July 2004

M9999-072204

(408) 955-1690

MLF and

Micro

LeadFrame is a trademark of Amkor Technology

MIC2295

High Power Density 1.2A Boost Regulator

General Description

The MIC2295 is a 1.2Mhz, PWM dc/dc boost
switching regulator available in low profile Thin
SOT23 and 2mm x 2mm MLF package options.
High power density is achieved with the MIC2295's
internal 34V / 1.2A switch, allowing it to power large
loads in a tiny footprint.

The MIC2295 implements constant frequency
1.2MHz PWM current mode control. The MIC2295
offers 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 scheme also
reduces spurious switching noise and ripple to the
input power source.

The MIC2295 is available in a low-profile Thin
SOT23 5-lead package and a 2mm x2mm 8-lead
MLF leadless package. The 2mm x 2mm MLF
package option has an output over-voltage
protection feature.

The MIC2295 has an operating junction temperature
range of 40°C to +125°C

Features

2.5V to 10V input voltage range

Output voltage adjustable to 34V

1.2A switch current

1.2MHz PWM operation

Stable with small size ceramic capacitors

High efficiency

Low input and output ripple

<1mA shutdown current

UVLO

Output over-voltage protection (MIC2295BML)

Over temperature shutdown

Thin SOT23-5 package option

2mm x 2mm leadless 8-lead MLF package
option

C to +125

C junction temperature range

Applications

Organic EL power supplies

3.3V to 5V/500mA conversion

TFT-LCD bias supplies

Flash LED drivers

Positive and negative output regulators

SEPIC converters

Positive to negative Cuk converters

12V supply for DSL applications

Multi-output dc/dc converters

µH

R2
9.01K

R1
100k

MIC2295BML

VIN

1-Cell
Li Ion
3V to 4.2V

OUT

15V/100mA

AGND

C1
2.2

µF

2.2

µF

PGND

OVP

µH

R2
3.3k

R1
10k

MIC2295 BD5

VIN

1-Cell
Li Ion

OUT

5V/500mA

GND

C1
2.2

µF

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

Ordering Information

Part Number

Output Over

Voltage

Protection

Marking Code

Junction

Temperature

Range

Package

Standard

Lead-Free

Standard

Lead-Free

MIC2295BD5

MIC2295YD5

SVAA

-40°C to 125°C

Thin SOT23-

MIC2295BML

MIC2295YML

34V

SXA

-40°C to 125°C

2mm x2mm

MLF-8L

Pin Configuration

Pin Description

MIC2295BD5

Thin SOT-23-5

MIC2295BML

2x2 MLF-8L

Pin Name

Pin Function

Switch Node (Input): Internal power BIPOLAR collector.

GND

Ground (Return): Ground.

Feedback (Input): 1.24V output voltage sense node.
V

OUT

= 1.24V ( 1 + R1/R2)

Enable (Input): Logic high enables regulator. Logic low
shuts down regulator.

VIN

Supply (Input): 2.5V to 10V input voltage.

OVP

Output Over-Voltage Protection (Input): Tie this pin to
V

OUT

to clamp the output voltage to 34V maximum in fault

conditions. Tie this pin to ground if OVP function is not
required.

N/C

No connect. No internal connection to die.

AGND

Analog ground

PGND

Power ground

GND

Ground (Return). Exposed backside pad.

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

Absolute Maximum Rating

(1)

Supply voltage (V

) .............................

12V

Switch voltage (V

) ........................

-0.3V to 34V

Enable pin voltage (V

) ..........................

-0.3 to V

FB Voltage
(V

)..................................................6V

Switch Current (I

) .......................................

2.5A

Ambient Storage Temperature (T

) .... -65°C to +150°C

ESD Rating

(3)

................................. ........2KV

Operating Range

(2)

Supply Voltage (V

) .............................

2.5V to 10V

Junction Temperature Range (T

) ...... -40°C to +125°C

Package Thermal Impedance

2x2 MLF-8L lead ........................

93°C/W

ThinSOT23-5 lead ........................ 256°C/W

Electrical Characteristics

=25

C, V

= 3.6V, V

OUT

= 15V, I

OUT

= 40mA, unless otherwise noted. Bold values

indicate -40°C T

125°C.

Symbol

Parameter

Condition

Min

Typ

Max

Units

Supply Voltage Range

2.5

UVLO

Under-Voltage Lockout

1.8

2.1

2.4

VIN

Quiescent Current

= 2V (not switching)

2.8

Shutdown Current

= 0V

(4)

0.1

Feedback Voltage

(+/-1%)

1.227

1.24

1.252

(+/-2%) (Over Temp)

1.215

1.265

Feedback Input Current

= 1.24V

-450

Line Regulation

3V V

0.04

Load Regulation

5mA I

OUT

40mA

1.5

MAX

Maximum Duty Cycle

Switch Current Limit

Note 5

1.2

1.7

Switch Saturation Voltage

= 1.2A

600

Switch Leakage Current

= 0V, V

= 10V

0.01

Enable Threshold

TURN ON
TURN OFF

1.5

0.4

Enable Pin Current

= 10V

Oscillator Frequency

1.05

1.2

1.35

MHz

OVP

Output over-voltage protection

MIC2295BML only

150

°C

Over-Temperature Threshold
Shutdown

Hysteresis

°C

Notes:

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,

, and the ambient temperature, T

. The maximum

allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.

This device is not guaranteed to operate beyond its specified operating rating.

IC devices are inherently ESD sensitive. Handling precautions required. Human body model rating: 1.5K in series with 100pF.

4. I

= I

VIN

Guaranteed by design.

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

Typical Characteristics

MIC2295 -5V Output

100

200

300

Output Current

Efficiency

Vin=4V

Vin=5V

Vin=5.5V

VIN

GND

MIC2295BML

OUT

= -5V @ 0.15A

4.7uF/

6.3V

CMHSH5-2L

10K

2.49K

1 F/
6.3V

= 5V

1uF/16V

L1 = Murata LQH32CN4R7M23
L2 = Murata LQH32CN4R7M23

1uF/
6.3V

10K

MIC6211

OVP

15V Short circuit

protected Boost

100

OUTPUT CURRENT (mA)

EFFICIENCY (%)

Vin=2.5

Vin=3V

VIN

GND

MIC2295

1-Cell
Li Ion

OUT

= 15V / 50mA

4.7µH

4.7µF/

25V

Sumida

CDRH4D18

160K

10K

10µF/

6.3V

= JMK212BJ106MG (Taiyo Yuden)

0.1uF/

6.3V

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

MIC2295 SEPIC 5V Output

100

150

200

250

OUTPUT CURRENT (mA)

EFFICIENCY (%)

Vin=3V
Vin=3.5V
Vin=4V
Vin=5V
Vin=5.5V

VIN

GND

MIC2295BML

OUT

= 5V @ 0.3A

4.7uH

4.7uF/

6.3V

MBRX140

43.2K

14.3K

6.3V

= 3.3V to 5.5V

4.7uH

1uF/16V

L1 = Murata LQH32CN4R7M23
L2 = Murata LQH32CN4R7M23

470pF/

10V

5V MIC2295 SEPIC with one

coupled inductor

100

150

200

250

300

LOAD CURRENT (mA)

EFICIENCY (%)

Vin=2.5

Vin=3.3

Vin=5V

VI N

G N D

M IC2 2 9 5BM L

OUT

= 5 V @ 0 .3 A

4 .7 uH

4 .7 uF/

6.3 V

M BRX1 4 0

4 3.2 K

1 4.3 K

4.
4.7 µF/

6 .3V

I N

= 3 .3 V to 5.5 V

4.7 uH

C 2

1 uF/1 6V

L 1 = Sum ida CLS

5 D1 1/HP

4 7 0pF/

1 0V

MIC2295 12V output Efficiency

100

150

200

OUTPUT CURRENT (mA)

EFFICIENCY (%)

Vin=3.3V
Vin=4.2V
Vin=3.6V

Max Duty Cycle vs Input Voltage

100

2.5

5.5

8.5

SUPPLY VOLTAGE (V)

DUTY CYCLE

Input Voltage

vs. Supply Voltage

0.5

0.7

0.9

1.1

1.3

1.5

2.5

5.5

8.5

SUPPLY VOLTAGE (V)

FREQUENCY (MHz)

Switch Voltage

vs. Supply Voltage

100

150

200

250

300

2.5

4.5

6.5

8.5

Input Voltage (V)

Switch Voltage (mV)

MIC2295 15V output Efficiency

100

150

200

OUTPUT CURRENT (mA)

EFFICIENCY (%)

Vin=3.3V

Vin=4V

Vin=4.2V

1.10

1.12

1.14

1.16

1.18

1.20

1.22

1.24

1.26

1.28

1.30

-40 -20 0

20 40 60 80 100 120

FEEDBACK VOLTAGE (V)

TEMPERATURE (°C)

Feedback Voltage

vs. Temperature

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

Functional Description

The MIC2295 is a high power density, PWM dc/dc
boost regulator. The block diagram is shown in
Figure 1. The MIC2295 is composed of an oscillator,
slope compensation ramp generator, current
amplifier, gm error amplifier, PWM generator, and a
1.2A 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

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

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 constant frequency
current-mode PWM control

GND

PWM

Generator

Ramp

Generator

1.2MHz

Oscillator

OVP*

VIN

1.24V

OVP available on MLF

package option only.

OVP*

REF

MIC2295

MIC2295 Block Diargam

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

Application Information

DC to DC PWM Boost Conversion
The MIC2295 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.

10uH

1A/40V

Schottky

10uF

Vin

Gnd

Vout

MIC2288BML

Gnd

VIN

GND

Figure 2. Typical Application

OVP

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 Schottkey diode (D1). Voltage
regulation is achieved my modulating the pulse
width or pulse width modulation (PWM).

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

OUT

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.

Over Voltage Protection

For MLF package of MIC2295, there is an over
voltage 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 MIC2295 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 MIC2295 OVP pin will shut the switch
off when an over-voltage 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 10uH is the recommended inductor
value. It is usually a good balance between these
considerations. Efficiency is affected by inductance
value in that larger inductance values reduce the
peak to peak ripple current. This has an effect of
reducing both the DC losses and the transition
losses.
There is also a secondary effect of an inductors 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 MIC2295 operating current)
is passed through the inductor, higher DCR
inductors will reduce efficiency.
Also, 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;

Frhpz =

OUT

L I

OUT

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

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

or X7R dielectric ceramic capacitors are
recommended for designs with the MIC2295. 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

10µF

<16V

4.7µF

<34V

2.2µF

Diode Selection

The MIC2295 requires an external diode for
operation. A Schottkey 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.

Input Capacitor

A minimum 1uF ceramic capacitor is recommended
for designing with the MIC2295. 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 MIC2295, with short traces for good noise
performance.

Feedback Resistors

The MIC2295 utilizes a feedback pin to compare the
output to an internal reference. The output voltage is
adjusted by selecting the appropriate feedback
resistor values. The desired output voltage can be
calculated as follows;

OUT

= V

REF

+ 1

Where Vref is equal to 1.24V.

Duty-Cycle

The MIC2295 is a general-purpose step up DC-DC
converter. The maximum difference between the
input voltage and the output voltage is limited by the
maximum duty-cycle (D

max

) of the converter. In the

case of MIC2295, D

MAX

= 85%. The actual duty

cycle for a given application can be calculated as
follows:

D = 1

OUT

The actual duty-cycle, D, cannot surpass the
maximum rated duty-cycle, D

max

Output Voltage Setting

The following equation can be used to select the
feedback resistors R1 and R2 (see figure 1).

= R

OUT

1.24V

A high value of R2 can increase the whole system
efficiency, but the feedback pin input current (I

) of

the gm operation amplifier will affect the output
voltage. An R2 value of xx KW is suitable for most
applications
Inductor Selection
In MIC2295, the switch current limit is 1.2A. The
selected inductor should handle at least 1.2A current
without saturating. The inductor should have a low
DC resistor to minimize power losses. The inductor's
value can be 4.7uH to 10uH for most applications.
Capacitor Selection
Multi-layer ceramic capacitors are the best choice for
input and output capacitors. They offer extremely
low ESR, allowing very low ripple, and are available
in very small, cost effective packages. X5R
dielectrics are preferred. A 4.7uF to 10uF output
capacitor is suitable for most applications.
Diode Selection
For maximum efficiency, Schottky diode is
recommended for use with MIC2295. An optimal
component selection can be made by choosing the
appropriate reverse blocking voltage rating and the
average forward current rating for a given
application. For the case of maximum output voltage
(34V) and maximum output current capability, a 40V
/ 1A Schottky diode should be used.
Open-Circuit Protection
For MLF package option of MIC2295, there is an
output over-voltage protection function that clamps
the output to below 34V in fault conditions. Possible
fault conditions may include: if the device is
configured in a constant current mode of operation
and the load opens, or if in the standard application
the feedback resistors are disconnected from the
circuit. In these cases the FB pin will pull to ground,
causing the MIC2295 to switch with a high duty-
cycle. As a result, the output voltage will climb out of
regulation, causing the SW pin to exceed its
maximum voltage rating and possibly damaging the
IC and the external components. To ensure the
highest level of safety, the MIC2295 has a dedicated
pin, OVP, to monitor and clamp the output voltage in
over-voltage conditions. The OVP function is
offered in the 2mm x 2mm MLF-8L package option
only. To disable OVP function, tie the OVP pin to
ground

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

3.3V

to 5V

OUT

@ 400mA

µH

4.7µF

16V

R2
5k

R1
31.6k

MIC2295BML

VIN

3V to 4.2V

OUT

9V @ 180mA

GND

OVP

GND

2.2

µF

10V

- 4.2V

to 9V

OUT

@ 180mA

µH

4.7µF

16V

R2
5k

R1
43.2k

MIC2295BML

VIN

3V to 4.2V

OUT

12V @ 120mA

GND

OVP

GND

2.2

µF

10V

- 4.2Vin to 12V

OUT

@ 120mA

µH

4.7µF

16V

R2
5k

R1
43.2k

MIC2295BML

VIN

3V to 5V

OUT

12V @ 120mA

GND

OVP

GND

2.2

µF

10V

 5V

to 12V

OUT

@ 120mA

µH

2.2µF

16V

R2
5k

R1
43.2k

MIC2295BML

VIN

3V to 5V

OUT

12V @ 120mA

GND

OVP

GND

2.2

µF

10V

 5V

to 12V

OUT

@ 120mA

4.7

µH

4.7µF

16V

R2
1.87k

5.62k

MIC2295BML

VIN

3V to 4.2V

OUT

5V @ 400mA

GND

OVP

GND

4.7

µF

6.3V

470 pF

- 4.2V

to 5V

OUT

@ 400mA

µH

4.7µF

16V

R2
5k

R1
43.2k

MIC2295BML

VIN

3V to 5V

OUT

12V @300mA

GND

OVP

GND

2.2

µF

10V

to 5V

to 12V

OUT

@ 300mA

µH

2.2µF

25V

R2
5k

R1
43.2k

MIC2295BML

VIN

OUT

24V@80mA

GND

OVP

GND

2.2

µF

10V

to 24V

OUT

@ 80mA

Micrel

MIC2295

July 2004

M9999-052402

(408) 955-1690

MICREL, INC. 1849 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.

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