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onsemi MC34166T
- Part No.:
- MC34166T
- Manufacturer:
- onsemi
- Package:
- TO-220-5
- Datasheet:
-
MC34166T.pdf
- Description:
- IC REG BUCK BST ADJ 3.3A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:2,916
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Product details
Overview
MC34166T 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, high-gain error amplifier with 5.05 V ±2% reference, latching PWM controller, and 3.0 A output switch. It operates from 7.5 V to 40 V input and delivers regulated outputs in automotive, industrial, and cost-sensitive consumer power supplies.
For engineers reviewing the MC34166T datasheet, pinout, applications, or equivalent options, key selection criteria include its 3.0 A switch current capability, cycle-by-cycle current limiting, undervoltage lockout (5.9 V startup), thermal shutdown, and standby mode reducing supply current to 36 µA - all critical for robust, low-component-count offline and battery-fed converters.
Technical Context
The MC34166T implements voltage-mode control using an internal 5.05 V reference and error amplifier with 80 dB open-loop gain and 600 kHz unity-gain bandwidth. Its oscillator generates a 72 kHz ramp with 95% max duty cycle, feeding a comparator that drives a latch to control the output switch.
Current protection uses cycle-by-cycle sensing via an internal trimmed resistor and comparator, triggering immediate switch turn-off when peak current reaches 4.3 A (typ). Undervoltage lockout provides 0.9 V hysteresis, and thermal shutdown activates at ~170°C, forcing latch reset to disable the output stage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 72 kHz (fixed, internally trimmed; enables predictable EMI filtering and stable loop compensation) |
| Reference Voltage | 5.05 V ±2% (precision internal bandgap; sets base output without external divider in 5 V designs) |
| Output Switch Current | 3.0 A (continuous, with 4.3 A typical current limit threshold; supports ≥2.0 A load in step-down with proper heatsinking) |
| Input Voltage Range | 7.5 V to 40 V (enables direct operation from 12 V/24 V automotive rails and pre-regulated industrial supplies) |
| Standby Supply Current | 36 µA at 12 V (achieved by clamping Pin 5 < 150 mV; reduces idle power in battery-backed systems) |
| UVLO Threshold | 5.9 V startup with 0.9 V hysteresis (prevents erratic switching during brown-out; ensures full functionality before enable) |
| Thermal Shutdown | ~170°C junction (internal sensor forces latch reset; protects against sustained overload or poor heatsinking) |
Pinout & Package
The MC34166T is housed in a 5-lead TO-220 package (Case 314B), with the metal tab electrically connected to Pin 3 (Ground) and intended for heatsink mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 (Compensation) | Error amplifier output / compensation node | Connects to RC network (RF, CF) for loop stability; 100 µA pull-up enables soft-start via external capacitor |
| Pin 2 (Switch Output) | Collector of internal NPN power transistor | Drives external inductor; rated for 40 V max VCE and 3.0 A continuous; requires Schottky rectifier (e.g., 1N5822) in flyback configurations |
| Pin 3 (Ground) | Circuit common reference | Connected to heatsink tab; serves as return for error amp, UVLO, oscillator, and switch emitter |
| Pin 4 (VCC) | Power supply input | Accepts 7.5–40 V; powers all internal circuitry; UVLO monitors this pin |
| Pin 5 (Feedback) | Inverting input of error amplifier | Internally biased to 5.05 V reference; compares output voltage (via resistor divider) to regulate VO; clamp < 150 mV enables standby mode |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 72 kHz oscillator with on-chip timing | Eliminates external timing components; ensures consistent switching frequency across temperature and line variations |
| 0% to 95% output duty cycle range | Supports wide input-to-output voltage ratios in step-down and inverting topologies without external duty cycle limiting |
| Cycle-by-cycle current limiting | Protects switch under short-circuit or overload by terminating each conduction cycle independently - no cumulative thermal stress |
| Undervoltage lockout with hysteresis | Prevents unstable startup or oscillation near minimum supply; 0.9 V hysteresis ensures clean turn-on/turn-off transitions |
| Internal thermal shutdown | Automatically disables output above ~170°C junction; safeguards device during transient overloads or cooling failure |
Applications
| Automotive Body Control Module Power | Industrial 24 V to ±12 V Dual-Rail Supply |
|---|---|
|
Use Scenario: Generating stable 5 V and −12 V rails from a noisy 12 V vehicle battery for microcontroller and analog sensor subsystems. IC Role / Device Role / Timing Role: MC34166T acts as the primary switching controller in a voltage-inverting configuration (Fig. 23), regulating negative output while rejecting battery ripple. Use Value: Achieves 81.2% efficiency at 1.0 A load with < 80 mVpp output ripple, meeting automotive EMC and thermal constraints without external current sense resistors. |
Use Scenario: Providing isolated dual-polarity outputs for op-amp biasing and data acquisition in factory automation PLC I/O modules. IC Role / Device Role / Timing Role: MC34166T serves as the core regulator in a triple-output converter (Fig. 25), generating +5 V/2.0 A, +12 V/300 mA, and −12 V/100 mA from 24 V input. Use Value: Delivers < ±0.04% line regulation on main rail and 83.3% total efficiency, enabling compact design with shared magnetics and single heatsink (5903B). |
| Cost-Sensitive Consumer DC-DC Adapter | Brushed DC Motor Speed Controller |
|
Use Scenario: Building a 12 V input to 5 V/3 A USB-C power adapter for home electronics with minimal BOM count. IC Role / Device Role / Timing Role: MC34166T operates in step-down mode (Fig. 19) with integrated switch, eliminating external MOSFET and simplifying layout. Use Value: Meets ±0.05% line regulation and 82.8% efficiency at full load using only 6 external components - ideal for high-volume, low-margin adapters. |
Use Scenario: Regulating speed of 18 V brushed motors in cordless power tools using back-EMF feedback for closed-loop control. IC Role / Device Role / Timing Role: MC34166T functions as the PWM generator in variable-speed motor drive (Fig. 27), modulating switch duty cycle based on sensed EMF voltage. Use Value: Maintains ±1% speed stability across 12–24 V input range at low speed, leveraging internal oscillator accuracy and fast 100 ns switch rise time. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MC33166D2TR4G | Wider operating ambient range (−40°C to +85°C vs. 0°C to +70°C); identical electrical specs and pinout | Preferred for extended-temperature industrial or automotive under-hood use; same PCB layout and compensation network | Select MC33166D2TR4G when ambient exceeds 70°C; otherwise MC34166T offers lower cost for commercial-temp applications |
| LM2576T-5.0 | 5 V fixed-output version; 3 A switch; 52 kHz frequency; requires external diode; no inverting capability | Limited to step-down only; lacks voltage-inverting and step-up/down modes supported by MC34166T | Choose LM2576T-5.0 only for simple 5 V step-down where inverting or multi-rail flexibility is unnecessary |
Compared with MC33166D2TR4G, MC34166T trades extended temperature rating for lower unit cost in commercial environments; compared with LM2576T-5.0, it offers broader topology support (inverting, step-up/down) and higher oscillator frequency for smaller magnetics - critical for space-constrained designs.
Availability
MC34166T is available at Aetrix Electronics and suitable for automotive body control, industrial dual-rail power supplies, cost-sensitive consumer adapters, brushed motor controllers, and offline preconverter applications requiring stable component supply and long-term manufacturability.
Supply support for MC34166T 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, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and IoT markets.
The MC34166T belongs to onsemi's legacy monolithic switching regulator product line, engineered for high-reliability, low-BOM-count dc-dc conversion in cost-driven applications where integration, thermal robustness, and topology flexibility are essential.
FAQ
What is the maximum output current achievable with the MC34166T in a step-down configuration?
The MC34166T supports up to 3.0 A continuous output current in step-down mode when used with adequate heatsinking (e.g., AAVID 5903B), proper PCB copper area, and a low-forward-voltage Schottky rectifier like the 1N5822. At 12 V input and 5 V output, the datasheet confirms 3.0 A operation with 82.8% efficiency and < 10 mVpp ripple. Peak switch current reaches 4.3 A (typ), so inductor saturation and thermal limits must be verified per design.
Can the MC34166T be used in a voltage-inverting topology, and what is required to implement it?
Yes, the MC34166T is explicitly designed for voltage-inverting applications, as shown in Figure 23 of its datasheet. Implementation requires connecting the IC's ground pin (Pin 3) to the negative output rail, which reverses the error amplifier's effective inputs and keeps the switch emitter within its −1.5 V limit. A 5.05 V reference sets the magnitude, and resistor R1 establishes regulation - no external op-amp or level-shifting circuitry is needed.
Does the MC34166T support synchronous rectification?
No, the MC34166T does not support synchronous rectification. It features a single NPN bipolar output switch and requires an external Schottky diode (e.g., 1N5822) for freewheeling in step-down and inverting topologies. The datasheet specifies diode forward voltage (VF ≈ 0.5 V) in design equations and warns against using slow or high-VF rectifiers due to efficiency loss and potential switch overstress.
How is standby mode activated on the MC34166T, and what is its effect on system power consumption?
Standby mode on the MC34166T is activated by clamping the Compensation pin (Pin 1) to < 150 mV - typically via a transistor or logic signal - which reduces total supply current to 36 µA at 12 V. This feature is documented in Figures 11 and 16 of the datasheet and enables ultra-low-power sleep states in battery-powered systems without disabling the entire power stage.
What package options are available for the MC34166T, and is the TO-220 variant still in production?
The MC34166T is specified in the 5-lead TO-220 package (Case 314B, TV suffix), with the heatsink tab internally connected to Pin 3 (Ground). While the datasheet notes MC33166TVG as discontinued, the MC34166T TO-220 variant remains active and supported per onsemi's current product status - confirmed by ordering codes including "MC34166T" and packaging diagrams on page 1 of the August 2024 Rev. 9 datasheet.
MC34166T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-220-5
- 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
MC34166T FAQ
1.How can I place an order for MC34166T through Aetrix?
Please submit a Request for Quotation (RFQ) for MC34166T 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 MC34166T reliable?
The price and inventory of MC34166T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC34166T is usually 5 days.
3.What payment methods are accepted for MC34166T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC34166T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC34166T?
MC34166T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC34166T 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 MC34166T?
For technical support, including MC34166T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC34166T requirements.
6.How does Aetrix verify that MC34166T is sourced from the original manufacturer or authorized distributors?
All MC34166T 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 MC34166T meets industry standards.
7.What is the process for return or replacement of MC34166T?
All MC34166T units undergo pre-shipment inspection (PSI). If there is an issue with MC34166T, 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 MC34166T part is unused and in its original packaging.
Return procedure for MC34166T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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