MIC2290
2mm × 2mm PWM Boost Regulator
with Internal Schotty Diode
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, 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
October 2007
M9999-101907
General Description
The MIC2290 is a 1.2MHz, PWM, boost-switching
regulator housed in the small size 2mm × 2mm 8-pin MLF
®
package. The MIC2290 features an internal Schottky diode
that reduces circuit board area and total solution cost. High
power density is achieved with the MIC2290’s internal
34V/0.5A switch, allowing it to power large loads in a tiny
footprint.
The MIC2290 implements a constant frequency 1.2MHz
PWM control scheme. The high frequency operation saves
board space by reducing external component sizes. The
fixed frequency PWM topology also reduces switching
noise and ripple to the input power source.
The MIC2290’s wide 2.5V to 10V input voltage allows
direct operation from 3- to 4-cell NiCad/NiMH/Alkaline
batteries, 1-and 2-cell Li-Ion batteries, as well as fixed
3.3V and 5V systems.
The MIC2290 is available in a low-profile 2mm×2mm 8-pin
MLF
®
leadless package and operates from a junction
temperature range of –40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• Internal Schottky diode
• 2.5V to 10V input voltage
• Output voltage adjustable to 34V
• Over 500mA switch current
• 1.2MHz PWM operation
• Stable with ceramic capacitors
• <1% line and load regulation
• Low input and output ripple
• <1µA shutdown current
• UVLO
• Output overvoltage protection
• Over temperature protection
• 2mm × 2mm 8-pin MLF
®
package
• –40°C to +125°C junction temperature range
Applications
• Organic EL power supply
• TFT LCD bias supply
• 12V DSL power supply
• CCD bias supply
• SEPIC converters
___________________________________________________________________________________________________________
Typical Application
4, 8
L1
10µH
R2
R1
1
7
3
2
MIC2290
VIN
Li Ion
Battery
V
OUT
12V
EN
SW
OUT
GND
V
IN
C1
1µF
C2
10µF
FB
6
Simple 12V Boost Regulator
60
65
70
75
80
85
0 0.02 0.04 0.06 0.08 0.1
EFFICIENCY (%)
LOAD CURRENT (A)
12
V
OUT Efficienc
y
V
IN
=4.2V
V
IN
=3.2V
V
IN
=3.6V
Micrel, Inc. MIC2290
October 2007
2 M9999-101907
Ordering Information
Part Number Marking
Code Output
Voltage Overvoltage
Protection Junction
Temp. Range
Package
Lead Finish
MIC2290BML SRC Adj. 34V –40° to +125°C 8-Pin 2x2 MLF
®
Standard
MIC2290YML SRC Adj. 34V –40° to +125°C 8-Pin 2x2 MLF
®
Pb-Free
Pin Configur ation
OUT
VIN
EN
A
GND
PGND
SW
FB
NC
1
2
3
4
8
7
6
5
8-Pin 2mm x 2mm MLF
®
(ML)
(Top View)
Pin Description
Pin Number Pin Name Pin Function
1 OUT
Output pin (Output): Output voltage. Connect to FB resistor divider. This pin
has an internal 34V output overvoltage clamp. See “Block Diagram” and
“Applications” section for more information.
2 VIN Supply (Input): 2.5V to 10V input voltage.
3 EN Enable (Input): Logic high enables regulator. Logic low shuts down regulator.
4 AGND Analog ground.
5 NC No connect (no internal connection to die).
6 FB
Feedback (Input): Output voltage sense node. Connect feedback resistor
network to this pin. ⎟
⎠
⎞
⎜
⎝
⎛+= R2
R1
11.24VV
OUT
.
7 SW Switch node (Input): Internal power Bipolar collector.
8 PGND Power ground.
EP GND Ground (Return): Exposed backside pad.
Micrel, Inc. MIC2290
October 2007
3 M9999-101907
Absolute Maximum Ratings(1)
Supply Voltage (V
IN
).......................................................12V
Switch Voltage (V
SW
)....................................... –0.3V to 34V
Enable Pin Voltage (V
EN
)................................... –0.3V to V
IN
FB Voltage (V
FB
)...............................................................6V
Switch Current (I
SW
) .........................................................2A
Storage Temperature (T
s
) .........................–65°C to +150°C
ESD Rating
(3)
.................................................................. 2kV
Operating Ratings(2)
Supply Voltage (V
IN
).......................................... 2.5V to 10V
Ambient Temperature (T
J
)......................... –40°C to +125°C
Package Thermal Resistance
2x2 MLF-8 (θ
JA
) .................................................93°C/W
Electrical Characteristics(4)
T
A
= 25°C, V
IN
= V
EN
= 3.6V, V
OUT
= 15V, I
OUT
= 40mA, unless otherwise noted. Bold values indicate –40°C ≤ T
J
≤ ±125°C.
Symbol Parameter Condition Min Typ Max Units
V
IN
Supply Voltage Range 2.5 10 V
V
UVLO
Undervoltage Lockout 1.8 2.1 2.4 V
I
VIN
Quiescent Current V
FB
= 2V, (not switching) 2.5 5 mA
I
SD
Shutdown Current V
EN
= 0V, Note 5 0.2 1 µA
V
FB
Feedback Voltage (±1%)
(±2%) (Over Temp)
1.227
1.215
1.24 1.252
1.265
V
V
I
FB
Feedback Input Current V
FB
= 1.24V –450 nA
Line Regulation 3V ≤ V
IN
≤ 5V 0.1 1 %
Load Regulation 5mA ≤ I
OUT
≤ 20mA 0.2 %
D
MAX
Maximum Duty Cycle 85 90 %
I
SW
Switch Current Limit 0.75 A
V
SW
Switch Saturation Voltage I
SW
= 0.5A 450 mV
I
SW
Switch Leakage Current V
EN
= 0V, V
SW
= 10V 0.01 5 µA
V
EN
Enable Threshold Turn on
Turn off
1.5
0.4 V
V
I
EN
Enable Pin Current V
EN
= 10V 20 40 µA
f
SW
Oscillator Frequency 1.05 1.2 1.35 MHz
V
D
Schottky Forward Drop I
D
= 150mA 0.8 1 V
I
RD
Schottky Leakage Current V
R
= 30V 4 µA
V
OVP
Overvoltage Protection (nominal voltage) 30 32 34 V
T
J
Overtemperature
Threshold Shutdown
Hysteresis
150
10
°C
°C
Notes:
1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating
the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, T
J(max)
, the
junction-to-ambient thermal resistance, θ
JA
, and the ambient temperature, T
A
. The maximum allowable power dissipation will result in excessive die
temperature, and the regulator will go into thermal shutdown.
2. The device is not guaranteed to function outside its operating rating.
3. IC devices are inherently ESD sensitive. Handling precautions required. Human body model rating: 1.5K in series with 100pF.
4. Specification for packaged product only.
5. I
SD
= I
VIN
.
Micrel, Inc. MIC2290
October 2007
4 M9999-101907
Typical Characteristics
50
55
60
65
70
75
80
85
90
0 25 50 75 100
)%(YCNEICIFFE
OUTPUT CURRENT (mA)
Efficiency at V
OUT
= 12V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3.3V
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
2.5 4 5.5 7 8.5 10
)A(TIMILTNERRUC
SUPPLY VOLTAGE (V)
Current Limit
vs. Supply Voltage
0
100
200
300
400
500
600
700
-40 -20 0 20 40 60 80 100 120
)Vm(EGATLOVNOITARUTASHCTIWS
TEMPERATURE (°C)
Switch Saturation Voltage
vs. Temperature
V
IN
= 3.6V
I
SW
= 500mA
1.00
1.05
1.10
1.15
1.20
1.25
1.30
1.35
1.40
-40-20 0 20 40 60 8010012
0
)zHM(YCNEUQERF
TEMPERATURE (°C)
Frequency
vs. Temperature
85
87
89
91
93
95
97
99
-40 -20 0 20 40 60 80 100 120
)%(ELCYCYTUDMUMIXAM
TEMPERATURE (°C)
Maximum Duty Cycle
vs. Temperature
V
IN
= 3.6V
0
100
200
300
400
500
600
700
-40-20 0 20 40 60 8010012
0
)An(TNERRUCKCABDEEF
TEMPERATURE (°C)
FB Pin Current
vs. Temperature
Micrel, Inc. MIC2290
October 2007
5 M9999-101907
Typical Characteristics (continued)
Micrel, Inc. MIC2290
October 2007
6 M9999-101907
Functional Characteristics
Micrel, Inc. MIC2290
October 2007
7 M9999-101907
Functional Diagram
GND
CA
V
REF
PWM
Generator
Ramp
Generator
1.2MHz
Oscillator
SW
ENFB OUTVIN
1.24V
g
m
OVP
S
Figure 1. MIC2290 Block Diagram
Functional Description
The MIC2290 is a constant frequency, PWM current
mode boost regulator. The block diagram is shown in
Figure 1. The MIC2290 is composed of an oscillator,
slope compensation ramp generator, current amplifier,
g
m
error amplifier, PWM generator, and a 0.5A bipolar
output transistor. The oscillator generates a 1.2MHz
clock. The clock’s two functions are to trigger the PWM
generator that turns on the output transistor, and to reset
the slope compensation ramp generator. The current
amplifier is used to measure the switch current by
amplifying the voltage signal from the internal sense
resistor. The output of the current amplifier is summed
with the output of the slope compensation ramp
generator. This summed current-loop signal is fed to one
of the inputs of the PWM generator.
The g
m
error amplifier measures the feedback voltage
through the external feedback resistors and amplifies the
error between the detected signal and the 1.24V
reference voltage. The output of the g
m
error amplifier
provides the voltage-loop signal that is fed to the other
input of the PWM generator. When the current-loop
signal exceeds the voltage-loop signal, the PWM
generator turns off the bipolar output transistor. The next
clock period initiates the next switching cycle,
maintaining the constant frequency current-mode PWM
control.
Micrel, Inc. MIC2290
October 2007
8 M9999-101907
Application Information
DC-to-DC PWM Boost Conversion
The MIC2290 is a constant frequency boost converter. It
operates by taking a DC input voltage and regulating a
higher DC output voltage. Figure 2 shows a typical
circuit. Boost regulation is achieved by turning on an
internal switch, which draws current through the inductor
(L1). When the switch turns off, the inductor’s magnetic
field collapses, causing the current to be discharged into
the output capacitor through an internal Schottky diode
(D1). Voltage regulation is achieved through pulse-width
modulation (PWM).
L1
10µH
C2
10µF
R2
R1
MIC2290
VIN
V
IN
V
OUT
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
Figure 2. Typical Application Circuit
Duty Cycle Considerations
Duty cycle refers to the switch on-to-off time ratio and
can be calculated as follows for a boost regulator:
OUT
IN
V
V
1D −=
The duty cycle required for voltage conversion should be
less than the maximum duty cycle of 85%. Also, in light
load conditions where the input voltage is close to the
output voltage, the minimum duty cycle can cause pulse
skipping. This is due to the energy stored in the inductor
causing the output to overshoot slightly over the
regulated output voltage. During the next cycle, the error
amplifier detects the output as being high and skips the
following pulse. This effect can be reduced by increasing
the minimum load or by increasing the inductor value.
Increasing the inductor value reduces peak current,
which in turn reduces energy transfer in each cycle.
Overvoltage Protection
For the MLF
®
package option, there is an overvoltage
protection function. If the feedback resistors are discon-
nected from the circuit or the feedback pin is shorted to
ground, the feedback pin will fall to ground potential.
This will cause the MIC2290 to switch at full duty cycle in
an attempt to maintain the feedback voltage. As a result,
the output voltage will climb out of control. This may
cause the switch node voltage to exceed its maximum
voltage rating, possibly damaging the IC and the
external components. To ensure the highest level of
protection, the MIC2290 OVP pin will shut the switch off
when an overvoltage condition is detected, saving itself
and other sensitive circuitry downstream.
Component Selection
Inductor
Inductor selection is a balance between efficiency,
stability, cost, size, and rated current. For most
applications, a 10µH is the recommended inductor
value; it is usually a good balance between these
considerations.
Large inductance values reduce the peak-to-peak ripple
current, affecting efficiency. This has an effect of
reducing both the DC losses and the transition losses.
There is also a secondary effect of an inductor’s DC
resistance (DCR). The DCR of an inductor will be higher
for more inductance in the same package size. This is
due to the longer windings required for an increase in
inductance. Since the majority of input current (minus
the MIC2290 operating current) is passed through the
inductor, higher DCR inductors will reduce efficiency.
To maintain stability, increasing inductor size will have to
be met with an increase in output capacitance. This is
due to the unavoidable “right half plane zero” effect for
the continuous current boost converter topology. The
frequency at which the right half plane zero occurs can
be calculated as follows:
2πILV
V
F
OUTOUT
2
IN
rhpz
×××
=
The right half plane zero has the undesirable effect of
increasing gain, while decreasing phase. This requires
that the loop gain is rolled off before this has significant
effect on the total loop response. This can be
accomplished by either reducing inductance (increasing
RHPZ frequency) or increasing the output capacitor
value (decreasing loop gain).
Output Capacitor
Output capacitor selection is also a trade-off between
performance, size, and cost. Increasing output
capacitance will lead to an improved transient response,
but also an increase in size and cost. X5R or X7R
dielectric ceramic capacitors are recommended for
designs with the MIC2290. Y5V values may be used, but
to offset their tolerance over temperature, more
capacitance is required. The following table shows the
recommended ceramic (X5R) output capacitor value vs.
output voltage.
Output Voltage Recommended Output Capacitance
<6V 22µF
<16V 10µF
<34V 4.7µF
Table 1. Output Capacitor Selectio n
Micrel, Inc. MIC2290
October 2007 9
M9999-101907
Input capacitor
A minimum 1µF ceramic capacitor is recommended for
designing with the MIC2290. Increasing input
capacitance will improve performance and greater noise
immunity on the source. The input capacitor should be
as close as possible to the inductor and the MIC2290,
with short traces for good noise performance.
Feedback Resistors
The MIC2290 utilizes a feedback pin to compare the
output to an internal reference. The output voltage is
adjusted by selecting the appropriate feedback resistor
network values. The R2 resistor value must be less than
or equal to 5kΩ (R2 ≤ 5kΩ). The desired output voltage
can be calculated as follows:
⎟
⎠
⎞
⎜
⎝
⎛+×= 1
R2
R1
VV
REFOUT
where VREF is equal to 1.24V.
Micrel, Inc. MIC2290
October 2007 10
M9999-101907
Application Circuits
L1
4.7µH
C2
10µF
6.3V
R2
5k
R1
15k
MIC2290
VIN
V
IN
3.3V
V
OUT
5V @ 180mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0805 X5R Ceramic Capacitor 08056D475MAT AVX
C2 10µF, 6.3V, 0805 X5R Ceramic Capacitor 08056D106MAT AVX
L1 4.7µH, 450mA Inductor LQH32CN4R7N11 Murata
Figure 3. 3.3V
IN
to 5V
OUT
@ 180mA
L1
10µH
C2
10µF
16V
R2
5k
R1
31.6k
MIC2290
VIN
V
IN
3V to 4.2V
V
OUT
9V @ 80mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0603 X5R Ceramic Capacitor 06036D225MAT AVX
C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX
L1 10µH, 450mA Inductor LQH32CN100K11 Murata
Figure 4. 3.3V
IN
to 4.2V
OUT
to 9V
OUT
@ 80mA
L1
10µH
C2
10µF
16V
R2
5k
R1
43.2k
MIC2290
VIN
V
IN
3V to 4.2V
V
OUT
12V @ 50mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0603 X5R Ceramic Capacitor 06036D225MAT AVX
C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX
L1 10µH, 450mA Inductor LQH32CN100K11 Murata
Figure 5. 3.3V
IN
to 4.2V
OUT
to 12V
OUT
@ 50mA
L1
10µH
C2
10µF
16V
R2
5k
R1
54.9k
MIC2290
VIN
V
IN
3V to 4.2V
V
OUT
15V @ 45mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0603 X5R Ceramic Capacitor 06036D225MAT AVX
C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX
L1 10µH, 450mA Inductor LQH32CN100K11 Murata
Figure 6. 3.3V
IN
to 4.2V
OUT
to 15V
OUT
@ 45mA
L1
10µH
C2
10µF
16V
R2
5k
R1
31.6k
MIC2290
VIN
V
IN
5V
V
OUT
9V @ 160mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0603 X5R Ceramic Capacitor 06036D225MAT AVX
C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX
L1 10µH, 450mA Inductor LQH32CN100K11 Murata
Figure 7. 5V
IN
to 9V
OUT
@ 160mA
L1
10µH
C2
10µF
16V
R2
5k
R1
43.2k
MIC2290
VIN
V
IN
5V
V
OUT
12V @ 110mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0603 X5R Ceramic Capacitor 06036D225MAT AVX
C2 10µF, 16V, 1206 X5R Ceramic Capacitor 1206YD106MAT AVX
L1 10µH, 450mA Inductor LQH32CN100K11 Murata
Figure 8. 5V
IN
to 12V
OUT
@ 110mA
Micrel, Inc. MIC2290
October 2007 11
M9999-101907
L1
10µH
C2
4.7µF
25V
R2
1k
R1
18.2k
MIC2290
VIN
V
IN
5V
V
OUT
24V @ 40mA
EN
SW
FB
GND
GND
OUT
GND
C1
2.2µF
6.3V
C1 2.2µF, 6.3V, 0603 X5R Ceramic Capacitor 06036D225MAT AVX
C2 4.7µF, 25V, 1206 X5R Ceramic Capacitor 12063D475MAT AVX
L1 10µH, 450mA Inductor LQH32CN100K11 Murata
Figure 9. 5V
IN
to 24V
OUT
@ 40mA
Micrel, Inc. MIC2290
October 2007 12
M9999-101907
Package Information
8-Pin 2mm x 2mm MLF
®
(ML)
Grey Shaded area indica tes Thermal Via. Size should be 0 .300mm in diameter and it should
be connec ted to GND for maximum thermal performance
Recommended L an d Pattern fo r (2mm x 2mm) 8-Pin MLF
®
Micrel, Inc. MIC2290
October 2007 13
M9999-101907
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
