MIC2145
Micrel, Inc.
MIC2145
High Efficiency 2.5W Boost Converter
General Description
Features
The MIC2145 is a small size boost switching regulator that
can provide over 2.5W of output power. The input voltage
range is between 2.4V to 16V, making the device suitable for
one-cell Li-Ion and 3- to 4-cell alkaline/NiCad/NiMH applications. The output voltage of the MIC2145 can be adjusted up
to 16V.
The MIC2145 is well suited for portable, space-sensitive
applications. Its typical 450kHz operation allows small surface mount external components to be used. The MIC2145
has a low quiescent current of 200µA, and a typical shutdown
current of 0.5µA. The MIC2145 is capable of high efficiencies
in a small board area.
The MIC2145 features a low-on resistance internal switch
that allows it to provide over 2.5W of output power. The peak
switch current can be programmed through an external
resistor. This allows the user to set the peak switch current at
the level where maximum efficiency occurs. It also allows the
user to further optimize for efficiency and inductor size by
setting the peak current below the level of inductor saturation.
The MIC2145 is available in an MSOP-8 and 3mm×3mm
MLF™-10L package with an ambient operating temperature
range from –40°C to +85°C.
•
•
•
•
•
•
•
•
•
•
2.4V to 16V input voltage
Output adjustable to 16V
Programmable peak current limit
Soft start
Up to 450kHz switching frequency
0.5µA shutdown current
200µA quiescent current
Capable of 5V/ 500mA output with 3.3V input
Achieves over 85% efficiency
Implements low power BOOST, SEPIC, and FLYBACK
topologies
• MSOP-8 and 3mm×3mm MLF™-10L
Applications
•
•
•
•
•
Flash LED driver
LCD bias supply
White LED driver
DSL bias supply
Local 3V to 5V conversion
Ordering Information
Part Number
Standard
Pb-Free
Voltage
Ambient
Temp. Range
Package
MIC2145BMM
MIC2145YMM
Adj
–40°C to +85°C
8-lead MSOP
MIC2145BML
MIC2145YML
Adj
–40°C to +85°C
10-lead MLF™
Typical Application
L1
VIN
3.0V to 5.0V
10V Output
Efficiency
10µH
90
D1
1
4
EN
PGND
SW
VDD
VOUT
10V/150mA
5
6
COUT
10µF/16V
MIC2145BMM
3
2
RSET
SS
FB
7
SGND
8
85
EFFICIENCY (%)
CIN
10µF/6.3V
80
75
70
65
I Limit
60
10
VIN = 3.0V
100
1000
OUTPUT CURRENT (mA)
Adjustable Output Boost Converter with Programmable Peak Switch Current
MLF and MicroLeadFrame are trademarks of Amkor Technologies, Inc.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 2005
1
M9999-042205
MIC2145
Micrel, Inc.
Pin Configuration
EN 1
8 SGND
SS 2
7 FB
RSET 3
6 VDD
PGND 4
5 SW
EN 1
SS 2
RSET 3
PGND 4
PGND 5
10 SGND
9 FB
8 VDD
7 SW
6 SW
3mm×
×3mm MLF-10L (ML)
8-Lead MSOP (MM)
Pin Description
Pin Number
MSOP
Pin Number
MLF
Pin Name
1
1
EN
Enable (Input): Logic high (≥1.5V) enables regulator. Logic low (≤0.7V)
shuts down regulator. Do not float.
2
2
SS
Soft Start Capacitor (External Component): Connect external capacitor to
ground to control the rise time of the output voltage.
3
3
RSET
Current Limit (External Component): Sets peak current limit of the internal
power MOSFET using an external resistor.
4
4, 5
PGND
Power Ground (Return): Internal power MOSFET source.
5
6, 7
SW
Switch Node (Input): Internal power MOSFET drain.
6
8
VDD
Supply (Input): +2.4V to +16V for internal circuitry.
7
9
FB
8
10
SGND
M9999-042205
Pin Function
Feedback (Input): Output voltage sense node.
Small Signal Ground (Return): Ground
2
April 2005
MIC2145
Micrel, Inc.
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VDD) .................................................... 18V
Switch Voltage (VSW) .................................................... 18V
Feedback Voltage (VFB) ................................................ 18V
Switch Current (ISW) ........................................................ 2A
Enable Voltage(VEN), Note 5 ........................................ 18V
RSET Voltage (VRSET) .................................................... 6V
ESD Rating, Note 3 ...................................................... 2kV
Ambient Storage Temperature(TS) .......... –65°C to +150°C
Supply Voltage (VDD) ....................................... 2.4V to 16V
Switch Voltage (VSW) .................................................... 16V
Ambient Temperature (TA) ......................... –40°C to +85°C
Junction Temperature (TJ) ....................... –40°C to +125°C
Package Thermal Resistance MSOP
θJA (MSOP-8) .................................................... 206°C/W
θJA (3mm×3mm MLF-10) .................................... 60°C/W
Electrical Characteristics (Note 6)
VDD = 10V, VOUT = 10V, IOUT = 100mA; TJ =25°C, unless otherwise noted, bold values indicate –40°C ≤ TJ ≤ 125°C.
Parameter
Condition
Min
Supply Voltage
Typ
2.4
Max
Units
16
V
Shutdown Current
EN = 0.3V, VDD = 10V, VFB=1.35V
0.5
5
µA
Quiescent Current
EN = VDD, VDD = 10V, VFB = 1.35V
200
300
µA
Feedback Voltage Reference
(±2%)
1.058
1.08
1.102
V
(±3%)
1.048
1.112
V
Comparator Hysteresis
18
mV
Feedback Input Current
VFB=1.35V
40
nA
Peak Current Limit
RSET=200Ω, VDD = 3.6V, Note 4
0.8
A
RSET=1kΩ, VDD = 10V, Note 4
0.9
A
500
ns
Current Limit Comparator
Propagation Delay
Switch On-Resistance
ISW = 150mA, VDD = 3.0V
500
750
mΩ
ISW = 1.2A, VDD = 10V
250
400
mΩ
Maximum Off Time
Enable Input Voltage
Enable Input Current
Soft Start Current
1000
Logic Low (turn-off)
1.1
ns
0.7
Logic High (turn-on)
1.5
1.1
V
VEN = 0V
–1
0.01
1
µA
VEN = 2V
–1
0.01
1
µA
VEN = 2V, VDD=3.0V
–8
–12
–16
µA
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5KΩ in series with 100pF.
Note 4.
The current is measured in a DC mode. Actual peak switching current will be higher due to internal propagation delay of the circuit.
Note 5.
VEN ≤ VDD.
Note 6.
Specification for packaged product only.
April 2005
V
3
M9999-042205
MIC2145
Micrel, Inc.
Typical Characteristics
Efficiency-Bootstrapped
Configuration
90
10.0
8 10 12
VDD (V)
14
0.30
0.25
0.20
0.15
0.10
0.05
4
6
0.4
0.3
0.2
0.1
0.0
0
0.6
0.5
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Feedback Current
vs. Temperature
1.08
1.07
1.06
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
Shutdown Current
vs. Temperature
SHUTDOWN CURRENT (µA)
0.8
0.7
8 10 12 14 16 18
VDD (V)
1.05
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
1.5
1.0
0.9
6
1.09
Off Time
vs. Temperature
1.2
1.1
4
1.1
8 10 12 14 16 18
VDD (V)
1.4
1.3
2
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
4
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0
0.01
0.08
0.07
0.04
0.03
0.6
0.5
1.0
Feedback Voltage
vs. Temperature
FEEDBACK VOLTAGE (V)
0.40
0.35
SWITCH ON-RESISTANCE (Ω)
VOUT (V)
SWITCH ON-RESISTANCE (Ω)
16
0.8
0.7
FEEDBACK CURRENT (µA)
6
1.0
0.9
Quiescent Current
vs. Temperature
QUIESCENT CURRENT (mA)
4
Quiescent Current
vs. VDD
M9999-042205
0.02
Switch On-Resistance
vs. Temperature
L = 10µH
2
0.01
Switch On-Resistance
vs. VDD
14.4
14.2
QUIESCENT CURRENT (Ω)
0
Line Regulation
14.8
14.6
0
9.2
VIN = 3.6V
L = 10µH
OUTPUT CURRENT (A)
15.2
15.0
0.00
9.4
OUTPUT CURRENT (A)
IOUT = 10mA
0.50
0.45
9.6
OUTPUT CURRENT (A)
15.6
15.4
2
50
9.8
VIN = 3.3V
VOUT = 10V
L = 10µH
60
16.0
15.8
14.0
70
0.08
0.07
0.04
0.03
0.02
0.01
0
50
0.06
VIN = 3.3V
VOUT = 10V
L = 10µH
0.06
70
80
0.05
80
VOUT (V)
90
EFFICIENCY (%)
10.2
60
OFF TIME (µs)
Load Regulation
100
0.05
EFFICIENCY (%)
Efficiency-Basic
Configuration
100
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
VIN = 3.6V
0.00
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
April 2005
MIC2145
Micrel, Inc.
Peak Current Limit
vs. Temperature
12
10
8
6
4
2
VIN = 3.6V
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
April 2005
PEAK CURRENT LIMIT (A)
SOFT START CURRENT (µA)
14
1.4
RSET = 200
1.3
1.2
1.1 R
= 500
1.0 SET
RSET = 1k
0.9
0.8
0.7
0.6
0.5
0.4 V = 3.6V
RSET = 10k
0.3 IN
0.2 VOUT = 10V
0.1 L = 10µH
0
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
5
Peak Current Limit
vs. RSET
2000
PEAK CURRENT LIMIT (mA)
Soft Start Current
vs. Temperature
VIN =
1800
15V
1600
12V
1400
10V
1200
8.0V
1000
800
600
L = 10µH
400 VOUT/VIN > 1.25
100
1000
10000
RSET(Ω)
5.0V
4.2V
3.6V
3.3V
3.0V
2.4V
100000
M9999-042205
MIC2145
Micrel, Inc.
Functional Diagram
10µH
VIN
L1
CIN
D1
VDD
6
SW
VOUT
5
R1
RSET
3
Thermal
Shutdown
COUT
R2
Current Limit
Comparator
RSET
CFF
Soft
Start
One Shot
800nS
POWER
MOSFET
SGND
8
PGND
4
Feedback
Comparator
FB
7
/S
/Q
EN
VREF
/R
On(/Off)
R1
VOUT = 1.08 1 +
R2
1
SS
2
CSS
Figure 1. Block Diagram
M9999-042205
6
April 2005
MIC2145
Micrel, Inc.
Output
The maximum output voltage is limited by the voltage capability of the output switch. Output voltages of up to 16V can be
achieved with the boost circuit. Higher output voltages require a flyback configuration.
Peak Current Limit
The peak current limit is externally set with a resistor. The
peak current range is from 420mA to 2A. There is a minimum
resistor value for RSET at lower VDD voltages. For resistor
value selections, see the “Typical Characteristics: Peak
Current Limit vs. RSET”.
Soft Start
The MIC2145 has a built in soft start that controls the rise time
of the output voltage and the peak current limit threshold
during start up.
Functional Description
See “Application Information” for component selection and
pre-designed circuits.
Overview
The MIC2145 is a 2.5W boost regulator with programmable
peak current limit and a constant off time. Quiescent current
for the MIC2145 is typically 200µA when the switch is in the
off state. Efficiencies above 80% throughout most operating
conditions can be realized.
Regulation
Regulation is achieved by both of the comparators, which
regulate the inductor current and the output voltage by gating
the power MOSFET. Initially, power is applied to the SW and
VDD pins. When the part is enabled, the power MOSFET
turns on and current flows. When the current exceeds the
peak current limit threshold, the current limit comparator fires
the one-shot to turn off the power MOSFET for 1000ns and
resets the SR flip-fop. The current limit comparator continues
to cycle the power MOSFET on and off until the output voltage
trips the upper threshold of the feedback comparator, which
terminates the cycle. The cycle will begin again when the
output voltage drops below the lower hysteresis threshold of
the feedback comparator. The feedback comparator has a
typical hysteresis of 18mV. Due to the gain of the feedback
resistor divider, the voltage at VOUT experiences a typical
167mV of hysteresis for 10V output at 2.4V VDD. This can be
reduced by adding a feed-forward capacitor, CFF (See
“Output Voltage” section).
VEN
(2V/div)
VIN = 3V
VOUT = 10V
RSET = 10k
CSS = 0.01µF
VOUT
(5V/div)
VSW
(5V/div)
IINDUCTOR
(500mA/div)
Time 200µs
Figure 3. Typical Soft Start Waveforms
Thermal Shutdown
Built-in thermal protection circuitry turns off the power MOSFET
when the junction temperature exceeds about 150°C.
VOUT
AC Couple
(100mV/div)
VSW
(5V/div)
IINDUCTOR
(500mA/div)
Time 20µs
Figure 2. Typical Regulator Waveforms
April 2005
7
M9999-042205
MIC2145
Micrel, Inc.
Application Information
A value of 1MΩ is recommended for R1 to minimize the
quiescent current when the part is off. Then, R2 can be solved
using the above equation. A feed-forward capacitor, CFF,
ranging from 5pF to 100pF can be used in parallel with R1 to
reduce the peak-to-peak output voltage ripple, which is
shown in Figures 4 and 5.
Pre-designed circuit information is at the end of this section.
Output Voltage
The output voltage of the regulator can be set between 2.4V
and 16V by connecting a resistor divider at the FB pin. The
resistor values are selected by the following equations:
R2 =
1.08 × R1
VOUT − 1.08
VOUT
AC
(100mV/div)
VOUT
AC
(100mV/div)
VSW
(5V/div)
VSW
(5V/div)
Time 4µs
Time 20µs
Figure 5. With Feed-Forward Capacitor (100pF)
Figure 4. Without Feed-Forward Capacitor
M9999-042205
8
April 2005
MIC2145
Micrel, Inc.
Bootstrap
A bootstrapped configuration is recommended for applications that require high efficiency at heavy loads (>70mA).
This is achieved by connecting the VDD pin to VOUT (see
Figure 7). For applications that require high efficiency at light
loads (
工商网监
湘ICP备2023018690号
