onsemi MC33166TH

Overview

MC33166TH from onsemi is a fixed-frequency voltage-mode switching regulator IC designed for step-down, voltage-inverting, and step-up/down DC-DC converter topologies. It integrates a 72 kHz oscillator, 5.05 V ±2% reference, latching PWM controller, high-gain error amplifier, and 3.0 A output switch - enabling compact, low-component-count power supplies operating from 7.5 V to 40 V input in industrial and automotive environments.

For engineers reviewing the MC33166TH datasheet, pinout, applications, or equivalent options, key selection considerations include its −40°C to +85°C operating temperature range, cycle-by-cycle current limiting (4.3 A typ), undervoltage lockout with hysteresis (5.9 V startup / 0.9 V hysteresis), thermal shutdown, and standby mode reducing supply current to 36 µA.

Technical Context

The MC33166TH implements voltage-mode control using an internal 72 kHz oscillator with fixed charge/discharge thresholds (4.1 V/2.3 V) and a 95% maximum duty cycle. Its error amplifier features 80 dB open-loop gain and 600 kHz unity-gain bandwidth, with the noninverting input tied internally to the 5.05 V reference - requiring external resistor dividers only for outputs >5.05 V.

Current protection uses cycle-by-cycle sensing via an internal trimmed sense resistor and comparator, resetting the PWM latch at 4.3 A typical peak switch current. Undervoltage lockout activates above 5.9 V with 0.9 V hysteresis, while thermal shutdown triggers at ~170°C to disable the output stage - all implemented monolithically in a 5-lead TO-220 package with heatsink tab connected to Pin 3 (GND).

Key Specifications

Pinout & Package

MC33166TH is housed in a 5-lead TO-220 package (Case 314B), with the metal tab thermally and electrically connected to Pin 3 (GND). The package supports vertical mounting and requires heatsinking for >1.5 A continuous operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC33166TH, MC34166D2TR4G offers identical functionality in a surface-mount package but sacrifices industrial temperature rating, while LM2596-5.0 simplifies design for basic buck conversion yet omits critical protections and multi-topology support needed in harsh environments.

Availability

MC33166TH is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, off-line preconverters, and distributed multi-rail systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MC33166TH 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient electronics, delivering silicon solutions for automotive, industrial, cloud, and IoT applications.

The MC33166TH belongs to onsemi's legacy high-performance analog power controller family, engineered specifically for robust, low-component-count DC-DC conversion in demanding industrial and automotive environments.

FAQ

What is the maximum recommended output current for MC33166TH in step-down configuration?

The MC33166TH supports up to 3.0 A continuous output current in step-down configuration when used with appropriate external components - including a low-forward-voltage Schottky rectifier (e.g., 1N5822), adequate heatsinking, and proper PCB copper area. Peak switch current is limited to 4.3 A typical, and thermal shutdown activates at ~170°C junction temperature to prevent damage.

Can MC33166TH be used in voltage-inverting applications, and how is grounding handled?

Yes, MC33166TH is explicitly designed for voltage-inverting configurations. To implement this, the IC's ground pin (Pin 1) is connected to the negative output rail - which reverses the error amplifier's effective inputs and keeps the switch emitter within its −1.5 V limit relative to ground. This configuration enables stable −12 V/1.0 A output with <±0.017% load regulation, as verified in Figure 23 of the datasheet.

Does MC33166TH support adjustable output voltages above 5.05 V?

Yes, MC33166TH supports adjustable output voltages above 5.05 V using an external resistor divider network at Pin 5 (Compensation). The output voltage is calculated as V_OUT = 5.05 × (1 + R₁/R₂). For example, a 6.8 kΩ (R₁) and 4.7 kΩ (R₂) divider sets V_OUT ≈ 12 V - demonstrated in the step-up/down application (Figure 21) with 82.8% efficiency at 0.6 A.

What is the purpose of the 36 µA standby current specification for MC33166TH?

The 36 µA standby current in MC33166TH is achieved by clamping Pin 5 (Compensation) to ≤150 mV, placing the internal circuitry into ultra-low-power mode. This feature is essential for battery-backed systems or always-on subsystems where quiescent power must be minimized - such as telematics modules that remain active during vehicle sleep cycles while drawing minimal current from the 12 V battery.

How does the undervoltage lockout (UVLO) function in MC33166TH, and what are its thresholds?

The MC33166TH incorporates an undervoltage lockout comparator monitoring V_CC. It enables the output stage only when V_CC exceeds 5.9 V (typical startup threshold) and disables it when V_CC falls below 5.0 V (5.9 V − 0.9 V hysteresis). This prevents erratic switching during brown-out conditions and ensures reliable start-up in automotive applications where battery voltage can dip below 6 V during cranking.