Micrel MIC2142 User Manual

MIC2142 Micrel

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MIC2142

Micropower Boost Converter

Preliminary Information

General Description

The MIC2142 is a micropower boost switching regulator
housed in a SOT23-5 package. The input voltage range is
between 2.2V to 16V, making the device suitable for one-cell
Li Ion and 3 to 4-cell alkaline/NiCad/NiMH applications. The
output voltage of the MIC2142 can be adjusted up to 22V.

The MIC2142 is well suited for portable, space-sensitive
applications. It features a low quiescent current of 85µA, and
a typical shutdown current of 0.1µA. It’s 330kHz operation
allows small surface mount external components to be used.
The MIC2142 is capable of efficiences over 85% in a small
board area.

The MIC2142 can be configured to efficiently power a variety
of loads. It is capable of providing a few mA output for
supplying low power bias voltages; it is also capable of
providing the 80mA needed to drive 4 white LEDs.

The MIC2142 is available in a SOT23-5 package with an
ambient operating temperature range from –40°C to +85°C

Typical Application

Features

• 2.2V to 16V input voltage

• Up to 22V output voltage

• 330kHz switching frequency

• 0.1µA shutdown current

•85µA quiescent current

• Implements low-power boost, SEPIC, or flyback

• SOT23-5 package

Applications

• LCD bias supply

• White LED driver

• 12V Flash memory supply

• Local 3V to 5V conversion

2.8V to 4.7V
V

IN

C

IN

10µF

L1

33µH

MIC2142

VCC SW

1

5

FB

GNDEN

D1

3

4

2

R2
365k

R1
124k

Typical Configuration

+5V @60mA

C

OUT

22µF

Efficiency

vs. Output Current

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

EFFICIENCY (%)

0.50

0.45

0.40
0 10203040506070

OUTPUT CURRENT (mA)

VIN = 4.2V

VIN = 3.0V

Efficiency vs. Output Current

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com

December 2000 1 MIC2142

MIC2142 Micrel

Ordering Information

Part Number Voltage Ambient Temp. Range Package

MIC2142BM5 Adj –40°C to +85°C SOT23-5

Pin Configuration

VCC

GND

SW

13

2

SBAA

45

FB

SOT23-5 (BM5)

EN

Part
Identification

Pin Description

Pin Number Pin Name Pin Function

1 VCC Chip Supply: +2.2V to +16V
2 GND Ground: Return for internal circuitry and internal MOSFET (switch) source.
3 SW Switch Node (Input): Internal MOSFET drain; 22V maximum.
4 FB Feedback (Input): Output voltage sense node.
5 EN Shutdown: Device shuts down to 0.1µA typical supply current.

MIC2142 2 December 2000

MIC2142 Micrel

Absolute Maximum Ratings (Note 1)

Supply voltage (VCC).....................................................18V

Switch voltage (V
Enable pin voltage (V
Feedback Voltage (VFB)

Adjustable version.......................................................8V

Ambient Storage Temperature (TS) .........–65°C to +150°C

) ....................................................24V

SW

) Note 3...................................18V

EN

Operating Ratings (Note 2)

Supply Voltage (VCC) ....................................... 2.2V to 16V

Enable pin voltage (V
Switch Voltage (V

Ambient Temperature (TA).........................–40°C to +85°C

Junction Temperature Range (T
Package Thermal Impedance

θ

SOT23-5 .....................................................220°C/W

JA

) Note 3......................... 0V to 16V

EN

)....................................................22V

SW

) ...........–40°C to +125°C

J

Electrical Characteristics

VCC =3.6V, V

Parameter Condition Min Typ Max Units

Input Voltage 2.2 16 V
Quiescent Current VEN = ON , VFB = 2.2V 85 125 µA

Feedback Voltage (VFB)(±2%) 1.254 1.28 1.306 V

Comparator Hysteresis 18 mV
Feedback Input Bias Current 30 nA

Note 4

Enable Input Voltage VIH (turn on) 0.6VCC0.55V

Enable Input Current –1 0.01 1 µA
Load Regulation 200µA ≤ I
Line Regulation 2.2V ≤ VCC ≤ 16V; I
SW on Resistance ISW = 100mA, VCC = 2.5V 5 Ω

Switch Leakage Current VEN = OFF, VSW = 12V 0.05 1 µA
Oscillator Frequency 295 330 365 kHz
Duty Cycle 50 57 65 %

OUT

= 5V, I

= 20mA, TA=25°C; unless otherwise specified. Bold values indicate 25°C ≤ TJ ≤ 125°C.

OUT

VEN = OFF (shutdown) 0.1 2 µA

(±3%) 1.241 1.312 V

VIL (turn off) 1.1 0.8 V

≤ 20mA 0.2 %V

OUT

= 4mA 0.25 %/V

OUT

ISW = 100mA, VCC = 12V 2 Ω

CC

V

OUT

Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when

Note 2: The device is not guaranteed to function outside its operating rating.
Note 3: VEN must be ≤ V
Note 4: The maximum suggested value of the programming resistor, whose series resistance is measured from feedback to ground, is 124kΩ. Use of

Note 5: Devices are ESD sensitive, handling precautions required.

operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction
temperature, T
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. The θJA of the power SOT23-5 is 220°C/W
mounted on a PC board.

larger resistor values can cause errors in the output voltage due to the feedback input bias current.

, the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power

J(Max)

IN

December 2000 3 MIC2142

MIC2142 Micrel

µ

g

Typical Characteristics

Quiescent Current

vs. Input Voltage

350

V

= 5V

OUT

300
250
200
150
100

50

QUIESCENT CURENT (µA)

0

0 2 4 6 8 10 12 14 16

INPUT VOLTAGE (V)

Output Ripple

1200

1000

OUTPUT RIPPLE (mV)

vs. Input Voltage

IL = 7mA
L = 22

H

800

600

V

= 15V

OUT

400

200

0

02468101214

INPUT VOLTAGE (V)

IL = 2mA
L = 220µH

VDS and R

vs. Input Voltage

600

500

400

(V)

300

DS

V

200

100

0

0 2 4 6 8 10 12 14

INPUT VOLTAGE (V)

DS(ON)

ISW= 100mA

Efficiency

vs. Input Voltage

85

80

75

IL = 7mA
L = 22µH

70

EFFICIENCY (%)

65

V

= 15V

OUT

60

2 4 6 8 101214

INPUT VOLTAGE (V)

IL = 2mA
L = 220µH

6

5

4

3

DS(ON)

R

2

1

0

16.5

15.5

14.5

OUTPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

Line Regulation

I

= 7mA

L

L = 22µH

16

IL= 2mA
L = 220µH

15

14

2 4 6 8 10 12 14

INPUT VOLTAGE (V)

MIC2142 Load

ulation

16
14
12
10

8
6
4
2
0

0 5 10 15 20 25 30

Re

L = 22µH
VIN = 5V

OUTPUT CURRENT (mA)

V

V

OUT

REF

Oscillator Characteristics

350
300
250
200
150
100

FREQUENCY (kHz)

vs. Input Voltage

Frequency

Duty Cycle

VO = 15V
I

= 100µA

O

50

L= 220µH

0

02468101214

INPUT VOLTAGE (V)

tON vs.

2

1.9

1.8

1.7

1.6

1.5

(µsec)

1.4

ON

t

1.3

1.2

1.1
1

-50 -30 -10 10 30 50 70 90 110

Temperature

TEMPERATURE (°C)

0.65

0.60

0.55

0.50

0.45

0.40

DUTY CYCLE

Quiescent Current

vs. Temperature

84
82
80
78
76
74
72

QUIESCENT CURRENT (µA)

70

-50 -30 -10 10 30 50 70 90 110

TEMPERATURE (°C)

Frequency vs.

340
335
330
325
320
315
310
305

FREQUENCY (kHz)

300
295

-50 -30 -10 10 30 50 70 90 110

Temperature

TEMPERATURE (°C)

VIN = 3.6V

V

and V

OUT

15.20

15.15

15.10

15.05

15.00

14.95

OUTPUT VOLTAGE (V)

14.90

Over Temperature

V

=

3.6V

IN

I

= 100µA

O

L = 22µH

V

OUT

V

REF

-50 -30 -10 10 30 50 70 90 110

TEMPERATURE (°C)

Timing Characteristics

Over Temperature

3.5

3.0

T (µsec)

2.5

2.0

1.5

tON (µsec)

1.0

0.5
Duty Cycle

0

OSCILLATOR CHARACTERISTICS

-50 -30 -10 10 30 50 70 90 110

TEMPERATURE (°C)

REF

1.290

1.285

1.280

1.275

REFERENCE VOLTAGE (V)

1.270

MIC2142 4 December 2000

MIC2142 Micrel

R

vs.

DS(ON)

Temperature

7
6
5

(Ω)

4
3

DS(ON)

R

2
1
0

-50 -30 -10 10 30 50 70 90 110

VCC=3.3V

VCC = 4.5V

TEMPERATURE (°C)

Timing Characteristics

Over Temperature

0.6

0.58

0.56

0.54

0.52

0.5

0.48

0.46

DUTY CYCLE (%)

0.44

0.42

0.4

-50 -30 -10 10 30 50 70 90 110

TEMPERATURE (°C)

December 2000 5 MIC2142

MIC2142 Micrel

Functional Diagram

EN

FB

Bandgap

Reference

Shutdown

MIC2142

VCC

Oscillator

330kHz

FIXED DUTY CYCLE

SW

GND

Functional Description

This MIC2142 is a fixed duty cycle, constant frequency, gated
oscillator, micropower, switch-mode power supply controller.
Quiescent current for the MIC2142 is only 85µA in the switch
off state, and since a MOSFET output switch is used, addi­tional switch drive current is minimized. Efficiencies above
85% throughout most operating conditions can be realized.

A functional block diagram is shown above and typical
schematic is shown on page 1. Regulation is performed by a
hysteretic comparator, which regulates the output voltage by
gating the internal oscillator. The internal oscillator operates
at a fixed 57% duty cycle and 330kHz frequency. For the fixed
output versions, the output is divided down internally and then
compared to the internal V
divider is use for the adjustable version.

The comparator has hysteresis built into it, which determines
the amount of low frequency ripple that will be present on the

input. An external resistive

REF

output. Once the feedback input to the comparator exceeds
the control voltage by 18mV, the high frequency oscillator
drive is removed from the output switch. As the feedback
input to the comparator returns to the reference voltage level,
the comparator is reset and the high frequency oscillator is
again gated to the output switch. The 18mV of hysteresis
seen at the comparator will be multiplied by the ratio of the
output voltage to the reference voltage. For a five volt output
this ratio would be 4, corresponding to a ripple voltage of
72mV at the output.

The maximum output voltage is limited by the voltage capa­bility of the output switch. Output voltages up to 22V can be
achieved with a standard boost circuit. Higher output volt­ages can be realized with a flyback configuration.

MIC2142 6 December 2000