9

LTC1595/LTC1596/LTC1596-1

Description

The LTC1595/LTC1596 are 16-bit multiplying DACs which

have serial inputs and current outputs. They use precision

R/2R technology to provide exceptional linearity and

stability. The devices operate from a single 5V supply and

provide

±10V reference input and voltage output ranges

when used with an external op amp. These devices have

a proprietary deglitcher that reduces glitch impulse to

1nV-s over a 0V to 10V output range.

Serial I/O

The LTC1595/LTC1596 have SPI/MICROWIRE compat-

ible serial ports that accept 16-bit serial words. Data is

accepted MSB first and loaded with a load pin.

The 8-pin LTC1595 has a 3-wire interface. Data is shifted

into the SRI data input on the rising edge of the CLK pin.

At the end of the data transfer, data is loaded into the DAC

register by pulling the LD pin low (see LTC1595 Timing

Diagram).

The 16-pin LTC1596 can operate in identical fashion to the

LTC1595 but offers additional pins for flexibility. Four

clock pins are available STB1, STB2, STB3 and STB4.

STB1, STB2 and STB4 operate like the CLK pin of the

LTC1595, capturing data on their rising edges. STB3

captures data on its falling edge (see Truth Table 1).

The LTC1596 has two load pins, LD1 and LD2. To load

data, both pins must be taken low. If one of the pins is

grounded, the other pin will operate identically to LTC1595’s

LD pin. An asynchronous clear input (CLR) resets the

LTC1596 to zero scale (and the LTC1596-1 to midscale)

when pulled low (see Truth Table 2).

The LTC1596 also has a data output pin SRO that can be

connected to the SRI input of another DAC to daisy-chain

multiple DACs on one 3-wire interface (see LTC1596

Timing Diagram).

Unipolar (2-Quadrant Multiplying) Mode

The LTC1595/LTC1596 can be used with a single op amp

to provide 2-quadrant multiplying operation as shown in

Figure 1. With a fixed –10V reference, the circuits shown

give a precision unipolar 0V to 10V output swing.

Table 1. Unipolar Binary Code Table

DIGITAL INPUT

BINARY NUMBER

IN DAC REGISTER

0V

LSB

1111 1111 1111

0000 0000 0000

0000 0000 0001

0000 0000 0000

ANALOG OUTPUT

MSB

1111

1000

0000

0000

(b)

LTC1595

GND

4

7

6

5

8

5V

–10V TO 10V

CLK

SRI

LD

1

2

3

OUT1

33pF

1595/96 F01b

LT1001

µP

0.1

µF

(a)

LTC1596

AGND

DGND

3

12

10

4

7

5

6

9

8

11

2

14

13

5V

–10V TO 10V

TO NEXT DAC

FOR DAISY-CHAINING

15

16

1

OUT1

33pF

0.1

µF

1595/96 F01a

OUT2

LT1001

CLR

STB3

STB1

SRI

LD1

SRO

LD2

STB2

STB4

µP