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onsemi MC33166T
- Part No.:
- MC33166T
- Manufacturer:
- onsemi
- Package:
- TO-220-5
- Datasheet:
-
MC33166T.pdf
- Description:
- IC REG BUCK BST ADJ 3.3A TO220-5
- Quantity:
- Payment:
- Shipping:
Inventory:3,273
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Product details
Overview
MC33166T from onsemi is a fixed-frequency voltage-mode switching regulator IC designed for step-down, 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, cycle-by-cycle current limiting, undervoltage lockout (5.9 V startup), and thermal shutdown - enabling compact, cost-effective power supplies in automotive and industrial environments.
For engineers reviewing the MC33166T datasheet, pinout, applications, or equivalent options, key selection considerations include its −40°C to +85°C operating range, TO-220-5 package with heatsink-connected Pin 3, 7.5–40 V input capability, 0–95% duty cycle control, and standby mode reducing supply current to 36 µA.
Technical Context
The MC33166T implements voltage-mode PWM 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 stable 72 kHz ramp signal 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, ensuring single-pulse metering per cycle. Cycle-by-cycle current limiting monitors switch conduction via an internal sense resistor and resets the latch when peak current exceeds 4.3 A (typical), while undervoltage lockout provides 0.9 V hysteresis for clean startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Input Voltage | 7.5 V to 40 V - supports wide-range unregulated inputs including automotive battery (cold-crank tolerant down to 7.5 V) |
| Output Switch Current | 3.0 A continuous - enables ≥15 W step-down or inverting converters without external MOSFETs |
| Oscillator Frequency | 72 kHz (typ) - fixed frequency simplifies EMI filtering and inductor sizing; stable over temperature and supply |
| Reference Voltage | 5.05 V ±2% - precise internal reference eliminates need for external divider in 5 V output designs |
| Duty Cycle Range | 0% to 95% - supports high step-down ratios and wide input/output differentials in inverting configurations |
| Standby Supply Current | 36 µA at 12 V - enables low-power sleep modes in battery-backed systems |
| UVLO Threshold | 5.9 V startup / 5.0 V turn-off (0.9 V hysteresis) - prevents erratic operation during brownout or soft-start |
Pinout & Package
MC33166T is housed in a 5-lead TO-220 package (Case 314B), with the metal tab thermally and electrically connected to Pin 3 (Ground). The package is Pb-free and moisture sensitivity level (MSL) 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 | Compensation | Output of error amplifier; connects to RC network for loop stability tuning |
| Pin 2 | Switch Output | Collector of internal NPN power transistor; drives external inductor/diode |
| Pin 3 | Ground | Power and signal ground; internally tied to heatsink tab for thermal path |
| Pin 4 | VCC | Primary power supply input (7.5–40 V); powers internal circuitry and bias networks |
| Pin 5 | Feedback | Inverting input of error amplifier; senses output voltage via resistive divider |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 3.0 A NPN switch | Eliminates need for external power transistor in ≤15 W converters, reducing BOM count and layout area |
| Fixed 72 kHz oscillator with on-chip timing | Removes external timing components; ensures consistent switching frequency across temperature and supply |
| 5.05 V ±2% precision reference | Enables accurate 5 V regulation without feedback resistor trimming; compensates for typical 1% cable drop |
| Cycle-by-cycle current limiting | Provides immediate overcurrent protection per switching cycle, preventing thermal runaway under short-circuit conditions |
| Undervoltage lockout with hysteresis | Guarantees functional reset before enabling output stage; avoids unstable operation during power ramp-up |
Applications
| Automotive Body Control Module | Industrial Sensor Power Supply |
|---|---|
|
Use Scenario: Generating stable 5 V rail from 9–16 V battery for microcontroller, CAN transceiver, and analog sensors in door modules. IC Role / Device Role / Timing Role: Primary step-down regulator controlling inductor current via PWM to maintain regulated output under load transients and cold-crank dips. Use Value: −40°C to +85°C rating ensures reliability across vehicle cabin environments; integrated current limit protects against motor stall faults. |
Use Scenario: Providing isolated −12 V bias for op-amps and ADC drivers in factory-floor pressure/temperature transmitters. IC Role / Device Role / Timing Role: Voltage-inverting regulator topology where Pin 3 (GND) connects to negative output, enabling true bipolar rail generation. Use Value: Internal 5.05 V reference and 95% max duty cycle support tight regulation of inverted outputs; thermal shutdown prevents field failure in enclosed enclosures. |
| Off-Line AC/DC Preconverter | Brushed DC Motor Speed Controller |
|
Use Scenario: Front-end 24 V pre-regulator in multi-output distributed power systems fed from rectified AC line via flyback transformer. IC Role / Device Role / Timing Role: Fixed-frequency PWM controller driving primary-side switch; synchronized with self-oscillating transformer T2 at 50 kHz. Use Value: 40 V max VCC rating allows safe operation with clamped rectified input; standby mode reduces no-load losses in standby states. |
Use Scenario: Variable-speed control of 12–24 V brushed motors in HVAC actuators, using back-EMF sensing for closed-loop RPM regulation. IC Role / Device Role / Timing Role: Step-down regulator modulating average motor voltage via PWM duty cycle; feedback derived from motor terminal voltage. Use Value: Wide 7.5–40 V input range accommodates battery and alternator fluctuations; 3.0 A switch handles stall currents up to 4.3 A (limited). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar switching regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MC34166D2TR4G | Same core architecture but rated for 0°C to +70°C ambient; D2PAK surface-mount package instead of TO-220 | Preferred for commercial-grade, space-constrained PCBs; lacks extended temperature qualification for automotive use | Select MC34166D2TR4G only if industrial temperature range suffices and SMT assembly is required. |
| LM2576T-5.0 | 5 V fixed-output buck regulator; 3 A switch; 52 kHz frequency; requires no feedback resistors but lacks inverting capability | Drop-in replacement for simple 5 V step-down only; cannot implement voltage inversion or adjustable outputs without external circuitry | Choose LM2576T-5.0 when design requires only fixed 5 V output and simplified layout - but verify compatibility with inverting or step-up/down needs. |
Compared with MC33166T, MC34166D2TR4G offers identical functionality in a surface-mount package but sacrifices automotive temperature range, while LM2576T-5.0 trades topology flexibility (no inverting mode) and adjustable feedback for fixed-output simplicity and broader vendor availability.
Availability
MC33166T is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor interfaces, off-line preconverters, and brushed motor controllers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for MC33166T 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 power management, analog, and sensor technologies for automotive, industrial, and cloud infrastructure markets.
The MC33166T belongs to onsemi's legacy monolithic switching regulator product line, engineered specifically for robust, low-component-count DC-DC conversion in harsh environments - emphasizing thermal resilience, wide input range, and integrated protection.
FAQ
What is the maximum input voltage rating for the MC33166T?
The MC33166T has an absolute maximum power supply input voltage (VCC) of 40 V, as specified in the Maximum Ratings table. Operation above this level risks permanent damage. For reliable long-term use, designs should maintain VCC ≤ 36 V under worst-case transient conditions, especially in automotive applications with load-dump spikes. The MC33166T datasheet confirms this rating applies across its full −40°C to +85°C operating junction temperature range.
Does the MC33166T support voltage-inverting converter topologies?
Yes, the MC33166T explicitly supports voltage-inverting configurations, as demonstrated in Figure 23 of the official datasheet. In this mode, the IC's ground pin (Pin 3) is connected to the negative output rail, reversing the error amplifier's effective inputs and allowing stable regulation of negative outputs such as −12 V/1.0 A. This capability is intrinsic to the MC33166T's architecture and does not require external op-amps or level-shifting circuitry.
What is the purpose of Pin 1 (Compensation) on the MC33166T?
Pin 1 is the output of the internal error amplifier and serves as the compensation node for the feedback loop. It must be connected to an external RC network (e.g., RF and CF in Figure 14) between Pins 1 and 5 to ensure stability across all operating conditions. Proper compensation prevents oscillation and overshoot during load transients. The MC33166T datasheet specifies that this network is mandatory - omitting it results in unstable regulation or no output control.
Can the MC33166T operate in low-power standby mode, and how is it activated?
Yes, the MC33166T features a low-power standby mode that reduces supply current to 36 µA (at 12 V). It is activated by clamping the voltage at Pin 1 (Compensation) to less than 150 mV - typically achieved using a transistor or logic-level signal pulling Pin 1 toward ground. This mode disables the output switch and oscillator while preserving internal reference and UVLO functionality, making it ideal for battery-powered sleep states. The behavior is fully documented in the MC33166T datasheet Section "Error Amplifier and Reference".
Is the MC33166T pin-compatible with the MC34166 series?
The MC33166T and MC34166 share identical pinout, electrical characteristics, and functional block diagram - differing only in guaranteed operating temperature range (MC33166T: −40°C to +85°C; MC34166: 0°C to +70°C) and ordering suffixes. Therefore, they are functionally interchangeable in circuits where ambient temperature remains within 0°C–70°C. However, MC33166T is not a drop-in replacement in automotive under-hood applications requiring the extended range, even though the pinout matches exactly.
MC33166T 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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-5
MC33166T FAQ
1.How can I place an order for MC33166T through Aetrix?
Please submit a Request for Quotation (RFQ) for MC33166T 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 MC33166T reliable?
The price and inventory of MC33166T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC33166T is usually 5 days.
3.What payment methods are accepted for MC33166T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC33166T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC33166T?
MC33166T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC33166T 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 MC33166T?
For technical support, including MC33166T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC33166T requirements.
6.How does Aetrix verify that MC33166T is sourced from the original manufacturer or authorized distributors?
All MC33166T 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 MC33166T meets industry standards.
7.What is the process for return or replacement of MC33166T?
All MC33166T units undergo pre-shipment inspection (PSI). If there is an issue with MC33166T, 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 MC33166T part is unused and in its original packaging.
Return procedure for MC33166T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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