MICREL MIC2290YML

MIC2290
2mm × 2mm PWM Boost Regulator
with Internal Schotty Diode
General Description
Features
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.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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
VOUT
12V
L1
10µH
Li Ion
Battery
3
C1
1µF
VIN
EN
SW
OUT
GND
FB
4, 8
VIN = 4.2V
80
MIC2290
2
12VOUT Efficiency
85
7
R1
1
C2
10µF
6
R2
EFFICIENCY (%)
VIN
VIN = 3.2V
75
VIN = 3.6V
70
65
60
0
0.02 0.04 0.06 0.08
LOAD CURRENT (A)
0.1
Simple 12V Boost Regulator
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
Micrel, Inc.
MIC2290
Ordering Information
Part Number
Marking
Code
Output
Voltage
Overvoltage
Protection
Junction
Temp. Range
Package
MIC2290BML
SRC
Adj.
34V
–40° to +125°C
8-Pin 2x2 MLF®
–40° to +125°C
®
MIC2290YML
SRC
Adj.
34V
8-Pin 2x2 MLF
Lead Finish
Standard
Pb-Free
Pin Configuration
OUT
1
8
PGND
VIN
2
7
SW
EN
3
6
FB
AGND
4
5
NC
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
5
NC
No connect (no internal connection to die).
6
FB
Feedback (Input): Output voltage sense node. Connect feedback resistor
Analog ground.
⎛
network to this pin. VOUT = 1.24V ⎜1 +
⎝
7
SW
8
PGND
EP
GND
October 2007
R1 ⎞
⎟.
R2 ⎠
Switch node (Input): Internal power Bipolar collector.
Power ground.
Ground (Return): Exposed backside pad.
2
M9999-101907
Micrel, Inc.
MIC2290
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) .......................................................12V
Switch Voltage (VSW)....................................... –0.3V to 34V
Enable Pin Voltage (VEN)................................... –0.3V to VIN
FB Voltage (VFB)...............................................................6V
Switch Current (ISW) .........................................................2A
Storage Temperature (Ts) .........................–65°C to +150°C
ESD Rating(3) .................................................................. 2kV
Supply Voltage (VIN).......................................... 2.5V to 10V
Ambient Temperature (TJ)......................... –40°C to +125°C
Package Thermal Resistance
2x2 MLF-8 (θJA) .................................................93°C/W
Electrical Characteristics(4)
TA = 25°C, VIN = VEN = 3.6V, VOUT = 15V, IOUT = 40mA, unless otherwise noted. Bold values indicate –40°C ≤ TJ ≤ ±125°C.
Symbol
Parameter
VIN
Supply Voltage Range
VUVLO
Undervoltage Lockout
2.1
2.4
V
IVIN
Quiescent Current
VFB = 2V, (not switching)
2.5
5
mA
ISD
Shutdown Current
VEN = 0V, Note 5
0.2
1
µA
VFB
Feedback Voltage
(±1%)
(±2%) (Over Temp)
1.24
1.252
1.265
V
V
IFB
Feedback Input Current
VFB = 1.24V
Line Regulation
3V ≤ VIN ≤ 5V
Load Regulation
5mA ≤ IOUT ≤ 20mA
DMAX
Maximum Duty Cycle
ISW
Switch Current Limit
Condition
Min
Typ
2.5
1.8
1.227
1.215
0.1
85
A
450
0.01
VEN
Enable Threshold
Turn on
Turn off
1.05
ID = 150mA
IRD
Schottky Leakage Current
VR = 30V
VOVP
Overvoltage Protection
(nominal voltage)
TJ
Overtemperature
Threshold Shutdown
Hysteresis
mV
5
µA
0.4
V
V
20
40
µA
1.2
1.35
MHz
0.8
1
V
4
µA
32
34
V
1.5
VEN = 10V
30
%
0.75
ISW = 0.5A
Schottky Forward Drop
1
%
VEN = 0V, VSW = 10V
VD
nA
%
Switch Saturation Voltage
Oscillator Frequency
V
90
Switch Leakage Current
fSW
10
0.2
ISW
Enable Pin Current
Units
–450
VSW
IEN
Max
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, TJ(max), the
junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. 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. ISD = IVIN.
October 2007
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Micrel, Inc.
MIC2290
Typical Characteristics
90
Efficiency at VOUT = 12V
EFFICIENCY (%)
85
VIN = 4.2V
80
75
70 VIN = 3.6V
65
VIN = 3.3V
60
55
50
0
0.9
25
50
75
100
OUTPUT CURRENT (mA)
Current Limit
vs. Supply Voltage
CURRENT LIMIT (A)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
10
700
Switch Saturation Voltage
vs. Temperature
400
300
100
MAXIMUM DUTY CYCLE (%)
VIN = 3.6V
ISW = 500mA
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
95
93
91
87
1.30
1.25
1.20
1.15
1.10
1.05
1.00
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Maximum Duty Cycle
vs. Temperature
97
89
FREQUENCY (MHz)
500
200
Frequency
vs. Temperature
1.35
600
99
VIN = 3.6V
85
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
October 2007
1.40
4
700
FEEDBACK CURRENT (nA)
4
5.5
7
8.5
SUPPLY VOLTAGE (V)
SWITCH SATURATION VOLTAGE (mV)
0
2.5
FB Pin Current
vs. Temperature
600
500
400
300
200
100
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
M9999-101907
Micrel, Inc.
MIC2290
Typical Characteristics (continued)
October 2007
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Micrel, Inc.
MIC2290
Functional Characteristics
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Micrel, Inc.
MIC2290
Functional Diagram
VIN
FB
OUT
EN
OVP
SW
PWM
Generator
gm
VREF
1.24V
S
1.2MHz
Oscillator
Ramp
Generator
CA
GND
Figure 1. MIC2290 Block Diagram
The gm 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 gm 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.
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,
gm 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.
October 2007
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Micrel, Inc.
MIC2290
when an overvoltage condition is detected, saving itself
and other sensitive circuitry downstream.
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
V IN
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:
VOUT
MIC2290
VIN
C1
2.2µF
SW
OUT
EN
C2
10µF
FB
GND
GND
R1
R2
GND
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:
D = 1−
2
VIN
VOUT
Frhpz =
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).
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.
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.
Overvoltage Protection
For the MLF® package option, there is an overvoltage
protection function. If the feedback resistors are disconnected 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
October 2007
VOUT
VIN
× L × IOUT × 2π
Output Voltage
<6V
<16V
<34V
Recommended Output Capacitance
22µF
10µF
4.7µF
Table 1. Output Capacitor Selection
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M9999-101907
Micrel, Inc.
MIC2290
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:
⎛ R1 ⎞
VOUT = VREF × ⎜
+ 1⎟
⎝ R2
⎠
where VREF is equal to 1.24V.
October 2007
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Micrel, Inc.
MIC2290
Application Circuits
L1
4.7µH
V IN
3.3V
C1
2.2µF
6.3V
SW
R1
15k
FB
GND
VIN
SW
EN
C2
10µF
16V
FB
GND
GND
R1
54.9k
OUT
GND
R2
5k
GND
C1
2.2µF
6.3V
C2
10µF
6.3V
OUT
EN
VOUT
15V @ 45mA
MIC2290
MIC2290
VIN
L1
10µH
VIN
3V to 4.2V
VOUT
5V @ 180mA
R2
5k
GND
C1
2.2µF, 6.3V, 0805 X5R Ceramic Capacitor
08056D475MAT
AVX
C1
2.2µF, 6.3V, 0603 X5R Ceramic Capacitor
06036D225MAT
AVX
C2
L1
10µF, 6.3V, 0805 X5R Ceramic Capacitor
4.7µH, 450mA Inductor
08056D106MAT
LQH32CN4R7N11
AVX
Murata
C2
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
L1
10µH, 450mA Inductor
LQH32CN100K11
Murata
Figure 6. 3.3VIN to 4.2VOUT to 15VOUT @ 45mA
Figure 3. 3.3VIN to 5VOUT @ 180mA
L1
10µH
VIN
3V to 4.2V
C1
2.2µF
6.3V
SW
R1
31.6k
OUT
EN
FB
GND
C1
2.2µF
6.3V
C2
10µF
16V
SW
VIN
EN
C2
10µF
16V
FB
R2
5k
GND
GND
R1
31.6k
OUT
GND
R2
5k
GND
VOUT
9V @ 160mA
MIC2290
MIC2290
VIN
L1
10µH
V IN
5V
VOUT
9V @ 80mA
GND
C1
2.2µF, 6.3V, 0603 X5R Ceramic Capacitor
06036D225MAT
AVX
C2
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
C1
C2
2.2µF, 6.3V, 0603 X5R Ceramic Capacitor
10µF, 16V, 1206 X5R Ceramic Capacitor
06036D225MAT
1206YD106MAT
AVX
AVX
L1
10µH, 450mA Inductor
LQH32CN100K11
Murata
L1
10µH, 450mA Inductor
LQH32CN100K11
Murata
Figure 7. 5VIN to 9VOUT @ 160mA
Figure 4. 3.3VIN to 4.2VOUT to 9VOUT @ 80mA
L1
10µH
VIN
3V to 4.2V
C1
2.2µF
6.3V
SW
R1
43.2k
OUT
EN
FB
GND
GND
VOUT
12V @ 110mA
MIC2290
MIC2290
VIN
L1
10µH
V IN
5V
VOUT
12V @ 50mA
R2
5k
C2
10µF
16V
C1
2.2µF
6.3V
VIN
SW
OUT
EN
FB
GND
GND
R1
43.2k
GND
R2
5k
C2
10µF
16V
GND
C1
C2
2.2µF, 6.3V, 0603 X5R Ceramic Capacitor
10µF, 16V, 1206 X5R Ceramic Capacitor
06036D225MAT
1206YD106MAT
AVX
AVX
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
L1
10µH, 450mA Inductor
LQH32CN100K11
Murata
Figure 5. 3.3VIN to 4.2VOUT to 12VOUT @ 50mA
October 2007
Figure 8. 5VIN to 12VOUT @ 110mA
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M9999-101907
Micrel, Inc.
MIC2290
L1
10µH
V IN
5V
VOUT
24V @ 40mA
MIC2290
VIN
C1
2.2µF
6.3V
SW
R1
18.2k
C2
4.7µF
25V
OUT
EN
FB
GND
GND
R2
1k
GND
C1
2.2µF, 6.3V, 0603 X5R Ceramic Capacitor
06036D225MAT
C2
4.7µF, 25V, 1206 X5R Ceramic Capacitor
12063D475MAT
AVX
AVX
L1
10µH, 450mA Inductor
LQH32CN100K11
Murata
Figure 9. 5VIN to 24VOUT @ 40mA
October 2007
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M9999-101907
Micrel, Inc.
MIC2290
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 connected to GND for maximum thermal performance
Recommended Land Pattern for (2mm x 2mm) 8-Pin MLF®
October 2007
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M9999-101907
Micrel, Inc.
MIC2290
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.
October 2007
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M9999-101907