hello,
I want to use an 74HC595 to be driven by arduino and in turn to drive an ULN2803A
from the ULN2803A data sheet I understand that it can be driven by both 74HC595 and 74HCT595, but which series is recommended for an new design with avr microcontrollers ?
thanks,
razvan radu
The difference is in the input levels and power-supply voltage - HCT are designed to interface to TTL levels (0.8V / 2.0V). In general HC are the ones to go for if interfacing to other CMOS chips (they take 2 to 6V so are voltage-agnostic). HCT will in general work fine too if your power supply is 5V. If you want a simple 3.3V to 5V level converter you can use an HCT buffer powered at 5V - its input levels of 0.8/2.0V should be happy with 3V3 drive.
HCT are cheap, reliable, and simple. Even those considering transistor solutions would be advised to look instead at HCT family ICs just for simple interfacing. Even a single channel interface made using transistors is larger in circuit board space, more complex to build, and likely to cost more - especially so if you put a value on time. Fault finding with HCT is ridiculously simple, whereas a transistor format has multiple points for potential faults, and will take much longer to fault find, and to replace a faulty component. "Keep it simple" usually pays well in the long run!!
ipadwarrior:
HCT are cheap, reliable, and simple. Even those considering transistor solutions would be advised to look instead at HCT family ICs just for simple interfacing. Even a single channel interface made using transistors is larger in circuit board space, more complex to build, and likely to cost more - especially so if you put a value on time. Fault finding with HCT is ridiculously simple, whereas a transistor format has multiple points for potential faults, and will take much longer to fault find, and to replace a faulty component. "Keep it simple" usually pays well in the long run!!
This reads like marketing. And it doesn't answer the original poster's question. And its wrong.
[edit: Oh I see, you've copy/pasted this from another reply where it did make sense - here it's not relevant since we are not talking about level-shifting to 5V]