LM5157
SNVSBK7 – JULY 2021
LM5157 2.2-MHz Wide VIN 50-V Boost/SEPIC/Flyback Converter with Dual Random
Spread Spectrum
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Audio amplifier power supply
Piezo driver/motor driver bias supply
1 Features
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Suited for wide operating range for battery
applications
3 Description
The LM5157 device is a wide input range, non-
synchronous boost converter with integrated 50-V
power switch.
– 2.9-V to 45-V input operating range
– 48-V maximum output (50-V abs max)
– Minimum boost supply voltage of 1.5 V when
BIAS ≥ 2.9 V
– Input transient protection up to 50 V
– Minimized battery drain
The device can be used in boost, SEPIC, and flyback
topologies. The device can start up from a single-cell
battery with a minimum of 2.9 V. It can operate with an
input supply voltage as low as 1.5 V if the BIAS pin is
greater than 2.9 V.
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Low shutdown current (IQ ≤ 2.6 µA)
Low operating current (IQ ≤ 670 µA)
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Small solution size and low cost
The BIAS pin operates up to 45 V (50-V absolute
maximum). The switching frequency is dynamically
programmable with an external resistor from 100 kHz
to 2.2 MHz. Switching at 2.2 MHz minimizes AM band
interference and allows for a small solution size and
fast transient response. To reduce the EMI of the
power supply, the device provides a selectable Dual
Random Spread Spectrum, which reduces the EMI
over a wide frequency range.
– Maximum switching frequency up to 2.2 MHz
– 16-pin QFN package (3 mm × 3 mm)
– Integrated error amplifier allows primary-side
regulation without optocoupler (flyback)
– Accurate current limit (see the Device
Comparison Table)
EMI mitigation
– Selectable dual random spread spectrum
– Lead-less package
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Higher efficiency with low-power dissipation
– 45-mΩ RDSON switch
The device features an accurate peak current limit
over the input voltage, which avoids overdesigning
power inductor. Low operating current and pulse-
skipping operation improve efficiency at light loads.
– Fast switching, small switching loss
Avoid AM band interference and crosstalk
– Optional clock synchronization
– Dynamically programmable wide switching
frequency from 100 kHz to 2.2 MHz
Integrated protection features
– Constant current limiting over input voltage
– Selectable hiccup mode overload protection
– Programmable line UVLO
– OVP protection
– Thermal shutdown
Accurate ±1% accuracy feedback reference
Adjustable soft start
PGOOD indicator
The device has built-in protection features such
as overvoltage protection, line UVLO, thermal
shutdown, and selectable Hiccup mode overload
protection. Additional features include low shutdown
IQ, programmable soft start, precision reference,
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a
power-good indicator, and external clock
synchronization.
Device Information
PART NUMBER
PACKAGE(1)
BODY SIZE (NOM)
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LM5157
WQFN (16)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Create a custom design using the LM5157x with
the WEBENCH® Power Designer
VLOAD
VSUPP LY
2 Applications
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Battery-powered wide input boost, SEPIC, flyback
converter
LED bias supply
Multiple-output flyback without optocoupler
Portable speaker application
Power module
BIAS VCC
SW
UVLO
RT
FB
COMP
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SS
PGOOD
PGND AGND MODE
Industrial PLC
Holdup capacitor charger
Typical Sepic Application
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.