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onsemi MC34166THG
- Part No.:
- MC34166THG
- Manufacturer:
- onsemi
- Package:
- TO-220-5 Formed Leads
- Datasheet:
-
MC34166THG.pdf
- Description:
- IC REG BUCK BST ADJ 3.3A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:4,646
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Product details
Overview
MC34166THG from onsemi is a fixed-frequency voltage-mode switching regulator IC optimized for step-down, voltage-inverting, and step-up/down dc-dc converter topologies. 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 and industrial power supplies.
For engineers reviewing the MC34166THG datasheet, pinout, applications, or equivalent options, key selection criteria include its 3.0 A switch current capability, 72 kHz fixed-frequency operation, 0–95% duty cycle range, cycle-by-cycle current limiting, and TO-220 package with heatsink-connected Pin 3.
Technical Context
The MC34166THG 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 uses an internal current source and external timing capacitor CT to generate a precise 72 kHz ramp waveform with 4.1 V/2.3 V thresholds.
Switching is managed by a latching PWM comparator that compares the error amp output against the oscillator ramp; conduction begins at valley detection and ends when ramp exceeds compensation voltage. Cycle-by-cycle current limiting monitors switch collector current via an internal sense resistor and resets the latch upon reaching 4.3 A typical threshold.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Switch Current | 3.0 A continuous - supports ≥3 A load in step-down/inverting configurations without external boost |
| Oscillator Frequency | 72 kHz nominal - enables compact magnetics and predictable EMI profile; stable over temperature and supply |
| Reference Voltage | 5.05 V ±2% - sets base output voltage; eliminates need for external divider in 5 V designs |
| Duty Cycle Range | 0% to 95% - allows wide input-to-output ratio coverage including deep step-down and high inversion ratios |
| Input Voltage Range | 7.5 V to 40 V - compatible with 12 V/24 V automotive and industrial bus systems |
| Standby Supply Current | 36 µA - enables low-power shutdown mode when compensation pin voltage < 0.15 V |
| Current Limit Threshold | 4.3 A typical - provides robust cycle-by-cycle protection; minimum guaranteed 3.3 A across temp |
| Thermal Shutdown | Activates at ~170°C junction - prevents catastrophic failure; requires external heatsink for >1.5 W dissipation |
Pinout & Package
The MC34166THG is housed in a Pb-free 5-lead TO-220 package (Case 314B), where the metal tab (heatsink surface) is electrically connected to Pin 3 (Ground). This configuration enables direct mechanical and thermal mounting to a heatsink while maintaining ground reference integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 (Comp) | Compensation Input | Connects to error amp output; used for loop stability compensation with RF/CF network |
| Pin 2 (VFB) | Voltage Feedback Input | Monitors regulated output via resistor divider; threshold = 5.05 V ±2% |
| Pin 3 (GND) | Power Ground / Heatsink | Common return for internal circuits; tab connection enables thermal management |
| Pin 4 (VCC) | Power Supply Input | Accepts 7.5–40 V; powers internal circuitry and gate drive; UVLO activates below 5.9 V |
| Pin 5 (SW) | Switch Output Collector | Drives external inductor; rated for 40 V max, 3.0 A continuous, with Vsat ≤ (VCC − 1.5) V |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 3.0 A switch | Eliminates need for external power transistor in ≤3 A step-down/inverting converters |
| Fixed 72 kHz oscillator | Reduces external component count; avoids frequency drift vs. temperature or supply |
| 5.05 V ±2% reference | Enables accurate 5 V output without feedback resistors; compensates for cable drop |
| Cycle-by-cycle current limit | Provides per-cycle overcurrent protection without requiring external sensing components |
| Undervoltage lockout with hysteresis | Ensures clean startup above 5.9 V and prevents oscillation near threshold via 0.9 V hysteresis |
| Thermal shutdown | Protects die at ~170°C; requires heatsink design for sustained >1.5 W power dissipation |
Applications
| Automotive Body Control Module (BCM) | Industrial Programmable Logic Controller (PLC) I/O Power |
|---|---|
Use Scenario: Regulating 5 V rail from 12 V battery in BCM, powering microcontrollers, CAN transceivers, and sensor interfaces under cold-crank (6.5 V) and load-dump (36 V) conditions. IC Role / Device Role / Timing Role: Primary step-down controller with integrated 3.0 A switch; manages duty cycle dynamically to maintain regulation across wide input range. Use Value: Single-chip solution reduces BOM count and PCB area; built-in UVLO and thermal shutdown enhance system reliability in harsh environments. | Use Scenario: Generating isolated ±12 V rails from 24 V DC bus in PLC backplane, powering analog I/O conditioning circuits and digital logic. IC Role / Device Role / Timing Role: Configured as voltage-inverting regulator (Figure 23); uses internal 5.05 V reference to regulate negative output with ground-referenced feedback. Use Value: Enables cost-effective dual-rail generation without transformer-based isolation; 95% max duty cycle supports high conversion ratios at full load. |
| Off-Line AC/DC Preconverter Stage | Brushed DC Motor Speed Control |
Use Scenario: Front-end pre-regulator converting rectified AC line (via flyback transformer) to stable 24 V intermediate bus for downstream MC34166 post-regulators. IC Role / Device Role / Timing Role: Step-down controller operating at 72 kHz; interfaces with self-oscillating transformer T2 to provide isolated, regulated intermediate voltage. Use Value: Enables distributed power architecture with multiple independently regulated outputs; 90% efficiency reduces thermal burden in enclosed enclosures. | Use Scenario: Closed-loop speed control of 18 V brushed motor using back-EMF sensing, requiring variable 0–18 V output with fast transient response. IC Role / Device Role / Timing Role: Step-down controller with soft-start (via Pin 5 current source) and adjustable duty cycle; feedback derived from motor EMF rather than output voltage. Use Value: Internal 72 kHz switching enables smooth low-speed torque; standby mode (<36 µA) supports low-power idle states in battery-powered tools. |
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 temperature range (−40°C to +85°C) and D2PAK package; identical electrical specs except TA rating | Suitable for extended-temp industrial or automotive under-hood use; requires surface-mount layout vs. through-hole TO-220 | Select when ambient exceeds +70°C or SMT assembly is required |
| LM2576HVSX-5.0/NOPB | 5 V fixed-output buck regulator with 3 A switch; 52 kHz frequency; no inverting capability; includes built-in diode | Limited to step-down only; simpler design but lacks voltage-inverting or step-up/down flexibility of MC34166THG | Choose for cost-sensitive 5 V-only applications where topology flexibility is unnecessary |
Compared with MC33166D2TR4G, MC34166THG offers lower-cost through-hole assembly and same core regulation performance but is restricted to 0°C to +70°C operation; versus LM2576HVSX-5.0, it trades integrated diode and fixed output for broader topology support and external component control.
Availability
MC34166THG is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC power supplies, off-line preconverters, and brushed motor controllers requiring stable component supply and long-term manufacturability.
Supply support for MC34166THG 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 specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.
The MC34166THG belongs to onsemi's legacy monolithic switching regulator product line, designed for cost-sensitive, high-reliability dc-dc conversion in automotive and industrial applications where fixed-frequency voltage-mode control and integrated protection are critical.
FAQ
What is the maximum output current supported by the MC34166THG in a step-down configuration?
The MC34166THG supports up to 3.0 A continuous output current in step-down configurations when properly heatsinked and operated within its 7.5–40 V input range. Its internal switch is rated for 3.0 A, with a typical current limit threshold of 4.3 A. Actual achievable output current depends on thermal design, ambient temperature, and duty cycle-derating is required above +70°C ambient due to its 0°C to +70°C operating range. The MC34166THG datasheet confirms this rating in both the Features section and Electrical Characteristics table.
Can the MC34166THG be used in a voltage-inverting (negative output) configuration?
Yes, the MC34166THG is explicitly designed for voltage-inverting applications, as confirmed in the datasheet title ("Inverting Switching Regulators – Step-Up/Down") and Figure 23. It achieves this by reconfiguring ground reference: the IC's GND pin (Pin 3) connects to the negative output rail, enabling the internal 5.05 V reference to regulate |VOUT|. The device maintains 3.0 A switch capability and full protection features in this topology. Application note examples show −12 V/1.0 A operation with 81.2% efficiency.
What is the purpose of the Comp pin (Pin 1) on the MC34166THG?
The Comp pin (Pin 1) on the MC34166THG is the error amplifier output node, used for external loop compensation to ensure converter stability. It connects to a series RC network (RF/CF) between Pins 1 and 5, forming a low-pass filter that shapes phase margin. The datasheet specifies this network is mandatory for all configurations (step-down, inverting, step-up/down) and provides component values for each. Without proper compensation, the MC34166THG may oscillate or exhibit poor transient response.
Does the MC34166THG support soft-start functionality?
Yes, the MC34166THG supports soft-start via its Comp pin (Pin 1), which features a built-in 100 µA current source. As shown in Figure 18, connecting a capacitor (CSS) from Pin 1 to ground creates a controlled voltage ramp at the error amp output, delaying full-duty-cycle startup and limiting inrush current. This function is independent of external enable signals and is inherent to the MC34166THG's architecture-no additional ICs or complex circuitry are needed to implement soft-start.
What package type and lead form does the MC34166THG use?
The MC34166THG uses a Pb-free 5-lead TO-220 package (Case 314B), with vertical mount orientation and offset leads. Its metal tab (heatsink surface) is internally connected to Pin 3 (GND), enabling direct thermal coupling to an external heatsink. The "THG" suffix explicitly denotes this TO-220 variant with Pb-free finish and TV leadform, as defined in the Ordering Information table on page 2 of the datasheet.
MC34166THG 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 Horizontal
MC34166THG FAQ
1.How can I place an order for MC34166THG through Aetrix?
Please submit a Request for Quotation (RFQ) for MC34166THG 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 MC34166THG reliable?
The price and inventory of MC34166THG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC34166THG is usually 5 days.
3.What payment methods are accepted for MC34166THG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC34166THG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC34166THG?
MC34166THG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC34166THG 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 MC34166THG?
For technical support, including MC34166THG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC34166THG requirements.
6.How does Aetrix verify that MC34166THG is sourced from the original manufacturer or authorized distributors?
All MC34166THG 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 MC34166THG meets industry standards.
7.What is the process for return or replacement of MC34166THG?
All MC34166THG units undergo pre-shipment inspection (PSI). If there is an issue with MC34166THG, 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 MC34166THG part is unused and in its original packaging.
Return procedure for MC34166THG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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