NC 1 10 SS Comp Voltage (VCOMP) ................... –0.3V to +6V
BS 2 9 EN SS Voltage (VSS)............................ –0.3V to +6V
NC 3 8 COMP Junction Temperature.............................+150°C
IN 4 7 FB Lead Temperature ..................................+260°C
SW 5 6 GND Storage Temperature ..............–65°C to +150°C
(2)
EXPOSED PAD
Recommended Operating Conditions
CONNECT TO PIN 6 MP1412_PD01-MSOP10 Supply Voltage (VIN) ...................... 4.75V to 23V
Operating Temperature.................–40°C to +85°C
(3)
Thermal Resistance θJA θJC
MSOP10 w/ Exposed Pad ..... 105 ..... 19... °C/W
Part Number* Package Temperature Notes:
MP1412DH MSOP10 –40°C to +85°C 1) Exceeding these ratings may damage the device.
2) The device is not guaranteed to function outside of its
* For Tape & Reel, add suffix –Z (eg. MP1412DH–Z) operating conditions.
For Lead Free, add suffix –LF (eg. MP1412DH–LF–Z) 3) Measured on approximately 1” square of 1 oz copper.

ELECTRICAL CHARACTERISTICS
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
Feedback Voltage VFB 4.75V ≤ VIN ≤ 23V 0.892 0.920 0.948 V
Upper Switch On Resistance RDS(ON)1 0.18 Ω
Lower Switch On Resistance RDS(ON)2 10 Ω
Upper Switch Leakage VEN = 0V, VSW = 0V 0 10 µA
Current Limit (4) 2.8 3.4 A
Current Sense Transconductance
GCS 1.95 A/V
Output Current to Comp Pin Voltage
Error Amplifier Voltage Gain AVEA 400 V/V
Error Amplifier Transconductance GEA ∆IC = ±10µA 550 830 1150 µA/V
Oscillator Frequency fS 380 KHz
Short Circuit Frequency VFB = 0V 240 KHz
Soft-Start Pin Equivalent
9 kΩ
Output Resistance

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MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

ELECTRICAL CHARACTERISTICS (continued)

VIN = 12V, TA = +25°C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
Maximum Duty Cycle DMAX VFB = 0.8V 90 %
Minimum On Time tON 100 ns
EN Shutdown Threshold ICC > 100µA 0.7 1.0 1.3 V
Enable Pull Up Current VEN = 0V 1.0 µA
EN UVLO Threshold Rising VEN Rising 2.37 2.50 2.62 V
EN UVLO Threshold Hysteresis 210 mV
Supply Current (Shutdown) VEN ≤ 0.4V 23 36 µA
Supply Current (Quiescent) VEN ≥ 3V 1.1 1.3 mA
Thermal Shutdown 160 °C
Note:
4) Slope compensation changes current limit above 40% duty cycle.

PIN FUNCTIONS
Pin # Name Description
1 NC No Connect.
2 BS Bootstrap. This capacitor (C5) is needed to drive the power switch’s gate above the supply
voltage. It is connected between the SW and BS pins to form a floating supply across the
power switch driver. The voltage across C5 is about 5V and is supplied by the internal +5V
supply when the SW pin voltage is low.
3 NC No Connect.
4 IN Supply Voltage. The MP1412 operates from a +4.75V to +23V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
5 SW Switch. This connects the inductor to either IN through M1 or to GND through M2.
6 GND Ground. This pin is the voltage reference for the regulated output voltage. For this reason care
must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to
prevent switching current spikes from inducing voltage noise into the part.
7 FB Feedback. An external resistor divider from the output to GND, tapped to the FB pin, sets the
output voltage. To prevent current limit runaway during a short circuit fault condition the
frequency foldback comparator lowers the oscillator frequency when the FB voltage is below
400mV.
8 COMP Compensation. This node is the output of the transconductance error amplifier and the input to the
current comparator. Frequency compensation is done at this node by connecting a series R-C to
ground. See the compensation section for exact details.
9 EN Enable/UVLO. A voltage greater than 2.62V enables operation. For compelte low current
shutdown the EN pin voltage needs to be less than 700mV.
10 SS Soft-Start. Connect SS to an external capacitor to program the soft-start. If unused, leave it
open.

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 TM

MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

OPERATION
The MP1412 is a current mode regulator. That MP1412 reverts to its initial M1 off, M2 on state.
is, the COMP pin voltage is proportional to the If the Current Sense Amplifier plus Slope
peak inductor current. At the beginning of a Compensation signal does not exceed the
cycle: the upper transistor M1 is off; the lower COMP voltage, then the falling edge of the CLK
transistor M2 is on (see Figure 1); the COMP resets the Flip-Flop.
pin voltage is higher than the current sense
The output of the Error Amplifier integrates the
amplifier output; and the current comparator’s
voltage difference between the feedback and
output is low. The rising edge of the 380KHz
the 0.92V bandgap reference. The polarity is
CLK signal sets the RS Flip-Flop. Its output
such that an FB pin voltage lower than 0.92V
turns off M2 and turns on M1 thus connecting
increases the COMP pin voltage. Since the
the SW pin and inductor to the input supply.
COMP pin voltage is proportional to the peak
The increasing inductor current is sensed and
inductor current an increase in its voltage
amplified by the Current Sense Amplifier. Ramp
increases current delivered to the output. The
compensation is summed to Current Sense
lower 10Ω switch ensures that the bootstrap
Amplifier output and compared to the Error
capacitor voltage is charged during light load
Amplifier output by the Current Comparator.
conditions. External Schottky Diode D1 carries
When the Current Sense Amplifier plus Slope
the inductor current when M1 is off.
Compensation signal exceeds the COMP pin
voltage, the RS Flip-Flop is reset and the

IN 4
INTERNAL CURRENT
REGULATORS SENSE
AMPLIFIER + 5V
OSCILLATOR
SLOPE
240KHz/ COMP --
380KHz 2 BS
CLK
+ + S Q
R Q
5 SW
0.7V -- SHUTDOWN -- CURRENT
COMPARATOR COMPARATOR
EN 9
LOCKOUT
-- COMPARATOR

2.50V/
2.30V + + -- 1.8V 6 GND

FREQUENCY -- 0.4V 0.92V + ERROR

FOLDBACK AMPLIFIER
COMPARATOR
7 FB SS 10 8 COMP MP1412_BD01

Figure 1—Functional Block Diagram

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 TM

MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

APPLICATION INFORMATION
COMPONENT SELECTION Choose an inductor that will not saturate under
Setting the Output Voltage the maximum inductor peak current. The peak
The output voltage is set using a resistive voltage inductor current can be calculated by:
divider from the output voltage to FB pin. The VOUT ⎛ V ⎞
voltage divider divides the output voltage down to ILP = ILOAD + × ⎜⎜1 − OUT ⎟⎟
2 × fS × L ⎝ VIN ⎠
the feedback voltage by the ratio:
R2 Where ILOAD is the load current.
VFB = VOUT
R1 + R2 Output Rectifier Diode
Where VFB is the feedback voltage and VOUT is The output rectifier diode supplies the current to
the output voltage. the inductor when the high-side switch is off. To
reduce losses due to the diode forward voltage
Thus the output voltage is: and recovery times, use a Schottky diode.
R1 + R2 Choose a diode whose maximum reverse
VOUT = 0.92 ×
R2 voltage rating is greater than the maximum
A typical value for R2 can be as high as 100kΩ, input voltage, and whose current rating is
but a typical value is 10kΩ. Using that value, R1 greater than the maximum load current.
is determined by: Input Capacitor
R1 = 10.87 × ( VOUT − 0.92)
The input current to the step-down converter is
discontinuous, therefore a capacitor is required
For example, for a 3.3V output voltage, R2 is to supply the AC current to the step-down
10kΩ, and R1 is 25.8kΩ. converter while maintaining the DC input
voltage. Use low ESR capacitors for the best
Inductor
performance. Ceramic capacitors are preferred,
The inductor is required to supply constant
but tantalum or low-ESR electrolytic capacitors
current to the output load while being driven by
may also suffice.
the switched input voltage. A larger value inductor
will result in less ripple current that will result in Since the input capacitor absorbs the input
lower output ripple voltage. However, the larger switching current it requires an adequate ripple
value inductor will have a larger physical size, current rating. The RMS current in the input
higher series resistance, and/or lower saturation capacitor can be estimated by:
current. A good rule for determining the
VOUT ⎛⎜ VOUT ⎞
inductance to use is to allow the peak-to-peak ICIN = ILOAD × × 1− ⎟
VIN ⎜⎝ VIN ⎟
⎠
ripple current in the inductor to be approximately
30% of the maximum switch current limit. Also, The worst-case condition occurs at VIN = 2VOUT,
make sure that the peak inductor current is below where:
the maximum switch current limit. The inductance
value can be calculated by: ILOAD
ICIN =
2
VOUT ⎛ V ⎞
L= × ⎜⎜1 − OUT ⎟⎟ For simplification, choose the input capacitor
fS × ∆IL ⎝ VIN ⎠
whose RMS current rating greater than half of
Where fS is the switching frequency, ∆IL is the the maximum load current.
peak-to-peak inductor ripple current and VIN is
the input voltage.

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MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

The input capacitor can be electrolytic, tantalum Compensation Components

or ceramic. When using electrolytic or tantalum The MP1412 employs current mode control for
capacitors, a small, high quality ceramic easy compensation and fast transient response.
capacitor, i.e. 0.1µF, should be placed as close The system stability and transient response are
to the IC as possible. When using ceramic controlled through the COMP pin. COMP pin is
capacitors, make sure that they have enough the output of the internal transconductance
capacitance to provide sufficient charge to error amplifier. A series capacitor-resistor
prevent excessive voltage ripple at input. The combination sets a pole-zero combination to
input voltage ripple caused by capacitance can control the characteristics of the control system.
be estimated by:
The DC gain of the voltage feedback loop is
ILOAD V ⎛ V ⎞ given by:
∆VIN = × OUT × ⎜⎜1 − OUT ⎟⎟
fS × CIN VIN ⎝ VIN ⎠ VFB
A VDC = R LOAD × G CS × A VEA ×
Where CIN is the input capacitance value. VOUT

Output Capacitor Where RLOAD is the load resistor value, GCS is

The output capacitor is required to maintain the the current sense transconductance and AVEA is
DC output voltage. Ceramic, tantalum, or low the error amplifier voltage gain.
ESR electrolytic capacitors are recommended. The system has two poles of importance. One
Low ESR capacitors are preferred to keep the is due to the compensation capacitor (C3) and
output voltage ripple low. The output voltage the output resistor of error amplifier, and the
ripple can be estimated by: other is due to the output capacitor and the load
VOUT ⎛ V ⎞ ⎛ 1 ⎞ resistor. These poles are located at:
∆VOUT = × ⎜1 − OUT ⎟⎟ × ⎜ R ESR + ⎟
f S × L ⎜⎝ VIN ⎠ ⎝
⎜ 8 × f S × CO
⎟
⎠ GEA
fP1 =
2π × C3 × A VEA
Where L is the inductor value, RESR is the
equivalent series resistance (ESR) value of the 1
output capacitor and CO is the output fP 2 =
2π × C O × R LOAD
capacitance value.
Where GEA is the error amplifier
In the case of ceramic capacitors, the
transconductance.
impedance at the switching frequency is
dominated by the capacitance. The output The system has one zero of importance, due to the
voltage ripple is mainly caused by the compensation capacitor (C3) and the
capacitance. For simplification, the output compensation resistor (R3). This zero is located at:
voltage ripple can be estimated by:
1
f Z1 =
VOUT ⎛ V ⎞ 2π × C3 × R3
∆VOUT = 2
× ⎜⎜1 − OUT ⎟⎟
8 × fS × L × CO ⎝ VIN ⎠ The system may have another zero of
importance, if the output capacitor has a large
In the case of tantalum or electrolytic capacitance and/or a high ESR value. The zero,
capacitors, the ESR dominates the impedance due to the ESR and capacitance of the output
at the switching frequency. For simplification, capacitor, is located at:
the output ripple can be approximated to:
1
VOUT ⎛ V ⎞ fESR =
∆VOUT = × ⎜1 − OUT ⎟⎟ × R ESR 2π × C O × R ESR
f S × L ⎜⎝ VIN ⎠

The characteristics of the output capacitor also

affect the stability of the regulation system. The
MP1412 can be optimized for a wide range of
capacitance and ESR values.

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MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

In this case, a third pole set by the If this is the case, then add the second
compensation capacitor (C6) and the compensation capacitor (C6) to set the pole fP3
compensation resistor (R3) is used to at the location of the ESR zero. Determine the
compensate the effect of the ESR zero on the C6 value by the equation:
loop gain. This pole is located at:
C O × R ESR
C6 =
1 R3
f P3 =
2π × C6 × R3
External Bootstrap Diode
The goal of compensation design is to shape It is recommended that an external bootstrap
the converter transfer function to get a desired diode be added when the system has a 5V
loop gain. The system crossover frequency fixed input or the power supply generates a 5V
where the feedback loop has the unity gain is output. This helps improve the efficiency of the
important. MP1412 regulator. The boost diode can be a
low cost one such as IN4148 or BAT54.
Lower crossover frequencies result in slower
line and load transient responses, while higher 5V
crossover frequencies could cause the system
to become unstable. A good rule of thumb is to 2
BS
set the crossover frequency to below one-tenth
10nF
of the switching frequency. To optimize the MP1412
5
compensation components, the following SW
procedure can be used:
MP1412_F02

1. Choose the compensation resistor (R3) to set

Figure 2—External Bootstrap Diode
the desired crossover frequency. Determine the
R3 value by the following equation: This diode is also recommended for high duty
cycle operation (when (VOUT/VIN)>65%) and
2π × C O × f C VOUT
R3 = × high output voltage (VOUT>12V) applications.
G EA × G CS VFB
Power Dissipation and Temperature Rise
Where fC is the desired crossover frequency, The power dissipation of the MP1412 is mostly
which is typically less than one tenth of the from the conduction loss of the internal main
switching frequency. switch. This power loss is estimated to be:
2. Choose the compensation capacitor (C3) to VOUT 2
achieve the desired phase margin. For PLOSS ≅ × IOUT × 0.18Ω × 1.3
VIN
applications with typical inductor values, setting
the compensation zero, fZ1, to below one forth Where 1.3 is a temperature coefficient factor
of the crossover frequency provides sufficient that reflects the increase in the RDS(ON)
phase margin. Determine the C3 value by the resistance at elevated temperatures.
following equation:
For example: for VIN = 12V, VOUT = 3.3V and
2 IOUT = 2A:
C3 >
π × R3 × f C 3 .3 V
PLOSS ≅ × (2A ) 2 × 0.18Ω × 1.3 = 0.26 W
Where R3 is the compensation resistor value. 12V

3. Determine if the second compensation Because the thermal resistance θJC is 65°C/W,
capacitor (C6) is required. It is required if the the resulting rise in temperature between
ESR zero of the output capacitor is located at junction and case is approximately 17°C.
less than half of the switching frequency, or the Therefore, caution must be exercised when
following relationship is valid: using the MP1412 in applications with high duty
cycles.
1 f
< S
2π × C O × R ESR 2

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 TM

MP1412 – 2A, 23V, 380KHz STEP-DOWN CONVERTER

PACKAGE INFORMATION

MSOP10 (WITH EXPOSED PAD)

0.114(2.90) 0.087(2.20)
0.122(3.10) 0.099(2.50)
10 6

0.114(2.90) 0.187(4.75) 0.062(1.58)

PIN 1 ID 0.122(3.10) 0.199(5.05) 0.074(1.88)
(NOTE 5)

Exposed Pad

1 5
0.007(0.18)
0.0197(0.50)BSC
0.011(0.28) BOTTOM VIEW

TOP VIEW

GAUGE PLANE
0.010(0.25)
0.030(0.75)
0.037(0.95) 0.043(1.10)MAX
0.004(0.10)
SEATING PLANE
0.008(0.20)
0.002(0.05) o o 0.016(0.40)
0 -6
0.006(0.15) 0.026(0.65)

FRONT VIEW SIDE VIEW

NOTE:
0.100(2.54)
1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN BRACKET IS
IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,
0.075(1.90) 0.181(4.60) PROTRUSION OR GATE BURR.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR
PROTRUSION.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING)
SHALL BE 0.004" INCHES MAX.
5) PIN 1 IDENTIFICATION HAS THE HALF OR FULL CIRCLE OPTION.
6) DRAWING MEETS JEDEC MO-187, VARIATION BA-T.
0.040(1.00)
7) DRAWING IS NOT TO SCALE.

0.012(0.30) 0.0197(0.50)BSC

RECOMMENDED LAND PATTERN

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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