If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

# TINA/Spice/TLC551: Square wave generation with 1.2/1.3V supply

Part Number: TLC551
Other Parts Discussed in Thread: TINA-TI, , TLC555

Tool/software: TINA-TI or Spice Models

Hi,

Can we make a circuit for square wave generation of peak voltage 1.2V, with the supply voltage as 1.2/1.3V?

If yes, please suggest a schematic of the circuit!

• Hi Prithviraj,

Just wondering .. on the TI part of this question you specified TLC551, do you have any specific question about how to use this part in generating square wave, was that what you're asking?

Herman
• Hi Herman,

I Just wanted to generate square wave with the range of 0.9V (being the lower) and 1.3V (being the upper)..

Else suggest any circuit that you know, preferably  with less BOM.

Prithviraj

• Prithviraj,

I suggest using the voltage most convenient for you then attenuating / offset the signal to get the VOL, VOH levels requested. I can help you with that.

Tell me your supply voltage, frequency, duty cycle, and the impedance of the load for the output square wave.

• Hi Ron,

VOL=0V , VOH=1.2V

Supply voltage=1.2V

duty cycle=0.125

the load would be 6 LED's in parallel ( impedance is not known exactly)

Regards,

Prithviraj

• Prithviraj,

TLC5551 with such a low supply voltage cannot provide much current drive, only about 150uA. 6 LED will certainly need more current. It is not good to drive LED with a voltage source. LED should be driven with a current source.

I would like come up with a different design. This leads to new questions.
How much LED current (each) is desired?
Do LED have to be in parallel?
Are there any other supply voltages other than 1.2V?
Repeat question, what is the pulse frequency?
• Hi Ron,

Yes, the 6 LED's are in parallel.

The current requirement would be in the range 40mA to 100mA.

No other supply voltages other than 1.2V.

The duty cycle would be 0.125, that is 0.1s ON and 0.7s OFF.

Let me know if you could suggest something.

Regards,

Prithviraj

• Prithviraj,

You will need more voltage to drive the 6 LED. How much more is uncertain because I don't know the characteristics of the LED array. In my example I use 3.6V

TLV6122 or a similar boost converter can be used to raise voltage. I replaced it with a ideal source for simulation.

Update: 2N3904 can do 100mA, I mistook the 40V limit as 40mA.

1V2 LED driver.TSC

• Hi Ron,

Can you replace TLC555 and TLV6122 with passive analog components only?

I don't want to use IC's as it will add to the BOM. I can't afford it as i am working on a low-cost application.

Regards,

Prithviraj

• Prithviraj,

I understand your point of view. This is the only passive way to do it. My simulation suggest that the LED current will be quite low. It might be visible in a completely dark room.