Datasheet MIC4680BM, MIC4680-5.0BM, MIC4680-3.3BM Datasheet (MICREL)

MIC4680 Micrel

SW

L1

68µH

IN

FB

GND

SHDN

C2
220µF
16V

D1
B260A or
SS26

3.3V/1A

MIC4680-3.3BM

C1

15µF

35V

+6V to +34V

SHUTDOWN

ENABLE

5–8

4

32

1

Power
SOP-8

MIC4680

1A 200kHz SuperSwitcher™ Buck Regulator

Final Information

General Description

The MIC4680 SuperSwitcher™ is an easy-to-use fixed or
adjustable output voltage step-down (buck) switch-mode
voltage regulator. The 200kHz MIC4680 achieves up to 1.3A
of continuous output current over a wide input range in a
8-lead SOP (small outline package).

The MIC4680 is available in 3.3V and 5V fixed output ver­sions or adjustable output down to 1.25V.

The MIC4680 has an input voltage range of 4V to 34V, with
excellent line, load, and transient response. The regulator
performs cycle-by-cycle current limiting and thermal shut­down for protection under fault conditions. In shutdown
mode, the regulator draws less than 2µA of standby current.

The MIC4680 SuperSwitcher™ regulator requires a mini­mum number of external components and can operate using
a standard series of inductors and capacitors. Frequency
compensation is provided internally for fast transient re­sponse and ease of use.

The MIC4680 is available in the 8-lead SOP with a
–40°C to +125°C junction temperature range.

Features

• SO-8 package with up to 1.3A output current

• All surface mount solution

• Only 4 external components required

• Fixed 200kHz operation

• 3.3V, 5V, and adjustable output versions

• Internally compensated with fast transient response

• Wide 4V to 34V operating input voltage range

• Less than 2µA typical shutdown-mode current

• Up to 90% efficiency

• Thermal shutdown

• Overcurrent protection

Applications

• Simple 1A high-efficiency step-down (buck) regulator

• Replacement of TO-220 and TO-263 designs

• Efficient preregulator (5V to 2.5V, 12V to 3.3V, etc.)

• On-card switching regulators

• Positive-to-negative converter (inverting buck-boost)

• Simple battery charger

• Negative boost converter

• Higher output current regulator using external FET

T ypical Applications

Fixed Regulator Circuit

+5V to +34V

C1

15µF

SHUTDOWN

ENABLE

SuperSwitcher is a trademark of Micrel, Inc.

June 2000 1 MIC4680

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

35V

Power
SOP-8

Adjustable Regulator Circuit

MIC4680BM

IN

1

SHDN

GND

5–8

SW

FB

32

4

L1

68µH

D1
B260A or
SS26

R1

3.01k

R2

2.94k

2.5V/1A

C2
220µF
16V

MIC4680 Micrel

Ordering Information

Part Number Voltage Junction Temp. Range Package

MIC4680BM Adjustable –40°C to +125°C 8-lead SOP
MIC4680-3.3BM 3.3V –40°C to +125°C 8-lead SOP
MIC4680-5.0BM 5.0V –40°C to +125°C 8-lead SOP

Pin Configuration

IN

SW

FB

Pin Description

Pin Number Pin Name Pin Function

1 SHDN Shutdown (Input): Logic low enables regulator. Logic high (>1.6V) shuts

2 VIN Supply Voltage (Input): Unregulated +4V to +34V supply voltage.
3 SW Switch (Output): Emitter of NPN output switch. Connect to external storage

4 FB Feedback (Input): Connect to output on fixed output voltage versions, or to

5–8 GND Ground

1SHDN
2
3
4

8 GND

GND

7

GND

6

GND

5

SOP-8 (M)

down regulator.

inductor and Shottky diode.

1.23V-tap of voltage-divider network for adjustable version.

MIC4680 2 June 2000

MIC4680 Micrel

Absolute Maximum Ratings (Note 1)

Supply Voltage (V
Shutdown Voltage (V

Steady-State Output Switch Voltage (VSW) ..................–1V

), Note 3 ......................................+38V

IN

) .......................... –0.3V to +38V

SHDN

Operating Ratings (Note 2)

Supply Voltage (V

Junction Temperature (TJ) ...................................... +125°C

Package Thermal Resistance (θJA), Note 6............63°C/W

), Note 4 .......................... +4V to +34V

IN

Feedback Voltage [Adjustable] (VFB)..........................+12V

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

ESD, Note 5

Electrical Characteristics

VIN = 12V; I

Parameter Condition Min Typ Max Units
MIC4680 [Adjustable]

Feedback Voltage (±1%) 1.217 1.230 1.243 V

Maximum Duty Cycle VFB = 1.0V 93 97 %
Output Leakage Current VIN = 34V, V

Quiescent Current VFB = 1.5V 7 12 mA

MIC4680-3.3

Output Voltage (±1%) 3.266 3.3 3.333 V

Maximum Duty Cycle VFB = 2.5V 93 97 %
Output Leakage Current VIN = 34V, V

Quiescent Current VFB = 4.0V 7 12 mA

MIC4680-5.0

Output Voltage (±1%) 4.950 5.0 5.05 V

Maximum Duty Cycle VFB = 4.0V 93 97 %
Output Leakage Current VIN = 34V, V

Quiescent Current VFB = 6.0V 7 12 mA

= 500mA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C, Note 7; unless noted.

LOAD

(±2%) 1.205 1.255 V
8V ≤ V

≤ 34V, 0.1A ≤ I

IN

VIN = 34V, V

= 5V, VSW = 0V 50 500 µA

SHDN

= 5V, VSW = –1V 4 20 mA

SHDN

LOAD

≤ 1A, V

= 5V 1.193 1.230 1.267 V

OUT

(±3%) 3.201 3.399 V
6V ≤ VIN ≤ 34V, 0.1A ≤ I

= 5V, VSW = 0V 50 500 µA

SHDN

VIN = 34V, V

= 5V, VSW = –1V 4 20 mA

SHDN

≤ 1A 3.168 3.3 3.432 V

LOAD

(±3%) 4.85 5.15 V
8V ≤ V

≤ 34V, 0.1A ≤ I

IN

VIN = 34V, V

= 5V, VSW = 0V 50 500 µA

SHDN

= 5V, VSW = –1V 4 20 mA

SHDN

≤ 1A 4.800 5.0 5.200 V

LOAD

1.180 1.280 V

3.135 3.465 V

4.750 5.250 V

June 2000 3 MIC4680

MIC4680 Micrel

Parameter Condition Min Typ Max Units
MIC4680/-3.3/-5.0

Frequency Fold Back 30 50 100 kHz
Oscillator Frequency 180 200 220 kHz
Saturation Voltage I

Short Circuit Current Limit VFB = 0V, see Test Circuit 1.3 1.8 2.5 A
Standby Quiescent Current V

Shutdown Input Logic Level regulator off 2 1.6 V

Shutdown Input Current V

Thermal Shutdown 160 °C

Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Absolute maximum rating is intended for voltage transients only, prolonged dc operation is not recommended.
Note 4. V
Note 5. Devices are ESD sensitive. Handling precautions recommended.
Note 6. Measured on 1" square of 1 oz. copper FR4 printed circuit board connected to the device ground leads.
Note 7. Test at TA = +85°C, guaranteed by design, and characterized to TJ = +125°C.

IN(min)

= V

+ 2.5V or 4V whichever is greater.

OUT

= 1A 1.4 1.8 V

OUT

= V

SHDN

V

SHDN

IN

= 5V (regulator off) 30 100 µA

1.5 µA

regulator on 1.0 0.8 V

= 5V (regulator off) –10 –0.5 10 µA

SHDN

V

= 0V (regulator on) –10 –1.5 10 µA

SHDN

V

Test Circuit

SHUTDOWN

Shutdown Input Behavior

ENABLE

ON

+12V

Device Under Test

IN

1

SHDN

GND

SOP-8 5–8

Current Limit Test Circuit

GUARANTEED

ON

0.8V

TYPICAL

ON

1V0V 1.6V V

Shutodwn Hysteresis

SW

FB

32

4

2V

68µH

GUARANTEED

OFF

TYPICAL

OFF

I

OFF

IN(max)

MIC4680 4 June 2000

MIC4680 Micrel

Typical Characteristics

5.06

5.05

5.04

5.03

5.02

5.01

5.00

4.99

4.98

OUTPUT VOLTAGE (V)

4.97

4.96

4.0

3.5

3.0

2.5

2.0

1.5

CURRENT (µA)

1.0

0.5

Line Regulation

I

= 1.0A

OUT

0 5 10 15 20 25 30 35

INPUT VOLTAGE (V)

Shutdown Current

vs. Temperature

VIN = 12V
V

= V

SHDN

IN

0

-50 -25 0 25 50 75 100 125

TEMPERATURE (°C)

5.04

5.02

5.00

4.98

OUTPUT VOLTAGE (V)

4.96

OUTPUT VOLTAGE (V)

Load Regulation

VIN = 12V
V

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

OUTPUT CURRENT (A)

Current Limit

6

5

4

3

2

1

0

Characteristic

VIN = 12V

0 0.2 0.4 0.6 0.8 1.01.2 1.4 1.6 1.8

OUTPUT CURRENT (A)

OUT

= 5V

Shutdown Current

100

CURRENT (µA)

202

201

200

199

198

FREQUENCY (kHz)

197

196

vs. Input Voltage

80

60

40

20

0

0 5 10 15 20 25 30 35

INPUT VOLTAGE (V)

Frequency vs.

Supply Voltage

0 5 10 15 20 25 30 35

SUPPLY VOLTAGE (V)

Frequency vs.

220

210

200

190

FREQUENCY (kHz)

180

-50 -25 0 25 50 75 100 125

80
70
60
50
40
30

EFFICIENCY (%)

20
10

0

Temperature

TEMPERATURE (°C)

3.3V Output
Efficiency

6V

24V

12V

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

OUTPUT CURRENT (A)

Feedback Voltage

1.242

1.240

1.238

1.236

1.234

1.232

1.230

FEEDBACK VOLTAGE (V)

1.228

EFFICIENCY (%)

vs. Temperature

VIN = 12V
V

OUT

I

OUT

-50 -25 0 25 50 75 100 125 150

TEMPERATURE (°C)

5V Output

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

Efficiency

7V

24V

12V

OUTPUT CURRENT (A)

= 5V

= 1A

Saturation Voltage

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

SATURATION VOLTAGE (V)

100

90
80
70
60
50
40
30

EFFICIENCY (%)

20
10

vs. Temperature

VIN = 12V

= 5V

V

OUT

= 1A

I

LOAD

0

-50 -25 0 25 50 75 100 125

TEMPERATURE (°C)

12V Output

Efficiency

15V 24V

0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

OUTPUT CURRENT (A)

June 2000 5 MIC4680

MIC4680 Micrel

Safe

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

OUTPUT CURRENT (A)

0.4

0.3

0.2

0.1
0

0 5 10 15 20 25 30 35

Operating Area

V

= 5V

OUT

T

= 60°C

A

Demonstration
board layout

INPUT VOLTAGE (V)

Minimum

Current Limit

Note

Note. For increased output current, see “Applications Information:

Functional Characteristics

Switching Frequency Foldback

(NORMAL)

SW

V

12V IN, 5V/1A OUT

(SHORTED)

SW

12V IN, 0V OUT

V

200kHz

60kHz

TIME

Increasing the Maximum Output Current” and Figure 3.

VIN = 12V

= 5V

V
Normal
Operation

Short
Circuit
Operation

V

I

OUT

(100mV/div.)

OUT

(500mA/div.)

OUT

= 1.0A to 0.1A

I

OUT

Load Transient

5.1V

5V

1A

0A

TIME (100ms/div.)

Frequency Foldback

The MIC4680 folds the switching frequency back during a hard
short-circuit condition to reduce the energy per cycle and
protect the device.

MIC4680 6 June 2000

MIC4680 Micrel

Bode Plots

The following bode plots show that the MIC4680 is stable over all conditions using a 68µF inductor (L) and a 220µF output
capacitor (C

). To assure stability, it is a good practice to maintain a phase margin of greater than 35°.

OUT

VIN = 7V

= 5.0V

V

OUT

= 0.0A

I

OUT

No-Load Stability

Phase Margin = 106°

TIME (100ms/div.)

No-Load Stability

Phase Margin = 117°

L = 68µF

= 220µF

C

OUT

VIN = 7V

= 5.0V

V

OUT

= 1.0A

I

OUT

Full-Load Stability

Phase Margin = 114°

TIME (100ms/div.)

Full-Load Stability

Phase Margin = 69°

L = 68µF

= 220µF

C

OUT

L = 68µF

= 220µF

C

OUT

VIN = 12V

= 5.0V

V

OUT

= 0.0A

I

OUT

VIN = 34V

= 5.0V

V

OUT

= 1.0A

I

OUT

TIME (100ms/div.)

No-Load Stability

Phase Margin = 125°

TIME (100ms/div.)

L = 68µF

= 220µF

C

OUT

L = 68µF
C

OUT

= 220µF

VIN = 12V

= 5.0V

V

OUT

= 1.0A

I

OUT

VIN = 34V
V

OUT

I

OUT

TIME (100ms/div.)

Full-Load Stability

Phase Margin = 71°

= 5.0V

= 1.0A

TIME (100ms/div.)

L = 68µF

= 220µF

C

OUT

June 2000 7 MIC4680

MIC4680 Micrel

Block Diagrams

V

IN

IN

SHDN

200kHz

Oscillator

MIC4680-x.x

Internal

Regulator

Thermal

Shutdown

Com-

parator

Reset

Error
Amp

GND

Fixed Regulator

Current

Limit

Driver

1.23V
Bandgap
Reference

1A

Switch

V

IN

V

SW

OUT

C

OUT

FB

IN

SHDN

200kHz

Oscillator

Com-

parator

MIC4680 [adj.]

Adjustable Regulator

Internal

Regulator

Thermal

Shutdown

Reset

Error
Amp

Current

Limit

Driver

1.23V
Bandgap
Reference

1A

Switch

VV

=+

REF

OUT



V

OUT

=−

R1 R2



V



REF

=

V 1.23V

REF

SW

FB

R1





1









R2



1




V

OUT

C

OUT

R1

R2

MIC4680 8 June 2000

MIC4680 Micrel

Functional Description

The MIC4680 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.

Supply Voltage

The MIC4680 operates from a +4V to +34V unregulated
input. Highest efficiency operation is from a supply voltage
around +15V. See the efficiency curves.

Enable/Shutdown

The shutdown (SHDN) input is TTL compatible. Ground the
input if unused. A logic-low enables the regulator. A logic­high shuts down the internal regulator which reduces the
current to typically 1.5µA when V
when V

= 5V. See “Shutdown Input Behavior: Shutdown

SHDN

Hysteresis.”

Feedback

Fixed-voltage versions of the regulator have an internal
resistive divider from the feedback (FB) pin. Connect FB
directly to the output voltage.

Adjustable versions require an external resistive voltage
divider from the output voltage to ground, center tapped to the

FB pin. See Figure 6b for recommended resistor values.

Duty Cycle Control

A fixed-gain error amplifier compares the feedback signal
with a 1.23V bandgap voltage reference. The resulting error
amplifier output voltage is compared to a 200kHz sawtooth
waveform to produce a voltage controlled variable duty cycle
output.

= VIN = 12V and 30µA

SHDN

A higher feedback voltage increases the error amplifier
output voltage. A higher error amplifier voltage (comparator
inverting input) causes the comparator to detect only the
peaks of the sawtooth, reducing the duty cycle of the com­parator output. A lower feedback voltage increases the duty
cycle. The MIC4680 uses a voltage-mode control architec­ture.

Output Switching

When the internal switch is on, an increasing current flows
from the supply V
output capacitor C

through external storage inductor L1, to

IN,

and the load. Energy is stored in the

OUT

inductor as the current increases with time.
When the internal switch is turned off, the collapse of the

magnetic field in L1 forces current to flow through fast
recovery diode D1, charging C

OUT

.

Output Capacitor

External output capacitor C

provides stabilization and

OUT

reduces ripple. See “Bode Plots” for additional information.

Return Paths

During the on portion of the cycle, the output capacitor and
load currents return to the supply ground. During the off
portion of the cycle, current is being supplied to the output
capacitor and load by storage inductor L1, which means that
D1 is part of the high-current return path.

June 2000 9 MIC4680

MIC4680 Micrel

Applications Information

Adjustable Regulators

Adjustable regulators require a 1.23V feedback signal. Rec­ommended voltage-divider resistor values for common out­put voltages are included in Figure 1b.

For other voltages, the resistor values can be determined
using the following formulas:

R1

R2



1





VV

=+

OUT

REF






SHUTDOWN

ENABLE

V

IN

C

IN

MIC4680BM

IN

1

SHDN C

GND

5–8

SW

FB

32

4

L1

R1

R2D1

V

OUT

OUT

=−

R1 R2

V 1.23V

REF

V

*1R*2RC

TUO

V8.1 k10.3k94.6
V5.2 k10.3k49.2
V3.3 k10.3k87.1
V0.5 k10.3679 Ω
V0.6 k10.3787 Ω



V

OUT



V



REF



1





Figure 1a. Adjustable Regulator Circuit

=

NI

V53Fµ51

0020R530651ESPTXVA

%1srotsiserllA*

snoitacilppaIFRwolrofscitengamdedleihs**

0084-644)508(.cnI,edoiD-yahsiV***

1D1LC

TUO

A5.1Hµ86

ykttohcSV06A2

086-B2PUscinortlioC

***.cnI,edoiD-yahsiVA062B

ro

rotcudnocimeSlareneG62SS

ro

**CM086-521HRDCadimuS

ro

V01Fµ022

0600R010722ESPTXVA

**CM086-421HRDCadimuS

Figure 1b. Recommended Components for Common Ouput Voltages

MIC4680 10 June 2000

MIC4680 Micrel

a

Thermal Considerations

The MIC4680 SuperSwitcher features the power-SOP-8.
This package has a standard 8-lead small-outline package
profile but with much higher power dissipation than a stan­dard SOP-8. The MIC4680 SuperSwitcher is the first dc-to-dc
converter to take full advantage of this package.

The reason that the power SOP-8 has higher power dissipa­tion (lower thermal resistance) is that pins 5 though 8 and the
die-attach paddle are a single piece of metal. The die is
attached to the paddle with thermally conductive adhesive.
This provides a low thermal resistance path from the junction
of the die to the ground pins. This design significantly im­proves package power dissipation by allowing excellent heat
transfer through the ground leads to the printed circuit board.

One of the limitation of the maximum output current on any
MIC4680 design is the junction-to-ambient thermal resis­tance (θJA) of the design (package and ground plane).

Examining θJA in more detail:

θJA = (θJC + θCA)

where:

θJC = junction-to-case thermal resistance

θCA = case-to-ambient thermal resistance
θJC is a relatively constant 20°C/W for a power SOP-8.
θCA is dependent on layout and is primarily governed by the

connection of pins 5 though 8 to the ground plane. The
purpose of the ground plane is to function as a heat sink.

θJA is ideally 63°C/W but will vary depending on the size of the

ground plane to which the power SOP-8 is attached.

Determining Ground-Plane Heat-Sink Area

There are two methods of determining the minimum ground
plane area required by the MIC4680.

Quick Method

Make sure that MIC4680 pins 5 though 8 are connected to a
ground plane with a minimum area of 6cm2. This ground
plane should be as close to the MIC4680 as possible. The
area maybe disributed in any shape around the package or
on any pcb layer

pins 5 though 8

as long as there is good thermal contact to

. This ground plane area is more than

sufficient for most designs.

SOP-8

θ

JA

θ

θ

JC

CA

printed circuit board

Figure 2. Power SOP-8 Cross Section

AM

BIENT

ground plane

heat sink are

Minimum Copper/Maximum Current Method

Using Figure 3, for a given input voltage range, determine the
minimum ground-plane heat-sink area required for the
application’s maximum output current. Figure 3 assumes a
constant die temperature of 75°C above ambient.

1.5

1.0

0.5

OUTPUT CURRENT (I)

0

12V

8V

24V

34V

TA = 50°C

Minimum Current Limit = 1.3A

0 5 10 15 20 25

AREA (cm2)

Figure 3. Output Current vs. Ground Plane Area

When designing with the MIC4680, it is a good practice to
connect pins 5 through 8 to the largest ground plane that is
practical for the specific design.

Checking the Maximum Junction Temperature:

For this example, with an output power (P

) of 5W, (5V

OUT

output at 1A maximum with VIN = 12V) and 65°C maximum
ambient temperature, what is the maximum junction tem­perature?

Referring to the “Typical Characteristics: 5V Output Effi­ciency” graph, read the efficiency (η) for 1A output current at
VIN = 12V or perform you own measurement.

η = 79%

The efficiency is used to determine how much of the output
power (P

P=

P=

) is dissipated in the regulator circuit (PD).

OUT

P

OUT

P

η

5W

0.79

−

OUT

5W

−

D

D

PD = 1.33W

A worst-case rule of thumb is to assume that 80% of the total
output power dissipation is in the MIC4680 (P

D(IC)

) and 20%

is in the diode-inductor-capacitor circuit.

P

= 0.8 P

D(IC)

P

= 0.8 × 1.33W

D(IC)

P

= 1.064W

D(IC)

D

Calculate the worst-case junction temperature:

TJ = P

D(IC)θJC

+ (TC – TA) + T

A(max)

where:

TJ = MIC4680 junction temperature
P

= MIC4680 power dissipation

D(IC)

θJC = junction-to-case thermal resistance.

The θJC for the MIC4680’s power-SOP-8 is
approximately 20°C/W. (Also see Figure 1.)

TC = “pin” temperature measurement taken at the

entry point of pins 6 or 7 into the plastic package

June 2000 11 MIC4680

MIC4680 Micrel

at the ambient temperature (TA) at which TC is

measured.
TA = ambient temperature at which TC is measured.
T

= maximum ambient operating temperature

A(max)

for the specific design.

Calculating the maximum junction temperature given a

maximum ambient temperature of 65°C:
TJ = 1.064 × 20°C/W + (45°C – 25°C) + 65°C
TJ = 106.3°C

This value is less than the allowable maximum operating
junction temperature of 125°C as listed in “Operating Rat­ings.” Typical thermal shutdown is 160°C and is listed in
“Electrical Characteristics.”

Increasing the Maximum Output Current

The maximum output current at high input voltages can be
increased for a given board layout. The additional three

MIC4680BM

SWIN

GND

5678

FB

SHDN

components shown in Figure 4 will reduce the overall loss in
the MIC4680 by about 20% at high VIN and high I

Even higher output current can be achieved by using the
MIC4680 to switch an external FET. See Figure 9 for a 5A
supply with current limiting.

Layout Considerations

Layout is very important when designing any switching regu­lator. Rapidly changing switching currents through the printed
circuit board traces and stray inductance can generate volt­age transients which can cause problems.

To minimize stray inductance and ground loops, keep trace
lengths, indicated by the heavy lines in Figure 5, as short as
possible. For example, keep D1 close to pin 3 and pins 5
through 8, keep L1 away from sensitive node FB, and keep
CIN close to pin 2 and pins 5 though 8. See “Applications
Information: Thermal Considerations” for ground plane lay­out.

The feedback pin should be kept as far way from the switching
elements (usually L1 and D1) as possible.

A circuit with sample layouts are provided. See Figure 6a
though 6e.

3

1N4148

2.2nF

82Ω

D1

OUT

.

J1

V

IN

4V to +34V

C1

15µF

35V

J3

GND

Figure 4. Increasing Maximum Output Current at High Input Voltages

V

IN

+4V to +34V

C

Power
SOP-8

IN

MIC4680BM

IN

1

SHDN

GND

5678

SW

FB

32

4

L1

68µH

C

OUT

R1

R2D1

V

OUT

GND

Figure 5. Critical Traces for Layout

U1 MIC4680BM

C2

0.1µF

OFF

ON

* C3 can be used to provide additional stability

and improved transient response.

50V

S1
NKK G12AP

IN

1

SHDN

SOP-8 5–8

SW

FB

GND

32

4

D1
B260A
or
SS26

L1

68µH

R6
optional

R1

3.01k
R2

6.49k

1

JP1a

1.8V

2

C3*
optional

R3

2.94kR41.78kR5976Ω

3

5

JP1b

JP1c

2.5V

4

3.3V

6

Figure 6a. Evaluation Board Schematic Diagram

Load

7

8

JP1d

5.0V

C4
220µF
10V

J2

V

OUT

1A

C5

0.1µF
50V

J4

GND

MIC4680 12 June 2000

MIC4680 Micrel

Printed Circuit Board Layouts

Figure 6b. Top-Side Silk Screen

Figure 6c. Top-Side Copper

Figure 6d. Bottom-Side Silk Screen

Figure 6e. Bottom-Side Copper

Abbreviated Bill of Material (Critical Components)

Reference Part Number Manufacturer Description Qty

C1 TPSD156M035R0300 AVX

ECE-A1HFS470 Panasonic

1

2

15µF 35V 1

47µF 50V, 8mm × 11.5mm
C4 TPSD227M010R0150 AVX 220µF 10V 1
D1 B260A Vishay-Diodes, Inc.

3

Schottky 1

SS26 General Semiconductor

L1 UP2B-680 Coiltronics

CDH115-680MC Sumida
CDRH124-680MC Sumida

U1 MIC4680BM Micrel Semiconductor

1

AVX: http://www.avxcorp.com

2

Panasonic: http://www.maco.panasonic.co.jp/eccd/index.html

3

Vishay-Diodes, Inc., tel: [phone], http://www.diodes.com

4

Coiltronics, tel: [phone], http://www.coiltronics.com

5

Sumida, tel: [phone], http://www.sumida.com

6

Micrel, tel: [phone], http://www.micrel.com

4
5
5

6

68µH, 1.5A, nonshielded 1
68µH, 1.5A, nonshielded
68µH, 1.5A, shielded

1A 200kHz power-SO-8 buck regulator 1

June 2000 13 MIC4680

MIC4680 Micrel

Applications Circuits*

For continuously updated circuits using the MIC4680, see

Application Hint 37

at www.micrel.com.

J1

+34V max.

22µF

35V

J3

GND

C1

OFF

ON

S1
NKK G12AP

J1

+12V

J2

GND

C5
220nF J2

R1

0.100Ω
C4

R7

10nF

4.99k

4

5

U2

10k

R6

R4

16.2k
R5

221k

3

U3

2

MIC6211BM5

C2

100nF

MIC4680BM

IN

1

SHDN

GND

SOP-8 5–8

SW

FB

32

4

L1

100µH

D1
MMBR140LT3

LM4041DIM3-1.2

D3

1N4148

C3
220µF
10V

Figure 7. Constant Current and Constant Voltage Battery Charger

C4
68µF
20V

C5
33µF
35V

U1 MIC4680BM

IN

1

SHDN

GND

SOP-8 5–8

SW

FB

32

4

L1

33µH

D1
ES1B
1A 100V

C3

0.022µF
50V

R1

8.87k

R2
1k

C1
68µF
20V

D2

1N4148

J3

GND

C2

0.1µF
J4

–12V/150mA

R2

3.01k
R3

976Ω

5V ±2%

800mA ±5%

J4

GND

To Cellular Telephone

SHUTDOWN

ENABLE

+4.5V to +17V

C1

330µF

25V

Figure 8. +12V to –12V/150mA Buck-Boost Converter

U1 MIC4680BMU2MIC4417BM4

IN

1

SHDN C2

GND

SOP-8 5–8

SW

FB

32

4

R1
1k

D1
5A

Si4425DY

L1*

50µH

220µF

* I

SAT

Figure 9. 5V to 3.3V/5A Power Supply

16V

= 8A

C3
220µF
16V

R2

20mΩ

R3
1k
1%

R4
1k
1%

R5
16k
1%

C4
1000pF

R6

16k 1%

U3

MIC6211BM5

3.01k

D2

1N4148

1.78k

R7

1%

R8

1%

3.3V/5A

C5

0.1µF

GND

* See Application Hint 37 for bills of material.

MIC4680 14 June 2000

MIC4680 Micrel

June 2000 15 MIC4680

MIC4680 Micrel

Package Information

0.026 (0.65)
MAX)

PIN 1

0.157 (3.99)

0.150 (3.81)

0.050 (1.27)

0.064 (1.63)

0.045 (1.14)

TYP

0.197 (5.0)

0.189 (4.8)

DIMENSIONS:
INCHES (MM)

0.020 (0.51)

0.013 (0.33)

0.0098 (0.249)

0.0040 (0.102)

0°–8°

SEATING

PLANE

8-Lead SOP (M)

45°

0.050 (1.27)

0.016 (0.40)

0.244 (6.20)

0.228 (5.79)

0.010 (0.25)

0.007 (0.18)

MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 [phone] FAX + 1 [phone] WEB http://www.micrel.com

This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or

other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.

© 2000 Micrel Incorporated

MIC4680 16 June 2000