MICREL MIC2179-3.3BSM, MIC2179-5.0BSM, MIC2179BSM Datasheet

MIC2179

Micrel

MIC2179

1.5A Synchronous Buck Regulator

General Description

The Micrel MIC2179 is a 200kHz synchronous buck (step­down) switching regulator designed for high-efficiency, bat­tery-powered applications.

The MIC2179 operates from a 4.5V to 16.5V input and
features internal power MOSFETs that can supply up to 1.5A
output current. It can operate with a maximum duty cycle of
100% for use in low-dropout conditions. It also features a
shutdown mode that reduces quiescent current to less than
5µA.

The MIC2179 achieves high efficiency over a wide output
current range by operating in either PWM or skip mode. The
operating mode is externally selected, typically by an intelli­gent system, which chooses the appropriate mode according
to operating conditions, efficiency, and noise requirements.
The switching frequency is preset to 200kHz and can be
synchronized to an external clock signal of up to 300kHz.

The MIC2179 uses current-mode control with internal current
sensing. Current-mode control provides superior line regula­tion and makes the regulator control loop easy to compen­sate. The output is protected with pulse-by-pulse current
limiting and thermal shutdown. Undervoltage lockout turns
the output off when the input voltage is less than 4.5V.

The MIC2179 and is packaged in a 20-lead SSOP package
with an operating temperature range of –40°C to +85°C.

Features

• 4.5V to 16.5V input voltage range

• Dual-mode operation for high efficiency (up to 96%)
PWM mode for > 150mA load current
Skip mode for <150mA load current

• 150mΩ internal power MOSFETs at 12V input

• 200kHz preset switching frequency

• Low quiescent current

1.0mA in PWM mode
600µA in skip mode
< 5µA in shutdown mode

• Current-mode control
Simplified loop compensation
Superior line regulation

• 100% duty cycle for low dropout operation

• Current limit

• Thermal shutdown

• Undervoltage lockout

Applications

• High-efficiency, battery-powered supplies

• Buck (step-down) dc-to-dc converters

• Cellular telephones

• Laptop computers

• Hand-held instruments

• Battery Charger

Typical Application

V

IN

5.4V to 16.5V
C1

10µF

20V

Output Good

Output Low

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

Skip Mode

PWM Mode

R1
20k

15

13

C4

6.8nF

U1

EN

6

PWRGD

5

PWM
SYNC

COMP

R2

10k

June 1998 1 MIC2179

8

16,17

VIN

MIC

2179-3.3

9–12 14

SW

PGND

FB

BIASSGND

3,4

1,2,
19,20

7

C3

0.01µF

L1

22µH

D1
MBRM120

Pins 4 and 18 are not connected.
Pins 3 and 4 can be connected

together for a low-impedance
connection.

C2
100µF

6.3V

V

OUT

3.3V/600mA

MIC2179

Ordering Information

Part Number Voltage Temperature Range Package

MIC2179BSM Adjustable –40°C to +85°C 20-lead SSOP
MIC2179-3.3BSM 3.3V –40°C to +85°C 20-lead SSOP
MIC2179-5.0BSM 5.0V –40°C to +85°C 20-lead SSOP

Pin Configuration

Micrel

PGND

SW

NC

PWM

PWRGD

FB

COMP

SGND
SGND

Pin Description

Pin Number Pin Name Pin Function

1, 2, 19, 20 PGND Power Ground: Connect all pins to central ground point.

3 SW Switch (Output): Internal power MOSFET output switches.
5 PWM PWM/Skip-Mode Control (Input): Logic-level input. Controls regulator

6 PWRGD Error Flag (Output): Open-drain output. Active low when FB input is 10%

7 FB Feedback (Input): Connect to output voltage divider resistors.
8 COMP Compensation: Output of internal error amplifier. Connect capacitor or

9–12 SGND Signal Ground: Connect all pins to ground, PGND.

13 SYNC Frequency Synchronization (Input): Optional. Connect an external clock

14 BIAS Internal 3.3V Bias Supply: Decouple with 0.01µF bypass capacitor to

15 EN Enable (Input): Logic high enables operation. Logic low shuts down

16, 17 VIN Supply Voltage (Input): Requires bypass capacitor to PGND. Both pins

4, 18 NC not internally connected.

1PGND
2
3
4
5
6
7
8
9

10

19
18
17
16
15
14
13
12
11

PGND20
PGND
NC
VIN
VIN
EN
BIAS
SYNC
SGND
SGND

20-Lead Wide SSOP

operating mode. Logic low enables PWM mode. Logic high enables skip
mode. Do not allow pin to float.

below the reference voltage (V

series RC network to compensate the regulator control loop.

signal to synchronize the oscillator. Leading edge of signal above 1.7V
terminates switching cycle. Connect to SGND if not used.

SGND. Do not apply any external load.

regulator. Do not allow pin to float.

must be connected to VIN.

REF

).

MIC2179 2 June 1998

MIC2179

Micrel

Absolute Maximum Ratings

Supply Voltage [100ms transient] (VIN).........................18V

Output Switch Voltage (VSW) ........................................18V

Operating Ratings

Supply Voltage (VIN) ..................................... 4.5V to 16.5V

Junction Temperature Range (TJ) ........... –40°C to +125°C

Output Switch Current (ISW).........................................6.0A

Enable, PWM Control Voltage (VEN, V
Sync Voltage (V

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

SYNC

) .................18V

PWM

Electrical Characteristics

VIN = 7.0V; TA = 25°C, bold indicates –40°C ≤ TA ≤ 85°C; unless noted.
Symbol Parameter Condition Min Typ Max Units

I

SS

V

BIAS

V

FB

V

OUT

V

TH

V

TL

I

FB

A

VOL

f

O

D

MAX

t

ON min

I

SYNC

I

LIM

R

ON

I

SW

Input Supply Current PWM mode, output not switching, 1.0 1.5 mA

4.5V ≤ VIN ≤ 16.5V
skip mode, output not switching, 600 750 µA

4.5V ≤ VIN ≤ 16.5V

VEN = 0V, 4.5V ≤ VIN ≤ 16.5V 1 25 µA
Bias Regulator Output Voltage VIN = 16.5V 3.10 3.30 3.4 V
Feedback Voltage MIC2179 [adj.]: V
Output Voltage MIC2179 [adj.]: V

5V ≤ VIN ≤ 16V, 10mA ≤ I

MIC2179-5.0: I

= 3.3V, I

OUT

= 3.3V, 3.20 3.3 3.40 V

OUT

LOAD

= 0 4.85 5.0 5.15 V

LOAD

= 0 1.22 1.245 1.27 V

LOAD

≤ 1A 3.14 3.46 V

MIC2179-5.0: 4.85 5.0 5.15

6V ≤ VIN ≤ 16V, 10mA ≤ I

MIC2179-3.3: I

= 0 3.20 3.3 3.40 V

LOAD

≤ 1A 4.75 5.25 V

LOAD

MIC2179-3.3: 3.20 3.3 3.40 V

5V ≤ VIN ≤ 16V, 10mA ≤ I

≤ 1A 3.14 3.46 V

LOAD

Undervoltage Lockout upper threshold 4.25 4.35 V

lower threshold 3.90 4.15 V
Feedback Bias Current MIC2179 [adj.] 60 150 nA

MIC2179-5.0, MIC2179-3.3 20 40 µA
Error Amplifier Gain 0.6V ≤ V

≤ 0.8V 15 18 20

COMP

Error Amplifier Output Swing upper limit 0.9 1.5 V

lower limit 0.05 0.1 V
Error Amplifier Output Current source and sink 15 25 35 µA
Oscillator Frequency 160 200 240 kHz
Maximum Duty Cycle VFB = 1.0V 100 %
Minimum On-Time VFB = 1.5V 300 400 ns
SYNC Frequency Range 220 300 kHz
SYNC Threshold 0.8 1.6 2.2 V
SYNC Minimum Pulse Width 500 ns
SYNC Leakage V

= 0V to 5.5V –1 0.01 1 µA

SYNC

Current Limit PWM mode, VIN = 12V 3.4 4.3 5.5 A

skip mode 600 mA
Switch On-Resistance high-side switch, VIN = 12V 160 350 mΩ

low-side switch, VIN = 12V 140 350 mΩ
Output Switch Leakage VSW = 16.5V 1 10 µA

June 1998 3 MIC2179

MIC2179

Micrel

Symbol Parameter Condition Min Typ Max Units

Enable Threshold 0.8 1.6 2.2 V

I

EN

Enable Leakage VEN = 0V to 5.5V –1 0.01 1 µA
PWM Threshold 0.6 1.1 1.4 V

I

PWM

PWM Leakage V

= 0V to 5.5V –1 0.01 1 µA

PWM

PWRGD Threshold MIC2179 [adj.]: measured at FB pin 1.09 1.13 1.17 V

MIC2179-5.0: measured at FB pin 4.33 4.54 4.75 V

MIC2179-3.3: measured at FB pin 2.87 3.00 3.13 V
PWRGD Output Low I
PWRGD Off Leakage V

General Note: Devices are ESD sensitive. Handling precautions recommended.

= 1.0mA 0.25 0.4 V

SINK

= 5.5V 0.01 1 µA

PWRGD

MIC2179 4 June 1998

MIC2179

1.238

1.240

1.242

1.244

1.246

1.248

1.250

1.252

-60 -30 0 30 60 90 120 150

REFERENCE VOLTAGE (V)

TEMPERATURE (°C)

16.0

16.5

17.0

17.5

18.0

18.5

19.0

-60 -30 0 30 60 90 120 150

AMPLIFIER VOLTAGE GAIN

TEMPERATURE (°C)

0

50

100

150

200

250

300

350

24681012141618

ON-RESISTANCE (mΩ)

INPUT VOLTAGE (V)

60

65

70

75

80

85

90

95

10 100 600

EFFICIENCY (%)

OUTPUT CURRENT (mA)

Typical Characteristics

Micrel

Oscillator Frequency

205

200

195

190

185

FREQUENCY (kHz)

180

175

vs. Temperature

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Reference Voltage

5.030

5.020

5.010

5.000

4.990

4.980

REFERENCE VOLTAGE (V)

4.970

vs. Temperature

MIC2179-5.0

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Reference Voltage

vs. Temperature

MIC2179 [adj.]

Error-Amplifier Gain

vs. Temperature

Reference Voltage

3.320

3.315

3.310

3.305

3.300

3.295

3.290

3.285

REFERENCE VOLTAGE (V)

3.280

vs. Temperature

MIC2179-3.3

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Feedback Input Bias Current

120

100

BIAS CURRENT (nA)

vs. Temperature

80

60

40

20

0

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

5.5

5.3

5.1

4.9

4.7

4.5

4.3

4.1

CURRENT LIMIT (A)

3.9

3.7

3.5

-60 -30 0 30 60 90 120 150

12

10

8

6

June 1998 5 MIC2179

4

2

SUPPLY CURRENT (mA)

0

24681012141618

Current Limit

vs. Temperature

TEMPERATURE (°C)

PWM-Mode

Supply Current

OUTPUT

SWITCHING

INPUT VOLTAGE (V)

High-Side Switch

On-Resistance

125°C

85°C
25°C

Skip- and PWM-Mode

Efficiency

5.4V

PWM

8.4V
Skip

8.4V

5.4V
Skip

PWM

0°C

Low-Side Switch

On-Resistance

125°C

0

24681012141618

INPUT VOLTAGE (V)

ON-RESISTANCE (mΩ)

400
350
300
250
200
150
100

50

85°C
25°C

0°C