Analog and Interface Solutions
Portable Power Conversion Design Guide
www.microchip.com/analog
Design Guide
Introduction and Contents
Portable power conversion applications present unique and challenging design considerations. Innovative, small electronics
require solutions with small footprints. In order to maintain battery life, portable applications require both high conversion
efficiency and low standby power dissipation. Multi-cell battery packs may require step-down (buck) conversions and single
cell batteries often require step-up (boost) conversions to maintain consistent power levels while the batteries discharge.
Some products require constant voltage regulation for microcontrollers, sensors or RF signal processing; while some
circuits need constant current regulation for backlighting or battery charging. Microchip offers a broad array of solutions
which feature small package sizes, high-efficiency, low standby power, accuracy and versatility solutions to solve these
portable power conversion challenges.
Table of Contents
Step-Down (Buck) Switch Mode Power Converters. . . . . . . . . . . . . . . . . . . . . . . 2
Linear (Low Drop Out) Regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Step-Up (Boost) Switch Mode Power Converters. . . . . . . . . . . . . . . . . . . . . . . 12
Backlighting Solutions with Switching Regulators . . . . . . . . . . . . . . . . . . . . . . 17
Backlighting Solutions with Charge Pump DC/DC Converters. . . . . . . . . . . . . . 19
Linear Battery Chargers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Programmable Battery Chargers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Application Notes and Demonstration Boards. . . . . . . . . . . . . . . . . . . . . . . . . 24
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
Step-Down (Buck) Switch Mode Power Converters
For wide input range voltage sources and high output current applications switch-mode power converters offer a significant
increase in efficiency compared to linear regulators. This results in longer battery run time in portable applications.
Step-down or buck converters are used to regulate an output voltage that is always lower than the source voltage. Using
inductors and capacitors for energy storage allows buck converters to commonly be more than 90% efficient, and under
some circumstances they can be more than 95% efficient.
Microchip offers a wide selection of buck converters and PWM controllers. Many of them are specifically designed to convert
power from NiMH, Ni-Cd, Li-Ion, Alkaline multi-cell or 12/24V SLA batteries. Converters integrate power MOSFET switches
used to commutate the supply current, while controllers rely on external power MOSFETs in diodes to switch the converter
current. Synchronous converters rely on two MOSFETs working together to control the current flow, while asynchronous
converters replace one MOSFET with a freewheeling power diode. Synchronous converters deliver higher efficiency for low
output voltages, especially less than 3.3V, while asynchronous converters work well for higher output voltages.
2
Portable Power Conversion Design Guide
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
MCP16301/H 36V Input Voltage Non-Synchronous Buck Converter
The MCP16301 is a highly integrated, high-efficiency, fixed-frequency, step-down DC-DC converter in a popular 6-pin SOT-23
package. This converter operates from voltage sources up to 30V, including the integrated high-side switch, fixed-frequency Peak
Current Mode Control, internal compensation, peak current limit and over-temperature protection. This device allows you to build
DC/DC conversion circuits with minimal external components.
■ 12V and 24V industrial/SLA
battery input DC-DC conversion
■ Up to 96% typical efficiency
■ Wide input voltage range:
• 4.0V to 30V (MCP16301)
• 4.7V to 36V (MCP16301H)
■ Output voltage range: 2.0V to 15V
■ 2% output voltage accuracy
■ Integrated 460 mΩ n-channel
buck switch
■ 600 mA output current
■ 500 kHz fixed frequency
■ Adjustable output voltage
■ Low device shutdown current
■ Peak current mode control
■ Internal compensation
■ Stable with ceramic capacitors
■
■
■
■
Internal soft-start
Cycle-by-cycle peak current limit
Under voltage lockout (UVLO) at 3.5V
Extended −40 to +125°C operating
temperature range
■ Over-temperature protection
■ D2PAK package linear regulator
replacement
■ Available in 6-pin SOT-23 package
Example MCP16301 Non-Synchronous Buck Regulator Application Circuit
1N4148
CBOOST
100 nF
VIN
4.5V to 30V
BOOST
VIN
CIN
10 µF
SW
EN
L1
15 μH
40V
Schottky
Diode
31.2 kΩ
COUT
2 × 10 μF
VFB
GND
10 kΩ
Typical MCP16301 Power Conversion Efficiency
with a Fixed 5.0V Output
100
VOUT
3.3V @ 600 mA
MCP16301 Light Load Operation
VIN = 6V
Efficiency (%)
90
VIN = 12V
80
70
VIN = 30V
60
VOUT = 5.0V
50
40
30
IL
0
100
200
300
400
500
600
IOUT (mA)
Portable Power Conversion Design Guide
3
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
MCP16311/2 30V Input, High-Efficiency, Integrated Synchronous Buck Regulator
The MCP16311 is a compact, high-efficiency, fixed-frequency PWM/PFM, synchronous step-down DC-DC converter in a
8-pin MSOP or 2 × 3 TDFN package that operates from input voltage sources up to 30V. Integrated features include a highside and a low-side switch, fixed-frequency Peak Current Mode Control, internal compensation, peak-current limit and overtemperature protection. The MCP16311 provides all the active functions for local DC-DC conversion, with fast transient
response and accurate regulation.
■■ Up to 95% efficiency
■■ Wide 4.4V to 30V input
voltage range
■■ Wide 2.0V to 24V output
voltage range
■■ Integrated high-performance
n-channel low- and high-side
switches: 170 mΩ low-side MOSFET,
300 mΩ high-side MOSFET
■■ Stable 0.8V reference voltage
■■ Automatic pulse-frequency
modulation/pulse-width modulation
(PFM/PWM) operation (on
MCP16311), or 500 kHz PWM only
operation (on MCP16312)
■■ Low 3 μA (typical) device
shutdown current
■■ Low 44 μA device quiescent current
(when not switching in PFM Mode)
■■ Internal compensation
■■
■■
■■
■■
Internal soft-start: 300 μs turn on
Peak current mode control
Cycle-by-cycle peak current limit
Under-voltage lockout
(UVLO) at 3.6V (typical) with
0.5V of hysteresis
■■ Thermal shutdown at 150°C, with
25°C hysteresis
Example MCP16311 Synchronous Buck Regulator Application Circuit
CBOOST
100 nF
VIN
4.5V to 30V
BOOST
VIN
CIN
2 ×10 µF
L1
15 μH
SW
VFB
VCC
10 kΩ
GND
MCP16311 Ouput Current Capability
Typical MCP16311 Efficiency, with and
without
V
PFM Operation Enabled
1600
Efficiency (%)
80
1000
VOUT = 12V
800
600
400
4
VOUT = 3.3V
70
60
50
40
30
VIN = 12V
PWM ONLY
PWM/PFM
20
200
0
V OUT = 5V
90
VOUT = 5V
1200
IOUT (mA)
100
VOUT = 3.3V
1400
COUT
2 × 10 μF
31.2 kΩ
EN
CvCC
1 µF
VOUT
3.3V @ 1A
10
0
5
10
15
VIN (V)
20
Portable Power Conversion Design Guide
25
30
0
1
10
IOUT (mA)
100
1000
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
MCP16311 12V Buck-Boost Application
Some power supplies require the ability step the voltage up or down from the input to the output. This is particularly useful
in battery-powered applications where the battery voltage may be above or below the desired output voltage, depending on
the type of battery used or battery charge remaining. By adding a few additional circuit components, the MCP16311 can be
adapted to work in a buck-boost topology that would address this issue. The application can either buck or boost the input
voltage in order to maintain the output voltage, operating from a 6V to 18V input and providing up to 300 mA of output current.
MCP16311 Buck-Boost Application Circuit
REN 1 MΩ
EN
GND
L1
SW
VIN = 4.5V to 18V
C1
10 µF
BOOST
VIN
VCC
CVCC
1 µF
AGND
56 μH
R6
C2
10 µF
FB
D1
4.7Ω
G
D
S
40V Schottky Diode
Q1
30V n-Channel
MOSFET
C3
10 µF
C4
10 µF
RB
140 kΩ
VOUT
RT
10 kΩ
PGND
GND1
Portable Power Conversion Design Guide
5
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
MCP16323 3A Synchronous Buck DC/DC Converter
The MCP16323 is a fully integrated synchronous buck dc/dc converter that operates from 6V to 18V input, regulates the
output voltage to any level between 0.9V to 5V, and supplies load currents up to 3A. Operating at a fixed 1 MHz switching
frequency offers small external inductor and capacitor sizes, minimizing board space. Integrating both high- and low-side
switches results in a compact, high-efficiency converter circuit. The device is available in a 3 × 3 mm QFN package with
exposed pad to reduce the thermal resistance from junction to case. With both adjustable and fixed output voltage
options, this device provides flexibility for generating custom output voltages or minimizing external resistor dividers and
obtaining fixed output voltages. The internal peak current mode control architecture results in fast transient response,
minimizing the change in output voltage with dynamic load conditions. Small ceramic capacitors are used at the input and
output for space-constrained applications.
■■ Integrated 120 mΩ n-channel lowside switch
■■ 1 MHz fixed frequency operation
with pulse skipping for efficient
operation in light load conditions
■■ Low device shutdown current
■■ Peak current mode control
■■ Internal compensation
■■ Stable with ceramic capacitors
■■ Internal soft-start
■■ Cycle-by-cycle peak current limit
MCP16323 Typical Application Circuit
VIN
6.0V to 18V
CBOOST
22 nF
BOOST
VIN
CIN
2 ×10 µF
L1
4.7 μH
SW
VOUT
EN
10 kΩ
PG
SGND
VOUT
3.3V @ 3A
COUT
2 × 22 μF
VFB
PGND
100
95
90
85
80
75
70
65
60
55
50
VIN = 6V
VIN = 18V
Portable Power Conversion Design Guide
VIN = 12V
VOUT = 5V
0.0
6
■■ Under-voltage lockout (UVLO)
at 5.75V
■■ Over-temperature protection
■■ Over-voltage protection will tri-state
the SW outputs to prevent damage
if the output exceeds 103% of the
regulation voltage
■■ Vout voltage status reported with
the power good output pin
■■ Available in 16-pin QFN (3 × 3 mm)
package with exposed thermal pad
Typical MCP16323 Efficiency with a 5V Fixed Output
Efficiency (%)
■■ Up to 95% typical efficiency
■■ Wide 6.0V to 18V input
voltage range
■■ 3A output current
■■ Multiple fixed output voltage options:
0.9V, 1.5V, 1.8V, 2.5V, 3.3V, 5.0V
with 2% output voltage accuracy
■■ Adjustable version output voltage
range: 0.9V to 5.0V with 1.5%
reference voltage accuracy
■■ Integrated 180 mΩ n-channel
high-side switch
0.6
1.2
1.8
IOUT (A)
2.4
3.0
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
MCP1603/L/B Synchronous Buck Regulators
The MCP1603 is a family of highly efficient, fully integrated 500 mA synchronous buck regulators. The 2.7V to 5.5V input
range makes these ideally suited for battery powered applications, including one-cell Li-ion; two- or three-cell NiMH; or twoor three-cell NiCd power sources. With heavy loads, the MCP1603/L operates in a 2.0 MHz fixed frequency PWM mode
which provides a low-noise, low output voltage ripple, small-footprint solution. With light loads, the MCP1603/L
automatically changes operation to a PFM mode to minimize quiescent current consumption, improving battery run time.
These two modes allow the MCP1603/L to achieve the best possible efficiency over the entire load current range. The
MCP1603B, in contrast, only switches in PWM mode, maintaining a low output voltage ripple over a wide output load range
in noise-sensitive applications (audio or RF). Only three additional external components are required for a complete
converter solution when using the fixed voltage options, or a flexible output voltage can be produced with a resistive divider
on the adjustable output device options. The low-profile, small-footprint packages also enable the system solution to be
achieved with minimal size.
■■ Typical efficiency over 90%
■■ Automatic PWM to PFM mode transitions (MCP1603/L)
or PWM only operation (MCP1603B)
■■ Supplies up to 500 mA of output current
■■ 100% duty cycle operation
■■ Low 45 μA typical PFM quiescent current
■■ Internally compensated
■■ Low 0.1 μA typical shutdown current
■■ Under-voltage lockout (UVLO) at 2.3V
■■ Adjustable output voltage range: 0.8V to 4.5V
■■ Over-temperature protection
■■ Fixed output voltage options: 1.2V, 1.5V, 1.8V,
2.5V, and 3.3V
■■ Space-saving 5-lead TSOT and 8-pin 2 × 3 DFN
packages
■■ 2.0 MHz operation
MCP1603 Typical Application Circuit
4.7 μH
VIN
LX
VOUT
1.5V @ 500 mA
100
90
4.7 μF
4.7 μH
SHDN
GND
VOUT
VIN = 3.6V
80
Efficiency (%)
E
VIN
2.0V to 5.5V
Typical MCP1603 Efficiency
70
60
50
VIN = 4.2V
40
30
VOUT = 3.3V
20
PFM/PWM
PWM Only
10
0
0.1
1
10
100
Output Current (mA)
1000
Portable Power Conversion Design Guide
7
DC/DC Conversion
Step-Down (Buck) Switch Mode Power Converters
Input
Voltage
Range (V)
Output
Voltage
Range (V)
Control
Scheme
0.8–4.5
PFM/PWM
or PWM
Only
2 MHz operation, UVLO, PFM/PWM
(MCP1603/L) or PWM only (MCP1603B)
mode, over-temperature protection, low
quiescent current, low shutdown current
5-pin TSOT, 8-pin
2 × 3 DFN
PFM/PWM
UVLO, over-temperature protection, output
short circuit protection, power good output,
independent shutdown, synchronous buck
and LDO combination device
10-pin DFN,
10-pin MSOP
0.8–4.5
PFM/PWM
UVLO, over-temperature protection, output
short circuit protection, power-good output,
synchronous buck and LDO combination,
sequenced startup and shutdown
10-pin DFN,
10-pin MSOP
2.7–5.5
0.8–4.5
PFM/PWM
UVLO, output short circuit protection,
over-temperature protection, independent
shutdown for buck and LDO outputs
10-pin DFN,
10-pin MSOP
Adjustable
4–30
2–15
PWM
Asynchronous, internal compensation,
UVLO, 500 kHz operation, low output ripple,
over-temperature protection, extended
temperature rating
6-pin SOT-23
MCP16301H
Adjustable
4.7–36
2–15
PWM
Asynchronous, internal compensation,
UVLO, 500 kHz operation, low output ripple,
over-temperature protection, extended
temperature rating
6-pin SOT-23
MCP16311/2
Adjustable
4.4–30
2–24
PFM/PWM
or PWM
Only
Synchronous, internal compensation, UVLO,
500 kHz operation, low output ripple,
over-temperature protection, extended
temperature rating
8-pin MSOP, 8-pin
2 × 3 TDFN
MCP16321/2
Fixed or
Adjustable
6–24
0.9–5
PWM
1A or 2A, synchronous, internal
compensation, UVLO, 1 MHz operation, power
good output, over-temperature protection,
extended temperature rating
16-pin 3 × 3 QFN
MCP16323
Fixed or
Adjustable
PWM
3A, synchronous, internal compensation,
UVLO, 1 MHz operation, power good output,
over-temperature protection, extended
temperature rating
16-pin 3 × 3 QFN
Device
Output
MCP1603/B/L
Fixed or
Adjustable
TC1303A/B/C
Fixed or
Adjustable
TC1304
Fixed or
Adjustable
2.7–5.5
TC1313
Fixed or
Adjustable
MCP16301
8
2.7–5.5
2.7–5.5
6–18
Portable Power Conversion Design Guide
0.8–4.5
0.9–5
Features
Packages
DC/DC Conversion
Linear Regulators
Linear Regulators
Linear regulators provide a precise regulated voltage to the system load from a varying input voltage source. Compared to
switching regulators, they are generally smaller, simpler, and can benefit from reduced electrical noise. They are generally
less efficient than buck regulators, but for small voltage changes or low currents the absolute power losses may be small.
There are trade-offs when selecting the proper LDO. Regulation tolerance, dropout voltage, power supply ripple rejection
(PSRR), dynamic performance, quiescent current, power dissipation capability and protection features can be important
device capabilities. Microchip’s LDO product line can address a wide input voltage range with some LDOs capable of
withstanding 40V transients. We offer devices that consume ultra-low power with input quiescent currents as low as 20 nA;
disable load circuits for low-power standby operation using shutdown inputs; filter noisy inputs with PSRR as high as 90
dB; and enjoy robust operation with integrated over-current protection, short-circuit protection, high-temperature operation
capabilities, and over-temperature protection features.
MCP1703A Low Quiescent Current 16 V Low Dropout Linear Regulator
The MCP1703A is a CMOS, low dropout voltage regulator with 250 mA maximum output current. Working with voltages up
to 16V and consuming only 2 µA of quiescent current, it is an ideal solution for applications using 9V alkaline, Li-ion, or
multi-cell power sources. It is available in space-efficient SOT-23A and SOT-89 packages; or in a thermally capable 3-pin
SOT-223 and 8-pin 2 × 3 DFN.
■■
■■
■■
■■
■■
■■
Wide 2.7V to 16V input operating voltage range
Supports load currents up to 250 mA
Low 2.0 μA typical quiescent current
Low ground current when operating in dropout
Fast startup time
Low dropout voltage, 625 mV typical
@ 250 mA for VR = 2.8V
■■ 0.4% Typical output voltage tolerance
■■ Many standard output voltage options: 1.2V, 1.5V, 1.8V,
2.5V, 2.8V, 3.0V, 3.3V, 4.0V, 5.0V
■■ Stable with 1.0 μF to 22 μF ceramic output capacitance
■■ Short-circuit protection
■■ Over-temperature protection
MCP1703A Typical Application Circuit
VIN
9V
Battery
VIN
VOUT
CIN
1 μF
Ceramic
VOUT
3.3V
IOUT
50 mA
COUT
1 μF
Ceramic
GND
Portable Power Conversion Design Guide
9
DC/DC Conversion
Linear Regulators
MCP1710 Ultra-Low Quiescent Current LDO Regulator
The MCP1710 is low dropout (LDO) linear regulator that provides up to 200 mA of current to the load while maintaining an
ultra-low 20 nA of quiescent current consumption, and it comes in a tiny 2 × 2 DFN package.
■■
■■
■■
■■
■■
■■
■■
■■
■■
■■
Ultra-low 20 nA (typical) quiescent current
Ultra-low 0.1 nA typical shutdown supply current
200 mA output current capability for Vout < 3.5V
100 mA output current capability for Vout > 3.5V
Wide 2.5V to 5.5V input operating voltage range
Standard output voltages: 1.2V, 1.8V, 2.5V, 3.3V, 4.2V
Low 450 mV (maximum) dropout voltage at 200 mA
Stable with a 1.0 µF ceramic output capacitor
Over-current protection
Space-saving, 8-lead plastic 8-pin 2 × 2 VDFN package
MCP1710 Typical Application Circuit
VOUT
VIN
COUT
CIN
MCP1710
SHDN
FB
GND
MCP1755 300 mA, 16V, High-Performance LDO
The MCP1755 and MCP1755S are 16V, high PSRR voltage regulators with short-circuit current fold-back. These regulators
provide up to 300 mA of output current and accept a continuous input voltage from 3.6V to 16V, making them ideal for
automotive and commercial 12V DC systems. Delivering 80 dB of ripple rejection at 1 kHz, these devices are ideal for
AC-sensitive applications like GFCI and AFCI circuit breaker designs. The current fold-back feature gradually reduces the
device current down to 30 mA under short-circuit conditions to protect against damage. When the short is removed, the
device will recover and continue operating.
■■
■■
■■
■■
High noise rejection, typical PSRR 80 dB at 1 kHz
Low 68 µA typical quiescent current
Wide 3.6V to 16.0V input operating voltage range
Supplies up to 300 mA output current for all
output voltages
■■ Low 300 mV typical dropout voltage with a 300 mA load
■■ High output accuracy, 0.85% typical output range
■■ Standard output voltage options: 1.8V, 2.5V, 2.8V, 3.0V,
3.3V, 4.0V, 5.0V
■■ Tight output tolerance ±2.0 % over entire operating
temperature range
■■ Stable with minimum 1.0 µF output capacitance
■■ Power good output
■■ Shutdown input
■■ Short-circuit protection with true output current fold-back
■■ Over-temperature protection
MCP1755 Typical Application Circuit
12V
CIN
1 μF
Ceramic
VIN
MCP1755S
GND
VOUT
5.0V
VOUT
COUT
1 μF
Ceramic
10
Portable Power Conversion Design Guide
IOUT
30 mA
DC/DC Conversion
Linear Regulators
Device
MCP1700
Max. Input
Voltage (V)
Output
Voltage
Range (V)
Output
Current
(mA)
6.0
1.2–5.0
250
Typical
Typical Dropout
Quiescent Voltage at Max.
Current (μA)
Iout (mV)
1.6
Features
Packages
178
Shutdown, power good
output with adjustable delay
3-pin SOT-23A,
3-pin SOT-89,
3-pin TO-92
3-pin
3-pin
3-pin
8-pin
SOT-23A,
SOT-89,
SOT-223,
2 × 3 DFN
MCP1703A
16
1.2–5.0
250
2
625
Low quiescent current, low
ground current in dropout
MCP1710
5.5
1.2–4.2
200
0.02
450
Ultra low quiescent current
8-pin 2 × 2 DFN
MCP1725
6.0
0.8–5.0
500
120
210
Shutdown, power good
output with adjustable delay
8-pin 2 × 3 DFN,
8-pin SOIC
MCP1726
6.0
0.8–5.0
1000
140
250
Shutdown, power good
output with adjustable delay
8-pin 2 × 3 DFN,
8-pin SOIC
MCP1727
6.0
0.8–5.0
1000
140
330
Shutdown, power good
output with adjustable delay
8-pin 2 × 3 DFN,
8-pin SOIC
300
Shutdown, power good, high
PSRR, true current fold-back
protection
5-pin
3-pin
3-pin
8-pin
SOT-23,
SOT-223,
SOT-89,
2 × 3 DFN
300
High PSRR, true current
fold-back protection
3-pin
3-pin
3-pin
8-pin
SOT-23A,
SOT-89,
SOT-223,
2 × 3 DFN
300
Shutdown, power good, high
PSRR, true current fold-back
protection
5-pin
3-pin
3-pin
8-pin
SOT-23,
SOT-223,
SOT-89,
2 × 3 DFN
300
High PSRR, true current
fold-back protection
3-pin
3-pin
3-pin
8-pin
SOT-23A,
SOT-89,
SOT-223,
2 × 3 DFN
Shutdown
3-pin
3-pin
5-pin
8-pin
SOT-23A,
SOT-89,
SOT-89,
2 × 3 DFN
MCP1754
MCP1754S
MCP1755
MCP1755S
16
16
16
16
1.8–5.0
1.8–5.0
1.8–5.0
1.8–5.0
150
150
300
300
56
56
68
68
MCP1804
28
1.8–18
150
50
1300
MCP1824
6.0
0.8–5.0
300
120
200
Shutdown, power good
5-pin SOT-223,
5-pin SOT-23
TC1016
6.0
1.8–3.0
80
50
150
Shutdown
5-pin SC-70
TC1017
6.0
1.8–4.0
150
53
285
Shutdown
5-pin SC-70,
SOT-23A
Portable Power Conversion Design Guide
11
DC/DC Conversion
Step-Up (Boost) Switch Mode Power Converters
Step Up (Boost) Switch Mode Power Converters
Boost converters increase the unregulated input voltage to a regulated output (unlike buck converters, which always reduce
the input voltage). Conceptually, both types of circuits use switched electromagnetic components to store energy and
maintain efficiency. Boost converters are commonly used in single- and two-cell Alkaline, NiMH and new non-rechargeable
lithium battery applications.
Microchip offers several boost converter solutions with integrated MOSFETs that are capable of starting and operating from a
single-cell battery (0.8V input, or less in some cases). Many devices offer pulse width modulation (PWM) and pulse frequency
modulation (PFM) modes of operation. PWM mode switches at constant frequency to minimize output ripple and noise while
delivering high-efficiency power conversion at high output loads. PFM mode dynamically reduces the switching frequency,
sometimes even allowing increased the output ripple, in order to dramatically reducing switching losses and improve efficiency
in light load conditions. Taking advantage of these functions, the MCP1640 and MCP16251/2 device families (and many
other Microchip parts) can automatically transition between PFM and PWM as the output current demand changes. In some
applications, the output ripple introduced by PFM mode may be too noisy for the desired circuit performance. For these
designs, the MCP1640B device can operate in PWM mode only, providing a low output ripple voltage and reducing electrical
noise. Many of these boost regulators can be disabled with a shutdown input signal; several are available with true load
disconnect (open the circuit from input to output) or with bypass (connected input and output) operation during shutdown.
Integrated boost converters are small-footprint, high-efficiency power conversion solutions for many portable applications.
MCP16251 Ultra-Low Quiescent Current, PFM/PWM Synchronous Boost Regulator with
True Output Disconnect or Input/Output Bypass Options
One of the advantages of the MCP16251/2 over other boost regulators is its low quiescent current (4 µA). This, combined
with the PFM mode operation and a high resistance feedback voltage divider, results in a converter that greatly increases
the run time of battery-powered applications at low load.
■■ Typical efficiency up to 96%
■■ High current output:
• Iout > 100 mA at Vout = 3.3V and Vin = 1.2V
• Iout > 250 mA at Vout = 3.3V and Vin = 2.4V
• Iout > 225 mA at Vout = 5.0V and Vin =3.3V
■■ Ultra-low device quiescent current:
• Output quiescent current less than 4 µA typical
(device is not switching, Vout > Vin)
• Input sleep current less than 1 µA
(device is not switching, Vout > Vin, no load)
• Typical no load input current of 14 µA
(device is switching)
• 0.6 µA typical shutdown current
■■ Low 0.82V start-up voltage
■■ Low 0.35V minimum operating input voltage
■■ Maximum input voltage ≤ Vout < 5.5V
■■ Adjustable output from 1.8V to 5.5V
■■ 1.23V feedback voltage
■■ Automatic PFM/PWM operation:
• 500 kHz PWM operation
• 100 mV typical PFM output ripple
■■ Internal synchronous rectifier
■■ Internal compensation
■■ Inrush current limiting
■■ Internal soft-start (1.5 ms typical)
■■ Selectable, logic-controlled shutdown states:
• True load disconnect option (MCP16251)
• Input to output bypass option (MCP16252)
■■ Anti-ringing control
■■ Over-temperature protection
■■ Available in 6-lead SOT-23 and 8-lead 2 × 3 TDFN
packages
MCP16251 Typical Application Circuit
MCP16251 Typical Circuit Efficiency
L1
4.7 μH
100
95
VIN = 3.0V
SW
VIN
0.9V TO 1.7V
VOUT
3.3V
VOUT
VIN
CIN
4.7 μF
1.69 MΩ
VFB
EN
1 MΩ
GND
12
COUT
10 μF
Portable Power Conversion Design Guide
Efficiency (%)
90
85
VIN = 1.5V
80
VIN = 2.4V
75
70
65
60
55
50
VOUT = 3.3V
0.1
1
10
IOUT (mA)
100
1000
DC/DC Conversion
Step-Up (Boost) Switch Mode Power Converters
MCP1640 High Performance PFM/PWM Synchronous Boost Converter with True Output
Disconnect or Input/Output Bypass Options
The MCP1640 is a compact, high-efficiency, fixed-frequency, synchronous step-up DC-DC converter. It provides an easy-to-use
power supply solution for applications powered by one-, two-, or three-cell alkaline, NiCd, NiMH; one-cell Li-ion; or one-cell
Li-polymer batteries. It provides very high efficiency through integration of the low-resistance n-channel boost switch and
synchronous p-channel switch, and is available with PFM/PWM, PWM only, true load disconnect or bypass options.
■■ Typical efficiency up to 96%
■■ High current output:
• Iout > 100 mA at Vout = 3.3V and Vin = 1.2V
• Iout > 350 mA at Vout = 3.3V and Vin = 2.4V
• Iout > 350 mA at Vout = 5.0V and Vin =3.3V
■■ Low 0.65V typical start-up input voltage
(3.3V Vout at 1 mA)
■■ Low 0.35V typical operating input voltage
(3.3V Vout at 1 mA)
■■ Wide 2.0V to 5.5V adjustable output voltage range
■■ Maximum input voltage ≤ Vout < 5.5V
■■ High frequency 500 kHz PWM operation, with PFM and
PWM device options:
• Automatic PFM/PWM operation (MCP1640/C)
• PWM only, PFM operation disabled (MCP1640B/D)
■■ Selectable, logic-controlled, shutdown states:
• True load disconnect option (MCP1640/B)
• Input to output bypass option (MCP1640C/D)
■■ Low < 1 μA shutdown current (all states)
■■ Low 19 μA typical device quiescent current
■■ Internal synchronous rectifier
■■ Internal compensation
■■ Inrush current limiting
■■ Internal soft-start
■■ Low noise, anti-ringing control
■■ Over-temperature protection
■■ Available in 6-lead SOT-23 and 8-lead 2 × 3
DFN packages
MCP1640 Application Circuit Using a Single Cell
Alkaline Battery
MCP1640 Application Circuit Using a Single Cell
Li-ion Battery
L1
4.7 μH
L1
4.7 μH
SW
VIN
0.9V TO 1.7V
VOUT
VIN
CIN
4.7 μF
VOUT
3.3V @ 100 mA
VIN
VFB
COUT
10 μF
VOUT
5.0V @ 300 mA
VOUTS
VOUTP
CIN
4.7 μF
976 kΩ
EN
SW
VIN
3.0V TO 4.2V
EN
PGND
COUT
10 μF
309 kΩ
562 kΩ
GND
976 kΩ
VFB
SGND
MCP1640 Typical Efficiency for a 3.3V Output
100
90
VIN = 2.5V
Efficiency (%)
80
70
60
VIN = 1.2V
VIN = 0.8V
50
40
30
20
10
0
0.01
VOUT = 3.3V
0.1
1
10
100
1000
IOUT (mA)
Portable Power Conversion Design Guide
13
DC/DC Conversion
Step-Up (Boost) Switch Mode Power Converters
Performance Tradeoffs – Matching the Boost Converter to the Load Requirements
In many cases, light or no load conditions have very different requirements than high load conditions. This tradeoff can be
readily observed by comparing the MCP1640 and MCP16251. The MCP1640 offers higher current capability, handing peak
loads up to 350 mA compared to only 225 mA for MCP16251. However, the MCP16251 reduces the input quiescent
current drawn from the battery even further than the MCP1640, and the MCP16251 PFM mode offers higher efficiency at
light load conditions. An 80% quiescent current reduction extends battery run time for applications that operate for long
periods of time in sleep mode. When powering a 100 µA load, the MCP16251 is nearly 12% more efficient than the
MCP1640. Applications that draw high currents may need the additional power capability of the MCP1640, while
applications with significant operating time at low or no load conditions may benefit from the reduced power consumption
of the MCP16251.
No Load Input Current Requirements for MCP1640
and MCP16251
80
70
60
MCP1640
50
40
30
20
MCP16251/2
1
1.2
1.4
1.6
1.8
2
Input Voltage (V)
Portable Power Conversion Design Guide
2.2
2.4
VIN = 2.5V
2 5V
80
VOUT = 3.3V
70
60
50
MCP16251/2
40
MCP1640
30
0.01
10
14
90
VOUT = 3.3V
90
0
100
Efficien
ncy (%))
No Loa
ad Input Current (µA)
100
Light Load Efficiency of MCP1640 and MCP16251
0.1
1
10
IOUT (mA)
100
1000
DC/DC Conversion
Step-Up (Boost) Switch Mode Power Converters
AAAA Battery Boost Circuit
An MCP1640 boost converter and PIC12F microcontroller can create a simple power solution which will deliver a 3.3V
output from a single alkaline battery cell, with very low power consumption and long battery run time, especially in lowcurrent applications. The circuit will run in standby mode, with the PIC12F617 in sleep mode and the MCP1640 disabled,
consuming only a few μA from the battery (in shutdown mode the MCP1640 typically consumes 0.75 μA). A charged
capacitor will maintain the output until the comparator on the PIC® microcontroller detects a low voltage. If the output
capacitor voltage drops too far, the PIC microcontroller will turn on the MCP1640, which will operate normally until the
output capacitor is charged, and then the microcontroller will disable the boost converter again. When the MCP1640 is in
normal operating mode, the no load input current is approximately 70 μA at 1.5V input. By pulsing the MCP1640’s enable
at low frequency, this method reduces the average input current by up to 80%.
This circuit is implimented in the MCP1640 Single Quadruple-A Battery Boost Converter Reference Design, available
through Microchip.
MCP1640 Single Quadruple-A Battery Boost
Coverter Demonstration Board (MCP1640RD-4ABC)
MCP1640 Boost Converter Reference
Design Circuit
Single Quadruple-A Battery Input
VIN
A/D
I/O
VOUT
EN
Load
VDD
ON/OFF
S1
1
MCP1640
Load Switch
P-MOS
I/O
2
I/O
PIC12F617
I/O
LED
Status
MCP1640 Boost Converter Reference Design No
Load Input Current
Standby No Load Input
Current (µA)
MCP1640 Boost Converter Reference Design
Behavior During Operation
*
30
25
20
15
10
0.8
1
1.2
1.4
Input Voltage (V)
1.6
Portable Power Conversion Design Guide
15
DC/DC Conversion
Step-Up (Boost) Switch Mode Power Converters
Device
MCP1623/4
MCP16251/2
MCP1640/B/C/D
16
Output
Adjustable
Adjustable
Adjustable
Input
Voltage
Range (V)
0.35/
0.65–5.0
0.35/
0.82–5.0
0.35/
0.65–5.0
Portable Power Conversion Design Guide
Output
Voltage
Range (V)
2–5.5
1.8–5.5
2–5.5
Control
Scheme
Features
Packages
PFM/PWM
or PWM
Only
425 mA peak current limit, 500 kHz
synchronous operation, PFM/PWM
(MCP1624) or PWM only (MCP1623) mode
switching operation, internal compensation,
over-temperature protection, 19 µA quiescent
current,
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