LTC2606/LTC2616/LTC2626
14
26061626fb
OPERATION
Chip Address
The state of CA0, CA1 and CA2 decides the slave address
of the part. The pins CA0, CA1 and CA2 can be each set
to any one of three states: VCC, GND or fl oat. This results
in 27 selectable addresses for the part. The slave address
assignments are shown in Table 1.
Table 1. Slave Address Map
CA2 CA1 CA0 A6 A5 A4 A3 A2 A1 A0
GND GND GND 0 0 1 0 0 0 0
GND GND FLOAT 0 0 1 0 0 0 1
GND GND VCC 0010010
GND FLOAT GND 0 0 1 0 0 1 1
GND FLOAT FLOAT 0 1 0 0 0 0 0
GND FLOAT VCC 0100001
GND VCC GND 0 1 0 0 0 1 0
GND VCC FLOAT 0 1 0 0 0 1 1
GND VCC VCC 01100 00
FLOAT GND GND 0 1 1 0 0 0 1
FLOAT GND FLOAT 0 1 1 0 0 1 0
FLOAT GND VCC 0110011
FLOAT FLOAT GND 1 0 0 0 0 0 0
FLOAT FLOAT FLOAT 1 0 0 0 0 0 1
FLOAT FLOAT VCC 1000010
FLOAT VCC GND 1 0 0 0 0 1 1
FLOAT VCC FLOAT 1 0 1 0 0 0 0
FLOAT VCC VCC 1010001
VCC GND GND 1 0 1 0 0 1 0
VCC GND FLOAT 1 0 1 0 0 1 1
VCC GND VCC 11000 00
VCC FLOAT GND 1 1 0 0 0 0 1
VCC FLOAT FLOAT 1 1 0 0 0 1 0
VCC FLOAT VCC 1100011
VCC VCC GND 1 1 1 0 0 0 0
VCC VCC FLOAT 1 1 1 0 0 0 1
VCC VCC VCC 11100 10
GLOBAL ADDRESS 1 1 1 0 0 1 1
In addition to the address selected by the address pins,
the parts also respond to a global address. This address
allows a common write to all LTC2606, LTC2616 and
LTC2626 parts to be accomplished with one 3-byte write
transaction on the I2C bus. The global address is a 7-bit
on-chip hardwired address and is not selectable by CA0,
CA1 and CA2.
The addresses corresponding to the states of CA0, CA1
and CA2 and the global address are shown in Table 1. The
maximum capacitive load allowed on the address pins
(CA0, CA1 and CA2) is 10pF, as these pins are driven during
address detection to determine if they are fl oating.
Write Word Protocol
The master initiates communication with the LTC2606/
LTC2616/LTC2626 with a START condition and a 7-bit slave
address followed by the Write bit (W) = 0. The LTC2606/
LTC2616/LTC2626 acknowledges by pulling the SDA pin
low at the 9th clock if the 7-bit slave address matches the
address of the parts (set by CA0, CA1 and CA2) or the
global address. The master then transmits three bytes of
data. The LTC2606/LTC2616/LTC2626 acknowledges each
byte of data by pulling the SDA line low at the 9th clock of
each data byte transmission. After receiving three complete
bytes of data, the LTC2606/LTC2616/LTC2626 executes the
command specifi ed in the 24-bit input word.
If more than three data bytes are transmitted after a valid
7-bit slave address, the LTC2606/LTC2616/LTC2626 do not
acknowledge the extra bytes of data (SDA is high during
the 9th clock).
The format of the three data bytes is shown in Figure 3.
The fi rst byte of the input word consists of the 4-bit com-
mand and four don’t care bits. The next two bytes consist
of the 16-bit data word. The 16-bit data word consists of
the 16-, 14- or 12-bit input code, MSB to LSB, followed by
0, 2 or 4 don’t care bits (LTC2606, LTC2616 and LTC2626
respectively).
A typical LTC2606 write transaction is shown
in Figure 4.
The command assignments (C3-C0) are shown in Table 2.
The fi rst four commands in the table consist of write and
update operations. A write operation loads a 16-bit data
word from the 32-bit shift register into the input register.
In an update operation, the data word is copied from the
input register to the DAC register and converted to an
analog voltage at the DAC output. The update operation
also powers up the DAC if it had been in power-down
mode. The data path and registers are shown in the Block
Diagram.