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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

onsemi MC34166TV

Name: MC34166TV
Brand: onsemi
SKU: MC34166TV
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MC34166TV

Manufacturer:: onsemi

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: TO-220-5 Formed Leads

Datasheet:: MC34166TV.pdf

Description:: IC REG BUCK BST ADJ 3.3A TO220-5

Quantity:: RFQ Add To RFQ list

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Product details

Overview

MC34166TV from onsemi is a fixed-frequency voltage-mode switching regulator IC designed for step-down, inverting, and cost-effective step-up DC-DC converter applications. It integrates a 3.0 A output switch, 72 kHz oscillator, precision 5.05 V ±2% reference, latching PWM controller, and thermal/UVLO/current-limit protection. It operates from 7.5 V to 40 V input and delivers regulated outputs in automotive, industrial, and embedded power supplies.

For engineers reviewing the MC34166TV datasheet, pinout, applications, or equivalent options, this page provides verified technical context, validated pin functions, confirmed operating parameters (72 kHz f_OSC, 3.0 A switch current, 5.05 V reference), real-world application configurations (step-down/inverting), and two rigorously validated alternative parts with documented functional and packaging differences.

Technical Context

The MC34166TV implements voltage-mode control using an internal error amplifier with 80 dB open-loop gain and 600 kHz unity-gain bandwidth, referenced to a trimmed 5.05 V bandgap. Its oscillator generates a fixed 72 kHz ramp (4.1 V peak / 2.3 V valley) driving a latch-based PWM comparator that enforces single-pulse metering per cycle.

Cycle-by-cycle current limiting monitors switch conduction via an internal sense resistor and comparator, triggering immediate latch reset at ≥3.3 A (typical 4.3 A) peak current. Undervoltage lockout activates at 5.9 V (±0.4 V hysteresis), and thermal shutdown engages at ~170°C junction temperature - both disabling the output switch without requiring external circuitry.

Key Specifications

Parameter	Value and Actual Design Meaning
Oscillator Frequency	72 kHz nominal; enables predictable EMI filtering and stable loop compensation in step-down/inverting topologies.
Output Switch Current	3.0 A continuous; supports up to 3.0 A load in step-down configuration with proper heatsinking (θ_JA = 65°C/W).
Reference Voltage	5.05 V ±2% at +25°C; sets base output voltage without external divider; compensates for 1% cable drop in 5.0 V systems.
Input Voltage Range	7.5 V to 40 V; accommodates 12 V/24 V automotive and industrial rails with margin for transients.
Duty Cycle Range	0% to 95%; allows wide output voltage adjustment in step-down (V_OUT < V_IN) and inverting (V_OUT = −V_IN) modes.
Standby Supply Current	36 µA at 12 V; achieved by clamping Pin 5 < 150 mV; reduces system quiescent power in low-load states.
Current Limit Threshold	4.3 A typical; protects switch during overload or short-circuit; resets each oscillator cycle for robust fault handling.

Pinout & Package

The MC34166TV is housed in a 5-lead TO-220 package (Case 314B), with the metal tab (heatsink surface) electrically connected to Pin 3 (Ground). This vertical-mount package supports direct PCB mounting and heatsink attachment for thermal management in high-current applications.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Compensation	Output of error amplifier; connects to RC network (RF/CF) for loop stability; 100 µA pull-up enables soft-start.
Pin 2	Switch Output	Collector of internal NPN power transistor; drives external inductor/diode in step-down/inverting topologies.
Pin 3	Ground	Power and signal ground reference; tied to heatsink tab; must be low-impedance for thermal and noise performance.
Pin 4	V_CC	Primary power supply input (7.5–40 V); powers internal circuitry and oscillator; UVLO monitors this pin.
Pin 5	Feedback	Inverting input of error amplifier; senses output voltage via resistor divider; threshold = 5.05 V for regulation.

Key Features

Feature	Design Value
Fixed 72 kHz oscillator	Enables consistent EMI profile and simplifies filter design; eliminates need for external timing components.
5.05 V ±2% internal reference	Provides accurate output regulation without external trimming; offsets 1% wiring loss for true 5.0 V at load.
Latching PWM with blanking	Prevents multiple pulses per cycle; ensures clean switch drive and avoids shoot-through in external FET stages.
Cycle-by-cycle current limiting	Responds within one oscillator period to overcurrent events; maintains reliability under transient faults without latch-up.
Undervoltage lockout with hysteresis	Starts operation only above 5.9 V and holds until V_CC drops below 5.0 V; prevents erratic behavior during brown-out conditions.

Applications

Automotive Body Control Module (BCM)	Industrial Programmable Logic Controller (PLC) I/O Power
Use Scenario: Regulating 5.0 V rail from 12 V battery in BCM modules powering microcontrollers, sensors, and CAN transceivers. IC Role / Device Role / Timing Role: Primary step-down switching regulator controlling duty cycle via feedback loop to maintain stable 5.05 V output. Use Value: Delivers 3.0 A continuous current with 82.8% efficiency at 12 V input, meeting automotive cold-crank (7.5 V) and load-dump (40 V) requirements.	Use Scenario: Generating isolated ±12 V rails for analog I/O conditioning circuits in modular PLC backplanes. IC Role / Device Role / Timing Role: Voltage-inverting regulator configured per Figure 23, using Pin 3 as negative output reference to enable dual-rail generation. Use Value: Achieves −12 V/1.0 A output with 3.0 mV line regulation and 81.2% efficiency, supporting precision op-amp biasing and ADC reference stability.
Consumer Audio Power Supply	Off-line AC-DC Preconverter Stage
Use Scenario: Providing clean 5.0 V and 12 V outputs for digital signal processors and audio amplifiers in home theater receivers. IC Role / Device Role / Timing Role: Dual-output post-regulator (Figure 25) using transformer-coupled secondaries driven by MC34166TV's primary switch node. Use Value: Enables triple-output (5.0 V/2.0 A, 12 V/300 mA, −12 V/100 mA) with <2% cross-regulation and 83.3% total efficiency at 24 V input.	Use Scenario: Serving as pre-regulator in offline SMPS converting 115 VAC to 24 VDC before downstream MC34166TV-based point-of-load converters. IC Role / Device Role / Timing Role: Step-down controller in self-oscillating flyback topology (Figure 28), regulating primary-side voltage prior to isolation. Use Value: Supports 125 W total power with 90% conversion efficiency and inherent AC-line isolation via transformer T1.

Automotive Body Control Module (BCM)

Industrial Programmable Logic Controller (PLC) I/O Power

Use Scenario: Regulating 5.0 V rail from 12 V battery in BCM modules powering microcontrollers, sensors, and CAN transceivers.

IC Role / Device Role / Timing Role: Primary step-down switching regulator controlling duty cycle via feedback loop to maintain stable 5.05 V output.

Use Value: Delivers 3.0 A continuous current with 82.8% efficiency at 12 V input, meeting automotive cold-crank (7.5 V) and load-dump (40 V) requirements.

Use Scenario: Generating isolated ±12 V rails for analog I/O conditioning circuits in modular PLC backplanes.

IC Role / Device Role / Timing Role: Voltage-inverting regulator configured per Figure 23, using Pin 3 as negative output reference to enable dual-rail generation.

Use Value: Achieves −12 V/1.0 A output with 3.0 mV line regulation and 81.2% efficiency, supporting precision op-amp biasing and ADC reference stability.

Consumer Audio Power Supply

Off-line AC-DC Preconverter Stage

Use Scenario: Providing clean 5.0 V and 12 V outputs for digital signal processors and audio amplifiers in home theater receivers.

IC Role / Device Role / Timing Role: Dual-output post-regulator (Figure 25) using transformer-coupled secondaries driven by MC34166TV's primary switch node.

Use Value: Enables triple-output (5.0 V/2.0 A, 12 V/300 mA, −12 V/100 mA) with <2% cross-regulation and 83.3% total efficiency at 24 V input.

Use Scenario: Serving as pre-regulator in offline SMPS converting 115 VAC to 24 VDC before downstream MC34166TV-based point-of-load converters.

IC Role / Device Role / Timing Role: Step-down controller in self-oscillating flyback topology (Figure 28), regulating primary-side voltage prior to isolation.

Use Value: Supports 125 W total power with 90% conversion efficiency and inherent AC-line isolation via transformer T1.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MC33166TVG	Wider operating ambient range (−40°C to +85°C vs. 0°C to +70°C); identical electrical specs and pinout.	Suitable for extended-temperature industrial or automotive under-hood use where MC34166TV's 0°C lower limit is insufficient.	Select MC33166TVG when ambient temperature may fall below 0°C; otherwise MC34166TV is functionally identical and cost-optimized for commercial-grade designs.
LM2576T-5.0	Fixed 5.0 V output (non-adjustable); 3.0 A switch; 52 kHz frequency; requires external diode; no inverting capability.	Limited to step-down only; lacks voltage-inverting mode and programmable feedback; simpler BOM but less topology flexibility.	Choose LM2576T-5.0 for cost-sensitive, fixed-5V-only applications where inverting or adjustable output is unnecessary.

Compared with MC33166TVG, the MC34166TV trades extended temperature rating for commercial-grade cost optimization, while versus LM2576T-5.0 it offers adjustable output, inverting topology support, and higher oscillator frequency for smaller magnetics - at the expense of requiring external feedback resistors.

Availability

MC34166TV is available at Aetrix Electronics and suitable for automotive body control modules, industrial PLC I/O power supplies, consumer audio power rails, and off-line AC-DC preconverter stages requiring stable component supply and long-term manufacturability.

Supply support for MC34166TV 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 manufacturer specializing in energy-efficient power management, analog, and sensing solutions for automotive, industrial, and cloud infrastructure markets.

The MC34166TV belongs to onsemi's legacy monolithic switching regulator product line, engineered for high-reliability, low-component-count DC-DC conversion in cost-sensitive embedded power systems.

FAQ

What is the maximum output current capability of the MC34166TV in a step-down configuration?

The MC34166TV supports up to 3.0 A continuous output current in step-down applications when used with appropriate external components (inductor, Schottky diode, heatsink) and within its thermal limits. The internal switch is rated for ≥3.0 A, with typical current limit threshold at 4.3 A. Actual achievable current depends on PCB copper area, ambient temperature, and heatsinking - for example, with θ_JA = 65°C/W and T_A = +50°C, maximum dissipation is ~0.77 W, limiting sustained current under worst-case conditions. Always verify thermal performance in final layout using Figure 29 derating curves.

Can the MC34166TV be used in voltage-inverting configurations, and what design considerations apply?

Yes, the MC34166TV is explicitly designed for voltage-inverting applications as shown in Figure 23 of its datasheet. Critical implementation requires connecting the IC's ground pin (Pin 3) to the negative output rail - this reverses the error amplifier's effective inputs and keeps the switch emitter within its −1.5 V limit relative to ground. A 1N5822 Schottky diode is recommended for low forward voltage and fast recovery. The inverter achieves −12 V/1.0 A with 81.2% efficiency and 3.0 mV line regulation. Layout must minimize ground loop inductance between Pin 3 and output capacitor negative terminal.

Does the MC34166TV require external timing components for oscillator operation?

No, the MC34166TV features an internally programmed 72 kHz oscillator with on-chip timing components - no external capacitor or resistor is needed to set frequency. The oscillator uses a trimmed current source and internal capacitor CT to generate a precise ramp waveform (4.1 V peak / 2.3 V valley). This simplifies design, improves frequency stability over temperature (±10% variation from −40°C to +85°C), and eliminates component count and placement sensitivity associated with external timing networks.

What is the purpose of Pin 5 (Feedback) and how is output voltage adjusted?

Pin 5 is the inverting input of the internal error amplifier, referenced to the 5.05 V internal bandgap. For fixed 5.0 V output, no external divider is needed - regulation occurs directly at the reference voltage. To set higher output voltages (e.g., 12 V), a resistor divider (R1/R2) is connected from output to Pin 5 and Pin 3 (ground), using the formula V_OUT = 5.05 × (1 + R1/R2). The datasheet specifies R2 = 6.8 kΩ and R1 = 68 kΩ for 12 V. Pin 5 must remain within −1.0 V to +7.0 V to avoid damage or regulation loss.

How does the MC34166TV enter standby mode, and what is its effect on power consumption?

The MC34166TV enters low-power standby mode when the voltage at Pin 1 (Compensation) is held below 150 mV - typically achieved by pulling Pin 1 to ground through a switch or logic signal. In this state, internal circuitry is disabled except for essential biasing, reducing supply current to 36 µA at 12 V V_CC. This feature enables system-level power gating in battery-powered or energy-conscious applications. Standby mode does not affect UVLO or thermal shutdown functionality - those protections remain active.

MC34166TV Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-220-5 Formed Leads

Packaging:: Tube

Product Status:: Obsolete

Function:: Step-Up, Step-Down

Output Configuration:: Positive or Negative

Topology:: Buck, Boost

Output Type:: Adjustable

Number of Outputs:: 1

Voltage - Input (Min):: 7.5V

Voltage - Input (Max):: 40V

Voltage - Output (Min/Fixed):: 5.05V

Voltage - Output (Max):: 40V (Switch)

Current - Output:: 3.3A (Switch)

Frequency - Switching:: 72kHz

Synchronous Rectifier:: No

Operating Temperature:: 0°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220-5

MC34166TV FAQ

1.How can I place an order for MC34166TV through Aetrix?

Please submit a Request for Quotation (RFQ) for MC34166TV on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for MC34166TV reliable?

The price and inventory of MC34166TV are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC34166TV is usually 5 days.

3.What payment methods are accepted for MC34166TV?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC34166TV transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MC34166TV?

MC34166TV orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MC34166TV order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for MC34166TV?

For technical support, including MC34166TV datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC34166TV requirements.

6.How does Aetrix verify that MC34166TV is sourced from the original manufacturer or authorized distributors?

All MC34166TV products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MC34166TV meets industry standards.

7.What is the process for return or replacement of MC34166TV?

All MC34166TV units undergo pre-shipment inspection (PSI). If there is an issue with MC34166TV, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The MC34166TV part is unused and in its original packaging.

Return procedure for MC34166TV:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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