Microchip Technology MIC4690BM-TR

Overview

MIC4690BM-TR from Micrel is a 500kHz synchronous buck regulator IC with internal NPN power switch, delivering up to 1A continuous output current across a 4V–30V input range in an 8-lead power-SO package. It features adjustable output voltage (set via external resistor divider), internal compensation, and built-in protections including overcurrent, frequency foldback, and thermal shutdown - used in compact 12V-to-5V/3.3V/2.5V/1.8V DC-DC conversion for embedded power rails.

For engineers reviewing the MIC4690BM-TR datasheet, MIC4690BM-TR pinout, MIC4690BM-TR application, or MIC4690BM-TR equivalent, key selection criteria include its fixed 500kHz switching frequency, 1.23V feedback reference, SO-8 thermal performance (θJC = 20°C/W), shutdown logic polarity (low-enable), and compatibility with surface-mount inductors ≥10µH for 1A loads.

Technical Context

The MIC4690BM-TR implements voltage-mode PWM control using a 1.23V bandgap reference and fixed-gain error amplifier comparing FB voltage against that reference. Its 500kHz oscillator generates a sawtooth waveform compared to the error amp output to determine duty cycle - enabling fast transient response without external compensation.

It integrates an NPN output switch with 1.2V saturation voltage at 1A, uses GND pins 5–8 as shared thermal and electrical return paths, and activates frequency foldback (220–300kHz) under short-circuit conditions to limit power dissipation while maintaining regulation integrity.

Key Specifications

Pinout & Package

Package: 8-lead Power-SO (SOP-8 M), with integrated thermal paddle connected to pins 5–8 (GND). Pins 5–8 are electrically and thermally common - must be soldered to a minimum 6 cm² copper ground plane for 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 and TPS54160DGQ, the MIC4690BM-TR offers simpler implementation for 1A, 4–30V adjustable buck conversion in space-constrained layouts - trading off input voltage headroom and current headroom for minimal BOM count and proven thermal reliability in SO-8.

Availability

MIC4690BM-TR is available at Aetrix Electronics and suitable for industrial PLCs, cable modems, hard disk drives, and portable instrumentation requiring stable component supply with long lifecycle visibility and consistent parametric performance.

Supply support for MIC4690BM-TR 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 Semiconductor (acquired by Microchip in 2015) specialized in high-performance analog and power ICs, with emphasis on integrated solutions for communications, computing, and industrial markets.

The MIC4690BM-TR belongs to Micrel's SuperSwitcher™ family of monolithic buck regulators - designed specifically to replace through-hole TO-220/TO-263 converters with surface-mount SO-8 packages delivering ≥1A while maintaining thermal robustness and ease of use.

FAQ

What is the recommended minimum ground plane area for reliable 1A operation of the MIC4690BM-TR?

The MIC4690BM-TR requires a minimum 6 cm² copper ground plane connected directly to pins 5–8 (GND) to achieve thermal performance supporting 1A continuous output. This area may be distributed across PCB layers but must maintain low-impedance thermal coupling to all four GND pins - verified by θJA ≤ 63°C/W in typical layouts. Smaller ground areas risk exceeding 125°C junction temperature under full load.

Does the MIC4690BM-TR support adjustable output voltages below 1.23V?

No, the MIC4690BM-TR does not support output voltages below its internal 1.23V feedback reference. The device is designed for outputs ≥1.23V set by the equation VOUT = 1.23V × (1 + R1/R2). For sub-1.23V regulation, a different topology such as a low-dropout linear regulator or a buck controller with external reference is required - the MIC4690BM-TR cannot be configured for 1.0V or 0.9V outputs.

How does frequency foldback operate in the MIC4690BM-TR during output short-circuit events?

During output short-circuit, the MIC4690BM-TR reduces switching frequency from 500kHz to 220–300kHz (measured at VFB = 0V), limiting peak inductor current and average power dissipation. This foldback behavior is automatic and does not require external circuitry - it maintains regulation attempt while preventing thermal runaway, allowing safe recovery once fault clears. Typical foldback onset occurs within microseconds of short detection.

Can the MIC4690BM-TR be used with ceramic output capacitors instead of electrolytic types?

Yes, the MIC4690BM-TR supports ceramic output capacitors, but total ESR must remain ≥5mΩ to ensure loop stability due to its internally compensated voltage-mode architecture. Recommended designs use 220µF aluminum polymer (e.g., 594D227X0010D2T) or parallel combinations of low-ESR ceramics (e.g., 10×22µF X5R) with added 5–10mΩ damping resistor if instability is observed. Pure low-ESR ceramic-only solutions may cause ringing or oscillation.

What is the maximum allowable duty cycle of the MIC4690BM-TR and how does it affect minimum output voltage at high input?

The MIC4690BM-TR has a maximum duty cycle of 93%, limiting the lowest practical output voltage at high input - e.g., at VIN = 30V, the theoretical minimum VOUT = 30V × 0.93 ≈ 27.9V. In practice, this means the device is optimized for step-down ratios ≤10:1 (e.g., 12V→1.5V works; 30V→1.5V does not). For high-input/low-output applications, a controller with 100% duty cycle or transformer-isolated topology is required - the MIC4690BM-TR is unsuitable for 30V-to-1.8V direct conversion.