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Copyright (C)
eCHIP INFOTEK
September 2007
eCHIP INFOTEK
September 2007
Rev 1.0
The ICSP needs two levels of voltages. One is the programming voltage of 13.5 volts and the other is 5 volts for the device.
A transformer of 0 - 12 volts @ 100 mA is more than sufficient for this purpose. At 230 volts, the secondary will provide 12 AC * 1.4 = 16.8 volts DC.
A transformer is connected to J1. This voltage is rectified and filtered.
A transformer of 0 - 12 volts @ 100 mA is more than sufficient for this purpose. At 230 volts, the secondary will provide 12 AC * 1.4 = 16.8 volts DC.
A transformer is connected to J1. This voltage is rectified and filtered.
At the first stage, a 7812 is used to develop 13.2 volts by lifting the ground pin by 1.2 volts. This is the VPP (programming) voltage.
The U1 (7805) will provide the 5 volts required by the device under programming.
The VPP voltage is fed to the Opto transistor U3 (PC817). This is controlled by the TX line from the serial port when VPP is required. A MCT2E too can be used instead of PC817.
Diodes D6 and D7 may be replaced by a LED to provide the appropriate voltage. This LED will also act as a power on indicator.
If you want to increase or decrease the VPP voltage, add or remove the diodes from ground pin of 7805 to ground.
The U1 (7805) will provide the 5 volts required by the device under programming.
The VPP voltage is fed to the Opto transistor U3 (PC817). This is controlled by the TX line from the serial port when VPP is required. A MCT2E too can be used instead of PC817.
Diodes D6 and D7 may be replaced by a LED to provide the appropriate voltage. This LED will also act as a power on indicator.
If you want to increase or decrease the VPP voltage, add or remove the diodes from ground pin of 7805 to ground.