SN74HC595: 8*8 LED Matrix

Naizeng Wang

Expert 4810 points

Part Number: SN74HC595
Other Parts Discussed in Thread: SN74LV595A, SN74AHC595, TPIC6C595, TLC59213

Hi team,

1. Can I remove ULN2003?

2. Should I add another ULN2003 after the upper 74HC595 because the sink current and source current of 595 are same?

Best regards,

Nison

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 285550 points

The ULN supports much higher currents than the HC. This makes sense when the controller drives entire rows at once, but at most one column. If you drive only one LED at once, then the ULN is not needed.

Other families have more drive strength than HC; the SN74AHC595 can drive 8 mA, the SN74LV595A, 16 mA (both at 5 V).

You can combine the shift register and the low-side driver in a single chip with a power logic device like the TPIC6C595.

The ULN is a low-side driver and is not capable of sourcing a current. There are high-side drivers like the TLC59213, but the voltage drop over the darlington transistors means that it is usually not used with 5 V.

0 ShreyasRao over 5 years ago in reply to Clemens Ladisch

TI__Guru 59070 points

You can consider using the LED expansion board TI design:

Logic

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SN74HC595: 8*8 LED Matrix