BETASupply range3–40 V
Buck / boost / inverting controller
MC34063A Specifications
Review MC34063A electrical specifications, operating conditions and package details.
Package view
Key specifications
The external inductor and diode carry the energy. CT controls timing, RSC limits peak current and the output divider sets the regulated voltage.
Peak switch limit1.5 A · not load current
Ambient range0–70 °C · MC34063A
Nominal reference1.25 V
Package details
MC34063AP · PDIP-8
| Property | Details |
|---|---|
| Manufacturer | Texas Instruments |
| Part number | MC34063AP |
| Package | PDIP-8 |
| Connections | 8 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | dip |
| Thermal reference | Board and package dependent; see manufacturer data |
Operating conditions
Selected commercial MC34063A
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply | 3–40 V | Recommended VCC range |
| Ambient temperature | 0 to +70°C | MC34063A; MC33063A is a separately specified −40 to +85°C option |
| Topologies | Buck / boost / inverting | External wiring and calculations differ |
| Maximum oscillator capability | 100 kHz | External CT and the operating conditions determine actual timing |
| Peak switch current | 1.5 A | Not a guaranteed continuous load current |
| Packages shown | PDIP-8 / SOIC-8 | TI P / D orderables |
No specifications match. Try a parameter name or a unit.
Keep voltage overshoot and thermal stress within the exact device ratings.
Oscillator and current limit
VCC = 5 V; TA = 25°C unless noted
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Frequency with CT = 1 nF | 24 / 33 / 42 kHz | Minimum / typical / maximum; pin 5 at 0 V |
| Capacitor charge current | 24 / 35 / 42 µA | VCC = 5–40 V |
| Capacitor discharge current | 140 / 220 / 260 µA | VCC = 5–40 V |
| Discharge / charge ratio | 5.2 / 6.5 / 7.5 | Pin 7 tied to VCC |
| Current-limit sense voltage | 250 / 300 / 350 mV | Characterized at equal charge and discharge currents |
| Nominal sense resistor | RSC ≈ 0.3 / IPEAK | Use threshold tolerance and waveform margins |
No specifications match. Try a parameter name or a unit.
The CT = 1 nF frequency is a test point, not the frequency of the illustrated 470 pF circuit.
Reference, switch and supply
TI electrical-characteristic conditions
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Reference at 25°C | 1.225 / 1.250 / 1.275 V | Minimum / typical / maximum |
| Reference over ambient range | 1.21–1.29 V | Commercial operating range |
| Reference line change | 1.4 mV typical; 5 mV maximum | VCC = 5–40 V |
| Darlington switch saturation | 1 V typical; 1.3 V maximum | ISW = 1 A; pins 1 and 8 joined |
| Non-Darlington saturation | 0.45 V typical; 0.7 V maximum | ISW = 1 A, 82 Ω driver feed, forced beta about 20 |
| Supply current | 4 mA maximum | VCC = 5–40 V; output-switch-off test conditions |
No specifications match. Try a parameter name or a unit.
Driver topology changes switching loss and turn-off behavior. Use the complete manufacturer conditions.
Buck example components
TI Figure 11 · 25 V input, approximately 5 V output
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| RSC | 0.33 Ω | Between VIN and the joined SC1 / IPK7 / DC8 feed |
| CT | 470 pF | Pin 3 to ground |
| L1 | 220 µH | Pin 2 to filtered output; select suitable saturation and RMS ratings |
| Catch diode | 1N5819 | Cathode at pin 2; anode at GND |
| CIN / COUT | 100 µF / 470 µF | Choose voltage/ripple ratings and suitable ESR; illustrated 50 V / 16 V |
| R2 / R1 | 3.8 kΩ / 1.2 kΩ | R2 from output to INV5; R1 from INV5 to GND |
| Reference load | 500 mA | Manufacturer application example, not the part’s universal current rating |
No specifications match. Try a parameter name or a unit.
The optional extra LC output filter is omitted from the illustration. The nominal resistor ratio gives 5.208 V before tolerance and losses.
Read the example correctly
Calculated illustrations
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Divider output | 5.208 V | 1.25 × (1 + 3.8/1.2) |
| Nominal current limit | 0.909 A | 0.300 V / 0.33 Ω |
| Threshold-only limit interval | 0.758–1.061 A | 0.250–0.350 V / 0.33 Ω; excludes resistor tolerance and dynamic effects |
| Ideal duty at 25 V | 20.8% | 5.208 / 25; excludes switch/diode drops |
| Output power at 0.5 A | Approximately 2.60 W | 5.208 V × 0.5 A |
| Simple resistor load | About 10.4 Ω | For an illustrative 0.5 A load; rate it above the dissipated power |
No specifications match. Try a parameter name or a unit.
These calculations explain the circuit. They are not live measurements or a switching simulation.
Layout and connection checks
Protect quiet nodes from switching currents
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Current-sense path | VIN6 → RSC → IPK7 / SC1 / DC8 | Use short, low-inductance paths and sense the resistor terminals |
| Switch node | SE2 → L1 and diode cathode | Keep copper compact |
| Catch path | GND → diode → SE2 → L1 | Short loop with the output capacitor |
| Feedback divider | Output → R2 → INV5 → R1 → GND | Route away from switch-node copper |
| Timing capacitor | CT3 → GND4 | Place close to the IC |
| Physical package mapping | Eight pins in both selected packages | Pin 1 indication remains visible |
No specifications match. Try a parameter name or a unit.
Changing from buck to boost or inverting operation requires a different power-stage connection.
Stress and thermal limits
Absolute maxima are not normal targets
Manufacturer specifications 6 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply / switch voltage | 40 V | Absolute limits require checking each referenced voltage |
| Driver collector current | 100 mA | Absolute maximum |
| Switch current | 1.5 A | Absolute maximum |
| Junction temperature | 150°C | Absolute maximum; thermal design must stay below it |
| Storage temperature | −65 to +150°C | Unpowered |
| Comparator input | −0.3 to +40 V | Absolute input range, not a desired feedback voltage |
No specifications match. Try a parameter name or a unit.
A headline current rating cannot replace dissipation and temperature calculations.
Connections by function
Select a pin for its function, connection guidance and electrical notes.