LTC1663 Linear Technology, LTC1663 Datasheet - Page 8

• Manufacturer Part Number: LTC1663
• Description: 10-Bit Rail-to-Rail Micropower DAC with 2-Wire Interface
• Manufacturer: Linear Technology

APPLICATIONS
LTC1663
Slave Address (SOT-23 Package)
The slave address for the SOT-23 package has been
factory programmed to be “0100 000.” If another address
is required, please consult the factory.
Command Byte
The stop condition normally initiates the update of the
DAC’s output latches. This allows for simultaneous update
of more than one DAC or other devices on the bus. This can
be overridden by setting the “SY” bit of the command byte.
Setting this bit sets the device to update the DAC output
latches at the reception of a SYNC address quick com-
mand. The actual update occurs on the rising edge of SCL
during the Acknowledge. In this way, all devices can
update on the reception of the SYNC address quick com-
mand instead of the STOP condition.
A Shutdown (SD) bit = HIGH will put the device in a low
power state but retain all data latch information. Shutdown
will occur at the reception of a STOP condition. This way
shutdown could be synchronized to other devices. The
output impedance of the DAC will go to a high impedance
state ( 500k to GND).
8
SY
SD
BG
X
X
7
1
0
1
0
1
0
X
X
6
Allows update on Acknowledge of SYNC Address only
Update on Stop condition only (Power-On Default)
Puts the device in power-down mode
Puts the device in standard operating mode
(Power-On Default)
Selects the internal bandgap reference
Selects the supply as the reference (Power-On Default)
Don’t Care
5
X
U
4
X
INFORMATION
U
3
X
W
BG
2
SD
1
U
SY
0
The Bandgap (BG) bit when set to “0” selects the DAC
supply voltage as its voltage reference. The full-scale
output of the DAC with this setting is equal to the supply
voltage. When the BG bit is set to “1,” the internal bandgap
reference ( 1.25V) is selected as the DAC’s reference. The
full-scale output voltage for this setting is 2.5V.
Data Bytes
Least Significant Data Byte
Most Significant Data Byte
X = Don’t care
Send Byte Protocol
The Send Byte protocol used on the LTC1663 is actually a
subset of the Write Word protocol described previously.
The Send Byte protocol can only be used to send the
command byte information to the LTC1663.
The Send Byte protocol is also used whenever the Write
Word protocol is interrupted for any reason. Reception of
a START or STOP condition after the Acknowledge of the
command byte, but before the Acknowledge of the last
data byte, will cause both data bytes to be ignored and the
command byte to be accepted.
Reception of a START or STOP condition before the
Acknowledge of the command byte will cause the inter-
rupted command byte to be ignored.
D7
7
X
7
S = Start Condition, Wr = Write Bit, A = Acknowledge, P = Stop Condition
1
S
D6
6
6
X
Slave Address
D5
7
5
X
5
Wr
D4
1
X
4
4
1
A
Command Byte
D3
3
X
3
8
D2
X
2
2
A
1
D1
D9
P
1
1
1
1663 TA04
D0
D8
0
0