Methods and systems for electrostatic discharge
View Patent ↗An indirect clamping topology may be used to protect against the damaging effects of an electrostatic discharge event. An input node of a device is protected by a guard. The guard is driven by a signal from a unity-gain amplifier that flows through a resistance. The input node is clamped to the guard by a diode, and the guard is clamped to a low-impedance rail by another diode. The resistance of the low-impedance rail is less than that of the resistance through which the signal from the unity-gain amplifier flows, so that voltage resulting from the event flows to the low-impedance rail and not to the amplifier.
1. A method of protecting a device from an electric surge using an indirect clamping topology, wherein the device includes an input node, the method comprising:
providing a first guard for the input node;
providing a second guard for inputs to a unity gain amplifier;
employing the unity gain amplifier to amplify a signal from the input node, wherein the amplified signal drives the first and second guards through a resistance, and wherein the resistance is higher than that of a low-impedance rail;
clamping the first and second guards to the low-impedance rail through at least one diode; and
clamping the input node to the first guard through at least one diode.
2. The method according to claim 1 , wherein clamping the input node comprises clamping the input node to the first guard through a pair of diodes connected in an anti-parallel configuration.
3. The method according to claim 1 , wherein the low-impedance rail comprises at least one zener diode connected to ground.
4. The method according to claim 1 , wherein the input node is a high-impedance input node of the device.
5. The method according to claim 1 , wherein the device is an instrument.
6. An indirect clamping topology to protect a device from an electric surge, wherein the device has at least one input node, the indirect clamping topology comprising:
a first guard connected to the input node;
a low-impedance rail;
a unity gain amplifier that receives a signal from the input node;
a second guard connected to inputs of the unity gain amplifier, the unity gain amplifier driving the first and second guards through a resistance, where the resistance is higher than that of the low-impedance rail;
at least one diode that clamps the first and second guards to the low-impedance rail; and
at least one diode that clamps the input node to the first guard.
7. The indirect clamping topology according to claim 6 , wherein a pair of diodes connected in anti-parallel clamps the input node to the first guard.
8. The indirect clamping topology according to claim 6 , wherein the low-impedance rail comprises at least one zener diode connected to ground.
9. The indirect clamping topology according to claim 6 , wherein the input node of the device is a high-impedance input node.
10. The indirect clamping topology according to claim 9 , wherein the device is an instrument.