Microchip Technology MIC38HC42-1YN

Overview

MIC38HC42-1YN from Micrel is a BiCMOS 1A peak-current-mode PWM controller in 14-pin SOIC package, featuring 50µA typical start-up current, 4.0mA typical operating current, and rail-to-rail CMOS output drive optimized for high-efficiency off-line and DC-DC power supplies. It supports up to 500kHz switching frequency with 96% maximum duty cycle and operates from 9V to 20V supply.

For engineers reviewing the MIC38HC42-1YN datasheet, MIC38HC42-1YN pinout, MIC38HC42-1YN application, or MIC38HC42-1YN equivalent, key selection criteria include UVLO thresholds (14.5V start/9V min), fast 20ns rise/15ns fall times, trimmed 5V bandgap reference, and compatibility with UC3842-based designs requiring enhanced efficiency and thermal performance.

Technical Context

The MIC38HC42-1YN implements current-mode control using an internal error amplifier, current-sense comparator, and oscillator with externally programmable RT/CT network. Its dual-ground architecture separates AGND and PGND to minimize noise coupling between analog and power sections.

It features a trimmed oscillator discharge current and bandgap reference for stable frequency and regulation accuracy across temperature. The 1A peak totem-pole output drives N-channel MOSFETs directly, supporting synchronous rectification and high-side switch configurations in buck, boost, flyback, and forward topologies.

Key Specifications

Pinout & Package

Package: 14-pin SOIC (M), surface-mount, 1.27mm pitch, JEDEC MS-012 compliant. Thermal resistance θ_JA = 145°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar current-mode PWM controller applications.

Compared with UC3842N and LM3478MM/NOPB, the MIC38HC42-1YN delivers superior efficiency via ultralow start-up current and 1A drive, maintains system-level flexibility with its dedicated 5V reference and dual-ground architecture, and supports both AC-DC and DC-DC topologies without redesign.

Availability

MIC38HC42-1YN is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC converters, and FPGA point-of-load regulators requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for MIC38HC42-1YN 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 MIC38HC4x family was designed as high-efficiency BiCMOS replacements for UC384x controllers, targeting off-line and isolated DC-DC power supplies where low start-up current, fast switching, and thermal robustness are critical.

FAQ

What is the UVLO behavior of the MIC38HC42-1YN?

The MIC38HC42-1YN features undervoltage lockout with hysteresis: it starts operation at 14.5V (typical) and remains active down to 9V (typical). This prevents erratic switching during brownout conditions and ensures clean startup from bulk capacitors charged through high-resistance bias networks. The MIC38HC42-1YN's UVLO threshold is fixed and not adjustable.

Can the MIC38HC42-1YN drive a high-side N-channel MOSFET directly?

No - the MIC38HC42-1YN's OUT pin is a totem-pole driver referenced to PGND and cannot float above ground. To drive a high-side N-channel MOSFET, an external bootstrap or isolated gate driver is required. The MIC38HC42-1YN is optimized for low-side or synchronous rectifier configurations where the switch source connects to PGND.

Does the MIC38HC42-1YN require external compensation components?

Yes - the MIC38HC42-1YN uses the COMP pin for error amplifier compensation. A Type II or Type III network (typically resistor + capacitor + optional capacitor/resistor) must be connected between COMP and FB to stabilize the control loop. The exact values depend on transformer turns ratio, output filter, and desired bandwidth - no internal compensation is provided.

What is the function of the VD and VDD pins on the MIC38HC42-1YN?

VD supplies the P-channel driver stage and returns to PGND; VDD supplies the analog controller circuitry and returns to AGND. This separation isolates power-stage noise from sensitive analog blocks. Applying voltage to VD without proper PGND routing causes malfunction. Both pins must be decoupled independently: VD with ≥1µF low-ESR capacitor to PGND, VDD with 0.1µF ceramic to AGND.

Is the MIC38HC42-1YN pin-compatible with the UC3842 in 14-pin packages?

Yes - the MIC38HC42-1YN is explicitly specified as pin-for-pin compatible with UC3842 in 14-pin DIP and SOIC packages. Pin functions match exactly, including COMP, FB, ISNS, RT/CT, GND (AGND/PGND split), OUT, VD, VDD, and VREF. No PCB changes are required when upgrading from UC3842-1N or UC3842-1M to MIC38HC42-1YN.