Microchip Technology MIC4681BM

Overview

MIC4681BM from Micrel is a 200kHz voltage-mode buck regulator IC with internal NPN switch, delivering up to 1A continuous output current and 2.2–4.5A short-circuit current limit across a 4V to 30V input range in an 8-lead SOP package. It features 1.23V ±1% feedback reference, thermal shutdown at 160°C, and <6µA shutdown quiescent current-designed for GSM battery chargers and high-efficiency step-down power supplies.

For engineers reviewing the MIC4681BM datasheet, MIC4681BM pinout, MIC4681BM application, or MIC4681BM equivalent, key selection considerations include its fixed 200kHz switching frequency, adjustable output down to 1.25V via external resistor divider, internal compensation, 93–95% maximum duty cycle, and power-SOP-8 thermal design requiring ≥6 cm² ground plane area for 1A operation.

Technical Context

The MIC4681BM implements voltage-mode control using a 1.23V bandgap reference and 200kHz sawtooth oscillator; error amplifier output compares against the sawtooth to generate variable-duty-cycle PWM. Cycle-by-cycle current limiting and thermal shutdown provide fault protection.

Its power-SOP-8 package integrates pins 5–8 and die-attach paddle as a single metal structure, achieving θJC = 20°C/W and enabling higher power dissipation than standard SOP-8-critical for sustaining 1A continuous output with junction temperature limited to +125°C.

Key Specifications

Pinout & Package

Package: 8-lead SOP (M), also designated "power-SOP-8", with integrated thermal paddle connected to pins 5–8 (GND). Dimensions per Micrel package drawing: 0.150–0.157" width, 0.228–0.244" length, 0.064" max height.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck regulator applications.

Compared with LM2576-5.0 and TPS54202DDCR, the MIC4681BM uniquely balances 30V input capability, 200kHz fixed frequency, SOP-8 thermal performance, and shutdown control-making it optimal for GSM chargers and industrial 1A buck supplies where input voltage headroom and pulse-current robustness are critical.

Availability

MIC4681BM is available at Aetrix Electronics and suitable for cellular phone battery chargers, industrial step-down power supplies, and positive-to-negative converter designs requiring stable component supply and long-term manufacturability.

Supply support for MIC4681BM includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Micrel, Inc. was a U.S.-based semiconductor company specializing in power management, analog, and timing solutions before its acquisition by Microchip Technology in 2015.

The MIC4681BM belongs to Micrel's SuperSwitcher™ family of integrated buck regulators-designed specifically for high-efficiency, low-component-count DC/DC conversion in portable and industrial power systems.

FAQ

What is the maximum continuous output current supported by the MIC4681BM?

The MIC4681BM supports up to 1A continuous output current under typical conditions: VIN = 12V, VOUT = 5V, TA ≤ 65°C, and ≥6 cm² PCB ground plane area connected to pins 5–8. Derating applies at higher input voltages or ambient temperatures-see SOA curves on page 7 of the datasheet for precise limits.

Does the MIC4681BM require external compensation components?

No, the MIC4681BM features internal frequency compensation optimized for stability with standard 68 µH inductors and 220 µF output capacitors. This eliminates external compensation networks and simplifies design-verified across no-load to full-load conditions with phase margins ≥53° per page 9 bode plots.

What is the function of the SHDN pin on the MIC4681BM?

The SHDN pin on the MIC4681BM is a TTL-compatible shutdown control input: logic low (<1.25V) enables regulation, logic high (>2V) disables it. In shutdown mode, the MIC4681BM draws only 6 µA (typical) when VSHDN = VIN, making it suitable for battery-backed systems requiring ultra-low standby power.

Can the MIC4681BM be used in an inverting buck-boost configuration?

Yes, the MIC4681BM can be configured as a positive-to-negative converter (inverting buck-boost) as shown in Figure 8 of the datasheet, generating –12V/150mA from a +12V input. Its 30V input rating, 200kHz fixed frequency, and robust SW node drive capability make it suitable for this topology with appropriate external magnetics and diode selection.

What thermal design guidance applies to the MIC4681BM's power-SOP-8 package?

The MIC4681BM's power-SOP-8 requires pins 5–8 to be connected to a minimum 6 cm² PCB ground plane for 1A operation. Thermal resistance is θJC = 20°C/W; junction temperature must stay ≤125°C. Layout must minimize trace inductance on VIN, SW, and GND paths-and keep FB routing distant from noisy switching nodes to ensure regulation accuracy.