PASSIVE TUNABLE INTEGRATED CIRCUIT WITH ELECTRO-STATIC DISCHARGE PROTECTION
A passive tunable integrated circuit (PTIC) having an electro-static discharge (ESD) protection circuit is disclosed. The ESD protection circuit includes at least one spark gap that has a breakdown voltage determined by design parameters. The at least one spark gaps are configured to route signals above a breakdown voltage to ground in order to protect a variable capacitor. The design parameters can be based on a material (Barium Strontium Titanate), a structure, and a fabrication process of the PTIC and further based on expected ESD signals for a mobile device application.
1 . A passive tunable integrated circuit, comprising:
a variable capacitor, including a capacitor array coupled between an input electrode and an output electrode, at least one capacitor in the capacitor array having a tunable dielectric coupled to a radio-frequency ground electrode; and
an input electro-static discharge protection circuit coupled between the input electrode and the radio-frequency ground electrode, the input electro-static discharge protection circuit including at least one spark gap.
2 . The passive tunable integrated circuit according to claim 1 , wherein the variable capacitor is a radio frequency (RF) capacitor.
3 . The passive tunable integrated circuit according to claim 1 , wherein the capacitor array includes a plurality of series-connected capacitors.
4 . The passive tunable integrated circuit according to claim 3 , wherein the plurality of series-connected capacitors has a curve-free topology.
5 . The passive tunable integrated circuit according to claim 1 , further comprising:
an output electro-static discharge protection circuit coupled between the output electrode and the radio-frequency ground electrode, the output electro-static discharge protection circuit including at least one spark gap.
6 . The passive tunable integrated circuit according to claim 5 , wherein:
the at least one spark gap of the input electro-static discharge protection circuit is planar and on a first metal layer; and
the at least one spark gap of the output electro-static discharge protection circuit is planar and on the first metal layer.
7 . The passive tunable integrated circuit according to claim 1 , wherein the input electrode, the output electrode, the radio-frequency ground electrode, and the at least one spark gap are on a first metal layer.
8 . The passive tunable integrated circuit according to claim 1 , wherein the at least one spark gap includes circular electrodes.
9 . The passive tunable integrated circuit according to claim 1 , wherein the at least one spark gap includes triangular electrodes.
10 . The passive tunable integrated circuit according to claim 1 , wherein the at least one spark gap includes electrodes that are exposed to reduce a trigger field strength.
11 . The passive tunable integrated circuit according to claim 1 , wherein the tunable dielectric is Barium Strontium Titanate (BST).
12 . A radio frequency tuner for a mobile device, the radio frequency tuner comprising:
a passive tunable integrated circuit including:
an input electro-static discharge protection circuit coupled between an input electrode and a radio-frequency ground electrode, the input electro-static discharge protection circuit including at least one spark gap configured to couple an electro-static discharge above a trigger field strength to the radio-frequency ground electrode.
13 . The radio frequency tuner for a mobile according to claim 12 , wherein the electro-static discharge is a radio frequency signal from an antenna of the mobile device.
14 . The radio frequency tuner for a mobile device according to claim 12 , wherein the trigger field strength is less than a break down voltage of tunable dielectric material used in a variable capacitor of the passive tunable integrated circuit.
15 . The radio frequency tuner for a mobile device according to claim 14 , wherein the tunable dielectric material is Barium Strontium Titanate.
16 . The radio frequency tuner for a mobile device according to claim 14 , wherein the variable capacitor includes a plurality of series-connected capacitors arranged according to curve-free topology.
17 . The radio frequency tuner for a mobile device, according to claim 12 , wherein the passive tunable integrated circuit further includes:
an output electro-static discharge protection circuit coupled between an output electrode and the radio-frequency ground electrode, the output electro-static discharge protection circuit including at least one spark gap configured to couple the electro-static discharge above the trigger field strength to the radio-frequency ground electrode.
18 . The radio frequency tuner for a mobile device according to claim 12 , wherein the passive tunable integrated circuit is in a wafer level chip scale package.
19 . A method to protect a passive tunable integrated circuit from an electro-static discharge, the method comprising:
fabricating a variable capacitor that includes a tunable dielectric material;
depositing a first metal layer on the variable capacitor, the first metal layer defining an input electrode, an output electrode, a radio-frequency ground electrode, and at least one spark gap coupled between the input electrode and the radio-frequency ground electrode; and
depositing an overcoat on at least a portion of the first metal layer, wherein the at least one spark gap of the first metal layer has no overcoat to lower a breakdown voltage of the at least one spark gap to below a breakdown voltage of the variable capacitor so that an electro-static discharge having a voltage that can damage the variable capacitor is routed to the radio-frequency ground electrode.
20 . The method to protect a passive tunable integrated circuit according to claim 19 , further comprising:
removing the overcoat from the at least one spark gap to lower a breakdown voltage of the at least one spark gap to below a breakdown voltage of the variable capacitor so that an electro-static discharge having a voltage that can damage the variable capacitor is routed to the radio-frequency ground electrode.
21 . The method according to claim 19 , wherein the tunable dielectric material is Barium Strontium Titanate.