I am trying to drive the rows and columns of an array of LEDs. I will be multiplexing so I have 1/7th duty cycle thus 7 times the steady state current for the same brightness. 3 of the columns are double led 7-segment displays, so 20mA per segment, 140mA total or 980mA peak if I want 100% brightness. For the other 4 they are 10mA leds or 490mA for full brightness at 1/7 duty.
On the low side ( rows ) I need up to 20 * 7 or 140mA.
I was planning on driving both high and low sides off 74595 shift registers and transistors, but I forgot about having to multiply the current by 1/duty cycle to get the same brightness.
Can you recommend low cost low density transistor(s), driver array, replacement for the shift registers, or whatever what would make this work? What if I can live with 500mA max current pulse?
p.s. I only have 5v.
Thanks.
On the low side ( rows ) I need up to 20 * 7 or 140mA.
I was planning on driving both high and low sides off 74595 shift registers and transistors, but I forgot about having to multiply the current by 1/duty cycle to get the same brightness.
Can you recommend low cost low density transistor(s), driver array, replacement for the shift registers, or whatever what would make this work? What if I can live with 500mA max current pulse?
p.s. I only have 5v.
Thanks.