AN1108 Advanced Linear Devices, AN1108 Datasheet - Page 14

• Manufacturer Part Number: AN1108
• Description: Application Note For Electrically Programmable Analog Device Applications
• Manufacturer: Advanced Linear Devices

For example, the circuit in Figure 16, In-System Program-
ming, is a modified circuit based on Figure 11 to provide
conditions suitable for programming mode. In this case, this
is accomplished by the addition of a single resistor R (iso).
When the gate terminal is now pulsed during programming,
the drain terminal is effectively isolated from the gate termi-
nal. During normal operation, the gate terminal voltage is
not appreciably affected as a result of R(iso) because the
gate input impedance is very high.
This in-system approach to programming the EPAD is po-
tentially the most powerful in adjusting system level errors
involving other components, such as variations in unit to unit
sensor parameters and passive component parameters. If
integration of the EPAD programming is desired, while sys-
tem testing and/or calibration is taking place, then more cir-
cuit design and software programming may be necessary.
A special In-System Programming extension cable allows
temporary connection of the EPAD programmer to the in-
system EPAD element directly within the application circuit.
The cable is disconnected for future use after programming.
CONTROL SOFTWARE
Control software supplied with the EPAD Programmer
Adapter is used to control the programming routines and to
send commands to the EPAD Programmer to control, mea-
sure and compute programming conditions for the specific
adapter module. In most cases, the recommended custom
adaptation of this control software is to input a desired volt-
age value that can be measured at the drain terminal of the
EPAD. The control software algorithm then takes over. When
in programming mode, the gate and programming terminals
are pulsed in a controlled, optimal sequence of voltage bias-
ing conditions. These conditions must be preserved by the
user in order for the programming system to function prop-
erly.
For more assistance in application-specific or in-system
EPAD programming, please contact an Advanced Linear De-
vices’ applications engineer. If you have a circuit question
or problem, Fax or e-mail us at:
APPLICATION NOTE AN1108
FAX [phone]
Attention: Applications
E-mail: [e-mail]
Advanced Linear Devices
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