April 1999

MIC2177

Micrel

MIC2177

Micrel

MIC2177

2.5A Synchronous Buck Regulator

General Description

The Micrel MIC2177 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency, bat-
tery-powered applications.

The MIC2177 operates from a 4.5V to 16.5V input and
features internal power MOSFETs that can supply up to 2.5A
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
5

The MIC2177 achieves high efficiency over a wide output
current range by switching between PWM and skip mode.
Operating mode is automatically selected according to output
conditions. Switching frequency is preset to 200kHz and can
be synchronized to an external clock signal of up to 300kHz.

The MIC2177 uses current-mode control with internal current
sensing. Current-mode control provides superior line regula-
tion and makes the regulator control loop easy to compen-
sate. 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 MIC2177 is packaged in a 20-lead wide power SO
package with an operating temperature range of 40

C to

+85

See the MIC2178 for externally selected PWM or skip-mode
operation.

Typical Application

Features

· 4.5V to 16.5V input voltage range
· Dual-mode operation for high efficiency (up to 96%)

PWM mode for > 200mA load current
Skip mode for < 200mA load current

· 100m

internal power MOSFETs at 12V input

· 200kHz preset switching frequency
· Low quiescent current

1.0mA in PWM mode
500

A in skip mode

< 5

A in shutdown mode

· 100% duty cycle for low dropout operation
· Current-mode control

Simplified loop compensation
Superior line regulation

· 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

BIAS

SGND

COMP

PGND

OUT

VIN

C3
220µF
10V

OUT

5V/2.5A

L1, 33µH

10nF

C4
0.01µF

MIC2177-5.0

AUTO

SYNC

15k

6V to 16.5V

22µF

35V

1417

3,8

1,2,9

D1
MBRS140

ENABLE

2.2nF

AUTO

MODE

PWM
MODE

Mode

OFF

22µF

35V

C7
220µF
10V

100

1000 2500

EFFICIENCY (%)

OUTPUT CURRENT (mA)

5V Output
Efficiency

= 6V

SKIP

PWM

MIC2177

Micrel

MIC2177

April 1999

Ordering Information

Part

Output

Switching

Temperature

Number

Voltage

Frequency

Range

Package

MIC2177-3.3BWM

3.3V

200kHz

C to +85

20-lead wide SOP

MIC2177-5.0BWM

5.0V

200kHz

C to +85

20-lead wide SOP

MIC2177BWM

adj.

200kHz

C to +85

20-lead wide SOP

Pin Description

Pin Number

Pin Name

Pin Function

1, 2, 9

VIN

Supply Input: Controller and switch supply. Unregulated supply input to
internal regulator, output switches, and control circuitry. Requires bypass
capacitor to PGND. All three pins must be connected to V

3,8

Switch (Output): Internal power MOSFET switch output. Both pins must be
externally connected together.

4,5,6,7

PGND

Power Ground: Output stage ground connections. Connect all pins to a
common ground plane.

OUT

Output Voltage Sense (Input): Senses output voltage to determine minimum
switch current for PWM operation. Connect directly to V

OUT

AUTO

Automatic Mode: Connect 2.2nF timing capacitor for automatic PWM-/skip-
mode switching. Regulator operates exclusively in PWM mode when pin is
pulled low.

Feedback (Input): Error amplifier inverting input. For adjustable output
version, connect FB to external resistive divider to set output voltage. For
3.3V and 5V fixed output versions, connect FB directly to output.

COMP

Compensation: Internal error amplifier output. Connect to capacitor or series
RC network to compensate the regulator control loop.

14,15,16,17

SGND

Signal Ground: Ground connection of control section. Connect all pins to
common ground plane.

SYNC

Frequency Synchronization (Input): Optional clock input. Connect to
external clock signal to synchronize oscillator. Leading edge of signal above
1.7V terminates switching cycle. Connect to SGND if not used.

BIAS

Bias Supply: Internal 3.3V bias supply output. Decouple with 0.01

bypass capacitor to SGND. Do not apply any external load.

Enable (Input): Logic high enables operation. Logic low shuts down
regulator. Do not allow pin to float.

Pin Configuration

VIN

PGND

VIN

BIAS

SYNC

SGND

OUT

11 AUTO

COMP

SGND

20-Lead Wide SOP

April 1999

MIC2177

Micrel

Absolute Maximum Ratings

Supply Voltage [100ms transient] (V

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

Output Switch Voltage (V

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

Output Switch Current (I

) ......................................... 6.0A

Enable, Output-Sense Voltage (V

, V

OUT

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

Sync Voltage (V

SYNC

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

Operating Ratings

Supply Voltage (V

) ..................................... 4.5V to 16.5V

Junction Temperature Range (T

) ........... 40

C to +125

Electrical Characteristics

= 7.0V; T

= 25

C, bold indicates 40

C; unless noted.

Symbol

Parameter

Condition

Min

Typ

Max

Units

Input Supply Current

PWM mode, output not switching,

1.0

1.5

4.5V

16.5V

skip mode, output not switching,

500

650

4.5V

16.5V

= 0V, 4.5V

16.5V

BIAS

Bias Regulator Output Voltage

= 16.5V

3.10

3.30

3.4

Feedback Voltage

MIC2177 [adj.]: V

OUT

= 3.3V, I

LOAD

= 0

1.22

1.245

1.27

OUT

Output Voltage

MIC2177 [adj.]: V

OUT

= 3.3V,

3.20

3.3

3.40

16V, 10mA

LOAD

3.14

3.46

MIC2177-5.0: I

LOAD

= 0

4.85

5.0

5.15

MIC2177-5.0:

4.85

5.0

5.15

16V, 10mA

LOAD

4.75

5.25

MIC2177-3.3: I

LOAD

= 0

3.20

3.3

3.40

MIC2177-3.3:

3.20

3.3

3.40

16V, 10mA

LOAD

3.14

3.46

Undervoltage Lockout

upper threshold

4.25

4.35

lower threshold

3.9

4.15

Feedback Bias Current

MIC2177 [adj.]

150

MIC2177-5.0, MIC2177-3.3

VOL

Error Amplifier Gain

0.6V

COMP

0.8V

Error Amplifier Output Swing

upper limit

0.9

1.5

lower limit

0.05

0.1

Error Amplifier Output Current

source and sink

Oscillator Frequency

160

200

240

kHz

MAX

Maximum Duty Cycle

= 1.0V

100

ON min

Minimum On-Time

= 1.5V

300

400

SYNC Frequency Range

220

300

kHz

SYNC Threshold

0.8

1.6

2.2

SYNC Minimum Pulse Width

500

SYNC

SYNC Leakage

SYNC

= 0V to 5.5V

0.01

LIM

Current Limit

PWM mode, V

= 12V

3.8

4.7

5.7

skip mode

600

Switch On-Resistance

high-side switch, V

= 12V

250

low-side switch, V

= 12V

110

250

Output Switch Leakage

= 16.5V

April 1999

MIC2177

Micrel

Typical Characteristics

175

180

185

190

195

200

205

-60 -30

90 120 150

FREQUENCY (kHz)

TEMPERATURE (

Oscillator Frequency

vs. Temperature

1.238

1.240

1.242

1.244

1.246

1.248

1.250

1.252

-60 -30

90 120 150

REFERENCE VOLTAGE (V)

TEMPERATURE (

Reference Voltage

vs. Temperature

MIC2177 [adj.]

3.280

3.285

3.290

3.295

3.300

3.305

3.310

3.315

3.320

-60 -30

90 120 150

REFERENCE VOLTAGE (V)

TEMPERATURE (

Reference Voltage

vs. Temperature

MIC2177-3.3

4.970

4.980

4.990

5.000

5.010

5.020

5.030

-60 -30

90 120 150

REFERENCE VOLTAGE (V)

TEMPERATURE (

Reference Voltage

vs. Temperature

MIC2177-5.0

16.0

16.5

17.0

17.5

18.0

18.5

19.0

-60 -30

90 120 150

AMPLIFIER VOLTAGE GAIN

TEMPERATURE (

Error-Amplifier Gain

vs. Temperature

100

120

-60 -30

90 120 150

BIAS CURRENT (nA)

TEMPERATURE (

Feedback Input Bias Current

vs. Temperature

4.0

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

5.0

-60 -30

90 120 150

CURRENT LIMIT (A)

TEMPERATURE (

Current Limit

vs. Temperature

100

150

200

250

10 12 14 16 18

ON-RESISTANCE (m

)

INPUT VOLTAGE (V)

High-Side Switch

On-Resistance

125

100

150

200

250

300

350

10 12 14 16 18

ON-RESISTANCE (m

)

INPUT VOLTAGE (V)

Low-Side Switch

On-Resistance

125

10 12 14 16 18

SUPPLY CURRENT (mA)

INPUT VOLTAGE (V)

PWM-Mode

Supply Current

OUTPUT

SWITCHING

100

1000 2500

EFFICIENCY (%)

OUTPUT CURRENT (mA)

= 5V

12V

3.3V Output

Efficiency

SKIP

PWM

100

1000 2500

EFFICIENCY (%)

OUTPUT CURRENT (mA)

12V

5V Output
Efficiency

= 6V

SKIP

PWM

April 1999

MIC2177

Micrel

Functional Description

Micrel's MIC2177 is a synchronous buck regulator that oper-
ates from an input voltage of 4.5V to 16.5V and provides a
regulated output voltage of 1.25V to 16.5V. It has internal
power MOSFETs that supply up to 2.5A of load current and
operates with up to 100% duty cycle to allow low-dropout
operation. To optimize efficiency, the MIC2177 operates in
PWM and skip mode. Skip mode provides the best efficiency
when load current is less than 200mA, while PWM mode is
more efficient at higher current. A patented technique allows
the MIC2177 to automatically select the correct operating
mode as the load current changes.

During PWM operation, the MIC2177 uses current-mode
control which provides superior line regulation and makes the
control loop easier to compensate. The PWM switching
frequency is set internally to 200kHz and can be synchro-
nized to an external clock frequency up to 300kHz. Other
features include a low-current shutdown mode, current limit,
undervoltage lockout, and thermal shutdown. See the follow-
ing sections for details.

Switch Output

The switch output (SW) is a half H-bridge consisting of a high-
side P-channel and low-side N-channel power MOSFET.
These MOSFETs have a typical on-resistance of 100m

when the MIC2177 operates from a 12V supply. Antishoot-
through circuitry prevents the P-channel and N-channel from
turning on at the same time.

Current Limit

The MIC2177 uses pulse-by-pulse current limiting to protect
the output. During each switching period, a current limit
comparator detects if the P-channel current exceeds 4.7A.
When it does, the P-channel is turned off until the next
switching period begins.

Undervoltage Lockout

Undervoltage lockout (UVLO) turns off the output when the
input voltage (V

) is too low to provide sufficient gate drive for

the output MOSFETs. It prevents the output from turning on
until V

exceeds 4.3V. Once operating, the output will not

shut off until V

drops below 4.2V.

Thermal Shutdown

Thermal shutdown turns off the output when the MIC2177
junction temperature exceeds the maximum value for safe
operation. After thermal shutdown occurs, the output will not
turn on until the junction temperature drops approximately
10

Shutdown Mode

The MIC2177 has a low-current shutdown mode that is
controlled by the enable input (EN). When a logic 0 is applied
to EN, the MIC2177 is in shutdown mode and its quiescent
current drops to less than 5

Internal Bias Regulator

An internal 3.3V regulator provides power to the MIC2177
control circuits. This internal supply is brought out to the BIAS
pin for bypassing by an external 0.01

F capacitor. Do not

connect any external load to the BIAS pin. It is not designed
to provide an external supply voltage.

Frequency Synchronization

The MIC2177 operates at a preset switching frequency of
200kHz. It can be synchronized to a higher frequency by
connecting an external clock to the SYNC pin. The SYNC pin
is a logic level input that synchronizes the oscillator to the
rising edge of an external clock signal. It has a frequency
range of 220kHz300kHz, and can operate with a minimum
pulse-width of 500ns. If synchronization is not required,
connect SYNC to ground.

Low-Dropout Operation

Output regulation is maintained in PWM or skip mode even
when the difference between V

and V

OUT

decreases below

1V. As V

OUT

decreases, the duty cycle increases until

it reaches 100%. At this point, the P-channel is kept on for
several cycles at a time, and the output stays in regulation
until V

OUT

falls below the dropout voltage (dropout

voltage = P-channel on resistance

load current).

PWM-Mode Operation

Refer to "PWM-Mode Functional Diagram" which is a simpli-
fied block diagram of the MIC2177 operating in PWM mode
with its associated waveforms.

When operating in PWM mode, the output P-channel and N-
channel MOSFETs are alternately switched on at a constant
frequency and variable duty cycle. A switching period begins
when the oscillator generates a reset pulse. This pulse resets
the RS latch which turns on the P-channel and turns off the
N-channel. During this time, inductor current (I

) increases

and energy is stored in the inductor. The current sense
amplifier (I

SENSE

Amp) measures the P-channel drain-to-

source voltage and outputs a voltage proportional to I

. The

output of I

SENSE

Amp is added to a sawtooth waveform

(corrective ramp) generated by the oscillator, creating a
composite waveform labeled I

SENSE

on the timing diagram.

When I

SENSE

is greater than the error amplifier output, the

PWM comparator will set the RS latch which turns off the P-
channel and turns on the N-channel. Energy is then dis-
charged from the inductor and I

decreases until the next

switching cycle begins. By varying the P-channel on-time
(duty cycle), the average inductor current is adjusted to
whatever value is required to regulate the output voltage.

The MIC2177 uses current-mode control to adjust the duty
cycle and regulate the output voltage. Current-mode control
has two signal loops that determine the duty cycle. One is an
outer loop that senses the output voltage, and the other is a
faster inner loop that senses the inductor current. Signals
from these two loops control the duty cycle in the following
way: V

OUT

is fed back to the error amplifier which compares

the feedback voltage (V

) to an internal reference voltage

REF

). When V

OUT

is lower than its nominal value, the error

amplifier output voltage increases. This voltage then inter-
sects the current-sense waveform later in switching period
which increases the duty cycle and average inductor current.
If V

OUT

is higher than nominal, the error amplifier output

voltage decreases, reducing the duty cycle.

The PWM control loop is stabilized in two ways. First, the
inner signal loop is compensated by adding a corrective ramp
to the output of the current sense amplifier. This allows the
regulator to remain stable when operating at greater than

MIC2177

Micrel

MIC2177

April 1999

50% duty cycle. Second, a series resistor-capacitor load is
connected to the error amplifier output (COMP pin). This
places a pole-zero pair in the regulator control loop.

One more important item is synchronous rectification. As
mentioned earlier, the N-channel output MOSFET is turned
on after the P-channel turns off. When the N-channel turns
on, its on-resistance is low enough to create a short across
the output diode. As a result, inductor current flows through
the N-channel and the voltage drop across it is significantly
lower than a diode forward voltage. This reduces power
dissipation and improves efficiency to greater than 95%
under certain operating conditions.

To prevent shoot through current, the output stage employs
break-before-make circuitry that provides approximately 50ns
of delay from the time one MOSFET turns off and the other
turns on. As a result, inductor current briefly flows through the
output diode during this transition.

Skip-Mode Operation

Refer to "Skip-Mode Functional Diagram" which is a simpli-
fied block diagram of the MIC2177 operating in skip mode
and its associated waveforms.

Skip-mode operation turns on the output P-channel at a
frequency and duty cycle that is a function of V

, V

OUT

, and

the output inductor value. While in skip mode, the N-channel
is kept off to optimize efficiency by reducing gate charge
dissipation. V

OUT

is regulated by skipping switching cycles

that turn on the P-channel.

To begin analyzing MIC2177 skip-mode operation, assume
the skip-mode comparator output is high and the latch output
has been reset to a logic 1. This turns on the P-channel and
causes I

to increase linearly until it reaches a current limit

of 600mA. When I

reaches this value, the current limit

comparator sets the RS latch output to logic 0, turning off the
P-channel. The output switch voltage (V

) then swings from

to 0.4V below ground, and I

flows through the Schottky

diode. L1 discharges its energy to the output and I

de-

creases to zero. When I

= 0, V

swings from 0.4V to

OUT

, and this triggers a one-shot that resets the RS latch.

Resetting the RS latch turns on the P-channel, which begins
another switching cycle.

The skip-mode comparator regulates V

OUT

by controlling

when the MIC2177 skips cycles. It compares V

to V

REF

and

has 10mV of hysteresis to prevent oscillations in the control
loop. When V

is less than V

REF

5mV, the comparator

output is logic 1, allowing the P-channel to turn on. Con-
versely, when V

is greater than V

REF

+ 5mV, the P-channel

is turned off.

Note that this is a self-oscillating topology which explains
why the switching frequency and duty cycle are a function of
V

, V

OUT

, and the value of L1. It has the unique feature (for

a pulse-skipping regulator) of supplying the same value of
maximum load current for any value of V

, V

OUT

, or L1. This

allows the MIC2177 to always supply up to 300mA of load
current (I

LOAD

) when operating in skip mode.

Changing from PWM to Skip Mode

Refer to "Block Diagram" for circuits described in the following
sections.

The MIC2177 automatically changes from PWM to skip mode
operation when I

LOAD

drops below a minimum value. I

MIN

determined indirectly by detecting when the peak inductor
current (I

L(peak)

) is less than 420mA. This is done by the

minimum current comparator which detects if the output P-
Channel current equals 420mA during each switching cycle.
If it does not, the PWM/skip-mode select logic places the
MIC2177 into skip-mode operation.

The value of I

MIN

that corresponds to I

L1(peak)

= 420mA is

given by the following equation:

420mA I

MIN

Where:

= inductor ripple current

This equation shows I

MIN

varies as a function of

. There-

fore, the user must select an inductor value that results in
I

MIN

= 200mA when I

L(peak)

= 420mA. The formulas for cal-

culating the correct inductor value are given in the "Applica-
tions Information" section. Note that

varies as a function

of input voltage, and this also causes I

MIN

to vary. In applica-

tions where the input voltage changes by a factor of two, I

MIN

will typically vary from 130mA to 250mA.

During low-dropout operation, the minimum current thresh-
old circuit reduces the minimum value of I

L1(peak)

for PWM

operation. This compensates for

decreasing to almost

zero when the difference between V

and V

OUT

is very low.

Changing from Skip to PWM Mode

The MIC2177 will automatically change from skip to PWM
mode when I

LOAD

exceeds 300mA. During skip-mode opera-

tion, it can supply up to 300mA, and when I

LOAD

exceeds this

limit, V

OUT

will fall below its nominal value. At this point, the

MIC2177 begins operating in PWM mode. Note that the
maximum value of I

LOAD

for skip mode is greater than the

minimum value required for PWM mode. This current hyster-
esis prevents the MIC2177 from toggling between modes
when I

LOAD

is in the range of 100mA to 300mA.

The low output comparator determines when V

OUT

is low

enough for the regulator to change operating modes. It
detects when the feedback voltage is 3% below nominal, and
pulls the AUTO pin to ground. When AUTO is less than 1.6V,
the PWM/skip-mode select logic places the MIC2177 into
PWM operation. The external 2.2nF capacitor connected to
AUTO is charged by a 10

A current source after the regulator

begins operating in PWM mode. As a result, AUTO stays
below 1.6V for several switching cycles after PWM operation
begins, forcing the MIC2177 to remain in PWM mode during
this transition.

External PWM-Mode Selection

The MIC2177 can be forced to operate in only PWM mode by
connecting AUTO to ground. This prevents skip-mode opera-
tion in applications that are sensitive to switching noise.

April 1999

MIC2177

Micrel

Application Information

Feedback Resistor Selection (Adjustable Version)

The output voltage is configured by connecting an external
resistive divider to the FB pin as shown in "MIC2177 Block
Diagram." The ratio of R1 to R2 determines the output
voltage. To optimize efficiency during low output current
operation, R2 should not be less than 20k

. However, to

prevent feedback error due to input bias current at the FB pin,
R2 should not be greater than 100k

. After selecting R2,

calculate R1 using the following formula:

R1 = R2

1.245V

OUT

Input Capacitor Selection

The input capacitor is selected for its RMS current and
voltage rating and should be a low ESR (equivalent series
resistance) electrolytic or tantalum capacitor. As a rule-of-
thumb, the voltage rating for a tantalum capacitor should be
twice the value of V

, and the voltage rating for an electrolytic

should be 40% higher than V

IN.

The RMS current rating must

be equal or greater than the maximum RMS input ripple
current. A simple, worst-case formula for calculating this
RMS current is:

RMS(max)

LOAD(max)

Tantalum capacitors are a better choice for applications that
require the most compact layout or operation below 0

C. The

input capacitor must be located very close to the VIN pin
(within 0.2 inches, 5mm). Also place a 0.1

F ceramic bypass

capacitor as close as possible to VIN.

Inductor Selection

The inductor must be at least a minimum value in order for the
MIC2177 to change from PWM to skip mode at the correct
value of output current. This minimum value ensures the
inductor ripple current never exceeds 600mA, and is calcu-
lated using the following formula:

= V

8.3 H/V

MIN

OUT

IN(max)

Where:

IN(max)

= maximum input voltage

In general, a value at least 20% greater than L

MIN

should be

selected because inductor values have a tolerance of

20%.

Two other parameters to consider in selecting an inductor are
winding resistance and peak current rating. The inductor
must have a peak current rating equal or greater than the
peak inductor current. Otherwise, the inductor may saturate,
causing excessive current in the output switch. Also, the
inductor's core loss may increase significantly. Both of these
effects will degrade efficiency. The formula for peak inductor
current is:

300mA

L(peak)

LOAD(max)

To maximize efficiency, the inductor's resistance must be
less than the output switch on-resistance (preferably 50m

or less).

Output Capacitor Selection

Select an output capacitor that has a low value of ESR. This
parameter determines a regulator's output ripple voltage
(V

RIPPLE

) which is generated by

ESR. As mentioned in

"Inductor Selection," the maximum value for

is 600mA.

Therefore, the maximum value of ESR is:

ESR

600mA

MAX

RIPPLE

Where:

RIPPLE

< 1% of V

OUT

Typically, capacitors in the range of 100

F to 220

F have

ESR less than this maximum value. The output capacitor can
be either a low ESR electrolytic or tantalum capacitor, but
tantalum is a better choice for compact layout and operation
at temperatures below 0

C. The voltage rating of a tantalum

capacitor must be 2

OUT

, and the voltage rating of an

electrolytic must be 1.4

OUT

Output Diode Selection

In PWM operation, inductor current flows through the output
diode approximately 50ns during the dead time when one
output MOSFET turns off and the other turns on. In skip
mode, the inductor current flows through the diode during the
entire P-channel off time. The correct diode for both of these
conditions is a 1A diode with a reverse voltage rating greater
than V

. It must be a Schottky or ultrafast-recovery diode

< 100ns) to minimize power dissipation from the diode's

reverse-recovery charge.

Compensation

Compensation is provided by connecting a series RC load to
the COMP pin. This creates a pole-zero pair in the regulator
control loop, allowing the regulator to remain stable with
enough low frequency loop-gain for good load and line
regulation. At higher frequencies, pole-zero reduces loop-
gain to a level referred to as the mid-band gain. The mid-band
gain is low enough so that the loop gain crosses 0dB with
sufficient phase margin. Typical values for the RC load are
4.7nF 10nF for the capacitor and 5k

20k

for the

resistor.

Printed Circuit Board Layout

A well designed PC board will prevent switching noise and
ground bounce from interfering with the operation of the
MIC2177. A good design takes into consideration component
placement and routing of power traces.

The first thing to consider is the locations of the input
capacitor, inductor, output diode, and output capacitor. The
input capacitor must be placed very close to the VIN pin, the
inductor and output diode very close to the SW pin, and the
output capacitor near the inductor. These components pass
large high-frequency current pulses, so they must use short,
wide power traces. In addition, their ground pins and PGND
are connected to a ground plane that is nearest the power
supply ground bus.

MIC2177

Micrel

MIC2177

April 1999

The feedback resistors, RC compensation network, and
BIAS pin bypass capacitor should be located near their
respective pins. To prevent ground bounce, their ground
traces and SGND should not be in the path of switching

currents returning to the power supply ground bus. SGND
and PGND should be tied together by a ground plane that
extends under the MIC2177.

BIAS

SGND

AUTO

COMP

PGND

VIN

C2
100µF
10V

OUT

3.3V/1A

L1, 50µH

6.8nF

C3
0.01µF

MIC2177

SYNC

10k

4.5V to 16.5V

C1
22µF
35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2177-3.3BWM

C1 AVX

TPSE226M035R0300, ESR = 0.3

C2 AVX

TPSD107M010R0100, ESR = 0.1

C3 Z5UorX7R Ceramic Dielectric Material
C4 X7RorNP0 Ceramic Dielectric Material
D1 Motorola

MBRS130LT3

Coiltronics CTX50-4P, DCR = 0.097

Coilcraft

DO3316P-473, DCR = 0.12

HM77-11003, DCR = 0.073

0.01

µF

OUT

Figure 1. MIC2177 4.5V16.5V to 3.3/1A Regulator

Suggested Manufacturers List

Inductors

Capacitors

Diodes

Transistors

Coilcraft

AVX Corp.

General Instruments (GI)

Siliconix

1102 Silver Lake Rd.

801 17th Ave. South

10 Melville Park Rd.

2201 Laurelwood Rd.

Cary, IL 60013

Myrtle Beach, SC 29577

Melville, NY 11747

Santa Clara, CA 96056

tel: (708) 639-2361

tel: (803) 448-9411

tel: (516) 847-3222

tel: (800) 554-5565

fax: (708) 639-1469

fax: (803) 448-1943

fax: (516) 847-3150

Coiltronics

Sanyo Video Components Corp.

International Rectifier Corp.

6000 Park of Commerce Blvd.

2001 Sanyo Ave.

233 Kansas St.

Boca Raton, FL 33487

San Diego, CA 92173

El Segundo, CA 90245

tel: (407) 241-7876

tel: (619) 661-6835

tel: (310) 322-3331

fax: (407) 241-9339

fax: (619) 661-1055

fax: (310) 322-3332

Bi Technologies

Sprague Electric

Motorola Inc.

4200 Bonita Place

Lower Main St.

MS 56-126

Fullerton, CA

60005 Sanford, ME 04073

3102 North 56th St.

tel: (714) 447-2345

tel: (207) 324-4140

Phoenix, AZ 85018

fax: (714) 447-2500

tel: (602) 244-3576
fax: (602) 244-4015

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MIC2177

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MIC2177