Datasheet

TC1320
DS21386C-page 6  2002-2012 Microchip Technology Inc.
3.0 DETAILED DESCRIPTION
The TC1320 is a monolithic 8-bit digital-to-analog con-
verter, that is designed to operate from a single supply
that can range from 2.7V to 5.5V. The DAC consists of
a data register (DATA), a configuration register
(CONF), and a current output amplifier. The TC1320
uses an external reference, which also determines the
maximum output voltage.
The TC1320 uses a current steering DAC, based on an
array of matched current sources. This current, along a
precision resistor, converts the contents of the Data
Register and V
REF
into an output voltage, V
OUT
given
by:
V
OUT
= V
REF
(DATA/256)
3.1 Reference Input
The reference pin, V
REF
, is a buffered high-impedance
input and because of this, the load regulation of the ref-
erence source needs only to be able to tolerate leakage
levels of current (less than 1A). V
REF
accepts a volt-
age range from 0 to (V
DD
– 1.2V). Input capacitance is
typically 10pF.
3.2 Output Amplifier
The TC1320 DAC output is buffered with an internal
unity gain rail-to-rail input/output amplifier, with a typical
slew rate of 0.8V/sec. Maximum full scale transition
settling time is 10sec to within ±1/2LSB when loaded
with 1k in parallel with 100pF.
3.3 Standby Mode
The TC1320 allows the host to put it into a Low Power
(I
DD
= 0.5A, typical) Standby mode. In this mode, the
D/A conversion is halted. The SMBus port operates
normally. Standby mode is enabled by setting the
SHDN bit in the CONFIG register. The table below
summarizes this operation.
TABLE 3-1: STANDBY MODE OPERATION
3.4 SMBus Slave Address
The TC1320 is internally programmed to have a default
SMBus address value of 1001 000b. Seven other
addresses are available by custom order (contact fac-
tory). See Figure 3-1 for locating address bits in SMBus
protocol.
FIGURE 3-1: SMBus PROTOCOLS
SHDN Bit Operating Mode
0Normal
1 Standby
S
Address R/W
ACK
Command
ACK
Data
ACK P
8-Bits7-Bits
8-Bits
Slave Address Command Byte: selects
which register you are
writing to.
Data Byte: data goes
into the register set
by the command byte.
Write 1-Byte Format
Read 1-Byte Format
S
Address R/W
ACKCommand
ACK
S
Address R/W ACK
Data
NACK
P
7-Bits
8-Bits
7-Bits
8-Bits
Slave Address
Command Byte: selects
which register you are
reading from.
Slave Address: repeated
due to change in data
flow direction.
Data Byte: reads from
the register set by the
command byte.
Receive 1-Byte Format
S
Address R/W ACK
Data NACK P
7-Bits 1
1
0
0
8-Bits
Data Byte: reads data from
the register commanded by
the last Read Byte or Write
Byte transmission.
S = START Condition
P = STOP Condition
Shaded = Slave Transmission