ELECTROSTATIC DISCHARGE PROTECTION
An integrated circuit chip including: a chip pin configured to direct signals on and off chip; a first signal path from the chip pin to a first electrostatic discharge (ESD) susceptible circuit susceptible to a voltage greater than a first voltage level; a first protection circuit coupled to a first node on the first signal path, the first protection circuit being operable to limit the voltage of a signal directed on chip to a second voltage level, the second voltage level being higher than the first voltage level; and a second protection circuit coupled to a second node on the first signal path between the first node and the first ESD susceptible circuit, the second protection circuit being operable to limit the voltage of the signal directed on chip to the first voltage level.
1 . An integrated circuit chip comprising:
a chip pin configured to direct signals on and off chip;
a first signal path from the chip pin to a first electrostatic discharge (ESD) susceptible circuit susceptible to a voltage greater than a first voltage level;
a first protection circuit coupled to a first node on the first signal path, the first protection circuit being operable to limit the voltage of a signal directed on chip to a second voltage level, the second voltage level being higher than the first voltage level; and
a second protection circuit coupled to a second node on the first signal path between the first node and the first ESD susceptible circuit, the second protection circuit being operable to limit the voltage of the signal directed on chip to the first voltage level.
2 . An integrated circuit chip as claimed in claim 1 , the second protection circuit being susceptible to a voltage greater than a third voltage level, the second voltage level being lower than the third voltage level.
3 . An integrated circuit chip as claimed in claim 1 , the second protection circuit being susceptible to a voltage greater than a third voltage level, the integrated circuit chip further comprising a passive component coupled between the first node and the second node, the passive component having a resistance so as to limit the voltage of the signal directed on chip to below the third voltage level.
4 . An integrated circuit chip as claimed in claim 3 , the passive component being configured to, when the integrated circuit chip receives a radio frequency signal, cause that received radio frequency signal to have a higher voltage on input to the first ESD susceptible circuit than when at the chip pin.
5 . An integrated circuit chip as claimed in claim 1 further comprising a second ESD susceptible circuit susceptible to a voltage greater than the second voltage level and coupled to a third node on the first signal path between the first node and the second node.
6 . An integrated circuit chip as claimed in claim 5 , the second ESD susceptible circuit being coupled to the third node so as to provide a second signal path from the chip pin to the second ESD susceptible circuit, the integrated circuit chip further comprising a switch coupling the first signal path between the third node and the first ESD susceptible circuit to ground and operable so as to isolate the first protection circuit from the second signal path.
7 . An integrated circuit chip as claimed in claim 5 , the first ESD susceptible circuit comprising a low noise amplifier for amplifying received radio frequency signals and the second ESD susceptible circuit comprising a power amplifier for amplifying radio frequency signals for transmission.
8 . An integrated circuit chip as claimed in claim 7 , the radio frequency signals being in accordance with a Bluetooth protocol.
9 . An integrated circuit chip as claimed in claim 1 , wherein the first protection circuit comprises a gate grounded transistor and the second protection circuit comprises a diode, and wherein the second protection circuit does not comprise a gate grounded transistor.
10 . A method comprising: manufacturing an integrated circuit chip as claimed in claim 1 ; disabling the first and/or second protection circuit; and packaging the integrated circuit chip.