Rainbow Electronics DS3904 - Manual (Page 11)

DS3904
DS3904 Triple 128-Position Nonvolatile
Variable Digital Resistor/Switch
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Following the start condition, the DS3904 monitors the
SDA bus checking the device-type identifier being
transmitted. Upon receiving the 101000 control code,
the appropriate device address bit, and the read/write
bit, the slave device outputs an acknowledge signal on
the SDA line.
Applications Information
Power-Supply Decoupling
To achieve the best results when using the DS3904,
decouple the power supply with a 0.01µF or 0.1µF
capacitor. Use a high-quality ceramic surface-mount
capacitor. Surface-mount components minimize lead
inductance, which improves performance, and ceramic
capacitors tend to have adequate high-frequency
response for decoupling applications.
Using the Resistor as a Switch
By taking advantage of the high-impedance mode, a
switch can be created to produce a digital output.
Setting one of the resistor registers to 00h creates the
low state. Writing 80h into the same resistor register
enables the high-impedance state. Furthermore, an
external pullup resistor can be used to generate a high
state as well.
High Resistor Terminal Voltage
It is possible to have a voltage on the resistor-high termi-
nals that is higher than the voltage connected to V
CC .
For instance, connecting V CC to 3.0V while one or more
of the resistor high terminals are connected to 5.0V
allows a 3V system to control a 5V system. The 5.5V
maximum still applies to the limit on the resistor high ter-
minals regardless of the voltage present on V
CC
.
Chip Information
TRANSISTOR COUNT: 9049
SUBSTRATE CONNECTED TO GROUND
Package Information
For the latest package outline information, go to www.maxim-ic.
com/packages .