MIC4685WREV MICREL [Micrel Semiconductor], MIC4685WREV Datasheet

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MIC4685WREV

Manufacturer Part Number
MIC4685WREV
Description
3A SPAK SuperSwitcher Buck Regulator
Manufacturer
MICREL [Micrel Semiconductor]
Datasheet
General Description
The MIC4685 is a high-efficiency 200kHz stepdown (buck)
switching regulator. Power conversion efficiency of above
85% is easily obtainable for a wide variety of applications.
The MIC4685 achieves 3A of continuous current in the
7-pin SPAK package.
The thermal performance of the SPAK allows it to replace
TO-220s and TO-263s (D
The SPAK saves board space with a 36% smaller footprint
than TO-263.
High-efficiency is maintained over a wide output current
range by utilizing a boost capacitor to increase the voltage
available to saturate the internal power switch. As a result
of this high-efficiency, only the ground plane of the PCB is
needed for a heat sink.
The MIC4685 allows for a high degree of safety. It has a
wide input voltage range of 4V to 30V (34V transient),
allowing it to be used in applications where input voltage
transients may be present. Built-in safety features include
over-current protection, frequency-foldback short-circuit
protection, and thermal shutdown.
The MIC4685 is available in a 7-pin SPAK package with a
junction temperature range of –40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
___________________________________________________________________________________________________________
Typical Application
SuperSwitcher is a trademark of Micrel, Inc
January 2010
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
2
PAKs) in many applications.
8V to 30V
V
IN
33µF
35V
C
IN
2
5
IN
EN
MIC4685_R
1.8V Output Converter
GND
4, Tab
SW
BS
FB
1
6
3
C
0.33µF/50V
BS
1
Features
• Low 2mm profile SPAK package
• 3A continuous output current
• Wide 4V to 30V input voltage range (34V transient)
• Fixed 200kHz PWM operation
• Over 85% efficiency
• Output voltage adjustable to 1.235V
• All surface mount solution
• Internally compensated with fast transient response
• Over-current protection
• Frequency foldback short-circuit protection
• Thermal shutdown
Applications
• Point-of-load power supplies
• Simple high-efficiency step-down regulators
• 5V to 3.3V/2A conversion
• 12V to 5V/3.3V/2.5V/1.8V 3A conversion
• Dual-output ±5V conversion
• Base stations
• LCD power supplies
• Battery chargers
D1
3A
40V
408
39mH
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
L1
3.01k
6.49k
R1
R2
3A SPAK SuperSwitcher™
1.8V/3A
Buck Regulator
C
330µF
6.3V
V
OUT
OUT
MIC4685
M9999-012610

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MIC4685WREV Summary of contents

Page 1

General Description The MIC4685 is a high-efficiency 200kHz stepdown (buck) switching regulator. Power conversion efficiency of above 85% is easily obtainable for a wide variety of applications. The MIC4685 achieves 3A of continuous current in the 7-pin SPAK package. The ...

Page 2

Micrel, Inc. Ordering Information Part Number Standard RoHS Compliant* MIC4685BR MIC4685WR MIC4685WR EV * RoHS compliant with ‘high-melting solder’ exemption. Pin Configuration Pin Description Pin Number Pin Name Tab GND ...

Page 3

Micrel, Inc. Detailed Pin Description Switch (SW, Pin 6) The switch pin is tied to the emitter of the main internal NPN transistor. This pin is biased up to the input voltage, minus the the main NPN ...

Page 4

Micrel, Inc. Absolute Maximum Ratings (1) Supply Voltage (V ) .................................................+34V IN Enable Voltage (V )......................................... –0. Steady-State Output Switch Voltage (V Feedback Voltage (V ) ...............................................+12V FB Storage Temperature (T ) .........................–65°C to +150°C s (3) ...

Page 5

Micrel, Inc. Test Circuit +12V Shutdown Input Behavior January 2010 Device Under Test 2 6 VIN GND FB 4, Tab 3 Current Limit Test Circuit OFF 0.8V 0V 1.25V 1.4V Enable Hysteresis 5 68µH I ...

Page 6

Micrel, Inc. Typical Characteristics (TA = 25°C unless otherwise noted) Efficiency vs. Output Current 100 12V 30V Standard 20 Configuration ...

Page 7

Micrel, Inc. Feedback Voltage vs. Input Voltage 1.250 1.245 1.240 1.235 1.230 1.225 1.220 1.215 I = 10mA OUT 1.210 V = 1.8V OUT 1.205 INPUT VOLTAGE (V) Feedback Voltage vs. Temperature 1.258 ...

Page 8

Micrel, Inc. Typical Safe Operating Area (SOA) (SOA measured on the MIC4685 Evaluation Board*) Typical 5V Output SOA Standard Configuration 5 25° 125° Max 3.5 3.0 2.5 2 ...

Page 9

Micrel, Inc. Functional Characteristics Frequency Foldback The MIC4685 folds the switching frequency back during a hard short circuit condition to reduce the energy per cycle and protect the device. January 2010 9 MIC4685 M9999-012610 ...

Page 10

Micrel, Inc. Functional Diagram Functional Description The MIC4685 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the above block diagram. Supply Voltage The MIC4685 operates from a +4V to +30V (34V transient) unregulated input. ...

Page 11

Micrel, Inc. Application Information Adjustable Regulators Adjustable regulators require a 1.235V feedback signal. Recommended voltage-divider common output voltages are detailed in Table 1. For other voltages, the resistor values can be determined using the following formulas: ⎛ ⎞ ...

Page 12

Micrel, Inc. Layout Considerations Layout is very important when designing any switching regulator. Rapidly changing 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, ...

Page 13

Micrel, Inc. Recommended Components for a Given Output Voltage (Bootstrap Configuration OUT OUT 5.0V 2.1A 3.01k 976Ω 7.5V – 16V 3.3V 2.2A 3.01k 1.78k 6.0V – 16V 2.5V 2.0A 3.01k 2.94k 5.0V – 16V 1.8V ...

Page 14

Micrel, Inc. Recommended Components for a Given Output Voltage (Standard Configuration OUT OUT 5.0V 2.0A 3.01k 976Ω 8V – 30V 3.3V 2.4A 3.01k 1.78k 8V – 26V 2.5V 2.35A 3.01k 2.94k 7V – 23V 1.8V ...

Page 15

Micrel, Inc. Printed Circuit Board January 2010 Figure 5a. Top Layer Figure 5b. Bottom Layer 15 MIC4685 M9999-012610 ...

Page 16

Micrel, Inc. Abbreviated Bill of Materials (Critical Components) Item Part Number C1 594D336X0035R2T C2, C7 VJ0805Y104KXAAB GRM426X7R334K50 C3 VJ1206Y334KXAAT C4* Optional C5 594D337X06R3D2T B340A B340LA-EA D1 SSA34A B340A B120-EA D2 B340A MBRX120 L1 CDRH127-390MC R1 CRCW08053011FKEY3 R2 CRCW08056491FKEY3 R3 CRCW08052941FKEY3 ...

Page 17

Micrel, Inc. Package Information MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. ...

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