Vdevice Control

This circuit provides two functions:

  1. On/Off Control: It enables the voltage to the programmed device to be turned on and off, since I've never liked removing a device from a socket while it is under power.
  2. VDD Level Control: A production programmers must verify the at its VDDmax and VDDmin levels specified on the device data sheet.
The voltages must be individually set, according to the data sheet for the specific device you are programming. The potentiometers are 10 turn devices for precision. To set the voltage, Pdevice Control must be high, and the control pin for the voltage must be high. There is a corresponding indicator LED for Pdevice Control and each individual voltage.

If the inputs are disconnected or connected to a high impedance, the voltage will be off.

Since every project of mine must have blinking lights, as part of the reset sequence, I turn the individual voltage controls on in sequence. This gives a visual indication that the programmer is active.

NOTE: The control pin for the voltage must be set before Pdevice Control is turned on. reversing the order could place voltages that are above the maximum for the part. In addition, only one of the individual voltage control signals should be high at any time.

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