TC1320

DS21386B-page 6

© 2002 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

by:

3.1

Reference Input

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

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/

µsec. Maximum full scale transition

settling time is 10

µsec to within ±1/2LSB when loaded

with 1k

Ω in parallel with 100pF.

3.3

Standby Mode

The TC1320 allows the host to put it into a Low Power

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-Bits

7-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

ACK

Command

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