MIC2296
High Power Density 1.2A
Boost Regulator
MLF and MicroLeadFrame is a trademark of Amkor Technology
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
M9999-042005
(408) 955-1690
General Description
The MIC2296 is a 600kHz, PWM dc/dc boost switching
regulator available in a 2mm x 2mm MLF™ package
option. High power density is achieved with the MIC2296’s
internal 34V / 1.2A switch, allowing it to power large loads
in a tiny footprint. The MIC2296 is a version of the
MIC2295 1.2MHz, PWM dc/dc boost switching regulator,
that offers improved efficiency resulting from 600kHz
operation.
The MIC2296 implements constant frequency 600kHz
PWM current mode control. The MIC2296 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 MIC2296 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 MIC2296 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
• 600kHz PWM operation
• Stable with small size ceramic capacitors
• High efficiency
• Low input and output ripple
• <1µA shutdown current
• UVLO
• Output over-voltage protection (MIC2296BML)
• Over temperature shutdown
• 2mm x 2mm leadless 8-lead MLF™ package option
• –40
o
C to +125
o
C junction temperature range
Applications
• Organic EL power supplies
• 3.3V to 5V/500mA conversion
• TFT-LCD bias supplies
• Positive and negative output regulators
• SEPIC converters
• Positive to negative Cuk converters
• 12V supply for DSL applications
• Multi-output dc/dc converters
10µH
R2
901
R1
10k
MIC2296BML
VIN
V
IN
1-Cell
Li Ion
3V to 4.2V
V
OUT
15V/100mA
EN FB
AGND
C1
2.2µF
2.2µF
PGND
SW
OVP
L1
10µH
R2
3.3k
R1
10k
MIC2296 BD5
VIN
1-Cell
Li Ion
V
OUT
5V/400mA
EN
SW
FB
GND
V
IN
C1
2.2µF
10µF
1000 pF
Micrel, Inc. MIC2296
April 2005
2 M9999-042005
(408) 955-1690
Ordering Information
Part Number Marking Code
Standard Lead-Free
Output Over
Voltage Protection Standard Lead-Free
Junction Temperature
Range Package
MIC2296BML MIC2296YML 34V WDA WDA -40°C to 125°C 2mm x2mm
MLF-8L
MIC2296BD5* MIC2296YD5* - WDAA WDAA -40°C to 125°C Thin SOT-23-5
* Contact factory for availability.
Pin Configur ation
FB GND
EN VIN
SW
31
5
2
4
TSOT-23-5 (BD5)
1OVP
VIN
EN
A
GND
8 PGND
SW
FB
NC
7
6
5
2
3
4EP
8-pin MLF™ (BML)
Pin Description
MIC2296BD5
Thin SOT-23-5 MIC2296BML
2x2 MLF-8L Pin Name Pin Function
— 1 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.
5 2 VIN Supply (Input): 2.5V to 10V input voltage.
4 3 EN
Enable (Input): Logic high enables regulator. Logic low shuts down
regulator.
— 4 AGND Analog ground
— 5 N/C No connect. No internal connection to die.
3 6 FB
Feedback (Input): 1.24V output voltage sense node. V
OUT
= 1.24V ( 1 +
R1/R2)
1 7 SW Switch Node (Input): Internal power BIPOLAR collector.
— 8 PGND Power ground
2 — GND Ground (Return): Ground.
— EP GND Ground (Return). Exposed backside pad.
Micrel, Inc. MIC2296
April 2005
3
M9999-042005
(408) 955-1690
Absolute Maximum Rating (1)
Supply voltage (V
IN
)........................................................12V
Switch voltage (V
SW
) ........................................-0.3V to 34V
Enable pin voltage (V
EN
)....................................... -0.3 to V
IN
FB Voltage (V
FB
)...............................................................6V
Switch Current (I
SW
) ......................................................2.5A
Ambient Storage Temperature (T
S
)............-65°C to +150°C
ESD Rating
(3)
................................................................. 2KV
Operating Range (2)
Supply Voltage (V
IN
).......................................... 2.5V to 10V
Junction Temperature Range (T
J
)..............-40°C to +125°C
Package Thermal Impedance
θ
JA
2x2 MLF-8L lead ..........................................93°C/W
Electrical Characteristics
(4)
T
A
=25
o
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
Under-Voltage Lockout
1.8
2.1
2.4
V
I
VIN
Quiescent Current V
FB
= 2V (not switching) 2.8 5 mA
I
SD
Shutdown Current V
EN
= 0V
(5)
0.1
1
µA
V
FB
Feedback Voltage (+/-1%) 1.227 1.24 1.252
(+/-2%) (Over Temp)
1.215
1.265
V
I
FB
Feedback Input Current V
FB
= 1.24V -450 nA
Line Regulation 3V
≤
V
IN
≤
5V 0.04
1
%
Load Regulation 5mA
≤
I
OUT
≤
40mA 0.5 %
D
MAX
Maximum Duty Cycle
90
95 %
I
SW
Switch Current Limit Note 5
1.2
1.7
2.5
A
V
SW
Switch Saturation Voltage I
SW
= 0.5A 250 mV
I
SW
Switch Leakage Current V
EN
= 0V, V
SW
= 10V 0.01
1
µA
V
EN
Enable Threshold TURN ON
TURN OFF
1.5
0.4
V
I
EN
Enable Pin Current V
EN
= 10V 20
40
µA
f
SW
Oscillator Frequency V
IN
= 3.6V 525 600 675 kHz
V
OVP
Output over-voltage protection MIC2296BML only 30 32 34 V
150
°
C
T
J
Over-Temperature Threshold
Shutdown Hysteresis 10
°
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. 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. I
SD
= I
VIN
.
Micrel MIC2296
April 2005
4
M9999-042005
(408) 955-1690
Typical Characteristics
72
74
76
78
80
82
84
0 50 100 150 200 250
OUTPUT CURRENT (mA)
12V Output with L = 4.7µH
V
IN
= 3.2V
V
IN
= 3.6V
V
IN
= 4.2V
70
72
74
76
78
80
82
84
86
88
90
0 200 400 600 800 1000
OUTPUT CURRENT (mA)
5V Output with L = 4.7µH
V
IN
= 3.2V
V
IN
= 3.6V
V
IN
= 4.2V
200
210
220
230
240
250
260
270
280
290
300
10
Input Voltage (V)
Switch Saturation Voltage
vs. Input Voltage
0
200
400
600
800
2.5 5 7.5 10
INPUT VOLTAGE (V)
Frequency
vs. Input Voltage
90
92
94
96
98
100
2.5 5 7.5 10
INPUT VOLTAGE (V)
Max Duty Cycle
vs. Input Voltage
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.5 5 7.5 10
INPUT VOLTAGE (V)
Current Limit
vs. Input Voltage
11.8
11.85
11.9
11.95
12
12.05
12.1
12.15
12.2
0 25 50 75 100 125 150
OUTPUT VOLTAGE (V)
LOAD (mA)
Load Regulation
V
IN =
3.6V
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
0
100
200
300
400
500
600
700
-40 -20 0 20 40 60 80 100 120
FEEDBACK CURRENT (nA)
TEMPERATURE (°C)
FB Pin Cu rrent
vs. Temperature
Micrel MIC2296
April 2005
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M9999-042005
(408) 955-1690
Functional Characteristics
Enable Characteristics
Enable Volta
g
e
(2V/div)
TIME (2µs/div)
V
IN
= 3.6V
V
OUT
= 12V
I
OUT
= 150mA
Outpu
t
Volta
g
e
(5V/div)
Step Load Response
Output Volta
g
e
(50mV/div)
Load Current
(100mA/div)
TIME (100µs/div)
V
IN
= 3.6V
V
OUT
= 12V
I
OUT
= 50mA to 150mA
Micrel MIC2296
April 2005
6
M9999-042005
(408) 955-1690
Functional Description
The MIC2296 is a high power density, PWM dc/dc boost
regulator. The block diagram is shown in Figure 1. The
MIC2296 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 600kHz 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 constant frequency
current-mode PWM control
GND
CA
PWM
Generator
Ramp
Generator
600kHz
Oscillator
SW
ENFB OVP*VIN
1.24V
*OVP available on MLF
TM
package option only.
gm
OVP*
V
REF
MIC2296
MIC2296 Block Diagram
Figure 1
Micrel MIC2296
April 2005
7
M9999-042005
(408) 955-1690
Application Information
DC to DC PWM Boost Conversion
The MIC2296 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.
EN
VIN SW
FB
GND
C2
10µF
GND
L1
10µH
R1
R2
GND
V
IN
U1
MIC2296-BML OVP
V
OUT
Figure 2
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. This causes 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−V
IN
V
OUT
The duty cycle required for voltage conversion should be
less than the maximum duty cycle of 90%. 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 MIC2296, 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 MIC2296 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
MIC2296 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 10µH 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
MIC2296 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 =V
IN
2
V
OUT
×L×I
OUT
×2
π
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
MIC2296. 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
Micrel
MIC2296
April 2005
8
M9999-042005
(408) 955-1690
Diode Selection
The MIC2296 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 1µF ceramic capacitor is recommended for
designing with the MIC2296. 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 MIC2296, with short traces
for good noise performance.
Feedback Resistors
The MIC2296 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;
V
OUT
=V
REF
×R1
R2 +1
⎛
⎝
⎜
⎞
⎠
⎟
Where V
REF
is equal to 1.24V.
Duty-Cycle
The MIC2296 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 MIC2296,
D
MAX
= 85%. The actual duty cycle for a given application
can be calculated as follows:
D=1−V
IN
V
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
1
=R
2
⋅V
OUT
1.24V −1
⎡
⎣
⎢
⎤
⎦
⎥
A high value of R2 can increase the whole system
efficiency, but the feedback pin input current (I
FB
) of the gm
operation amplifier will affect the output voltage. The R2
resistor value must be less than or equal to 5kΩ (R2 ≤
5kΩ).
Inductor Selection
In MIC2296, 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 4.7µH
to 10µH 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
4.7µF to 10µF output capacitor is suitable for most
applications.
Diode Selection
For maximum efficiency, Schottky diode is recommended
for use with MIC2296. 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 MIC2296, 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 MIC2296 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 MIC2296 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
MIC2296
April 2005
9
M9999-042005
(408) 955-1690
L1
4.7µH
C2
22µF
6.3V
R2
1.87k
R1
5.62k
MIC2296BML
VIN
V
IN
3V to 4.2V
V
OUT
5V @ 400mA
EN
SW
FB
GND
GND
OVP
GND
C1
4.7µF
6.3V
D1
470 pF
3V
IN
to 4.2V
OUT
@ 400mA
L1
4.7µH
C2
4.7µF
16V
R2
5k
R1
31.6k
MIC2296BML
VIN
V
IN
3V to 4.2V
V
OUT
9V @ 180mA
EN
SW
FB
GND
GND
OVP
GND
C1
2.2µF
10V
D1
560 pF
3V
IN
- 4.2V
IN
to 9V
OUT
@ 180mA
L1
15µH
C2
4.7µF
16V
R2
5k
R1
43.2k
MIC2296BML
VIN
V
IN
3V to 4.2V
V
OUT
12V @ 120mA
EN
SW
FB
GND
GND
OVP
GND
C1
2.2µF
10V
D1
1200 pF
3V
IN
- 4.2Vin to 12V
OUT
@ 120mA
L1
15µH
C2
2.2µF
25V
R2
2.32k
R1
43.2k
MIC2296BML
VIN
V
IN
5V
V
OUT
24V @160mA
EN
SW
FB
GND
GND
OVP
GND
C1
2.2µF
10V
D1
5V
IN
to 24V
OUT
@ 160mA
L1
15µH
C2
2.2µF
25V
R2
2.32k
R1
43.2k
MIC2296BML
VIN
V
IN
3V to 4.2V
V
OUT
24V@80mA
EN
SW
FB
GND
GND
OVP
GND
C1
2.2µF
10V
D1
1200 pF
3V
IN
to 4.2V
IN
to 24V
OUT
@ 80mA
Micrel
MIC2296
April 2005
10
M9999-042005
(408) 955-1690
Package Information
8-Pin Package 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
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.
© 2005 Micrel, Incorporated.
