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onsemi MC34166D2T
- Part No.:
- MC34166D2T
- Manufacturer:
- onsemi
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
MC34166D2T.pdf
- Description:
- IC REG BUCK BST ADJ 3.3A D2PAK-5
- Quantity:
- Payment:
- Shipping:
Inventory:2,584
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Product details
Overview
MC34166D2T 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, cycle-by-cycle current limiting, and undervoltage lockout (5.9 V startup). 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 MC34166D2T datasheet, pinout, applications, or equivalent options, this page provides verified technical context, package-specific pin functions, real-world converter configurations (step-down/inverting), thermal and current-limiting behavior, and validated alternative options for supply chain continuity and design flexibility.
Technical Context
The MC34166D2T implements voltage-mode PWM control with an internal 72 kHz oscillator (±10% over temperature), latching PWM comparator, and high-gain error amplifier (80 dB typical gain, 600 kHz unity-gain bandwidth). Its feedback threshold is fixed at 5.05 V with ±2% tolerance at 25°C, and it supports 0–95% duty cycle via compensation pin (Pin 5) voltage.
It features cycle-by-cycle current limiting (typical Ipk = 4.3 A), undervoltage lockout with 5.9 V startup and 0.9 V hysteresis, thermal shutdown at ~170°C, and standby mode reducing supply current to 36 µA when Pin 5 is clamped below 150 mV. The D2PAK package (Case 936A) has θJA = 70°C/W and θJC = 5.0°C/W.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 72 kHz nominal (62–79 kHz over full temp range); sets minimum external component count and defines switching loss vs. filter size trade-off. |
| Reference Voltage | 5.05 V ±2% at 25°C; enables stable 5.0 V output without external divider; compensates for 1% cable drop. |
| Output Switch Current | 3.0 A continuous (4.3 A typical current limit); supports up to 3 A load in step-down configuration with proper heatsinking. |
| Input Voltage Range | 7.5 V to 40 V; compatible with 12 V/24 V automotive and industrial rails; exceeds standard 36 V battery system requirements. |
| Standby Supply Current | 36 µA at 12 V (Pin 5 < 150 mV); enables low-power sleep modes in battery-backed systems. |
| UVLO Threshold | 5.9 V startup with 0.9 V hysteresis; prevents erratic operation during brown-out and ensures clean power-up sequencing. |
| Thermal Resistance (J–C) | 5.0°C/W; allows direct heatsink mounting via tab (Pin 3), enabling >2 W dissipation with modest heatsink. |
Pinout & Package
D2PAK (Case 936A) surface-mount package with exposed thermal pad connected internally to Pin 3 (GND). Heatsink surface is electrically tied to Pin 3 and must be soldered to PCB ground plane for thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - GND | Ground reference | Power and signal ground return; connects to internal thermal pad via Pin 3; must be low-impedance path. |
| 2 - Switch Output | Collector of internal NPN switch | Drives external inductor; rated for −1.5 V to +VIN; requires Schottky rectifier (e.g., 1N5822) for flyback recovery. |
| 3 - GND / Heatsink | Common ground & thermal interface | Electrically tied to package tab; primary thermal path; must be soldered to large copper area for θJA = 70°C/W. |
| 4 - VCC | Power supply input | Accepts 7.5–40 V; powers internal circuitry; bypass capacitor (≥330 µF) required close to pin. |
| 5 - Compensation | Error amplifier output & soft-start node | Controls PWM duty cycle; clamping below 150 mV enables 36 µA standby; 100 µA pull-up enables soft-start via external capacitor. |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 72 kHz oscillator with on-chip timing | Eliminates external timing resistor/capacitor; reduces BOM count and layout sensitivity in step-down/inverting converters. |
| 5.05 V ±2% internal reference | Enables accurate 5.0 V output without external resistors; improves load/line regulation (±0.02% load reg, ±0.05% line reg demonstrated). |
| Cycle-by-cycle current limiting | Protects switch under short-circuit or overload; resets PWM latch each cycle; limits peak current to ≥3.3 A across temperature. |
| Undervoltage lockout with hysteresis | Ensures reliable start-up above 5.9 V and prevents oscillation near threshold; 0.9 V hysteresis avoids chatter during input sag. |
| Low-power standby mode | Reduces ICC to 36 µA by pulling Pin 5 low; supports energy-efficient sleep states in portable or always-on systems. |
Applications
| Automotive Body Control Module (BCM) | Industrial 24 V to 5 V Step-Down Supply |
|---|---|
Use Scenario: Powering microcontrollers, CAN transceivers, and sensors in vehicle door modules with 12 V battery input. IC Role / Device Role / Timing Role: Primary step-down regulator delivering stable 5.0 V @ 3.0 A; uses internal 5.05 V reference and fixed 72 kHz switching for EMI control. Use Value: Eliminates need for external feedback divider; achieves ±0.05% line regulation over 8–36 V input range per test data. |
Use Scenario: Converting unregulated 24 V industrial rail to clean 5 V for PLC I/O logic and communication interfaces. IC Role / Device Role / Timing Role: Fixed-frequency voltage-mode controller in buck topology; leverages D2PAK thermal pad for conduction cooling on metal-core PCB. Use Value: Delivers 82.8% efficiency at 3.0 A load; thermal resistance of 5.0°C/W (J–C) enables >2 W dissipation without forced air. |
| Voltage-Inverting Power Supply (-12 V @ 1.0 A) | Triple-Output Off-Line Preconverter Stage |
Use Scenario: Generating isolated -12 V rail for op-amp biasing or RS-232 level-shifting in instrumentation systems. IC Role / Device Role / Timing Role: Inverting regulator using grounded negative output configuration (IC GND tied to VO−); relies on internal reference and 95% max duty cycle. Use Value: Achieves ±0.017% load regulation and 81.2% efficiency; emitter clamp keeps Q1 within −1.5 V limit per datasheet Figure 9. |
Use Scenario: First-stage AC/DC conversion feeding multiple downstream MC34166 post-regulators in distributed power architecture. IC Role / Device Role / Timing Role: Core controller in self-oscillating flyback preconverter (50 kHz); drives transformer T1 base winding via MJE13005. Use Value: Enables 125 W total output with 90% efficiency; D2PAK package withstands repeated surge currents in offline startup. |
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. | Suitable for extended-temperature environments (e.g., under-hood automotive, outdoor industrial). | Select MC33166D2TR4G when ambient exceeds 70°C; otherwise MC34166D2T offers cost advantage for commercial-temp designs. |
| LM2576-5.0 | 5 V fixed-output version; 3 A switch; 52 kHz frequency; no internal reference feedback pin (VFB tied internally). | Lacks compensation pin (Pin 5) and standby mode; simpler but less flexible for custom output voltages or low-power states. | Choose LM2576-5.0 for drop-in 5 V replacement where soft-start, standby, or inverting topologies are not required. |
Compared with MC33166D2TR4G, MC34166D2T trades extended temperature rating for lower cost in commercial applications; compared with LM2576-5.0, it offers greater design flexibility via Pin 5 compensation and ultra-low standby current, at the expense of higher external component count for non-5 V outputs.
Availability
MC34166D2T is available at Aetrix Electronics and suitable for automotive body electronics, industrial 24 V power supplies, voltage-inverting instrumentation, and off-line preconverter stages requiring stable component supply and long-term manufacturability.
Supply support for MC34166D2T 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, and sensor solutions for automotive, industrial, and cloud infrastructure markets.
The MC34166D2T belongs to the MC34166/MC33166 series of monolithic switching regulators, designed specifically for cost-sensitive, high-reliability DC-DC conversion in step-down, inverting, and step-up configurations with minimal external components.
FAQ
What is the maximum output current capability of the MC34166D2T in a step-down configuration?
The MC34166D2T supports up to 3.0 A continuous output current in step-down applications, as confirmed by datasheet Figure 19 test conditions and electrical characteristics (Ipk(switch) min = 3.3 A). Actual achievable current depends on thermal management-using the D2PAK's exposed tab (Pin 3) with a 2 oz. copper heatsink area enables sustained 3 A operation at +70°C ambient per Figure 29 derating curves. The MC34166D2T's 5.0°C/W junction-to-case thermal resistance is critical to maintaining safe junction temperature.
Does the MC34166D2T support voltage-inverting topologies, and what design modifications are required?
Yes, the MC34166D2T supports voltage-inverting configurations as shown in Figure 23. To implement this, the IC's ground pin (Pin 1) must be connected to the negative output rail-not system ground-thereby reversing the error amplifier's effective inputs and keeping the switch emitter within its −1.5 V limit. This configuration delivers −12 V at 1.0 A with 81.2% efficiency and ±0.017% load regulation per datasheet test results. The MC34166D2T's fixed 5.05 V reference remains functional in this arrangement.
How does the standby mode function on the MC34166D2T, and what is its power consumption?
The MC34166D2T enters standby mode when the compensation pin (Pin 5) voltage is held below 150 mV, reducing supply current to 36 µA at 12 V (per Electrical Characteristics table). This is achieved by clamping Pin 5 via an external transistor or logic signal. Standby mode disables the oscillator and PWM latch while preserving UVLO and thermal shutdown functionality. The MC34166D2T's 36 µA standby current enables battery-backed systems to extend runtime significantly-verified in Figure 11 across 0–40 V supply range.
What is the purpose of the compensation pin (Pin 5) on the MC34166D2T, and can it be used for soft-start?
Pin 5 is the error amplifier output and serves as the PWM control node-its voltage directly sets duty cycle (0–95%). It also enables soft-start: the internal 100 µA pull-up current charges an external capacitor (CSS), gradually raising Pin 5 voltage and ramping output voltage. Figure 18 shows this implementation. Unlike dedicated soft-start pins, Pin 5 requires careful RC selection to avoid instability; the MC34166D2T's open-loop gain (80 dB) and phase margin (70°) ensure stability when compensated per Figure 14 network.
Is the MC34166D2T pin-compatible with the MC33166D2T, and what are the key differences?
Yes, the MC34166D2T and MC33166D2T share identical pinout, package (D2PAK), and electrical specifications-including 72 kHz oscillator, 5.05 V reference, and 3.0 A switch-but differ only in operating temperature range: MC34166D2T is rated 0°C to +70°C, while MC33166D2T extends to −40°C to +85°C. Both use the same marking suffix "D2T" and ordering part numbers (e.g., MC34166D2TR4G vs. MC33166D2TR4G). No PCB changes are needed when substituting within their respective temperature envelopes.
MC34166D2T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- 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:
- Surface Mount
- Supplier Device Package:
- D2PAK-5
MC34166D2T FAQ
1.How can I place an order for MC34166D2T through Aetrix?
Please submit a Request for Quotation (RFQ) for MC34166D2T 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 MC34166D2T reliable?
The price and inventory of MC34166D2T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC34166D2T is usually 5 days.
3.What payment methods are accepted for MC34166D2T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC34166D2T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC34166D2T?
MC34166D2T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC34166D2T 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 MC34166D2T?
For technical support, including MC34166D2T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC34166D2T requirements.
6.How does Aetrix verify that MC34166D2T is sourced from the original manufacturer or authorized distributors?
All MC34166D2T 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 MC34166D2T meets industry standards.
7.What is the process for return or replacement of MC34166D2T?
All MC34166D2T units undergo pre-shipment inspection (PSI). If there is an issue with MC34166D2T, 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 MC34166D2T part is unused and in its original packaging.
Return procedure for MC34166D2T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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