Micrel MIC4721 User Manual

General Description

MIC4721

1.5A 2MHz Integrated Switch

Features

Buck Regulator

The Micrel MIC4721 is a high efficiency PWM buck (step­down) regulators that provides up to 1.5A of output
current. The MIC4721 operates at 2MHz and has
proprietary internal compensation that allows a closed loop
bandwidth of over 200KHz.

The low on-resistance internal p-channel MOSFET of the
MIC4721 allows efficiencies up to 94%, reduces external
components count and eliminates the need for an
expensive current sense resistor.

The MIC4721 operates from 2.7V to 5.5V input and the
output can be adjusted down to 1V. The devices can
operate with a maximum duty cycle of 100% for use in low­dropout conditions.

The MIC4721 is available in the 10-pin MSOP package
with a junction operating range from –40°C to +125°C.

Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.

• 2.7 to 5.5V supply voltage

• 2MHz PWM mode

• Output current to 1.5A

• Up to 94% efficiency

• 100% maximum duty cycle

• Adjustable output voltage option down to 1V

• Ultra-fast transient response

• Ultra-small external components

Stable with a 1µH inductor and a 4.7µF output capacitor

• Fully integrated 1.5A MOSFET switch

• Micropower shutdown

• Power Good pin

• Thermal shutdown and current limit protection

• Pb-free 10-pin MSOP package

• –40°C to +125°C junction temperature range

Applications

• FPGA/DSP/ASIC applications

• General point of load

• Broadband communications

• DVD/TV recorders

• Point of sale

• Printers/Scanners

• Set top boxes

• Computing peripherals

• Video cards

___________________________________________________________________________________________________________

Typical Application

May 2007

1.5A 2MHz Buck Regulator

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (

5VIN to 3.3VO Efficiency

94
92
90
88
86
84
82

408

) 944-0800 • fax + 1 [phone] • http://www.micrel.com

80
78
76

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

1

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Micrel, Inc. MIC4721

Ordering Information

Part Number Voltage Temperature Range Package Lead Finish

MIC4721YMM Adj. –40° to +125°C 10-Pin MSOP Pb-Free

Pin Configuration

Pin Description

Pin Number Pin Name Pin Function

1, 10 SW Switch (Output): Internal power P-Channel MOSFET output switch.

2, 9 VIN

3 SGND

4 BIAS

5 FB

6 EN

7 PGOOD

8 PGND Power Ground. Provides the ground return path for the high-side drive current.

10 SW

9

VIN

8

PGND

7

PGOOD

VIN

SGND

BIAS

FB EN65

1SW
2
3
4

10-Pin MSOP (MM)

Supply Voltage (Input): Supply voltage for the source of the internal P-channel
MOSFET and driver.

Requires bypass capacitor to GND.
Signal (Analog) Ground. Provides return path for control circuitry and internal

reference.
Internal circuit bias supply. Must be bypassed with a 0.1µF ceramic capacitor to

SGND.
Feedback. Input to the error amplifier, connect to the external resistor divider

network to set the output voltage.
Enable (Input). Logic level low will shutdown the device, reducing the current

draw to less than 5µA.
Power Good. Open drain output that is pulled to ground when the output voltage

is within ±7.5% of the set regulation voltage.

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Micrel, Inc. MIC4721

Absolute Maximum Ratings

(1)

Operating Ratings

(2)

Supply Voltage (VIN).......................................................+6V

Output Switch Voltage (V
Output Switch Current (I
Logic Input Voltage (V
Storage Temperature (T

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

SW

)............................................11A

SW

) ..................................–0.3V to VIN

EN

).........................–60°C to +150°C

s

Supply Voltage (VIN).....................................+2.7V to +5.5V

Logic Input Voltage (V
Junction Temperature (T

).......................................0V to VIN

EN

) ........................–40°C to +125°C

J

Junction Thermal Resistance
MSOP-10L (θ
MSOP-10L (θ

)...............................................130°C/W

JA

) ................................................43°C/W

JC

Electrical Characteristics

V

= VEN = 3.6V; L = 1µH; C

IN

Parameter Condition Min Typ Max Units

Supply Voltage Range
Under-Voltage Lockout

Threshold
UVLO Hysteresis 100 mV
Quiescent Current VFB = 0.9 * V
Shutdown Current VEN = 0V 2
[Adjustable] Feedback

Voltage
FB pin input current 1 nA
Current Limit in PWM Mode VFB = 0.9 * V
Output Voltage Line

Regulation
Output Voltage Load

Regulation
Maximum Duty Cycle
PWM Switch ON-

Resistance
Oscillator Frequency
Enable Threshold
Enable Hysteresis 50 mV
Enable Input Current 0.1
Power Good Range ±7 ±10 %
Power Good Resistance I
Over-Temperature

Shutdown
Over-Temperature

Hysteresis

Notes:

1. Exceeding the absolute maximum rating may damage the device.

2. The device is not guaranteed to function outside its operating rating.

3. Specification for packaged product only.

(3)

= 4.7µF; TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C.

OUT

2.7 5.5

(turn-on)

2.45

(not switching) 570

NOM

2.55

2.65

900

10

± 2% (over temperature) I

3.5 5 A

NOM

V

> 2V; VIN = V

OUT

V

< 2V; VIN = 2.7V to 5.5V; I

OUT

20mA < I

V

≤ 0.4V

FB

I

= 50mA; VFB = 0.7V

SW

< 3A 0.2 %

LOAD

+500mV to 5.5V; I

OUT

FB_NOM

= 100mA

LOAD

= 100mA

LOAD

= 100mA

LOAD

(High Side Switch)

0.98

0.07 %

100

%

95

1.8

0.5

2

0.85

1.02

200

300

2.2

1.3

2.3

= 500µA 145

PGOOD

250

160

20

V
V

µA
µA

V

mΩ
mΩ

MHz

V

µA

Ω

°C

°C

May 2007

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Micrel, Inc. MIC4721

Typical Characteristics

3.3VIN to 2.5VO Efficiency

94
93
92
91
90
89
88
87
86
85
84

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

3.3VIN to 1.2VO Efficiency

82
80
78
76
74
72
70
68
66

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

5VIN to 2.5VO Efficiency

100

90
80
70
60
50
40
30
20
10

0

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

5VIN to 1.2VO Efficiency

80
70
60
50
40
30
20
10

0

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

3.3VIN to 1.8VO Efficiency

90
88
86
84
82
80
78
76

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

3.3VIN to 1VO Efficiency

90
80
70
60
50
40
30
20
10

0

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

OUTPUT CURRENT (A)

5VIN to 1.8VO Efficiency

90
80
70
60
50
40
30
20
10

0

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

3.3VIN to 1.5VO Efficiency

86
84
82
80
78
76
74
72

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

5VIN to 3.3VO Efficiency

94
92
90
88
86
84
82
80
78
76

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

5VIN to 1.5VO Efficiency

90
80
70
60
50
40
30
20
10

0

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

5VIN to 1VO Efficiency

80
70
60
50
40
30
20
10

0

0 0.2 0.4 0.6 0.8 1.2 1.4 1.6

OUTPUT CURRENT (A)

1.0

May 2007

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Micrel, Inc. MIC4721

Typical Characteristics

Load Regulation

0.02

0.00

-0.02

-0.04

-0.06

-0.08
VO = 1.8V

= 3.3V

V

IN

-0.10

0 0.5 1.0 1.5 2.0

OUTPUT CURRENT (A)

Reference Voltage

1.002

1.001

1.000

0.999

0.998

0.997

0.996

0.995

vs. Input Voltage

2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)

Quiescent Current

3.5

3.0

2.5

2.0

1.5

1.0

0.5

vs. Temperature

VIN = 2.5V

0

TEMPERATURE (°C)

VIN = 3.3V

20 40 60 80

Switch On-Resistance

180
170
160
150
140
130
120
110
100

vs. Input Voltage

RON @ I

RON @ I

2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)

OUT

OUT

= 0.1A

= 1.5A

Line Regulation

0.000

-0.005

-0.010

-0.015

-0.020

-0.025

-0.030

-0.035

-0.040

-0.045
VO = 1.8V

-0.050

23456

I

= 100mA

OUT

I

= 1.5A

OUT

INPUT VOLTAGE (V)

1.005

1.000

0.995

0.990

0.985

0.980

0.975

0.970

Switching Frequency

2.04

2.02

2.00

1.98

1.96

1.94

1.92

1.90

vs. Temperature

20 40 60 80

TEMPERATURE (°C)

2.20

2.15

2.10

2.05

2.00

1.95

1.90

1.85

1.80

Quiescent Current

vs. Input Voltage

1.4

1.2

1.0

0.8

0.6

0.4

0.2
0

0123456

INPUT VOLTAGE (V)

Enable Threshold

1.10

1.05

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

vs. Input Voltage

Turn-on

Turn-off

2.5 3 3.5 4 4.5 5 5.5 6

INPUT VOLTAGE (V)

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

Reference Voltage

vs. Temperature

VIN = 3.3V

20 40 60 80

TEMPERATURE (°C)

Switching Frequency

vs. Input Voltage

2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)

Switch On-Resistance

200
180
160
140
120
100

vs. Temperature

RON @ 3.3V

80
60
40
20

0

TEMPERATURE (°C)

RON @ 2.7V

RON @ 5V

IN

20 40 60 80

IN

Enable Threshold

vs. Temperature

Turn-on

Turn-off

VIN = 3.3V

20 40 60 80

TEMPERATURE (°C)

IN

May 2007

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Micrel, Inc. MIC4721

Functional Characteristics

May 2007

6

M9999-052907-A