Low Power PWM geneartion problem

[manju_bhat]

low power pwm

Hi

I need to generate PWM signal for battery powered application to make ON/OFF for a swicth.The frequency is typically 1 second and I need to have a variable duty cycle by means of POT. I did look into 555 and 556 timer circuts and op amp PWM geneartion cicuits . It looks they all consume much current. Since it is battery operated the power consumption is targated as small as possible (<1mA). One thing i should say I am not allowed to use any microcontroller or any tiny processor.

Is there any solution for this ?

thanks.

 

[dick_freebird]

opamp pwm

There are low power CMOS versions of the 555.

But there are plenty of one-off solutions you could do
with a few transistors and large valued resistors (or
low current sources). Integrated, I've made PWM
ramp generators that run a lot faster at tens of uA
and used tens of transistors (like three 7-transistor
comparators, a S-R flip flop and RC timing network).

I would say that this homework problem is trying
to get you to invent, not copy.