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onsemi MC34166TG
- Part No.:
- MC34166TG
- Manufacturer:
- onsemi
- Package:
- TO-220-5
- Datasheet:
-
MC34166TG.pdf
- Description:
- IC REG BUCK BST ADJ 3.3A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:2,665
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Product details
Overview
MC34166TG from onsemi is a fixed-frequency, voltage-mode switching regulator IC designed for step-down, voltage-inverting, and step-up/down 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 cost-sensitive power supplies.
For engineers reviewing the MC34166TG datasheet, pinout, applications, or equivalent options, this page provides verified technical context, real-world design parameters, validated alternative options, and supply-chain support for production-grade embedded power designs.
Technical Context
The MC34166TG 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 (±7 kHz over temperature) with 95% max duty cycle and built-in blanking to prevent multiple pulses per cycle.
Cycle-by-cycle current limiting monitors switch conduction via an internal sense resistor, triggering latch reset at 4.3 A typical peak current. Undervoltage lockout activates at 5.9 V (±0.4 V) with 0.9 V hysteresis, and thermal shutdown engages above 170°C junction temperature - all implemented without external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Output Current | 3.0 A continuous; supports ≥3.3 A peak before current-limit activation in high-load transient conditions |
| Oscillator Frequency | 72 kHz nominal (62–79 kHz over temp); enables compact magnetics and predictable EMI profile |
| Reference Voltage | 5.05 V ±2% at +25°C; sets base output without external divider; compensates for 1% cable drop |
| Input Voltage Range | 7.5 V to 40 V; compatible with 12 V/24 V automotive and industrial bus systems |
| Duty Cycle Range | 0% to 95%; supports wide VIN/VOUT ratios in buck and inverting topologies |
| Standby Supply Current | 36 µA at 12 V; achieved by clamping Pin 5 <150 mV; enables low-power sleep modes |
| Thermal Resistance (JC) | 5.0 °C/W; requires heatsink attachment to Pin 3 tab for >1.5 W dissipation |
Pinout & Package
The MC34166TG is housed in a Pb-free 5-lead TO-220 package (Case 314B), where the metal tab is electrically connected to Pin 3 (Ground) and serves as the primary thermal path. The package meets MSL Level 1 and supports vertical mounting with heatsink interface.
| 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 |
| Pin 2 (Switch Output) | Collector of internal NPN power transistor | Drives external inductor; rated for −1.5 V to +VIN; must be isolated from ground in inverting configs |
| Pin 3 (Ground) | Power and signal reference / heatsink connection | Common return for all internal circuits; tab is electrically tied to this pin; mandatory heatsink interface |
| Pin 4 (VCC) | Primary power supply input | Accepts 7.5–40 V; powers internal circuitry; UVLO monitoring occurs here |
| Pin 5 (Feedback) | Inverting input of error amplifier | Monitors output via resistive divider; threshold = 5.05 V; clamping below 150 mV enables standby mode |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 3.0 A switch | Eliminates need for external power transistor in ≤3 A buck/inverting converters; reduces BOM count and layout area |
| Fixed 72 kHz oscillator | Enables consistent filter design and EMI filtering; eliminates external timing capacitor variability |
| 5.05 V ±2% reference | Provides stable feedback threshold; allows 5.0 V output without divider; improves load/line regulation accuracy |
| Cycle-by-cycle current limit | Protects switch under short-circuit or overload without external sensing; resets each cycle for fast recovery |
| Undervoltage lockout with hysteresis | Prevents erratic startup below 5.9 V; 0.9 V hysteresis avoids oscillation near threshold during brownout |
| Thermal shutdown at 170°C | Defends against catastrophic failure due to inadequate heatsinking; latch-based shutdown requires power cycle to reset |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC I/O Power Supply |
|---|---|
Use Scenario: Regulating 12 V battery input to stable 5 V for microcontroller, CAN transceiver, and sensor interfaces in door modules or lighting controllers. IC Role / Device Role / Timing Role: Primary step-down regulator with integrated switch; handles line transients up to 40 V and load dumps per ISO 7637-2. Use Value: Single-chip solution reduces footprint vs. controller+MOSFET; 72 kHz switching enables small 190 µH inductor; thermal shutdown protects during connector faults. | Use Scenario: Generating isolated ±12 V rails from 24 V DC bus for analog input conditioning and relay driver stages in programmable logic controllers. IC Role / Device Role / Timing Role: Core voltage-inverting regulator (Figure 23); ground pin referenced to negative output to enable dual-rail generation. Use Value: Eliminates need for separate inverting IC; 5.05 V reference ensures tight regulation; cycle-by-cycle limiting prevents damage during field-wiring shorts. |
| Consumer Appliance Motor Drive | Off-line AC-DC Preconverter |
Use Scenario: Controlling brushed DC motor speed in cordless vacuum cleaners or power tools using EMF feedback (Figure 27). IC Role / Device Role / Timing Role: PWM controller modulating motor voltage; uses Pin 5 feedback for back-EMF sensing and closed-loop RPM regulation. Use Value: Standby mode (36 µA) extends battery life in idle; 0–95% duty cycle enables full-speed range; integrated current limit protects motor windings. | Use Scenario: High-efficiency 24 V pre-regulator stage fed from rectified AC line via flyback transformer (Figure 28), feeding multiple downstream MC34166 post-regulators. IC Role / Device Role / Timing Role: Post-regulator in distributed power architecture; accepts 24 V from self-oscillating preconverter; provides accurate, isolated 5 V/12 V/−12 V outputs. Use Value: Enables 90% system efficiency; triple-output capability (Figure 25) reduces need for additional regulators; thermal resistance (θJC = 5.0 °C/W) supports convection-cooled operation. |
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) vs. MC34166TG (0°C to +70°C); identical electrical specs and pinout | Suitable for extended-temperature industrial or automotive under-hood use; same PCB layout and compensation network | Select when ambient exceeds 70°C or cold-start reliability below 0°C is required |
| LM2576T-5.0 | Fixed 5.0 V output (non-adjustable); 3.0 A switch; 52 kHz frequency; no internal reference trimming (±4% tolerance) | Lacks adjustable output and inverting capability; simpler compensation but lower reference accuracy | Choose for cost-sensitive 5 V-only applications where ±2% regulation and topology flexibility are not critical |
Compared with MC34166TG, MC33166D2TR4G offers broader temperature compliance without layout changes, while LM2576T-5.0 trades adjustability and precision for lower BOM cost and reduced external component count in fixed-output designs.
Availability
MC34166TG is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC power supplies, consumer appliance motor drives, and off-line preconverter systems requiring stable component supply across multi-year production cycles.
Supply support for MC34166TG 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 is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.
The MC34166TG belongs to onsemi's legacy monolithic switching regulator product line, engineered for cost-effective, high-reliability dc-dc conversion in space-constrained and thermally demanding environments.
FAQ
What is the maximum output current capability of the MC34166TG?
The MC34166TG features an integrated NPN power switch rated for 3.0 A continuous output current. Its current-limit threshold is typically 4.3 A, allowing brief peak loads without shutdown. Actual deliverable current depends on thermal management: with proper heatsinking attached to Pin 3 (tab), the MC34166TG sustains 3.0 A at ambient temperatures up to +70°C. Derating applies above that point per θJA = 65°C/W.
Can the MC34166TG be used in voltage-inverting configurations?
Yes, the MC34166TG is explicitly designed for voltage-inverting applications, as confirmed in its datasheet Figure 23 and Introduction section. It achieves this by referencing the IC ground (Pin 3) to the negative output rail, which reverses the error amplifier polarity and keeps the switch emitter within its −1.5 V limit. This configuration delivers tightly regulated negative outputs such as −12 V/1.0 A with 81.2% efficiency, as validated in the datasheet test results.
What is the purpose of Pin 5 (Feedback) on the MC34166TG?
Pin 5 is the inverting input of the internal error amplifier and serves as the voltage feedback node. It compares the scaled output voltage against the 5.05 V internal reference. When the voltage at Pin 5 equals 5.05 V, the output is in regulation. Clamping Pin 5 below 150 mV places the MC34166TG into low-power standby mode, reducing supply current to 36 µA. This pin must be connected through a resistor divider for outputs other than 5.05 V, per the equation VOUT = 5.05 × (1 + R2/R1).
Does the MC34166TG require an external timing capacitor?
No, the MC34166TG does not require an external timing capacitor. Its 72 kHz oscillator is fully internal, using a trimmed current source and on-chip capacitor (CT). This eliminates timing component variability and improves production consistency. The oscillator's charge/discharge thresholds (4.1 V peak, 2.3 V valley) and 95% max duty cycle are factory-set, making the MC34166TG a true "plug-and-play" switching regulator IC with minimal external parts.
How does thermal protection work in the MC34166TG?
The MC34166TG incorporates internal thermal shutdown that activates when junction temperature exceeds approximately 170°C. Upon triggering, the PWM latch is forced into reset, disabling the output switch until device cooldown and power cycle. This protection is distinct from thermal derating - it is a fail-safe mechanism, not a linear throttling feature. The datasheet specifies θJC = 5.0°C/W, meaning the metal tab (Pin 3) must be mounted to an adequate heatsink to maintain safe operation under sustained 3.0 A loads.
MC34166TG 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
MC34166TG FAQ
1.How can I place an order for MC34166TG through Aetrix?
Please submit a Request for Quotation (RFQ) for MC34166TG 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 MC34166TG reliable?
The price and inventory of MC34166TG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC34166TG is usually 5 days.
3.What payment methods are accepted for MC34166TG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC34166TG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC34166TG?
MC34166TG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC34166TG 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 MC34166TG?
For technical support, including MC34166TG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC34166TG requirements.
6.How does Aetrix verify that MC34166TG is sourced from the original manufacturer or authorized distributors?
All MC34166TG 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 MC34166TG meets industry standards.
7.What is the process for return or replacement of MC34166TG?
All MC34166TG units undergo pre-shipment inspection (PSI). If there is an issue with MC34166TG, 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 MC34166TG part is unused and in its original packaging.
Return procedure for MC34166TG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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