Техническая Спецификация для Linear Technology DC1333A-A - LTC2640-LM12: 12-Bit SPI DAC (2.5V ref, Reset to Mid-Scale), req DC590 DC1333A-A DC1333A-A

Модели

DC1333A-A

LTC2640

2640fc

For more information

www.linear.com/LTC2640

The LTC2640 is a family of single voltage-output DACs

in 8-lead ThinSOT packages. Each DAC can operate rail-

to-rail using an external reference, or with its full-scale

voltage set by an integrated reference. 12 combinations of

accuracy (12-, 10-, and 8-bit), power-on reset value (zero

or mid-scale), and full-scale voltage (2.5V or 4.096V) are

available. The LTC2640 is controlled using a 3-wire SPI/

MICROWIRE compatible interface.

Power-On Reset
The LTC2640-HZ/LTC2640-LZ clear the output to zero-

scale when power is first applied, making system initializa-

tion consistent and repeatable.
For some applications, downstream circuits are active

during DAC power-up, and may be sensitive to nonzero

outputs from the DAC during this time. The LTC2640

contains circuitry to reduce the power-on glitch: the

analog output typically rises less than 5mV above zero-

scale during power on if the power supply is ramped

to 5V in 1ms or more. In general, the glitch amplitude

decreases as the power supply ramp time is increased.

See “Power-On Reset Glitch” in the Typical Performance

Characteristics section.

The LTC2640-HM/LTC2640-LM provide an alternative

reset, setting the output to mid-scale when power is first

applied.
Default reference mode selection is described in the Refer-

ence Modes section.

Power Supply Sequencing
The voltage at REF (Pin 6) should be kept within the range

–0.3V ≤ V

REF

≤ V

+ 0.3V (see Absolute Maximum Rat-

ings). Particular care should be taken to observe these

limits during power supply turn-on and turn-off sequences,

when the voltage at V

(Pin 5) is in transition.

Transfer Function
The digital-to-analog transfer function is:

OUT(IDEAL)









REF

where k is the decimal equivalent of the binary DAC input

code, N is the resolution, and V

REF

is either 2.5V (LTC2640-

LM/LTC2640-LZ) or 4.096V (LTC2640-HM/LTC2640-HZ)

when in Internal Reference mode, and the voltage at REF

(Pin 6) when in External Reference mode.

operation

Figure 2. Command and Data Input Format

2640 F02

COMMAND

4 DON'T-CARE BITS

MSB

LSB

DATA (12 BITS + 4 DON'T-CARE BITS)

D11 D10 D9

COMMAND

4 DON'T-CARE BITS

DATA (10 BITS + 6 DON'T-CARE BITS)

COMMAND

INPUT WORD (LTC2640-12)

INPUT WORD (LTC2640-10)

INPUT WORD (LTC2640-8)

4 DON'T-CARE BITS

DATA (8 BITS + 8 DON'T-CARE BITS)