MP3435
19A, 600kHz, 22V Output Range,
Synchronous Boost Converter
with Input Disconnect Function
DESCRIPTION
FEATURES
The MP3435 is a 600kHz, fixed frequency,
high-efficiency,
highly
integrated
boost
converter that operates across a wide input
voltage (VIN) range, with optional input
disconnect and an input average current limit
function. The input disconnect feature provides
additional protection by isolating the input from
the output during an output short or shutdown.
For battery-operated applications, this feature
also helps prevent battery depletion. With a
configurable input average current limit, the
MP3435 supports a wide range of applications.
•
•
•
•
3V to 20V Wide Input Voltage (VIN) Range
Up to 22V Output Voltage (VOUT)
Integrated 10mΩ and 15mΩ MOSFET
19A Internal Switch Current Limit or
External Configurable Input Current Limit
Input Disconnect and Output Short-Circuit
Protection (SCP)
Configurable Under-Voltage Lockout
(UVLO) and Hysteresis
5.5V) for automatic start-up. This pin can
also configure VIN UVLO. Do not leave EN floating.
Driver for the input disconnect MOSFET. If this pin is floating or connected to the input
MOSFET gate, an external current-sense resistor is required. Connect GATE to ground
GATE
to use the internal current-sense circuit. Do not pull GATE down to ground through a
resistor.
Voltage sense. The voltage sensed between SENSE and IN determines the external
SENSE current-sense signal. Connect SENSE to IN if the internal current-sense function is
selected.
Power switch. Connect SW to the internal low-side MOSFET (LS-FET)’s drain and the
SW
internal, synchronous HS-FET source. Connect the power inductor to SW.
OUT
TM
BST
PGND
IN
Power ground.
Input supply. IN must be locally bypassed.
12
VDD
Internal bias supply. Decouple the VDD pin with a 2.2μF ceramic capacitor, placed as
close to VDD as possible.
13
COMP
Compensation. Connect a capacitor and resistor in series to the analog ground for loop
stability.
14
FB
Feedback input. The reference voltage (VREF) is 1.225V. Connect a resistor divider from
output to FB.
15
SS
Soft-start control. Connect a soft-start capacitor (CSS) to SS. CSS is charged with a
constant current. Leave SS disconnected if soft start is not used.
16
AGND
MP3435 Rev. 1.0
11/30/2021
Analog ground.
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
θJA
θJC
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
SW............................. -0.3V (-3.5V for VIN
Note:
9) After start-up, the VGATE ≥ VIN + 1.6V condition is registered if VGATE exceeds VIN + 1.6V one time. This means the MP3435 treats the
condition as VGATE ≥ VIN + 1.6V, even if VGATE falls below VIN + 1.6V again in protection mode (unless the device turns off due to hiccup
mode or if the power is cycled.
MP3435 Rev. 1.0
11/30/2021
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
If IL quickly ramps and IL(MAX) exceeds 100(mV) /
RSENSE (mΩ), the MP3435 immediately shuts
down, entering SCP hiccup mode. This fast
protection allows the MP3435 to survive all
SCP events.
When the MP3435 is shut down by EN or VIN,
GATE is pulled down to GND, so input and
output are well isolated by the input MOSFET.
This is the VIN to VOUT disconnect function.
Light-Load Operation
To optimize efficiency at light loads, the
MP3435 employs
frequency foldback and
pulse-skipping mechanisms. When the load
becomes lighter, VCOMP decreases, causing the
MP3435 to enter fold-back operation (the lighter
the load, the lower the frequency). However, if
the load becomes exceedingly low, the MP3435
enters pulse-skip mode (PSM). PSM operation
is optimized so that only one switching pulse is
launched in every burst cycle.
Enable (EN) and Configurable UVLO
EN enables and disables the MP3435. When a
voltage exceeding VEN_H (about 1V) is applied,
the MP3435 starts up some of the internal
circuits (micro-power mode). If the EN voltage
continues to rise above VEN_ON (about 1.33V),
the MP3435 enables all functions and begins
boost operation. Boost operation is disabled if
the EN voltage is below VEN_ON. To shut down
the MP3435 completely, a voltage below VEN_L
MP3435 Rev. 1.0
11/30/2021
(about 0.4V) is required on EN. After shutdown,
the MP3435 sinks a current below 1µA from the
input power.
The maximum recommended voltage on EN is
5.5V. If the EN control signal comes from a
voltage above 5.5V, a resistor should be added
between EN and the control source. An internal
Zener diode on EN clamps the EN voltage to
prevent runaway.
Ensure the Zener-clamped current flowing into
EN is below 0.3mA. EN configures the VIN
UVLO threshold (see the Under-Voltage
Lockout (UVLO) Hysteresis section on page 18
for additional details).
Output Over-Voltage Protection (OVP)
Except for controlling the COMP signal to
regulate VOUT, the MP3435 also provides OVP.
If the FB voltage exceeds 108% of VREF, boost
switching stops. When the FB voltage drops
below 104% of VREF, the device resumes
switching automatically.
Thermal Shutdown
The device has an internal temperature monitor.
If the die temperature exceeds 150°C, the
converter shuts down. Once the temperature
drops below 125°C, the converter turns on
again.
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17
MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
APPLICATION INFORMATION
Selecting the Current Limit Resistor
The MP3435 features an average current limit
when the external sensing resistor is used.
RSENSE is the resistor connected between IN
and SENSE, and it sets the current limit (ICL). ICL
can be calculated using Equation (1):
ICL = VCL /RSENSE
(1)
Where VCL is typically 54mV, ICL is in A, and
RSENSE is in mΩ.
Considering the parasitic inductance on the
sense resistor, a small package resistor (e.g.,
0805 package) is recommended. Add several
parallel resistors if the power rating is lower
than requested. To reduce parasitic resistance
and noise, a minimum 4mΩ current-sense
resistor is recommended.
Under-Voltage Lockout (UVLO) Hysteresis
The MP3435 features a configurable UVLO
hysteresis. During start-up, EN sinks a 4.5μA
current from the upper resistor, RTOP (see
Figure 2).
VIN
MP3435
RTOP
4.5μA
Figure 2: Configurable VIN UVLO
VIN must increase to overcome the current sink.
The VIN start-up threshold (VIN-ON) can be
estimated with Equation (2):
VIN−ON = VEN−ON (1 +
RTOP
) + 4.5A RTOP
RBOT
(2)
Where VEN-ON is the EN turn-on threshold
(typically 1.33V).
Once the EN voltage reaches VEN-ON, the 4.5µA
sink current turns off to create a reverse
hysteresis for the VIN falling threshold (VIN-UVLOVIN-UVLO-HYS can be calculated with
HYS).
Equation (3):
VIN−UVLO−HYS = 4.5A RTOP
MP3435 Rev. 1.0
11/30/2021
Setting the Output Voltage (VOUT)
VOUT is fed back through two sense resistors
placed in series. The FB reference voltage (VFB)
is typically 1.225V. VOUT can be estimated with
Equation (4):
VOUT = VREF (1 +
R1
)
R2
(4)
Where R1 is the top FB resistor, R2 is the
bottom FB resistor, and VREF is the reference
voltage (typically 1.225V).
Choose the FB resistors in the 10kΩ range (or
higher) for good efficiency.
EN
RBOT
Selecting the Soft-Start Capacitor (CSS)
The MP3435 includes a SS circuit that limits
VCOMP during start-up to prevent excessive IIN.
This prevents premature termination of the
source voltage at start-up due to IIN overshoot.
When power is applied to the MP3435 and EN
asserts, a 7μA internal current source charges
the external CSS. VSS clamps VCOMP (as well as
IL(MAX)) until the output is close to regulation, or
until VCOMP reaches 2V. For most applications, a
10nF CSS is sufficient. If the output capacitance
is large or the front power supply cannot
withstand the huge inrush current, use a largervalue capacitor.
Selecting the Input Capacitor
An input capacitor is required to supply the AC
ripple current to the inductor while limiting noise
at the input source. A low-ESR capacitor is
required to minimize noise. Ceramic capacitors
are recommended, but tantalum or low ESR
electrolytic capacitors are sufficient.
For loop stability, at least two 22µF capacitors
are recommended for high-power applications,.
The capacitor can be electrolytic, tantalum, or
ceramic. Since the capacitor absorbs the input
switching current, it requires an adequate ripple
current rating. Use a capacitor with an RMS
current rating exceeding the inductor ripple
current (see the Selecting the Inductor section
on page 19 to determine the inductor ripple
current).
(3)
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
To ensure stable operation, place the input
capacitor as close to the IC as possible.
Alternately, a smaller, high-quality, 0.1μF
ceramic capacitor can be placed close to the IC,
while a larger-value capacitor is placed further
away. If using this technique, an electrolytic or
tantalum capacitor is recommended for the
larger-value capacitor. All ceramic capacitors
should be placed close to the MP3435’s input.
Selecting the Output Capacitor
The output capacitor is required to maintain the
DC
VOUT.
Low-ESR
capacitors
are
recommended to minimize the output voltage
ripple (VRIPPLE). The characteristics of the output
capacitor affect regulation and control system
stability. Ceramic, tantalum, or low-ESR
electrolytic capacitors are recommended. If
using ceramic capacitors, the impedance of the
capacitor at fSW is dominated by the
capacitance, so VRIPPLE is independent of the
ESR. VRIPPLE can be calculated with Equation
(5):
VRIPPLE
V
(1 − IN ) ILOAD
VOUT
=
COUT fSW
(5)
If using tantalum or low-ESR electrolytic
capacitors, the ESR dominates the impedance
at fSW, so VRIPPLE can be estimated using
Equation (6):
(1 −
VRIPPLE =
(6)
Where RESR is the equivalent series resistance
of the output capacitors.
Choose an output capacitor to satisfy the
VRIPPLE and load transient design requirements.
Capacitance de-rating should be taken into
consideration when designing high VOUT
applications. Three 22μF ceramic capacitors
are suitable for most applications.
MP3435 Rev. 1.0
11/30/2021
Optimized Performance with
MPS Inductor MPL-AY1050 Series
The inductor is required to force a higher VOUT
while being driven by VIN. A larger-value
inductor has less ripple current, resulting in a
lower IL(MAX). This reduces stress on the internal
N-channel switch and enhances efficiency.
However, a larger-value inductor has a larger
physical size, a higher series resistance, and a
lower saturation current.
A good rule of thumb is to allow the peak-topeak ripple current to be approximately 30% to
40% of the maximum input current (IIN(MAX)).
Make sure that IL(MAX) is below 75% of ICL at the
operating duty cycle to prevent regulation loss
due to ICL. Additionally, make sure that the
inductor does not saturate under the worst-case
load transient and start-up conditions. The
required inductance value (L) can be estimated
with Equation (7):
L=
Where VIN and VOUT are the DC input and
output voltages, respectively, ILOAD is the load
current, fSW is the fixed 600kHz switching
frequency, and COUT is the output capacitor’s
capacitance.
VIN
) ILOAD
VOUT
I
RESR VOUT
+ LOAD
COUT fSW
VIN
Selecting the Inductor
VIN (VOUT − VIN )
VOUT fSW I
(7)
IIN(MAX) can be calculated with Equation (8):
IIN(MAX) =
VOUT ILOAD(MAX)
(8)
VIN
Where ILOAD(MAX) is the maximum load current,
ΔI is the peak-to-peak inductor ripple current, ΔI
= (30% to 40%) x IIN(MAX), and ŋ is the efficiency.
MPS inductors are optimized and tested for use
with our complete line of integrated circuits.
Table 2 lists the MPS power inductor
recommendations, where the part numbers can
be selected based on the design requirements.
Table 2: Power Inductor Selection
Part Number
Inductor Value Manufacturer
MPL-AY
0.47µH to 10µH
MPL-AY1050-1R5
1.5μH
MPL-AY1050-1R0
1μH
MPL-AY1050-2R2
2.2μH
MPS
MPS
MPS
MPS
For more information, visit the Inductors page
on the MPS website.
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
R4
L1
MPL-AY1050-1R5
D1
BST
Q1
GATE
SENSE
IN
U1
MP3435
CBST
L
Figure 4: Gate Protection Diode for High Output
Voltage Condition
BST
SW
1N5819
MP3435
OUT
COUT
SOUT
Figure 3: BST Charger for Low Output
Applications
Selecting the Input MOSFET
The MP3435 integrates one GATE pin to drive
an external N-channel MOSFET, which
disconnects the input power or limits IIN. The
parameters to select the input disconnect
MOSFET are described in greater detail below.
1. Drain-to-source voltage rating: This value
should exceed VIN.
2. Drain-to-source current rating: IIN(MAX) is the
maximum current through the input
disconnect MOSFET. This occurs when VIN
is at a minimum, and the load power is at a
maximum.
3. Safe operating area (SOA): When
conduction a current, the MOSFET should
be able to support a current pulse that has a
high level of VCL (mV) / RSENSE (mΩ) and
lasts for CSS (nF) x 0.7V / 7µA + 0.5ms.
4. Gate-to-source voltage rating: The positive
gate-to-source voltage rating should exceed
5.5V, while the negative voltage rating
should exceed VOUT. If VOUT is too high and
the MOSFET gate-to-source rating cannot
meet the requirement, placing a diode
between the source and disconnecting
MOSFET gate is recommended (see Figure
4).
MP3435 Rev. 1.0
11/30/2021
VIN
SW
BST Charger for Low Output Applications
In some low output applications (e.g. a 5V
output), the voltage across CBST may be
insufficient. In this case, a Schottky diode
should be connected from the output port to
BST, conducting the current into CBST when SW
goes low (see Figure 3).
5. Gate-to-source threshold voltage: The
threshold should be below 1.5V. A 1V to
1.2V range across the overall temperature
range is recommended.
6. On resistance (RDS_ON): This value should
be small for high conversion efficiency.
7. Low leakage current: This value should be
low for better isolation.
In addition to the parameters listed above,
consider the size and thermal temperature.
Compensation
The output of COMP compensates the
regulation control system. The system uses two
poles (FP1 and FP2) and one zero to stabilize the
control loop.
FP1 is set by the output capacitor (COUT) and the
load resistance (RLOAD), and FP2 starts from the
origin. The zero (FZ1) is set by the
compensation capacitor (CCOMP) and the
compensation resistor (RCOMP). FP1 and FZ1 can
be calculated with Equation (9) and Equation
(10), respectively:
FP1 =
FZ1 =
1
(Hz)
2 RLOAD COUT
1
(Hz)
2 RCOMP CCOMP
(9)
(10)
The DC loop gain can be calculated using
Equation (11):
A VDC =
A VEA VIN RLOAD VFB GCS x RCOMP
(V / V) (11)
2
2 VOUT
Where GCS is the compensation voltage to the IL
gain, AVEA is the error amplifier voltage gain,
and VFB is the feedback regulation threshold.
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
There is also a right half-plane zero (FRHPZ) that
exists in continuous conduction mode (CCM),
where IL does not drop to zero in each cycle.
FRHPZ can be calculated using Equation (12):
FRHPZ =
RLOAD
V
( IN )2 (Hz)
2 L VOUT
(12)
FRHPZ increases the gain and reduces the phase
simultaneously, resulting in a smaller phase
and gain margin. The worst-case condition
occurs when VIN is at its minimum and the
output power is at its maximum. See the Typical
Application Circuits section on page 23 for
compensation recommendations.
MP3435 Rev. 1.0
11/30/2021
Design Example
Table 3 shows a design example following the
application guidelines for the specifications
below.
Table 3: Design Example
VIN
VOUT
IOUT
3V to 10V
12V
0A to 2A
The maximum output current is determined by
the allowable temperature rise, ICL, and VIN.
Figure 6 and Figure 7 on page 23 show the
detailed application schematics. The typical
performance and circuit waveforms are shown
in the Typical Performance Characteristics
section on page 9. For more device
applications, refer to the related evaluation
board datasheet.
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
PCB Layout Guidelines
Efficient PCB layout is critical for high-frequency
switching power supplies. A poor layout can
result in reduced performance, excessive EMI,
resistive loss, and system instability. Use a 4layer PCB for high-power applications. For the
best results, refer to Figure 5 and follow the
guidelines below:
Via
1. Keep the output loop (OUT, PGND, and C2)
as small as possible.
2. Place a 0.1μF capacitor (C2D) close to the IC
to reduce the PCB parasitical inductance.
Top Layer
3. Connect SW to Mid-Layer 1 through two vias
on the right side of SW to enhance the
current capability (shown as the red
connections in the Top Layer and Mid-Layer
1 on Figure 5).
4. Place the FB dividers (R1 and R2) as close
as possible to FB.
5. Route the sensing traces (SENSE and IN)
closely in parallel with a small, closed area.
6. Use a 0805 package for the sensing resistor
(R4) to reduce parasitic inductance.
Mid-Layer 1
7. Connect the VOUT feedback wire close to the
output capacitor (C2C).
8. Connect the compensation components, CSS,
and VDD capacitor to AGND with a short loop.
9. Keep the input loop (C1, R4, Q1, L1, SW, and
PGND) as small as possible.
10. Make the BST path as short as possible.
11. Float the TM pin in application.
Mid-Layer 2
12. Place enough GND vias close to the MP3435
for good thermal dissipation.
13. Place wide copper or vias associated with the
input MOSFET’s drain pin for thermal
dissipation.
Bottom Layer
Figure 5: Recommended PCB Layout
MP3435 Rev. 1.0
11/30/2021
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
TYPICAL APPLICATION CIRCUITS
C1C
22µF
9, 20
R7
NS
7
GND
GND
GND
8
GND
11
C3
GATE
EN
GND
SENSE
SOUT
5
MP3435
VDD
GND
FB
10, 17,
18, 19
GND
GND
AGND
C5
SS
C4
10nF
R6
NS
C2C
22µF
COMP
GND
R2
34k
13
3.3nF
R3
24.9k
16
GND
GND
GND
R1
300k
14
EN
PGND
15
C2B
22µF
GND
2.2µF
6
C2A
22µF
U1
IN
12
R5
100k
C2D
0.1µF
1, 2
4
OUT
C1B
22µF
SW
C1A
VO UT = 12V at 2A
L1
MPL-AY1050-1R5
SiR800
22µF
C6
0.1µF
1.5µH
Q1
R4 4mx18m
BST
VIN = 3V to 10V
GND
GND
Figure 6: 12V Output Solution with Input Disconnect Function
VIN = 3V to 10V
C6
0.1µF
1.5µH
VOUT = 12V at 2A
L1
MPL-AY1050-1R5
9, 20
SW
C1C
7
GND
8
GND
11
C3
GND
SENSE
SOUT
IN
VDD
MP3435
GND
15
C4
10nF
R6
NS
GND
GND
FB
C2B
C2C
22µF
22µF
C5
10, 17,
18, 19
COMP
GND
R2
34k
13
3.3nF
16
R3
24.9k
GND
GND
GND
R1
300k
14
EN
SS
C2A
22µF
GND
2.2µF
6
5
U1
AGND
EN
R5
100k
12
GATE
PGND
GND
C2D
0.1µF
1, 2
4
OUT
C1B
22µF 22µF
BST
C1A
22µF
GND
GND
Figure 7: 12V Output Solution without Input Disconnect Function
MP3435 Rev. 1.0
11/30/2021
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
PACKAGE INFORMATION
QFN-20 (3mmx4mm)
PIN 1 ID
0.15x45°TYP.
PIN 1 ID
MARKING
PIN 1 ID
INDEX AREA
BOTTOM VIEW
TOP VIEW
SIDE VIEW
0.15x45°
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) LEAD COPLANARITY SHALL BE 0.08
MILLIMETERS MAX.
3) JEDEC REFERENCE IS MO-220.
4) DRAWING IS NOT TO SCALE.
RECOMMENDED LAND PATTERN
MP3435 Rev. 1.0
11/30/2021
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
CARRIER INFORMATION
Part Number
MP3435GL-Z
MP3435 Rev. 1.0
11/30/2021
Package
Description
QFN-20
(3mmx4mm)
Quantity/
Reel
Quantity/
Tube
Quantity/
Tray
Reel
Diameter
Carrier
Tape Width
Carrier
Tape Pitch
5000
N/A
N/A
13in
12mm
8mm
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MP3435 – 19A, 600kHz, 22V SYNCHRONOUS BOOST WITH INPUT DISCONNECT
REVISION HISTORY
Revision #
Revision Date
1.0
11/30/2021
Description
Pages Updated
Initial Release
-
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.
MP3435 Rev. 1.0
11/30/2021
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