Self-test circuitry

#The present disclosure relates to the field of self-test circuitry. In particular, the present disclosure relates to self-test systems for use in driver circuitry, for example a current sink driver system.

#Modern electronic devices such as mobile telephones, laptop and tablet computers, smart glasses, gaming devices such as games consoles, and accessory devices such as headphones, earphones, ear buds and virtual reality/augmented reality headsets include complex circuitry and processing systems. It is desirable in such devices to be able to test that the circuitry and/or processing systems are functioning correctly before use of the device, to ensure that the device can be used reliably and/or safely by a user.

#A built-in self-test (BIST) system is a mechanism that permits a machine or device such as an integrated circuit (IC) to test itself. It is useful to provide BIST systems that can be used for the testing of different components within such a device. For example, an electronic device of the kind discussed above may include one or more BIST systems configured to perform self-testing of ICs or other circuitry, systems or subsystems of the device.

#Embodiments of the invention will now be described, strictly by way of example only, with reference to the accompanying drawings, of which:

#FIG. 1 is a schematic diagram illustrating driver circuitry having a plurality of current sources for driving a load;

#FIG. 2 is a schematic diagram illustrating self-test circuitry for testing a current source of the driver circuitry of FIG. 1 for short circuits a supply rail or a reference voltage rail that provide a reference voltage such as ground, and for detecting short circuits between current sources;

#Referring first to FIG. 1, driver circuitry for driving a load is shown generally at 100. The driver circuitry 100 includes an integrated circuit (IC) 110 having one or more selectively operable current control subsystems. In the illustrated example the one or more current control subsystems include one or more selectively operable current source subsystems 120-1, 120-2, 120-n and one or more selectively operable current sink subsystems 130-1, 120-2, 130-m which are configured to drive a load 140 that is coupled to one or more of the current source subsystems 120-1-120-n and one or more of the current sink subsystems 130-1-130-m.

#In the illustrated example three current source and current sink subsystems are shown, but it is to be appreciated that the IC 110 may include more (e.g. four, five or more), or fewer (e.g. one or two) current source or current sink subsystems. Further, the number of current source subsystems need not be equal to the number of current sink subsystems (i.e. n is not necessarily equal to m). Instead, the circuitry 100 may include more current sink subsystems than current source subsystems, or vice versa.

#Each current source subsystem 120-1-120-n is coupled to a supply voltage rail 112 of the IC 110, which provides a supply voltage VDD to the current source subsystems 120-1-120-n. Each current source subsystem 120-1-120-n includes a current source 122 and a controllable switch device 124 (e.g. a MOSFET) which can be actuated in response to a control signal so as to selectively couple the current source 122 to the load 140. (For clarity, in FIG. 1 only the current source subsystem 110-1 is shown as being coupled to the supply voltage rail 112 and having a current source 122 and controllable switch device 124, but it is to be understood that each of the current source subsystems 110-1-110-n is coupled to the supply voltage rail 112 and includes a current source 122 and controllable switch device 124).