MICREL MIC2288BML

MIC2288
Micrel, Inc.
MIC2288
1A 1.2MHz PWM Boost Converter in
×2 MLF™
Thin SOT-23 and 2×
General Description
Features
The MIC2288 is a 1.2MHz PWM, DC/DC boost switching
regulator available in low-profile Thin SOT-23 and
2mm × 2mm MLF™ package options. High power density is
achieved with the MIC2288’s internal 34V/1A switch, allowing it to power large loads in a tiny footprint.
The MIC2288 implements a constant frequency, 1.2MHz
PWM, current mode control scheme with internal compensation that offers excellent transient response and output regulation performance. The high frequency operation saves
board space by allowing small, low-profile, external components. The fixed frequency PWM topology also reduces
spurious switching noise and ripple to the input power source.
The MIC2288 is available in a low-profile Thin SOT-23-5
package and a 2mm × 2mm MLF™-8 leadless package. The
2mm × 2mm MLF™-8 package option has an output overvoltage protection feature.
The MIC2288 has a junction temperature range of –40°C to
+125°C.
All support documentation can be found on Micrel’s web
site at www.micrel.com.
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•
•
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•
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2.5V to 10V input voltage range
Output voltage adjustable to 34V
Over 1A switch current
1.2MHz PWM operation
Stable with ceramic capacitors
High-efficiency
<1% line and load regulation
Low input and output ripple
<1µA shutdown current
UVLO
Output overvoltage protection (MIC2288BML)
Over temperature shutdown
Thin SOT-23-5 package option
2mm × 2mm leadless MLF™-8 package option
–40°C to +125°C junction temperature range
Applications
•
•
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•
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Organic EL power supply
TFT-LCD bias supply
12V supply for DSL applications
Multi-output DC/DC converters
Positive and negative output regulators
SEPIC converters
Typical Application
L1
10µH
VIN
VOUT
15V
90
4
C1
2.2µF
SW
EN
FB
GND
EFFICIENCY (%)
1-Cell
Li Ion
VIN
VIN = 4.2V
85
MIC2288BD5
5
15VOUT Efficiency
1
R1
3
R2
C2
10µF
2
80
75
VIN = 3.2V
70
VIN = 3.6V
65
60
0
0.05
0.1
0.15
LOAD (A)
0.2
2mm × 2mm MLF™ Boost Regulator
MLF and MicroLeadFrame are 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
April 2005
1
M9999-042205
MIC2288
Micrel, Inc.
Ordering Information
Part Number
Marking
Code
Output
Voltage
Overvoltage
Protection
Junction
Temp. Range
Package
Lead Finish
MIC2288BD5
SHAA
Adjustable
–
–40°C to 125°C
Thin SOT-23-5
Standard
MIC2288YD5
SHAA
Adjustable
–
–40°C to 125°C
Thin SOT-23-5
Lead Free
MIC2288BML
SJA
Adjustable
34V
–40°C to 125°C
2×2 MLF™-8
Standard
MIC2288YML
SJA
Adjustable
34V
–40°C to 125°C
2×2 MLF™-8
Lead Free
Pin Configuration
FB GND SW
1
2
3
4
EN
5
VIN
TSOT-23-5 (D5)
OVP
1
8
PGND
VIN
2
7
SW
EN
3
6
FB
AGND
4
5
NC
EP
8-Pin MLF™ (ML)
(Top View)
Fused Lead Frame
Pin Description
Pin Number
TSOT-23-5
Pin Number
2×
×2 MLF™-8
Pin Name
1
7
SW
2
GND
Pin Function
Switch Node (Input): Internal power Bipolar collector.
Ground (Return): Ground.
3
6
FB
Feedback (Input): 1.24V output voltage sense node.
 R1

VOUT = 1.24V 1 +
R2 
4
3
EN
Enable (Input): Logic high enables regulator. Logic low shuts down regulator.
5
2
VIN
Supply (Input): 2.5V to 10V input voltage.
1
OVP
Output Overvoltage Protection (Input): Tie this pin to VOUT to clamp the
output voltage to 34V maximum in fault conditions. Tie this pin to ground if
OVP function is not required.
5
NC
4
AGND
Analog ground.
8
PGND
Power ground.
EP
GND
M9999-042205
No Connect: No internal connection to die.
Exposed backside pad.
2
April 2005
MIC2288
Micrel, Inc.
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) ..................................................... 12V
Switch Voltage (VSW) ..................................... –0.3V to 34V
Enable Pin Voltage (VEN) ................................... –0.3 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
Junction Temperature Range (TJ) ........... –40°C to +125°C
Package Thermal Impedance
2mm × 2mm MLF™-8 (θJA) ................................. 93°C/W
Thin SOT-23-5 (θJA) .......................................... 256°C/W
Electrical Characteristics(4)
TA = 25°C, VIN = VEN = 3.6V, VOUT = 10V, IOUT = 20mA, unless otherwise noted. Bold values indicate –40°C ≤ TJ ≤ ±125°C.
Symbol
Parameter
Condition
Min
VIN
Supply Voltage Range
2.5
VUVLO
Under Voltage Lockout
1.8
IVIN
Quiescent Current
VFB = 2V, (not switching)
0V(5)
Typ
Max
Units
10
V
2.1
2.4
V
2.8
5
mA
0.1
1
µA
1.24
1.252
1.265
V
V
ISD
Shutdown Current
VEN =
VFB
Feedback Voltage
(±1%)
(±2%) (Over Temp)
IFB
Feedback Input Current
VFB = 1.24V
Line Regulation
3V ≤ VIN ≤ 5V
0.1
Load Regulation
5mA ≤ IOUT ≤ 40mA
0.2
%
90
%
1.2
A
mV
1.227
1.215
–450
DMAX
Maximum Duty Cycle
85
ISW
Switch Current Limit
VSW
Switch Saturation Voltage
ISW = 1A
550
ISW
Switch Leakage Current
VEN = 0V, VSW = 10V
0.01
VEN
Enable Threshold
Turn on
Turn off
nA
1
5
µA
0.4
V
V
20
40
µA
1.05
1.2
1.35
MHz
30
32
34
V
1.5
IEN
Enable Pin Current
fSW
Oscillator Frequency
VOVP
Output Overvoltage Protection
MIC2288 MLF™ package option only
TJ
Overtemperature
Threshold Shutdown
Hysteresis
%
VEN = 10V
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. This device is not guaranteed to operate beyond its specified 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.
April 2005
3
M9999-042205
MIC2288
Micrel, Inc.
Typical Characteristics
83
81
79
VIN = 3.6V
VIN = 3.3V
77
75
0
1.8
25 50 75 100 125 150
OUTPUT CURRENT (mA)
12.1
12.05
12
11.95
11.9
11.8
0
Current Limit
vs. Supply Current
1.4
1.4
1.2
1
0.8
0.6
0.4
300
200
VIN = 3.6V
200 400 600 800 1000
SWITCH CURRENT (mA)
700
88
86
84
82
4
5.5
7
8.5
SUPPLY VOLTAGE (V)
10
1.22
1.20
1.18
1.16
1.14
1.12
1.10
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
300
400
300
200
VIN = 3.6V
I = 500mA
100
200
150
100
50
ISW = 500mA
0
2.5
1.4
SW
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
95
93
91
89
VIN = 3.6V
87
85
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
4
4
5.5
7
8.5
SUPPLY VOLTAGE (V)
10
Frequency
vs. Temperature
1.3
1.2
1.1
1.0
0.9
0.8
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Maximum Duty Cycle
vs. Temperature
97
Switch Saturation
vs. Supply Voltage
250
Switch Saturation
vs. Temperature
500
Feedback Voltage
vs. Temperature
1.26
1.24
600
99
92
90
M9999-042205
0.4
Maximum Duty Cycle
vs. Supply Voltage
96
94
80
2.5
0.6
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
SWITCH SATURATION VOLTAGE (mV)
Switch Saturation
vs. Current
400
100
98
0.8
10
500
0
0
Current Limit
vs. Temperature
1.0
MAXIMUM DUTY CYCLE (%)
SWITCH SATURATION VOLTAGE (mV)
MAXIMUM DUTY CYCLE (%)
4
5.5
7
8.5
SUPPLY VOLTAGE (V)
600
100
50 75 100 125 150
LOAD (mA)
0.2
0.2
700
25
1.2
CURRENT LIMIT (A)
CURRENT LIMIT (A)
1.6
0
2.5
VIN = 3.6V
11.85
FEEDBACK VOLTAGE (V)
85
12.15
1.30
1.28
SWITCH SATURATION VOLTAGE (mV)
VIN = 4.2V
87
Load Regulation
FREQUENCY (MHz)
EFFICIENCY (%)
89
12.2
700
FEEDBACK CURRENT (nA)
Efficiency at VOUT = 12V
OUTPUT VOLTAGE (V)
91
FB Pin Current
vs. Temperature
600
500
400
300
200
100
0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
April 2005
MIC2288
Micrel, Inc.
Function Characteristics
OUTPUT VOLTAGE
(1mV/div) AC-Coupled
Line Transient Response
Enable Voltage
3.6VIN
12VOUT
150mA Load
3.2V
12VOUT
150mA Load
Time (400µs/div)
Load Transient Response
Switching Waveforms
10mA
3.6VIN
12VOUT
COUT = 10µF
5
SWITCH SATURATION
(5V/div)
150mA
OUTPUT VOLTAGE
(50mV/div)
Time (400µs/div)
Time (400µs/div)
April 2005
4.2V
INPUT VOLTAGE
(2V/div)
Output Voltage
INDUCTOR CURRENT
(500mA/div)
LOAD CURRENT
OUTPUT VOLTAGE
(100mA/div)
(100mV/div) AC-Coupled
ENABLE VOLTAGE
(2V/div)
OUTPUT VOLTAGE
(5V/div)
Enable Characteristics
Output Voltage
Inductor Current
(10µH)
VSW
3.6VIN
12VOUT
150mA
Time (400ns/div)
M9999-042205
MIC2288
Micrel, Inc.
Functional Diagram
VIN
FB
OVP*
EN
OVP*
SW
PWM
Generator
gm
VREF
1.24V
Σ
1.2MHz
Oscillator
Ramp
Generator
CA
GND
*OVP available on MLFTM package option only.
Figure 1. MIC2288 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 MIC2288 is a constant frequency, PWM current mode
boost regulator. The block diagram is shown in Figure 1. The
MIC2288 is composed of an oscillator, slope compensation
ramp generator, current amplifier, gm error amplifier, PWM
generator, and a 1A 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.
M9999-042205
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April 2005
MIC2288
Micrel, Inc.
Applications Information
Component Selection
DC-to-DC PWM Boost Conversion
The MIC2288 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
external Schottky diode (D1). Voltage regulation is achieved
by modulating the pulse width or pulse-width modulation
(PWM).
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.
Larger inductance values reduce the peak-to-peak ripple
current, affecting efficiency. This has the 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 MIC2288 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:
L1
10µH
VIN
D1
VOUT
MIC2288BML
VIN
C1
2.2µF
SW
OVP
EN
C2
10µF
FB
GND
GND
R1
R2
GND
Figure 2. Typical Application Circuit
Frhpz =
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
VOUT × L × IOUT × 2π
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 MIC2288. 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.
VIN
VOUT
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 disconnected from the circuit or the feedback pin is shorted to
ground, the feedback pin will fall to ground potential. This will
cause the MIC2288 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 MIC2288 OVP pin will shut the
switch off when an overvoltage condition is detected, saving
itself and other sensitive circuitry downstream.
April 2005
VIN
Output Voltage
Recomended Output Capacitance
<6V
22µF
<16V
10µF
<34V
4.7µF
Table 1. Output Capacitor Selection
Diode Selection
The MIC2288 requires an external diode for operation. A
Schottky diode is recommended for most applications due to
their lower forward voltage drop and reverse recovery time.
Ensure the diode selected can deliver the peak inductor
current and the maximum reverse voltage is rated greater
than the output voltage.
7
M9999-042205
MIC2288
Micrel, Inc.
Input capacitor
A minimum 1µF ceramic capacitor is recommended for
designing with the MIC2288. 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 MIC2288, with short traces for good
noise performance.
Feedback Resistors
The MIC2288 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.
M9999-042205
8
April 2005
MIC2288
Micrel, Inc.
Application Circuits
L1
4.7µH
VIN
3V to 4.2V
L1
10µH
VIN
3V to 4.2V
VOUT
5V @ 400mA
D1
MIC2288BML
MIC2288BML
C1
4.7µF
6.3V
R1
5.62k
SW
VIN
FB
R2
1.87k
GND
GND
R1
54.9k
SW
VIN
C1
2.2µF
10V
C2
22µF
6.3V
OVP
EN
VOUT
15V @ 100mA
D1
EN
FB
R2
5k
GND
GND
GND
C2
10µF
16V
OVP
GND
C1
4.7µF, 6.3V, 0805 X5R Ceramic Capacitor
08056D475MAT
AVX
C1
2.2µF, 10V, 0805 X5R Ceramic Capacitor
08052D225KAT
AVX
C2
22µF, 6.3V, 0805 X5R Ceramic Capacitor
12066D226MAT
AVX
C2
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
L1
4.7µH, 650mA Inductor
LQH32CN4R7M11 Murata
L1
10µH, 650mA Inductor
LQH43CN100K03
Murata
Figure 6. 3.3VIN – 4.2VIN to 15VOUT @ 100mA
Figure 3. 3.3VIN to 5VOUT @ 400mA
L1
10µH
VIN
3V to 4.2V
L1
10µH
VIN
3V to 4.2V
VOUT
9V @ 180mA
D1
MIC2288BML
MIC2288BML
C1
2.2µF
10V
VIN
R1
31.6k
SW
FB
GND
C1
2.2µF, 10V, 0805 X5R Ceramic Capacitor
GND
08052D225KAT
AVX
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
10µH, 650mA Inductor
LQH43CN100K03
Murata
L1
10µH
FB
R2
1k
GND
2.2µF, 10V, 0805 X5R Ceramic Capacitor
08052D225KAT
AVX
C2
4.7µF, 25V, 1206 X5R Ceramic Capacitor
12063D475MAT
AVX
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
L1
10µH, 650mA Inductor
LQH43CN100K03
Murata
Figure 7. 3.3VIN – 4.2VIN to 24VOUT @ 50mA
L1
10µH
VIN
5V
VOUT
12V @ 100mA
D1
EN
C1
Figure 4. 3.3VIN – 4.2VIN to 9VOUT @ 180mA
VIN
3V to 4.2V
C2
4.7µF
25V
OVP
GND
C2
L1
R1
18.2k
SW
GND
R2
5k
GND
VIN
C1
2.2µF
10V
C2
10µF
16V
OVP
EN
VOUT
24V @ 50mA
D1
VOUT
9V @ 330mA
D1
MIC2288BML
MIC2288BML
C1
2.2µF
10V
VIN
SW
R1
42.3k
C2
10µF
16V
OVP
EN
FB
GND
GND
C1
2.2µF
10V
VIN
SW
OVP
EN
FB
GND
R2
5k
R1
31.6k
GND
R2
5k
C2
10µF
16V
GND
GND
C1
2.2µF, 10V, 0805 X5R Ceramic Capacitor
08052D225KAT
AVX
C1
2.2µF, 10V, 0805 X5R Ceramic Capacitor
08052D225KAT
AVX
C2
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
C2
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
L1
10µH, 650mA Inductor
LQH43CN100K03
Murata
L1
10µH, 650mA Inductor
LQH43CN100K03
Murata
Figure 8. 5VIN to 9VOUT @ 330mA
Figure 5. 3.3VIN – 4.2VIN to 12VOUT @ 100mA
April 2005
9
M9999-042205
MIC2288
Micrel, Inc.
L1
10µH
VIN
5V
L1
10µH
VIN
5V
VOUT
12V @ 250mA
D1
MIC2288BML
MIC2288BML
C1
2.2µF
10V
VIN
SW
R1
43.2k
OVP
EN
FB
GND
GND
VOUT
24V @ 80mA
D1
R2
5k
C1
2.2µF
10V
C2
10µF
16V
VIN
SW
OVP
EN
FB
GND
GND
GND
R1
18.2k
R2
1k
C2
4.7µF
25V
GND
C1
2.2µF, 10V, 0805 X5R Ceramic Capacitor
08052D225KAT
AVX
C1
2.2µF, 10V, 0805 X5R Ceramic Capacitor
08052D225KAT
AVX
C2
10µF, 16V, 1206 X5R Ceramic Capacitor
1206YD106MAT
AVX
C2
4.7µF, 25V, 1206 X5R Ceramic Capacitor
12066D475MAT
AVX
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
D1
1A, 40V Schotty Diode
MBRM140T3
ON Semi.
L1
10µH, 650mA Inductor
LQH43CN100K03
Murata
L1
10µH, 650mA Inductor
LQH32CN4R7M11 Murata
Figure 10. 5VIN to 24VOUT @ 80mA
Figure 9. 5VIN to 12VOUT @ 250mA
M9999-042205
10
April 2005
MIC2288
Micrel, Inc.
Package Information
All Dimensions are in millimeters
5-Pin TSOT (D5)
8-Pin MLF™ (ML)
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
This 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.
April 2005
11
M9999-042205