Tool/software:
Hello,
We are planning to use the TPS3808G33DBVR voltage supervisor IC in our power ON/OFF control circuit. This circuit includes the TPS3808G33DBVR, an OR gate (U6), an NPN transistor, and a P-channel MOSFET to control the system power.
Normal Operation:
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When the 5V input is present, the voltage at the SENSE pin of the TPS3808G33DBVR is 3.3V.
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As a result, the RESET pin goes HIGH.
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The controller monitors the RESET pin via SHDN_INIT (GPIO1_12).
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The BB_PWR_ON (GPIO1_13) signal is LOW by default. However, once the controller powers ON (i.e., when 5V_BB is available), it sets GPIO1_13 to HIGH.
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The OR gate (U6) has two inputs:
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Pin 3 connected to the RESET output (HIGH)
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Pin 6 connected to BB_PWR_ON (initially LOW)
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Since one input is HIGH, the output of the OR gate is also HIGH.
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This HIGH output turns ON the NPN transistor, which pulls the gate of the P-channel MOSFET LOW.
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As a result, the P-channel MOSFET turns ON and supplies 5V_BB to power the controller.
Turn OFF Operation:
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If the voltage at the SENSE pin drops below 3.07V (undervoltage condition), the RESET pin goes LOW.
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The controller detects this LOW signal through SHDN_INIT (GPIO1_12) and begins a proper shutdown procedure.
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Before 5V_BB is cut off, the controller sets BB_PWR_ON (GPIO1_13) to LOW.
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With both OR gate inputs now LOW, its output goes LOW as well.
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This turns OFF the NPN transistor, which then allows the gate of the P-channel MOSFET to go HIGH, turning it OFF.
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As a result, 5V_BB is disconnected, cutting power to the controller after a clean shutdown.
Power Restore (After 5V Returns):
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When the 5V supply is restored, the SENSE pin goes back to 3.3V.
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The RESET pin goes HIGH again.
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With RESET HIGH and BB_PWR_ON still LOW (since the controller hasn’t powered up yet), the OR gate output becomes HIGH.
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This turns ON the NPN transistor, which pulls the MOSFET gate LOW, turning it ON again.
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5V_BB is restored, and the controller powers up.
Could you please review our design and let us know if any changes are required?
