Datasheet

DS3906
Triple NV Low Step Size Variable
Resistor Plus Memory
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Reading Multiple Bytes from a Slave: The read oper-
ation can be used to read multiple bytes with a single
transfer. When reading bytes from the slave, the master
simply ACKs the data byte if it desires to read another
byte before terminating the transaction. After the mas-
ter reads the last byte it must NACK to indicate the end
of the transfer and generates a stop condition.
Application Information
Power Supply Decoupling
To achieve best results, it is highly recommended that a
decoupling capacitor is used on the I.C. power supply
pins. Typical values of decoupling capacitors are 0.01µF
and 0.1µF. Use a high-quality, ceramic, surface-mount
capacitor, and mount it as close as possible to the V
CC
and GND pins of the I.C. to minimize lead inductance.
High Resistor Terminal Voltage
It is permissible to have a voltage on the resistor-high
terminals 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 terminals regardless of the voltage present on V
CC
.
DS3906
R0
A0
A1
R
EXT0
= 105Ω
R1 R
EXT1
= 105Ω
R2
H2
H1
H0
R
EXT2
= 310Ω
A2
SCL
LED
DRIVERS
SDA
FROM SYSTEM
CONTROLLER
V
CC
V
CC
GND
4.7kΩ
300Ω
4.7kΩ
0.1µF
RED LED PANEL
300Ω 300Ω 300Ω
LED
DRIVERS
300Ω
GREEN LED PANEL
300Ω 300Ω 300Ω
LED
DRIVERS
300Ω
BLUE LED PANEL
300Ω 300Ω 300Ω
DESIGN NOTES:
1. IN THIS APPLICATION A NUMBER OF LED DRIVERS ARE SET USING THE DS3906'S VARIABLE RESISTORS.
2. THE PARALLEL COMBINATION OF THE DS3906 VARIABLE RESISTOR R0 AND 105Ω (R
EXT0
) IS EQUIVALENT TO A VARIABLE
RESISTOR WITH LINEAR STEP INCREMENTS OF 0.6Ω RANGING FROM 66Ω TO 101Ω. THE SAME APPLIES FOR RESISTOR 1 (R1).
THE PARALLEL COMBINATION OF R2 AND 310Ω (R
EXT2
) IS EQUIVALENT TO A VARIABLE RESISTOR WITH LINEAR STEP INCREMENTS OF
1Ω RANGING FROM 187Ω TO 255Ω.
3. VALUES LARGER THAN THE SHOWN EXTERNAL RESISTORS (R
EXT0
, R
EXT1
, AND R
EXT2
) RESULT IN LARGER STEP INCREMENTS AND
RESISTOR VALUES LOWER THAN THE SHOWN VALUES RESULT IN SMALLER STEP INCREMENTS. REFER TO THE RESISTOR TABLES AND
COMPUTE EQUIVALENT RESISTANCE TO FIND OUT THE RANGES.
Typical Operating Circuit