MICREL MIC2619

MIC2619
1.2MHz PWM Boost Converter
with OVP
General Description
Features
The MIC2619 is a 1.2MHz pulse width modulated (PWM)
step-up switching regulator that is optimized for low power,
high output voltage applications. With a maximum output
voltage of 35V, and a switch current of over 350mA, the
MIC2619 can easily supply most high voltage bias
applications, such as TV tuners.
The MIC2619 implements a constant frequency 1.2MHz
PWM current-mode control scheme. The high frequency
PWM operation saves board space by reducing external
component sizes. The additional benefit of the constant
frequency PWM control scheme as opposed to variable
frequency control schemes is lower output noise and
smaller input ripple injected back to the battery source.
The MIC2619 has programmable overvoltage protection to
ensure output protection in case of fault condition.
The MIC2619 is available in a low profile Thin SOT-23 6pin package. The MIC2619 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.
•
•
•
•
•
•
•
•
•
•
•
•
2.8V to 6.5V Input Voltage
350mA Switch Current
Output Voltage up to 35V
1.2MHz PWM Operation
1.265V Feedback Voltage
Programmable Over-Voltage Protection (OVP)
<1% Line Regulation
<1µA Shutdown Current
Over-Temperature Protection
Under-Voltage Lock Out (UVLO)
Low Profile Thin SOT-23-6 Package
–40°C to +125°C Junction Temperature Range
Applications
• Bias Supply Applications:
- Tuner Varactor Bias
- High Voltage Bias Supplies
- Avalanche Photo Diode
- High Voltage Display Bias
• DSL/Broadband applications
• Constant Current Power Supplies
_________________________________________________________________________________________________________________________
Typical Application
1.2MHz Boost Converter with OVP in Thin SOT-23-6
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
March 2010
M9999-030410-A
Micrel, Inc.
MIC2619
Ordering Information
Part Number
MIC2619YD6
Marking(1)
Overvoltage
Protection
Junction Temp.
Range
Package
Lead Finish
2619
Programmable
-40°C to +125°C
Thin SOT-23-6
Lead Free
Note:
1. Under bar( ) symbol may not be to scale.
Pin Configuration
6-Pin TSOT-23 (YD6)
Pin Description
Pin Number
Pin Name
1
SW
2
GND
3
FB
Feedback (Input): Output voltage sense node. Connect external resistor network to set
output voltage. Nominal feedback voltage is 1.265V.
4
EN
Enable (Input): Logic high enables regulator. Logic low shuts down regulator. Do not
leave floating.
5
OVP
Over-Voltage Protection (Input): Programmable to 35V, adjustable through resistor divider
network.
6
VIN
Supply (Input): 2.8V to 6.5V for internal circuitry. Requires a minimum 1.0µF ceramic
capacitor.
March 2010
Pin Function
Switch Node (Input): Internal power bipolar collector.
Ground.
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M9999-030410-A
Micrel, Inc.
MIC2619
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) .........................................................7V
Switch Voltage (VSW)....................................... –0.3V to 40V
Enable Pin Voltage (VEN)..................................... –0.3 to VIN
Feedback Voltage (VFB), (VOVP)........................................6V
Ambient Storage Temperature (TS)...........–65°C to +150°C
ESD Rating (3) ................................................................. 2kV
Supply Voltage (VIN)......................................... 2.8V to 6.5V
Output Voltage (VOUT) .......................................... VIN to 35V
Junction Temperature Range (TJ)............. –40°C to +125°C
Package Thermal Impedance
Thin SOT-23-6 (θJA).........................................177°C/W
Electrical Characteristics (4)
TA = 25°C, VIN = VEN = 3.6V, VOUT = 10V, IOUT = 10mA, unless otherwise noted. Bold values indicate –40°C ≤ TJ ≤125°C.
Parameter
Min
Condition
Supply Voltage Range
2.8
Under Voltage Lockout
1.8
Typ
Max
Units
6.5
V
2.1
2.4
V
Quiescent Current
VFB > 1.265V, (not switching)
2.1
5
mA
Shutdown Current
VEN = 0V
0.04
1
µA
1.265
1.303
V
1.227
Feedback Voltage
Feedback Input Current
VFB = 1.265V
-450
Line Regulation
2.8V ≤ VIN ≤ 6.5V
0.2
Load Regulation
5mA ≤ IOUT ≤ 20mA
0.3
%
90
%
85
Maximum Duty Cycle
(5)
Switch Saturation Voltage
VIN = 3.6V, ISW = 300mA
400
Switch Leakage Current
VEN = 0V, VSW = 10V
0.01
Enable Threshold
TURN ON
mV
1
µA
1.5
TURN OFF
0.4
14
VEN = 6.5V
40
1.2
Oscillator Frequency
1.202
Overvoltage Protection
Overtemperature Threshold
Shutdown
%
mA
VIN = 3.6V
OVP Input Current
1
350
Switch Current Limit
Enable Pin Current
nA
VOVP = 1.265V
Hysteresis
1.265
V
µA
MHz
1.328
V
–200
nA
150
°C
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, 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 ratings.
3. Devices are inherently ESD sensitive. Handling precautions required. Human body model: 1.5kΩ in series with 100pF.
4. Specification for packaged product only.
5. Guaranteed by design.
March 2010
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M9999-030410-A
Micrel, Inc.
MIC2619
Typical Characteristics
Efficiency V OUT = 10V
Efficiency V OUT = 5V
Efficiency V OUT = 12V
90%
90%
90%
80%
80%
80%
70%
60%
V IN =4.2V
V IN =3.6V
50%
V IN =3V
40%
30%
30%
20%
30%
20%
20
40
60
80
100
0
35.3
V IN =6.5V
30%
20%
L = 10µH
C = 1µF
OUTPU T VOLTAGE (V)
35.4
10.06
50%
10.04
10.02
10.00
9.98
9.96
9.94
V IN = 3.6V
L = 10µH
C = 1µF
9.92
Line Regulation (V OUT =12V)
35.4
12.12
35.3
OUTPUT VOLTAGE (V)
35.5
12.16
12.04
12.00
11.96
11.92
11.88
IOU T = 40mA
L = 10µH
C = 1µF
11.84
34.9
34.8
34.7
10 20 30 40 50 60
LOAD CURR ENT (mA)
70
35.2
35.1
35.0
34.9
34.8
IOU T = 10mA
L = 10µH
C = 1µF
34.7
34.6
11.80
0
4 4.5 5 5.5 6
INPUT VOLTAGE (V)
6.5
4.5
Switch Current Limit
vs. Input Voltage
800
900
700
C URRENT LIMIT (mA)
900
1000
800
700
600
500
V OU T = 12V
L = 10µH
C = 1µF
300
500
400
300
V IN = 3.6V
200
V OU T = 12V
L = 10µH
C = 1µF
0
March 2010
3.5
4 4.5 5 5.5 6
IN PU T VOLTAGE (V)
6.5
-40 -20
0
20 40 60 80 100 120
TEMPERATUR E (°C)
4
12
V OU T = 12V
L = 10µH
C = 1µF
ILOAD = 40mA
3
6.5
600
100
200
3
1.50
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
0.95
0.90
3.5
4 4.5 5 5.5 6
INPUT VOLTAGE (V)
6.5
Quiescent Current
vs. Input Voltage
Switch Current Limit
vs. T emperature
1100
400
4.9
5.3
5.7
6.1
INPUT VOLTAGE (V)
QUIESCENT CURRENT (mA)
3.5
2
4
6
8
10
LOAD CURR ENT (mA)
Frequency
vs. Input Voltage
34.5
3
V IN = 5V
L = 10µH
C = 1µF
Line Regulation (V OUT =35V)
12.20
12.08
35.0
34.5
0
16
35.1
FREQUENCY (MHz)
4
8
12
LOAD CURRENT (mA)
35.2
34.6
9.90
0%
80
35.5
60%
V IN =5V
20
40
60
LOAD CUR RENT (mA)
Load Regulation (V OUT =35V)
Load Regulation (V OUT =10V)
10.08
0
L = 10µH
C = 1µF
10%
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
40%
10.10
40%
V IN =3.3V
0%
0
200
V IN =5V
50%
70%
10%
OUTPUT VOLTAGE (V)
60%
0%
Efficiency V OUT = 35V
CU RRENT LIMIT (mA)
L = 10µH
C = 1µF
10%
0%
50
100
150
LOAD CURR ENT (mA)
V IN =3.3V
40%
L = 10µH
C = 1µF
0
V IN =5V
50%
20%
10%
70%
60%
EFFICIENCY (%)
70%
EFFICIENCY (%)
EFFICIENCY (%)
100%
3.50
3.25
3.00
2.75
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
V F B = 3V
No Switching
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
INPUT VOLTAGE (V)
M9999-030410-A
Micrel, Inc.
MIC2619
Typical Characteristics (Continued)
Feedback Voltage
vs. T emperature
Switching Frequency
vs. T emperature
1.35
1.30
1.28
1.26
1.24
V IN = 3.6V
V OU T = 12V
1.22
IOU T = 25mA
L = 10µH
C = 1µF
1.20
SWITCHING FREQUENCY (M Hz)
1.40
1.32
FEEDB ACK VOLTAGE (V)
1.34
1.30
1.25
1.20
1.15
1.10
V IN = 3.6V
1.05
V OU T = 12V
1.00
IOU T = 25mA
L = 10µH
C = 1µF
0.95
0.90
1.18
-40 -20
March 2010
0 20 40 60 80 100 120
TEMPER ATURE (°C)
-40 -20
0 20 40 60 80 100 120
Temperature (°C)
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MIC2619
Functional Characteristics
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MIC2619
Functional Characteristics (Continued)
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MIC2619
Functional Diagram
MIC2619 Block Diagram
VIN
VIN provides power to the control and reference circuitry
as well as the switch mode regulator MOSFETs. Due to
the high speed switching, a 1µF capacitor is
recommended as close as possible to the VIN and GND
pin.
Functional Description
The MIC2619 is a constant frequency, PWM current
mode boost regulator. It is composed of an oscillator,
slope compensation ramp generator, current amplifier,
gm error amplifier, PWM generator, and bipolar output
transistor. The oscillator generates a 1.2MHz clock
which triggers the PWM generator to turn on the output
transistor and resets the slope compensation ramp
generator. The current amplifier is used to measure
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 currentloop signal is then fed to one of the inputs of the PWM
generator.
The gm error amplifier measures the feedback voltage
through the external feedback resistors and amplifies the
error between the detected signal and the 1.265V
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.
March 2010
EN
The enable pin provides a logic level control of the
output. In the off state, supply current of the device is
greatly reduced (typically <0.1µA). Also, in the off state,
the output drive is placed in a “tri-stated” condition,
where the bipolar output transistor is in an “off” state or
non-conducting state.
OVP
The OVP pin provides over-voltage protection on the
output of the MIC2619. When the OVP circuit is tripped,
the output voltage remains at the set OVP voltage.
Because the OVP circuit operates at a lower frequency
than the feedback circuit, output ripple will be higher
while in an OVP state. OVP requires a resistor divider
network to the output and GND to set the OVP voltage.
If the output voltage overshoots the set OVP voltage,
then the MIC2619 OVP circuit will shut off the switch;
saving itself and other sensitive circuitry downstream.
The accuracy of the OVP pin is ±5% and therefore
should be set above the output voltage to ensure noise
or other variations will not cause a false triggering of the
OVP circuit.
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M9999-030410-A
Micrel, Inc.
MIC2619
voltage associated with this pin, the switch node should
be routed away from sensitive nodes.
FB
The feedback pin provides the control path to control the
output. FB requires a resistor divider network to the
output and GND to set the output voltage.
GND
The ground pin is the ground path for high current PWM
mode. The current loop for the power ground should be
kept as small as possible.
SW
The switching pin connects directly to one end of the
inductor to VIN and the anode of the Schottky diode to
the output. Due to the high switching speed and high
March 2010
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MIC2619
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 slightly overshoot 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 also reduces the peak
current.
Application Information
DC-to-DC PWM Boost Conversion
The MIC2619 is a constant-frequency boost converter. It
can convert a low DC input voltage to a higher DC
output voltage. Figure 1 shows a typical circuit. Boost
regulation is achieved by turning on an internal switch,
which draws current through the inductor. 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 Schottky diode (D1). The
Functional Characteristics show Input Voltage ripple,
Output Voltage ripple, SW Voltage, and Inductor Current
for 10mA load current. Regulation is achieved by
modulating the pulse width i.e., pulse-width modulation
(PWM).
Input Capacitors
A 1µF ceramic capacitor is recommended on the VIN pin
for bypassing. Increasing input capacitance will improve
performance and provide greater noise immunity. The
input capacitor should be as close as possible to the
inductor and the MIC2619, with short traces for good
noise performance.
X5R or X7R dielectrics are recommended for the input
capacitor. Y5V dielectrics lose most of their capacitance
over temperature and are therefore not recommended.
Also, tantalum and electrolytic capacitors alone are not
recommended because of their reduced RMS current
handling, reliability, and ESR increases.
Output Capacitors
Output capacitor selection is also a trade-off between
performance,
size,
and
cost.
The
minimum
recommended output capacitor is 1µF. Increasing output
capacitance will lead to an improved transient response
but also an increase in size and cost. X5R or X7R
dielectrics are recommended for the output capacitor.
Y5V dielectrics lose most of their capacitance over
temperature and are therefore not recommended.
Figure 1. 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−
VIN
VOUT
Inductor
Inductor selection will be determined by the following
(not necessarily in order of importance);
However at light loads, the inductor will completely
discharge before the end of a switching cycle. The
current in the inductor reaches 0A before the end of the
switching cycle. This is known as discontinuous
conduction mode (DCM). DCM occurs when:
IOUT <
VIN IPEAK
⋅
VOUT
2
(VOUT
− VIN ) ⎛ VIN
⋅ ⎜⎜
L⋅f
⎝ VOUT
⎞
⎟
⎟
⎠
f ⋅ 2 ⋅ L ⋅ IOUT ⋅ (VOUT − VIN )
March 2010
•
Rated current value
•
Size requirements
DC resistance (DCR)
The MIC2619 was designed for use with a 10µH
inductor. Proper selection should ensure the inductor
can handle the maximum average and peak currents
required by the load. Maximum current ratings of the
inductor are generally given in two methods; permissible
DC current and saturation current. Permissible DC
current can be rated either for a 40°C temperature rise
or a 10 to 20% loss in inductance. Ensure the inductor
selected can handle the maximum operating current.
When saturation current is specified, make sure that
there is enough margin so that the peak current will not
In DCM, the duty cycle is smaller than in continuous
conduction mode. In DCM the duty cycle is given by:
D=
Inductance
•
Where
IPEAK =
•
VIN
10
M9999-030410-A
Micrel, Inc.
MIC2619
saturate the inductor. Peak current can be calculated as
follows:
Diode Selection
The MIC2619 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.
⎡
⎛ 1 − VOUT ⋅ VIN ⎞⎤
IPEAK = ⎢IOUT + VOUT ⎜
⎟⎥
⎝ 2 × f × L ⎠⎦
⎣
As shown by the previous calculation, the peak inductor
current is inversely proportional to the switching
frequency and the inductance; the lower the switching
frequency or the inductance the higher the peak current.
As input voltage increases the peak current also
increases.
The size of the inductor depends on the requirements of
the application.
DC resistance (DCR) is also important. While DCR is
inversely proportional to size, DCR can represent a
significant efficiency loss. Refer to the Efficiency
Considerations.
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:
Soft-start
Feed-forward capacitors can be used to provide softstart for the MIC2619. Figure 2 shows a typical circuit
for soft-start applications. Typically a 0.22nF feedforward capacitor will yield 5ms in rise time.
2
Frequency =
VOUT
VIN
⋅ L ⋅ IOUT ⋅ 2π
Figure 2. Soft-start Circuit
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).
Feedback resistors
The MIC2619 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. Using the evaluation board schematic
as a reference, the desired output voltage can be
calculated as follows:
⎛R
⎞
VOUT = VREF ⋅ ⎜⎜ 4 + 1 ⎟⎟
R
⎝ 5
⎠
Where VREF is equal to 1.265V. Over-voltage Protection
uses the same equation as the feedback pin.
⎛R
⎞
VOVP = VREF ⋅ ⎜⎜ 1 + 1 ⎟⎟
R
⎝ 2
⎠
March 2010
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M9999-030410-A
Micrel, Inc.
MIC2619
MIC2619 Evaluation Board Schematic
Bill of Materials
Item
C1
Part Number
C1608X5R1A105K
GRM185R61A105KE36D
Manufacturer
TDK
(1)
Description
Capacitor, 1.0µF, 10V, X5R, 0603 size
(2)
Murata
Capacitor, 1.0µF, 10V, X5R, 0603 size
0603ZD105KT2A
AVX(3)
Capacitor, 1.0µF, 10V, X5R, 0603 size
C2
TAJA106M010R
AVX
C3
C1608X7R11H223K
C4
TDK
Capacitor, 22nF, 50V, X7R, 0603 size
Capacitor, 22nF, 50V, X7R, 0603 size
06035C223JAT2A
AVX
Capacitor, 22nF, 50V, X7R, 0603 size
08055D105MAT2A
AVX
Capacitor, 1.0µF, 50V, X5R, 0805 size
GRM21BR71H105KA12L
CL21B105KBFNNNE
D1
SK14
B140/B
L1
Capacitor, 10.0µF, 10V, A Case
Murata
GRM188R71H223KA01D
C1G22L100MNE
VLF3012ST-100MR59
LQH32PN100MN0L
Qty.
Murata
Capacitor, 1.0µF, 50V, X5R, 0805 size
Samsung(4)
Capacitor, 1.0µF, 50V, X7R, 0805 size
MCC(5)
Schottky Diode, 1A, 40V
(6)
Diode, Inc.
Schottky Diode, 1A, 40V
Samsung
Inductor, 10.0µH, 0.8A, 2.5 x 2.0 x 1.0mm
TDK
Inductor, 10.0µH, 0.59A, 2.8 x 3.0 x 1.2mm
Murata
(7)
Vishay
1
1
1
1
1
1
Inductor, 10.0µH, 0.7A, 3.2 x 2.5 x 1.55mm
R1
CRCW0603267KFKEA
Resistor, 267kΩ, 1%, 1/16W, 0603 size
1
R2, R5
CRCW060310K0FKEA
Vishay
Resistor, 10kΩ, 1%, 1/16W, 0603 size
2
R3
CRCW0603100KFKEA
Vishay
Resistor, 100kΩ, 1%, 1/16W, 0603 size
1
R4
CRCW0603226KFKEA
Vishay
Resistor, 226kΩ, 1%, 1/16W, 0603 size
1
U1
MIC2619YD6
1.2MHz PWM Boost Converter with OVP
1
Micrel, Inc.(8)
Notes:
1. TDK: www.tdk.com
2. Murata: www.murata.com
3. AVX: www.avx.com
4. Samsung: www.sem.samsung.com
5. MCC: www.mccsemi.com
6. Diode, Inc.: www.diodes.com
7. Vishay: www.vishay.com
8. Micrel, Inc.: www.micrel.com
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MIC2619
Recommended Layout
Top Layout
Bottom Layout
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MIC2619
Package Information
6-Pin TSOT (YD6)
March 2010
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Micrel, Inc.
MIC2619
Recommended Land Pattern
6-Pin TSOT (YD6)
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.
© 2009 Micrel, Incorporated.
March 2010
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