| 摘要 |
A programming circuit is coupled to an input/output pin of a device and is operative to generate a selected one of a plurality of electrical stimuli, such as a programming voltage, high and low logic levels, and a high impedance output, to the device in selected electrical state, without affecting normal device operation. The programming circuit includes a switchmode power converter, a linear regulator, and a control circuit. The programming voltage is generated by the switchmode power converter only when required for programming the device. The linear regulator includes a transistor having its collector-emitter path coupled in circuit with the switchmode converter and an output node, as well as to a voltage divider network. The voltage divider network is coupled to the control input of a precision shunt regulator device, which supplies a base reference for the transistor to establish the value of a voltage to be applied provided from the output node to the device. The base of the linear regulator's transistor is also controllably coupled to ground through the collector-emitter path of a steering transistor of the control circuit. The regulator's output node is also controllably coupled to ground through the collector-emitter path of a steering transistor of the control circuit. The output node is coupled to a programming (I/O) pin of the device.
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