DS3503U Ver la hoja de datos (PDF) - Maxim Integrated
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DS3503U Datasheet PDF : 13 Pages
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NV, I2C, Stepper Potentiometer
TYPICAL I2C WRITE TRANSACTION
MSB
LSB
MSB
LSB
MSB
LSB
START
0
1
0
1
0
0
0
R/W
SLAVE
ACK
b7 b6 b5 b4 b3 b2 b1 b0
SLAVE
ACK
b7 b6 b5 b4 b3 b2 b1 b0
SLAVE
ACK
STOP
SLAVE
READ/
REGISTER ADDRESS
DATA
ADDRESS
WRITE
EXAMPLE I2C TRANSACTIONS
A) SINGLE-BYTE WRITE
-WRITE STEP CONTROL
REGISTER (SCR) TO 1Fh
50h
01h
1Fh
START
01010000
SLAVE
ACK
00000 001
SLAVE
ACK
00011111
SLAVE
ACK
STOP
50h
02h
51h
B) SINGLE-BYTE READ
-READ CONTROL REGISTER (CR)
START
01010000
SLAVE
ACK
00000 010
SLAVE
ACK
REPEATED
START
01010 001
SLAVE
ACK
DATA
MASTER
NACK
STOP
Figure 3. I2C Communication Examples
Reading a single byte from a slave: Unlike the write
operation that uses the specified memory address byte
to define where the data is to be written, the read opera-
tion occurs at the present value of the memory address
counter. To read a single byte from the slave, the master
generates a START condition, writes the slave address
byte with R/W = 1, reads the data byte with a NACK to
indicate the end of the transfer, and generates a STOP
condition. However, because requiring the master to
keep track of the memory address counter is impracti-
cal, the following method should be used to perform
reads from a specified memory location.
Manipulating the address counter for reads: A dummy
write cycle can be used to force the address counter to a
particular value. To do this the master generates a
START condition, writes the slave address byte (R/W =
0), writes the memory address where it desires to read,
generates a repeated START condition, writes the slave
address byte (R/W = 1), reads data with ACK or NACK
as applicable, and generates a STOP condition.
See Figure 3 for a read example using the repeated
START condition to specify the starting memory location.
Applications Information
Power-Supply Decoupling
To achieve the best results when using the DS3503,
decouple both the power-supply pin (VCC) and the
wiper-bias voltage pin (V+) with a 0.01µF or 0.1µF
capacitor. Use a high-quality ceramic surface-mount
capacitor if possible. Surface-mount components mini-
mize lead inductance, which improves performance,
and ceramic capacitors tend to have adequate high-
frequency response for decoupling applications.
SDA and SCL Pullup Resistors
SDA is an I/O with an open-collector output that
requires a pullup resistor to realize high-logic levels. A
master using either an open-collector output with a
pullup resistor or a push-pull output driver must be
used for SCL. Pullup resistor values should be chosen
to ensure that the rise and fall times listed in the I2C AC
Electrical Characteristics are within specification. A typ-
ical value for the pullup resistors is 4.7kΩ.
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