MIC2619YD6 - Micrel, Inc.

MIC2619

1.2MHz PWM Boost Converter

with OVP

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

General Description

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 6-

pin 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.

Features

• 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 w ith OVP in Thin SOT- 23-6

Micrel, Inc. MIC2619

March 2010 2 M9999-030410-A

Ordering Information

Part Number Marking(1) Overvoltage

Protection Junction Temp.

Range Package Lead Finish

MIC2619YD6 2619 Programmable -40°C to +125°C Thin SOT-23-6 Lead Free

Note:

1. Under bar( ) symbol may not be to scale.

Pin Configur ation

6-Pin TSOT-23 (YD6)

Pin Description

Pin Number Pin Name Pin Function

1 SW Switch Node (Input): Internal power bipolar collector.

2 GND Ground.

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.

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Absolute Maximum Ratings(1)

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

Operating Ratings(2)

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 Condition Min Typ Max Units

Supply Voltage Range 2.8 6.5 V

Under Voltage Lockout 1.8 2.1 2.4 V

Quiescent Current VFB > 1.265V, (not switching) 2.1 5 mA

Shutdown Current VEN = 0V 0.04 1 µA

Feedback Voltage 1.227 1.265 1.303 V

Feedback Input Current VFB = 1.265V -450 nA

Line Regulation 2.8V ≤ VIN ≤ 6.5V 0.2 1 %

Load Regulation 5mA ≤ IOUT ≤ 20mA 0.3 %

Maximum Duty Cycle 85 90 %

Switch Current Limit VIN = 3.6V(5) 350 mA

Switch Saturation Voltage VIN = 3.6V, ISW = 300mA 400 mV

Switch Leakage Current VEN = 0V, VSW = 10V 0.01 1 µA

TURN ON 1.5

Enable Threshold

TURN OFF 0.4 V

Enable Pin Current VEN = 6.5V 14 40 µA

Oscillator Frequency 1.2 MHz

Overvoltage Protection 1.202 1.265 1.328 V

OVP Input Current VOVP = 1.265V –200 nA

150 °C

Overtemperature 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, 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.

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March 2010 4 M9999-030410-A

Typical Characteristics

Efficiency V

OUT

= 5 V

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 50 100 150 200

LOAD CURRENT (mA)

EFFICIENCY (%)

=3V

=3.6V

=4.2V

L = 10µH

C = 1µF

Efficiency V

OUT

= 1 0 V

10%

20%

30%

40%

50%

60%

70%

80%

90%

0 20406080100

LOAD CURRENT (mA)

EFFICIENCY (%)

=3.3V

=5V

L = 10µH

C = 1µF

Efficiency V

OUT

= 12V

10%

20%

30%

40%

50%

60%

70%

80%

90%

0 20406080

LOAD CURRENT (mA)

EFFICIENCY (%)

=3.3V

=5V

L = 10µH

C = 1µF

Frequency

vs. Input Voltage

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

3 3.5 4 4.5 5 5.5 6 6.5

INPUT VOLTAGE (V)

FREQUENCY (MHz)

OUT

= 12V

L = 10µH

C = 1µF

LOAD

= 40mA

Switch Current Lim it

vs. Input Voltage

200

300

400

500

600

700

800

900

1000

1100

33.544.555.566.5

INPUT VOLTAGE (V)

CURRENT LIMIT (mA)

OUT

= 12V

L = 10µH

C = 1µF

Efficiency VOUT = 35V

10%

20%

30%

40%

50%

60%

70%

0481216

LOAD CURRENT (mA)

EFFICIENCY (%)

VIN=5V

VIN=6.5V

L = 10µH

C = 1µF

Load Regulation (V

OUT

=35V)

34.5

34.6

34.7

34.8

34.9

35.0

35.1

35.2

35.3

35.4

35.5

024681012

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

VIN = 5V

L = 10µH

C = 1µF

Load Regulation (V

OUT

=10V)

9.90

9.92

9.94

9.96

9.98

10.00

10.02

10.04

10.06

10.08

10.10

0 10203040506070

LOAD CURRENT (mA)

OUTPUT VOLTAGE (V)

VIN = 3.6V

L = 10µH

C = 1µF

Line Regulation (V

OUT

=12V)

11.80

11.84

11.88

11.92

11.96

12.00

12.04

12.08

12.12

12.16

12.20

33.544.555.566.5

INPUT VOLTA GE (V)

OUTPUT VOLTAGE (V)

IOUT = 40mA

L = 10µH

C = 1µF

Line Regulation (V

OUT

=35V)

34.5

34.6

34.7

34.8

34.9

35.0

35.1

35.2

35.3

35.4

35.5

4.5 4.9 5.3 5.7 6.1 6.5

INPUT VOLTA GE (V)

OUTPUT VOLTAGE (V)

OUT

= 10mA

L = 10µH

C = 1µF

Switch Current Lim it

vs. Temperature

100

200

300

400

500

600

700

800

900

-40 -20 0 20 40 60 80 100 120

TEMPERATURE (°C)

CURRENT LIMIT (mA)

= 3.6V

OUT

= 12V

L = 10µH

C = 1µF

Quiescent Current

vs. Input Voltage

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

2.75

3.00

3.25

3.50

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5

INPUT VOLTAGE (V)

QUIESCENT CURRENT (mA)

= 3V

No Switching

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Typical Characteristics (Continued)

Feedback Voltage

vs. Temperature

1.18

1.20

1.22

1.24

1.26

1.28

1.30

1.32

1.34

-40 -20 0 20 40 60 80 100 120

TEMPERATURE (°C)

FEEDBACK VOLTAGE (V)

= 3.6V

OUT

= 12V

OUT

= 25mA

L = 10µH

C = 1µF

Switching Frequency

vs. T e m p erature

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

-40-20 0 20406080100120

Temperature (°C)

SWITCHING FREQUENCY (MHz)

= 3.6V

OUT

= 12V

OUT

= 25mA

L = 10µH

C = 1µF

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Functional Characteristics

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Functional Characteristics (Continued)

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Functional Diagram

MIC2619 Block Diagram

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 current-

loop 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.

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.

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.

Micrel, Inc. MIC2619

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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.

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

voltage associated with this pin, the switch node should

be routed away from sensitive nodes.

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.

Micrel, Inc. MIC2619

March 2010 10 M9999-030410-A

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).

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:

OUT

1D −=

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:

IPEAK

OUT

OUT ⋅<

Where

()

⎟

⎠

⎞

⎜

⎝

⎛

⋅

−

OUT

INOUT

PEAK V

In DCM, the duty cycle is smaller than in continuous

conduction mode. In DCM the duty cycle is given by:

()

INOUTOUT

VVIL2f

D−⋅⋅⋅⋅

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.

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.

Inductor

Inductor selection will be determined by the following

(not necessarily in order of importance);

• Inductance

• 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

Micrel, Inc. MIC2619

March 2010 11 M9999-030410-A

saturate the inductor. Peak current can be calculated as

follows:

⎥

⎦

⎤

⎢

⎣

⎡⎟

⎠

⎞

⎜

⎝

⎛

××

⋅−

+= Lf2

VV1

VII INOUT

OUTOUTPEAK

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:

2ILV

Frequency

OUTOUT

⋅⋅⋅

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).

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.

Soft-start

Feed-forward capacitors can be used to provide soft-

start for the MIC2619. Figure 2 shows a typical circuit

for soft-start applications. Typically a 0.22nF feed-

forward capacitor will yield 5ms in rise time.

Figure 2. Soft-start Circuit

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:

⎟

⎠

⎞

⎜

⎝

⎛+⋅= 1

VV 5

REFOUT

Where VREF is equal to 1.265V. Over-voltage Protection

uses the same equation as the feedback pin.

⎟

⎠

⎞

⎜

⎝

⎛+⋅= 1

VV 2

REFOVP

Micrel, Inc. MIC2619

March 2010 12 M9999-030410-A

MIC2619 Evaluation Board Schematic

Bill of Materials

Item Part Number Manufacturer Description Qty.

C1608X5R1A105K TDK(1) Capacitor, 1.0µF, 10V, X5R, 0603 size

GRM185R61A105KE36D Murata(2) Capacitor, 1.0µF, 10V, X5R, 0603 size

0603ZD105KT2A AVX(3) Capacitor, 1.0µF, 10V, X5R, 0603 size

C2 TAJA106M010R AVX Capacitor, 10.0µF, 10V, A Case 1

C1608X7R11H223K TDK Capacitor, 22nF, 50V, X7R, 0603 size

GRM188R71H223KA01D Murata Capacitor, 22nF, 50V, X7R, 0603 size

06035C223JAT2A AVX Capacitor, 22nF, 50V, X7R, 0603 size

08055D105MAT2A AVX Capacitor, 1.0µF, 50V, X5R, 0805 size

GRM21BR71H105KA12L Murata Capacitor, 1.0µF, 50V, X5R, 0805 size

CL21B105KBFNNNE Samsung(4) Capacitor, 1.0µF, 50V, X7R, 0805 size

SK14 MCC(5) Schottky Diode, 1A, 40V D1

B140/B Diode, Inc.(6) Schottky Diode, 1A, 40V 1

C1G22L100MNE Samsung Inductor, 10.0µH, 0.8A, 2.5 x 2.0 x 1.0mm

VLF3012ST-100MR59 TDK Inductor, 10.0µH, 0.59A, 2.8 x 3.0 x 1.2mm

LQH32PN100MN0L Murata Inductor, 10.0µH, 0.7A, 3.2 x 2.5 x 1.55mm

R1 CRCW0603267KFKEA Vishay(7) 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 Micrel, Inc.(8) 1.2MHz PWM Boost Converter with OVP 1

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

Micrel, Inc. MIC2619

March 2010 13 M9999-030410-A

Recommended Layout

Top Layout

Bottom Layout

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Package Information

6-Pin TSOT (YD6)

Micrel, Inc. MIC2619

March 2010 15 M9999-030410-A

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

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indemnify Micrel for any damages resulting from such use or sale.