MIC4680

Part: MIC4680 SuperSwitcher™ — Micrel Inc.

Type: Step-down (buck) switch-mode voltage regulator

Description: An easy-to-use 200kHz step-down (buck) switch-mode voltage regulator achieving up to 1.3A continuous output current over a wide 4V to 34V input range, available in fixed 3.3V, 5V, or adjustable output down to 1.25V.

Operating Conditions:

• Supply voltage: +4V to +34V
• Junction Temperature: -40°C to +125°C

Absolute Maximum Ratings:

• Max supply voltage: +38V
• Max storage temperature: -65°C to +150°C

Key Specs:

• Oscillator Frequency: 180 kHz (min), 200 kHz (typ), 220 kHz (max)
• Adjustable Feedback Voltage: 1.217 V (min), 1.230 V (typ), 1.243 V (max) (at ±1%)
• Fixed 3.3V Output Voltage: 3.266 V (min), 3.3 V (typ), 3.333 V (max) (at ±1%)
• Fixed 5.0V Output Voltage: 4.950 V (min), 5.0 V (typ), 5.05 V (max) (at ±1%)
• Short Circuit Current Limit: 1.3 A (min), 1.8 A (typ), 2.5 A (max) (VFB = 0V)
• Standby Quiescent Current: 1.5 μA (typ) (VSHDN = VIN)
• Quiescent Current: 7 mA (typ), 12 mA (max) (VFB = 1.5V for adjustable)
• Maximum Duty Cycle: 93% (min), 97% (typ) (VFB = 1.0V for adjustable)

Features:

• SOIC-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 pre-regulator (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

Package:

• 8-Pin SOIC

• SOIC-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

• Simple 1A high-efficiency step-down (buck) regulator
• Replacement of TO-220 and TO-263 designs
• Efficient pre-regulator (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

Adjustable Regulator Circuit

VIN = 12V; ILOAD = 500mA; TJ = 25°C, bold values indicate -40°C ≤ TJ ≤ +125°C, Note 7 ; unless noted.

• Shutdown Voltage (V SHDN )............................. -0.3V to +38V
• Steady-State Output Switch Voltage (V SW ) ....................-1V
• Feedback Voltage [Adjustable] (V FB ) ...........................+12V
• Storage Temperature (T s ) .........................-65°C to +150°C EDS Rating (5)

The MIC4680 SuperSwitcher features the power-SOIC8. This package has a standard 8-pin small-outline package profile but with much higher power dissipation than a standard SOIC-8. The MIC4680 SuperSwitcher is the first dc-to-dc converter to take full advantage of this package.

The reason that the power SOIC-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 ( θ JA) of the design (package and ground plane).Examining θ JA in more detail:

θ

θ

where:

JC = junction-to-case thermal resistance CA = case-to-ambient thermal resistance

θ JC is a relatively constant 20°C/W for a power SOIC-8.

θ CA 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.

θ JA is ideally 63°C/W but will vary depending on the size of the ground plane to which the power SOIC-8 is attached.

Fixed Regulator Circuit

SuperSwitcher is a trademark of Micrel, Inc.

Micrel Inc. · 2180 Fortune Drive · San Jose, CA 95131 · USA · tel +1 (408) 944-0800 · fax + 1 (408) 474-1000 · http://www.micrel.com

8-Pin SOIC (M)