Power-logic shift register — what it is and why it matters
The Texas Instruments TPIC6B595N is a power-logic 8-bit shift register with open-drain outputs, designed to drive loads directly — relays, solenoids, LEDs, small motors — without external driver transistors or Darlington arrays. It belongs to the TPIC series, TI's power-logic family that integrates high-current output stages with standard shift-register control logic. The part accepts serial data input and shifts it through an 8-bit register, then latches the parallel data onto eight open-drain output stages.
Open-drain outputs — the design difference
The open-drain output stage is the defining characteristic that separates this part from a standard 74HC595 shift register. Each of the eight outputs can sink substantial current — rated for 150 mA per output continuously — and the outputs can be paralleled for higher load currents on a single channel. The open-drain configuration means the outputs pull low only; the load connects between the output pin and a positive supply voltage (up to the output breakdown voltage, typically 50 V). This allows the TPIC6B595N to switch loads at a different voltage than the logic supply, a capability a push-pull shift register cannot match.
The through-hole 20-pin DIP package (0.300" body width) suits prototyping, breadboard work, and legacy PCB retrofits where surface-mount rework is impractical. The industrial temperature range also covers the thermal extremes in sealed enclosures with minimal airflow.