Circuits for bleeding supply voltage from a device in a power down state
Embodiments of the present disclosure include an apparatus. The apparatus includes a voltage supply line, a sense circuit coupled to the voltage supply line, and a bleeder circuit. The sense circuit is configured to sense a voltage level of the voltage supply line. The bleeder circuit is configured to bleed a remaining charge available on a capacitor when the voltage level reaches a device threshold voltage. The device threshold voltage arises from a device connected to the apparatus.
1. An apparatus, comprising:
a voltage supply line;
a sense circuit coupled to the voltage supply line, the sense circuit configured to sense a voltage level of the voltage supply line; and
a bleeder circuit configured to bleed a remaining charge available on a capacitor when the voltage level reaches a device threshold voltage, the device threshold voltage arising from a device connected to the apparatus, the bleeder circuit including:
a resistor including a first side coupled to the voltage supply line;
a first transistor having a first terminal coupled to a second side of the resistor; and
a second transistor having a first terminal coupled to a second terminal of the first transistor, a second terminal coupled to ground, wherein the gate of the second transistor is communicatively coupled to the output of the sense circuit through a coupling capacitor.
2. The apparatus of claim 1 , further comprising a control circuit coupled to the sense circuit and the bleeder circuit, the control circuit configured to:
detect that a value of the voltage supply line is less than or equal to the device threshold voltage; and
in response to detecting that the value of the voltage supply line is less than or equal to the device threshold voltage, output a control signal configured to allow current to flow between the voltage supply line and ground.
3. The apparatus of claim 1 , further comprising a control circuit coupled to the sense circuit and the bleeder circuit, the control circuit configured to:
detect that a voltage on the voltage supply line is greater than a device threshold voltage of transistors in the device; and
in response to detecting that the voltage on the voltage supply line is greater than the device threshold voltage of transistors in the device, output a control signal configured to inhibit current flow between the voltage supply line and ground.
4. The apparatus of claim 2 , wherein the sense circuit and the control circuit are implemented within a same circuit.
5. The apparatus of claim 2 , wherein the control circuit comprises a Schmitt trigger.
6. The apparatus of claim 1 , wherein the second transistor includes a transistor threshold voltage that is less than the device threshold voltage.
7. The apparatus of claim 1 , wherein the second transistor includes a gate communicatively coupled to an output of the control circuit.
8. The apparatus of claim 1 , wherein the first transistor is a medium voltage native transistor with a very low threshold voltage.
9. The apparatus of claim 1 , wherein
the second transistor is a low voltage transistor.
10. A method, comprising:
sensing, with a sense circuit, a voltage level of a voltage supply line on an apparatus; and
bleeding, with a bleeder circuit, a remaining charge available on a capacitor when the voltage level reaches a device threshold voltage, the device threshold voltage arising from a device connected to the apparatus, by, within the bleeder circuit:
coupling a first side of a to the voltage supply line;
coupling a first terminal of a first transistor to a second side of the resistor;
coupling a first terminal of a second transistor to a second terminal of the first transistor;
coupling a second terminal of the second transistor to ground; and
communicatively coupling the gate of the second transistor to the output of the sense circuit through a coupling capacitor.
11. The method of claim 10 , further comprising:
detecting that a value of the voltage supply line is less than or equal to the device threshold voltage; and
in response to detecting that the value of the voltage supply line is less than or equal to the device threshold voltage, outputting a control signal configured to allow current to flow between the voltage supply line and ground.
12. The method of claim 10 , further comprising:
detecting that a voltage on the voltage supply line is greater than a device threshold voltage of transistors in the device; and
in response to detecting that the voltage on the voltage supply line is greater than the device threshold voltage of transistors in the device, outputting a control signal configured to inhibit current flow between the voltage supply line and ground.
13. The method of claim 10 , wherein the device is a flash memory, and further comprising preserving a read/write state of the flash memory depending upon an on/off state of the flash memory as detected through the voltage supply line.