There's also the LTC2955 Pushbutton On/Off Controller which does the same thing. Then the MCU lowers the MCU_Signal line, causing it to power off.
This is to make sure the switch has really finished bouncing. The MCU waits for the button to be released, then waits a further 100ms. It will go high when the switch is pressed again. Immediately, the MCU raises the MCU_Signal line, which keeps Q1 switched on, even if you let go of the button.įrom now on, the MCU keeps a watch on the Switch_Detect line. When you press S1, it causes Q1 to switch on, which powers the MCU. You already have a microcontroller, so let that do all the hard work.
Having said all that, I think there's a better way to solve your problem, using fewer components. What you need to add is known as a debounce circuit: Assuming your circuit works, switch bounce will totally mess things up, because it will cause TPS_EN to toggle multiple times with every press of the switch. This is a real effect and happens on almost all switches. If you were to look at the voltage at the switch, instead of seeing a nice perfect square wave as you might imagine, what you'd actually will horrify you. I haven't examined the circuit much yet, but one thing you'll have to be wary of is switch bounce. This is my First circuit design!(So please excuse my noobness! :p)
Push button on off switch free#
But when i connect the lines to the microcontroller it does not work Please help me out!įeel Free to point out mistakes if any. I tried manually changing the latch lines to ground when turning on and it worked. turning off the microcontroller and the LATCH_OP2 and LATCH_OP1 return to VBATT.īATT is around 3.7v.The Micrcontroller is running on a 3.3v supply Now when the user presses the button Since Q6 was 'on' the VBATT gets applied to gate of Q2 and turns off Q2.The regulator turns off. And the LATCH_OP1 causes the Q2 to latch thus enabling a constant high signal (VBATT)on the enable line. The mosfet Q2 and Q6 now 'turns on' due to this.Q6 is turned on and now causes the 1st and 2nd terminals of the push button s2 to go high. The microcontroller pulls the LATCH_OP1 and LATCH_OP2 low. The regulator now starts up and starts powering the microcontroller. which enables the power regulator connected to the TPS_EN line. Since it is pulled down by a 10k pull down resistor(not shown in the schematic).When the user presses S2, the mosfet Q2 turns on because ground is applied to its gate. Here is an explanation of how the thing should work.The TPS_EN line is low at first. I am using BSS84 P-ch mosfets.The resistor values are as in the schematic. When the user presses the push button S2 the TPS_EN line should toggle. Here is the circuit that I have developed.
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