Microchip Technology MIC4690BM

Overview

MIC4690BM from Micrel is an adjustable 500kHz synchronous buck regulator IC delivering up to 1A continuous output current in a power-SO-8 package. It operates from 4V to 34V input, regulates output down to 1.23V via external feedback divider, and integrates internal compensation, overcurrent protection, frequency foldback, and thermal shutdown - used in 12V-to-5V/3.3V/2.5V/1.8V DC-DC conversion for hard disk drives and cable modems.

For engineers reviewing the MIC4690BM datasheet, MIC4690BM pinout, MIC4690BM application, or MIC4690BM equivalent, this page delivers verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative parts with functional differences, and supply support details for industrial embedded and connected-device programs.

Technical Context

The MIC4690BM implements voltage-mode PWM control using a fixed 500kHz oscillator and a 1.23V bandgap reference. Its error amplifier compares FB voltage against 1.23V and modulates duty cycle by comparing the error output to a sawtooth waveform.

It integrates an NPN power switch with 1.2V saturation voltage at 1A, supports shutdown via TTL-compatible SHDN pin (active-low), and features frequency foldback during short-circuit events - reducing switching frequency from 500kHz to ~220–300kHz to limit power dissipation.

Key Specifications

Pinout & Package

The MIC4690BM is housed in an 8-lead power-SO-8 (SOP-8 M) package with exposed die-attach paddle thermally connected to pins 5–8. Pins 5–8 must be soldered to a ≥6 cm² PCB ground plane for thermal integrity and 1A operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2678-5.0/NOPB, MIC4690BM offers adjustable output, higher frequency, and SO-8 integration; versus TPS54160DGQ, it delivers higher current in same footprint but at lower switching frequency - making MIC4690BM optimal for cost-sensitive, thermally demanding 1A buck applications with moderate size constraints.

Availability

MIC4690BM is available at Aetrix Electronics and suitable for hard disk drives, cable modems, industrial PLC I/O modules, POS terminals, and on-card switching regulators requiring stable component supply across extended temperature and long-lifecycle programs.

Supply support for MIC4690BM 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 analog, power management, and timing solutions before its acquisition by Microchip Technology in 2015.

The MIC4690BM belongs to Micrel's SuperSwitcher™ family of integrated buck regulators - designed specifically to replace through-hole power packages with surface-mount alternatives while maintaining 1A+ output capability in standard SO-8 footprints.

FAQ

What is the minimum input voltage required for stable operation of the MIC4690BM?

The MIC4690BM requires a minimum input voltage of 4V to maintain regulation across its full output range. Below 4V, the internal bias circuitry cannot sustain proper oscillator and error amplifier operation, leading to dropout or shutdown. This 4V lower limit is specified across the full –40°C to +125°C junction temperature range and applies regardless of output voltage setting. The MIC4690BM remains functional up to 34V for transient conditions, but continuous operation above 30V is not recommended per absolute maximum ratings.

How does the MIC4690BM achieve 1A output current in an SO-8 package?

The MIC4690BM achieves 1A continuous output in an SO-8 package through its proprietary power-SO-8 construction: pins 5–8 and the internal die-attach paddle form a single low-thermal-resistance metal structure. When soldered to a ≥6 cm² PCB ground plane, this design achieves θ_JA ≈ 63°C/W and θ_JC = 20°C/W, allowing safe dissipation of ~1.3W at 50°C ambient. Standard SO-8 packages lack this thermal architecture and cannot sustain 1A without derating.

Can the MIC4690BM be used to generate negative output voltages?

Yes, the MIC4690BM can be configured as a positive-to-negative buck-boost converter by reconfiguring the inductor and diode connections per standard inverting topology - though this is not its primary intended use. In such configurations, the SW pin becomes the negative output node, FB must be referenced to the new negative rail, and output voltage magnitude is still set by the 1.23V feedback threshold. Efficiency and transient response will differ from standard buck operation, and thermal performance must be re-evaluated due to altered current paths.

What is the purpose of the frequency foldback feature in the MIC4690BM?

The frequency foldback feature in the MIC4690BM reduces the switching frequency from 500kHz to approximately 220–300kHz during output short-circuit or severe overload conditions. This lowers average switching losses and limits junction temperature rise, enabling the device to survive sustained fault conditions without immediate thermal shutdown. It acts as a first-line protection mechanism that precedes thermal shutdown, improving system robustness in applications prone to intermittent shorts like motor drives or hot-plug interfaces.

Is the MIC4690BM pin-compatible with other members of the MIC4690 family?

Yes, the MIC4690BM is pin-compatible with all MIC4690 variants including MIC4690YM (lead-free version) and fixed-output versions like MIC4690-3.3BM. All share identical SO-8 M pinout, thermal pad configuration, and electrical pin functions. Differences are limited to output voltage configuration (adjustable vs. fixed) and RoHS compliance - allowing direct substitution in existing layouts when adjusting for feedback network or environmental requirements.