UCN5804B.com
The Allegro 5804b was a robust Stepper Translator IC with built-in Drivers. Its simple 3-signal interface [Step, Dir, Enable] and choice of three stepping modes made it popular with hobbyists. Unfortunately, this device has been discontinued. The limitation of the 5804 was its low current drive capability-- 1.25 amps per phase.
Click here to download data sheet for UCN5804B.pdf
Click here to download the data sheet for StepGenie.pdf
The StepGenie IC shares the design philosophy of the 5804 – a simple interface, and robust performance requiring few external parts. The control signals and stepping modes of the two devices are identical. The StepGenie, however, can drive much much larger motors because the driver section is brought outside the chip, allowing it to cope with much higher currents.
StepGenie vs Allegro UCN5804b
The StepGenie IC generates the sequence of signals required to produce the stepping movement of a stepper motor. These repeating signals occur on 4 outputs lines and advance the motor though one complete step cycle. The four outputs are HEXFET compatible allowing the designer to tailor a power stage to the requirements of the application. A complete high-current unipolar application requires only five external components – four HEXFETs and a bypass capacitor.
Where the 5804 has a limit of 1.25 amps per phase, the StepGenie current drive is limited only by the choice of external HEXFETs. A typlical low-cost HEXFET has a current rating of 15 amps (This spec assumes heatsinking, without heatsinking 5 amps per phase is easily achievable.) Recently introduced HEXFETs have a current rating (with heatsinking) of 200 amps!
The 5804 requires 5 external components – a bypass capacitor and 4 protection diodes.
The StepGenie requires 5 external components – a bypass capactitor and 4 HEXFETs.
HEXFETs (N-Channel MOSFETs) are extremely efficient - more so than the older Darlington technology, which also require protection diodes on the outputs.
The outputs of the StepGenie are compatible with HEXFETs and can drive them directly. No intermediate components or protection diodes are required.
The StepGenie provides two output signals not found on the 5804 – TP0 and TP1. These can be used to diagnose (or display with LED) the current status of the device without loading the input or output signals.
Although the interface and timing of the two devices are the same, the StepGenie is not pin compatible with the 5804. It is, however, a very good replacement. The StepGenie can drive much larger motors and provides two output signals not found on the 5804.
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