A complete DC-DC converter control circuit in SOIC-8, one of the oldest and most widely used switching-regulator chips. On board it has a temperature-compensated reference, a comparator, an oscillator whose frequency a single capacitor sets, a current-limit sense, a driver, and a 1.5 A output switch. With a handful of external parts (inductor, diode, resistors) it builds a step-down (buck), step-up (boost), or voltage-inverting converter over a 3 to 40 V input. It is the go-to for a cheap adjustable boost or buck when an integrated-inductor module is overkill.

Pinout

Pin	Name	Type	Function
1	Switch Collector	output	High-current internal switch (Q1) collector. Rated 40 V max, up to 1.5 A peak switch current. Connects to the inductor/diode node of the boost/buck/inverting converter.
2	Switch Emitter	output	High-current internal switch (Q1) emitter output. Rated 40 V max. Combined with pin 1 forms the internal Darlington output switch used to drive the converter's power inductor.
3	Timing Capacitor	passive	Oscillator timing capacitor (C_T) pin. An external capacitor to GND sets the oscillator frequency (up to 100 kHz). Charge current typ. 35 uA, discharge typ. 220 uA, giving discharge/charge ratio ~6.5.
4	GND	power_in	Device ground reference. On the DRJ (QFN) package the exposed thermal pad is bonded internally to this pin.
5	Comparator Inverting Input	input	Inverting input to the internal error comparator. Non-inverting input is internally tied to the 1.25-V (typ.) reference. Connect a resistor divider from Vout to set the regulated output voltage. Input bias current typ. -20 nA (max -400 nA). Absolute range -0.3 V to 40 V.
6	VCC	power_in	Logic supply voltage. Tie to VIN. Operating range 3 V to 40 V (absolute max 40 V). Standby supply current typ. ~2.5 mA (max 4 mA at 5 V, C_T = 1 nF).
7	Ipk Sense	input	Current-limit sense input. An external resistor (Rsc) between VCC (pin 6) and this pin sets the peak switch current; the internal circuit terminates the switch on-time when the voltage across Rsc reaches ~300 mV (typ., 250-350 mV).
8	Driver Collector	output	Darlington driver transistor (Q2) collector input. Provides access to the driver stage for external switch configurations or Darlington operation (tie to pin 1 for internal Darlington). Rated 40 V max, driver collector current 100 mA max.

Key specifications

Parameter	Value
Type	DC-DC converter controller
Topologies	buck, boost, inverting
Switch current	1.5 A (on-chip)
Input voltage	3-40 V
Oscillator	set by one capacitor (up to 100 kHz)
Reference	1.25 V
Current limit	Ipk sense pin
Package	SOIC-8

Ordering variants

Same part, different packaging or reel option.

MC34063AD (SOIC-8)
MC34063AP (PDIP-8)

CAD (KiCad official)

Symbol: Regulator_Switching:MC34063AD
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (32 pp, sha256 bad86a3b68c35766, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF