MC34063ADG
onsemi
IC REG BUCK BST ADJ 1.5A 8SOIC
MOQ 1 · Tube · RoHS · EIA-481 · DAP/DDP · T/T
Technical specifications
| Parameter / Attribute | Specification / Value |
|---|---|
| Output type | Adjustable |
| Mounting | Surface Mount |
| Voltage - input | 40V |
| Voltage - output | 40V (Switch) |
| Voltage - output (Min (Fixed)) | 1.25V |
| Output current | 1.5A (Switch) |
| Frequency - switching | 100kHz |
| I/O channels | 1 |
| Operating temperature | 0°C ~ 70°C (TA) |
| Package | Tube |
| Function | Step-Up, Step-Down |
| Topology | Buck, Boost |
| Case | 8-SOIC (0.154\", 3.90mm Width) |
| Output configuration | Positive or Negative |
| Synchronous rectifier | No |
Need Stock or a Drop-in Second-Source for MC34063ADG?
Package: DIP-8 / SOIC-8 · Pin-compatible replacements with immediate Shenzhen spot stock
The MC34063 is the 8-pin answer to everything cheap and switching: buck, boost and inverting converters built from one die with a 1.25V reference, an internal Darlington switch and current limiting set by a single sense resistor. It appears in ten million car chargers, adapter boards and appliance supplies, and its substitution story is the cleanest in the analog world: MC34063A and MC33063A are the same silicon under different temperature grades (commercial and industrial), with NCV and CW prefixes walking the same line. The design story is also the buying story: almost every failure and every fake argument in this part lives in the sense resistor and the timing capacitor - the two components the datasheet formulas exist for.
Verified Pin-Compatible Replacements (2 verified alternatives)
The Industrial-Temperature Grade
Shenzhen Spot Stock (24-48h Dispatch)
The same die, same pinout and same design formulas, characterized over -40 to +85C against the commercial 0-70C of the MC34063A - and the NCV33063 automotive grade extends further for under-hood designs.
Operation to 40V input; the core rule of the topology: the sum of input plus output voltage stays within 40V.
The Clone Row - Grade by Behavior
Shenzhen Spot Stock (24-48h Dispatch)
The Chinese-fab member of the same design: identical function for the consumer-adapter and charger market where the part was born.
Same envelope on paper; per-lot behavior is the verification item.
Buyer & Quality Checklist for Sourcing Alternatives
- The family letter is temperature, not function: MC34063A commercial, MC33063A industrial, MC35063 military, NCV automotive. Read the requirement off the environment, not the price column.
- The sense resistor is the current limit: Rsc = 0.3V / Ipk. A wrong or drifted sense resistor is the most common failure and fake-symptom in this part - the converter either runs cool and weak or hot and dead, and the resistor is the first meter reading.
- The capacitor across CT sets the switching frequency (CT = 4e-5 x ton): frequency drift in a clone shows up as audible whine or ripple complaints - measure the actual switching frequency on suspect lots.
- The 40V wall: input plus output voltage must sum within 40V in buck and inverting topologies. 24V-in to -12V-out designs sit near the edge - check before promising a substitute grade.
- Efficiency expectations are period-correct: about 90 percent boost, 80 buck, 65 inverting, with the Darlington drop (about 1V) doing the damage. A modern synchronous replacement module will be cooler - but it is a redesign.
- For current beyond 1.5A peaks the datasheet pattern adds an external PNP/NPN boost transistor - repairs that replaced only the IC on such a board miss half the circuit.
- Output ripple scales inversely with frequency: the datasheets noise figures assume the intended CT and inductor. Do not chase ripple with bigger capacitors before checking whether the CT capacitor value drifted.
Frequently Asked Technical Questions
Q: What is the difference between MC34063 and MC33063?
A: Temperature grade only: 34063 is characterized 0-70C, 33063 over -40 to +85C. Same die, same pinout, same formulas; choose by the environment.
Q: How is the current limit set on an MC34063?
A: By the sense resistor: Rsc = 0.3V divided by the peak switch current. It is the first component to inspect when a converter misbehaves, and its drift is the classic silent failure in this family.
Q: Can the MC34063 make a negative supply?
A: Yes - the inverting topology is one of its three native modes, with the input plus output sum inside the 40V limit. It is the classic cheap negative rail in instruments and audio.