MIC4680YM

Part: MIC4680BM-TR — Micrel Inc.

Type: Step-Down (Buck) Switch-Mode Regulator

Description: 4–34 V input, up to 1.3 A output, fixed 200 kHz buck regulator with integrated NPN switch, available in 3.3 V, 5 V and adjustable (down to 1.25 V) versions, with up to 90% efficiency in an 8-pin SOIC.

Operating Conditions:

• Supply voltage: +4 to +34 V (VIN(min) = VOUT + 2.5 V or 4 V, whichever is greater)
• Junction temperature: -40 to +125 °C
• Fixed switching frequency: 200 kHz (180–220 kHz)
• Package thermal resistance θJA: 63 °C/W (SOIC-8, on 1" square 1 oz. copper FR4 PCB)

Absolute Maximum Ratings:

• Max supply voltage (VIN): +38 V (intended for transients only)
• Shutdown voltage (VSHDN): -0.3 to +38 V
• Steady-state output switch voltage (VSW): -1 V
• Feedback voltage, adjustable (VFB): +12 V
• Storage temperature: -65 to +150 °C

Key Specs:

• Feedback voltage (adjustable): 1.230 V typ (1.217–1.243 V at TJ = 25 °C; VIN = 12 V, ILOAD = 500 mA)
• Output voltage (fixed): 3.3 V or 5.0 V, ±1% at 25 °C
• Oscillator frequency: 200 kHz typ (180–220 kHz)
• Maximum duty cycle: 97% typ (93% min)
• Switch saturation voltage: 1.4 V typ, 1.8 V max at IOUT = 1 A
• Short-circuit current limit: 1.8 A typ (1.3–2.5 A)
• Quiescent current: 7 mA typ, 12 mA max
• Standby quiescent current: 1.5 μA typ (VSHDN = VIN); 30 μA typ, 100 μA max (VSHDN = 5 V)
• Thermal shutdown: 160 °C typ
• Frequency foldback: 50 kHz typ (30–100 kHz)

Features:

• SOIC-8 package with up to 1.3 A output current
• All surface-mount solution
• Only 4 external components required
• Fixed 200 kHz operation
• 3.3 V, 5 V and adjustable output versions
• Internally compensated with fast transient response
• Less than 2 μA typical shutdown-mode current
• Thermal shutdown and cycle-by-cycle overcurrent protection
• Frequency foldback during short-circuit

Applications:

• Simple 1 A high-efficiency step-down (buck) regulator
• Replacement of TO-220 and TO-263 designs
• Efficient pre-regulator (5 V to 2.5 V, 12 V to 3.3 V, 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 (power SOIC-8, pins 5–8 as ground/heat-sink)

• 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

Fixed Regulator Circuit

Adjustable 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

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

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:

$$\theta_{JA} = (\theta_{JC} + \theta_{CA})$$

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.

8-Pin SOIC (M)