June 2001

MIC2178

Micrel

MIC2178

2.5A Synchronous Buck Regulator

Final Information

General Description

The Micrel MIC2178 is a 200kHz synchronous buck (step-
down) switching regulator designed for high-efficiency, bat-
tery-powered applications.

The MIC2178 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 MIC2178 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 intelli-
gent 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 MIC2178 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 MIC2178 and is packaged in a 20-lead wide power SOIC
package with an operating temperature range of 40

C to

+85

See the MIC2177 for automatic selection of 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
600

A in skip mode

< 5

A 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
· Palmtop computers
· Laptop computers
· Cellular telephones
· Hand-held instruments
· Battery Chargers

BIAS

SGND

COMP

PGND

OUT

VIN

220

10V

OUT

5V/2.5A

L1, 33

6.8nF

C4
0.01

R2
10k

MIC2178-5.0

PWM

SYNC

10k

5.4V to 18V

C2
22

35V

1417

3,8

1,2,9

D1
MBRS140

ENABLE

OFF

PWRGD

20k

Skip Mode

PWM Mode

Ouput Good

Output Low

C6
220

10V

35V

100

1000 2500

EFFICIENCY (%)

OUTPUT CURRENT (mA)

5V Output
Efficiency

= 6V

SKIP

PWM

Micrel, Inc. · 1849 Fortune Drive · San Jose, CA 95131 · USA · tel + 1 (408) 944-0800 · fax + 1 (408) 944-0970 · http://www.micrel.com

MIC2178

Micrel

MIC2178

June 2001

Pin Description

Pin Number

Pin Name

Pin Function

1, 2, 9

VIN

Supply Voltage (Input): Requires bypass capacitor to PGND. All three pins
must be connected to V

3, 8

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

4, 5, 6, 7

PGND

Power Ground: Connect all pins to central ground point.

PWM

PWM/Skip-Mode Control (Input): Logic-level input. Controls regulator
operating mode. Logic low enables PWM mode. Logic high enables skip
mode. Do not allow pin to float.

PWRGD

Error Flag (Output): Open-drain output. Active low when FB input is 10%
below the reference voltage (V

REF

Feedback (Input): Connect to output voltage divider resistors.

COMP

Compensation: Output of internal error amplifier. Connect capacitor or
series RC network to compensate the regulator control loop.

14, 15, 16, 17

SGND

Signal Ground: Connect all pins to ground, PGND*.

SYNC

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

BIAS

Internal 3.3V Bias Supply: Decouple with 0.01

F 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

PWM

11 PWRGD

COMP

SGND

20-Lead Wide Power SOIC

Ordering Information

Part Number

Voltage

Temperature Range

Package

MIC2178BWM

Adjustable

C to +85

20-lead Wide SOIC

MIC2178-3.3BWM

3.3V

C to +85

20-lead Wide SOIC

MIC2178-5.0BWM

5.0V

C to +85

20-lead Wide SOIC

June 2001

MIC2178

Micrel

Absolute Maximum Ratings

Supply Voltage [100ms transient] (V

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

Output Switch Voltage (V

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

Output Switch Current (I

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

Enable, PWM Control Voltage (V

, V

PWM

) ................. 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,

600

750

4.5V

16.5V

= 0V, 4.5V

16.5V

BIAS

Bias Regulator Output Voltage

= 16.5V

3.10

3.30

3.4

Feedback Voltage

MIC2178 [adj.]: V

OUT

= 3.3V, I

LOAD

= 0

1.22

1.245

1.27

OUT

Output Voltage

MIC2178 [adj.]: V

OUT

= 3.3V,

3.20

3.3

3.40

16V, 10mA

LOAD

3.14

3.46

MIC2178-5.0: I

LOAD

= 0

4.85

5.0

5.15

MIC2178-5.0:

4.85

5.0

5.15

16V, 10mA

LOAD

4.75

5.25

MIC2178-3.3: I

LOAD

= 0

3.20

3.3

3.40

MIC2178-3.3:

3.20

3.3

3.40

16V, 10mA

LOAD

3.14

3.46

Undervoltage Lockout

upper threshold

4.25

4.35

lower threshold

3.90

4.15

Feedback Bias Current

MIC2178 [adj.]

150

MIC2178-5.0, MIC2178-3.3

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

June 2001

MIC2178

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

MIC2178 [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

MIC2178-3.3

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

MIC2178-5.0

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

June 2001

MIC2178

Micrel

Functional Description

Micrel's MIC2178 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. Its has internal
power MOSFETs that supply up to 2.5A load current and
operates with up to 100% duty cycle to allow low-dropout
operation. To optimize efficiency, the MIC2178 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. PWM or skip-mode operation
is selected externally, allowing an intelligent system (i.e.
microprocessor controlled) to select the correct operating
mode for efficiency and noise requirements.

During PWM operation, the MIC2178 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 more detail.

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 MIC2178 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 MIC2178 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 to 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 MIC2178
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 MIC2178 has a low-current shutdown mode that is
controlled by the enable input (EN). When a logic 0 is applied
to EN, the MIC2178 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 MIC2178
control circuits. This internal supply is brought out to the BIAS
pin for bypassing by an external 0.01

F capacitor. Do not

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

Frequency Synchronization

The MIC2178 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.

Power Good Flag

The power good flag (PWRGD) is an error flag that alerts a
system when the output is not in regulation. When the output
voltage is 10% below its nominal value, PWRGD is logic low,
signaling that V

OUT

is to low. PWRGD is an open-drain output

that can sink 1mA from a pull-up resistor connected to V

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 MIC2178 operating in PWM mode
and 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 MIC2178 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

MIC2178

Micrel

MIC2178

June 2001

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 the 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
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 simplified
block diagram of the MIC2178 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 MIC2178 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, and this
begins another switching cycle.

The skip-mode comparator regulates V

OUT

by controlling

when the MIC2178 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

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 MIC2178 to always supply up to 300mA of load
current when operating in skip mode.

Selecting PWM- or Skip-Mode Operation

PWM or skip mode operation is selected by an external logic
signal applied to the PWM pin. A logic low places the
MIC2178 into PWM mode, and logic high places it into skip
mode. Skip mode operation provides the best efficiency
when load current is less than 200mA, and PWM operation is
more efficient at higher currents.

The MIC2178 was designed to be used in intelligent systems
that determine when it should operate in PWM or skip mode.
This makes the MIC2178 ideal for applications where a
regulator must guarantee low noise operation when supply-
ing light load currents, such as cellular telephone, audio, and
multimedia circuits.

There are two important items to be aware of when selecting
PWM or skip mode. First, the MIC2178 can start-up only in
PWM mode, and therefore requires a logic low at PWM during
start-up. Second, in skip mode, the MIC2178 will supply a
maximum load current of approximately 300mA, so the
output will drop out of regulation when load current exceeds
this limit. To prevent this from occurring, the MIC2178 should
change from skip to PWM mode when load current exceeds
200mA.

June 2001

MIC2178

Micrel

Application Information

Feedback Resistor Selection (Adjustable Version)

The output voltage is programmed by connecting an external
resistive divider to the FB pin as shown in "MIC2178 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 with 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 0.2in, 5mm). Also, place a 0.1

F ceramic bypass

capacitor as close as possible to VIN.

Inductor Selection

The MIC2178 is a current-mode controller with internal slope
compensation. As a result, the inductor must be at least a
minimum value to prevent subharmonic oscillations. This
minimum value is calculated by the following formula:

= V

3.0 H/V

MIN

OUT

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:

= I

L(peak)

LOAD(max)

L(max)

Where:

= V

5 s

L(max)

OUT

IN(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

x ESR. Therefore, ESR

must be equal or less than a maximum value calculated for a
specified V

RIPPLE

(typically less than 1% of the output volt-

age) and

L(max)

ESR

MAX

RIPPLE

L(max)

Typically, capacitors in the range of 100 to 220

F have ESR

less than this maximum value. The output capacitor can be
a low ESR electrolytic or tantalum capacitor, but tantalum is
a better choice for compact layout and operation at tempera-
tures 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 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 condi-
tions 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, the 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 to 10nF for the capacitor and 5k

to 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
MIC2178. A good design takes into consideration compo-
nent 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.

MIC2178

Micrel

MIC2178

June 2001

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

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
100

10V

OUT

3.3V/1A

6.8nF

0.01

R3
10k

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R1
20k

10k

4.5V to 16.5V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178-3.3BWM

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

Figure 1. MIC2178 4.5V16.5V to 3.3V/1A Regulator

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
100

10V

OUT

5V/1A

6.8nF

C3
0.01

R3
10k

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R1
20k

10k

5.4V to 16.5V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178-5.0BWM

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

Figure 2. MIC2178 5.4V16.5V to 5V/1A Regulator

currents returning to the power supply ground bus. SGND
and PGND should be tied together by a ground plane that
extends under the MIC2178.

June 2001

MIC2178

Micrel

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
68

20V

OUT

12V/1A

6.8nF

C3
0.01

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R2
174k
1%

R1
20k
1%

R1
20k

10k

12.5V to 16.5V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178BWM

C1 AVX

TPSE226M035R0300, ESR = 0.3

C2 AVX

TPSE686M020R0150, ESR = 0.15

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

MBRS130LT3

Coiltronics CTX68-4P, DCR = 0.238

Coilcraft

DO3316P-683, DCR = 0.016

HM77-11003, DCR = 0.233

R3
10k

Figure 3. MIC2178 12.5V16.5V to 12V/1A Regulator

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
220

10V
X2

OUT

3.3V/2.5A

6.8nF

C3
0.01

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R1
20k

10k

10V to 16.5V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178-3.3BWM

C1 AVX

TPSE226M035R0300, ESR = 0.3

C2 AVX

TPSE227M010R0100, ESR = 0.1

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

MBRS130LT3

HM77-18004, DCR = 0.075

R3
10k

Figure 4. MIC2178 10V16.5V to 3.3V/2.5A Regulator

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
100

10V

OUT

3.3V/1A

6.8nF

C3
0.01

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R1
20k

10k

4.5V to 10V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178-3.3BWM

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 CTX33-3P, DCR = 0.077

Coilcraft

DO3316-333, DCR = 0.088

HM77-60002, DCR = 0.035

R3
10k

Figure 5. MIC2178 4.5V10V to 3.3V/1A Regulator

MIC2178

Micrel

MIC2178

June 2001

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
100

10V

OUT

3.3V/1A

6.8nF

C3
0.01

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R1
20k

10k

4.5V to 16.5V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178-3.3BWM

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

Q1 Siliconix

Si9435DY PMOS

Coiltronics CTX50-4P, DCR = 0.097

Coilcraft

DO3316-473, DCR = 0.12

HM77-11003, DCR = 0.073

SI9435

C3
0.01

Figure 6. MIC2178 Reversed Battery Protected Regulator

BIAS

SGND

PWRGD

COMP

PGND

VIN

C2
100

10V

OUT

/+I

OUT

5V/0.5A

6.8nF

C5
0.01

MIC2178

PWM

Skip Mode

PWM Mode

SYNC

R1
20k

10k

8V to 16.5V

35V

1417

3,8

1,2,9

D1
MBRS130L

U1 Micrel

MIC2178-5.0BWM

C1 AVX

TPSE226M035R0300, ESR = 0.3

C2 AVX

TPSD107M010R0100, ESR = 0.1

C3 AVX

TPSD107M010R0100, ESR = 0.1

C4 AVX

TPSD107M010R0100, ESR = 0.1

C5 Z5UorX7R Ceramic Dielectric Material
C6 X7RorNP0 Ceramic Dielectric Material
D1 Motorola

MBRS130LT3

D2 Motorola

MBRS130LT3

Coiltronics CTX50-4P, DCR = 0.097

100

10V

MBRS130L

C2
100

10V

OUT

/-I

OUT

5V/0.5A

OUT

+ (I

OUT

)

DC = +

OUT

40% then I

OUT

+ I

OUT

40% then I

OUT

+ I

OUT

(1 DC)

R3
10k

Figure 7. MIC2178 8V16.5V to

5V/500mA Regulator

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MIC2178-5.0

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MIC2178-5.0