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LTC1590

Dual Serial 12-Bit

Multiplying DAC

Daisy-Chained Control Outputs

The LTC

1590 is a dual, serial input 12-bit multiplying

digital-to-analog converter (DAC). It includes two current

output multiplying CMOS DACs and an easy SPI compat-

ible serial interface with daisy-chain output. An asynchro-

nous CLR pin sets both DACs to zero scale.

Excellent accuracy, stability and versatility are combined

with the smallest package available for a dual 12-bit

multiplying DAC.

Parts are available in 16-pin PDIP and narrow SO pack-

ages and are specified over the commercial and industrial

temperature ranges.

DESCRIPTION

FEATURES

■

DNL and INL Over Temperature:

0.5LSB Max

■

Gain Error:

1LSB Max

■

Low Supply Current: 10

A Max

■

4-Quadrant Multiplication

■

Power-On Reset

■

Asynchronous Clear Input

■

Daisy-Chain 3-Wire Serial Interface

■

16-Pin Narrow SO and PDIP Packages

APPLICATIONS

■

Process Control and Industrial Automation

■

Software Controlled Gain Adjustment

■

Digitally Controlled Filter and Power Supplies

■

Automatic Test Equipment

, LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATION

Integral Nonlinearity Over

Temperature DAC A

DIGITAL INPUT CODE

INL (LSB)

1024 2048

3072

4095

LTC1590 • TA02

1.0

0.5

0

–0.5

–1.0

512 1536

2560

3584

THREE 

SUPERIMPOSED 

CURVES

= –40°C, 

25°C, 85°C

DIGITAL INPUT CODE

INL (LSB)

1024 2048

3072

4095

LTC1590 • TA03

1.0

0.5

0

–0.5

–1.0

512 1536

2560

3584

THREE 

SUPERIMPOSED 

CURVES

= –40°C, 

25°C, 85°C

Integral Nonlinearity Over

Temperature DAC B

16 9 1 2

LTC1590 • TA01

OUT B

±10V

OUT A

±10V

IN A

±10V

IN B

±10V

33pF

1112

15V

–15V

DAC B

REF B

FB B

REF A

FB A

DAC A

24-BIT

SHIFT

REG

AND

LATCH

OUT

CLK

CS/LD

CLR DGND AGND

LTC1590

OUT1 B

OUT2 B

OUT1 A

OUT2 A

µP

–

Dual 12-Bit 2-Quadrant Multiplying DAC

Summary of content (12 pages)

PAGE 1
LTC1590 Dual Serial 12-Bit Multiplying DAC U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DNL and INL Over Temperature: ±0.5LSB Max Gain Error: ± 1LSB Max Low Supply Current: 10µA Max 4-Quadrant Multiplication Power-On Reset Asynchronous Clear Input Daisy-Chain 3-Wire Serial Interface 16-Pin Narrow SO and PDIP Packages The LTC®1590 is a dual, serial input 12-bit multiplying digital-to-analog converter (DAC).
PAGE 2
LTC1590 W U U W W W VCC to AGND ............................................... – 0.5V to 7V VCC to DGND .............................................. – 0.5V to 7V AGND to DGND ............................................. VCC + 0.5V DGND to AGND ..............................................VCC + 0.5V VREF to AGND ........................................................ ±25V RFB to AGND .......................................................... ±25V Digital Inputs to DGND ................... – 0.
PAGE 3
LTC1590 ELECTRICAL CHARACTERISTICS VCC = 4.5V to 5.5V, VREF = 10V, VOUT1 = VOUT2 = AGND = DGND = 0V, TA = TMIN to TMAX, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX 60 30 90 60 UNITS Analog Outputs COUT Output Capacitance (Note 3) DAC Register Loaded to All 1s DAC Register Loaded to All 0s ● ● pF pF Digital Input VIH Digital Input High Voltage ● VIL Digital Input Low Voltage ● IIN Digital Input Current CIN Digital Input Capacitance 2.4 0.
PAGE 4
LTC1590 U W TYPICAL PERFORMANCE CHARACTERISTICS Full-Scale Settling Waveform Integral Nonlinearity (INL) INTEGRAL NONLINEARITY (LSB) 1.0 DIFFERENTIAL NONLINEARITY (LSB) 1.0 VDD = 5V 0V TO 5V OUTPUT RANGE LT1363 OP AMP CFB 30pF OUTPUT VOLTAGE (1V/DIV) Differential Nonlinearity (DNL) 0.5 0 –0.5 –1.0 0.20 USING AN LT1363 WITH 500kHz FILTER –90 –100 DIFFERENTIAL NONLINEARITY (LSB) VDD = 5V INTEGRAL NONLINEARITY (LSB) 0.15 0.10 0.
PAGE 5
LTC1590 U W TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Logic Input Voltage Logic Threshold vs Supply Voltage Midscale Glitch Impulse 1.0 3 2 1 0 TIME (500ns/DIV) SUPPLY CURRENT (mA) LOGIC THRESHOLD (V) OUTPUT VOLTAGE (50mV/DIV) 4 VDD = 5V LT1363 OP AMP CFB = 30pF 0 5 10 SUPPLY VOLTAGE (V) 15 0.5 0 0 1 3 2 INPUT VOLTAGE (V) 4 5 1590 G11 1590 G04 1590 G01 U U U PIN FUNCTIONS VREF B, VREF A (Pins 1, 9): Reference Inputs for DAC A/B. Typically ±10V, accepts up to ±25V.
PAGE 6
LTC1590 W BLOCK DIAGRA 20k VREF B 20k 20k 2 RFB B 1 40k 40k 40k 40k 40k 40k 40k 10k 3 OUT1 B 4 OUT2 B DECODER D11 (MSB) DAC B D10 D9 D8 D0 (LSB) DAC REGISTER B LOAD 12 VREF A 8 RFB A 9 6 OUT1 A DAC A 5 OUT2 A CS/LD 11 12 CLK CLK 14 INPUT 24-BIT SHIFT REGISTER 12 DOUT OUT IN DIN 13 1590 • BD 16 VCC 10 DGND 7 AGND W UW TIMING DIAGRAMS OPERATING SEQUENCE DAC A INPUT DAC B INPUT MSB LSB MSB DIN D11 D10 D9 D8 D7 D6 CLK 1 2 3 4 5 6 D5 7 D4 D3 8 9 D2
PAGE 7
LTC1590 W UW TIMING DIAGRAMS TIMING DIAGRAM t8 t1 t7 t6 t2 3 CLK 1 2 D11 A MSB DIN D10 A 23 t3 t4 D9 A 24 D0 B LSB D1 B CS/LD t5 t9 DOUT D11 A PREVIOUS WORD D10 A PREVIOUS WORD D9 A PREVIOUS WORD D0 B PREVIOUS WORD D11 A CURRENT WORD 1590 TD02 U W U U APPLICATIONS INFORMATION Description Equivalent Circuit The LTC1590 is a dual 12-bit multiplying DAC that has serial inputs and current outputs.
PAGE 8
LTC1590 U U W U APPLICATIONS INFORMATION Unipolar 2-Quadrant Multiplying Mode (VOUT = 0V to – VREF) Table 1. Unipolar Binary Code Table DIGITAL INPUT BINARY NUMBER IN DAC REGISTER The LTC1590 can be used with a dual op amp to provide a dual 2-quadrant multiplying DAC as shown in Figure 2. The unipolar DAC transfer function is shown in Table 1. The 33pF feedback capacitor is recommended to compensate for the pole caused by the internal feedback resistor and the OUT1 output capacitance.
PAGE 9
LTC1590 U U W U APPLICATIONS INFORMATION Op Amp Selection To maintain the excellent accuracy and stability of the LTC1590 thought should be given to op amp selection. Fortunately, the sensitivity of INL and DNL to op amp offset has been significantly reduced compared to competing parts of this type. The op amp’s VOS causes DAC output offset. In addition, because the DAC’s equivalent output resistance RO changes as a function of code, there is a code-dependent DAC output error proportional to VOS.
PAGE 10
LTC1590 U TYPICAL APPLICATIONS Very Low Power Single Supply Dual VOUT DAC 500k 50k – 1/4 LT1179 VOUT A + 500k 50k – 1/4 LT1179 V+ 3.3V 2 16 VCC 1 9 VREF B RFB B 3 OUT1 B V+ 3.3V VOUT B 0V TO 2.2V + DAC B 0.2V 4 OUT2 B 120k 8 – LT1004-1.2 210k + 1/4 LT1179 LTC1590 RFB A 6 OUT1 A VREF A DAC A 5 OUT2 A 0.1µF 50k AGND DGND 7 10 ISUPPLY TOTAL = 100µA (TYP) (WORSE-CASE CODE) 1590 TA06 Dual Programmable Gain Amplifier VIN B ±10V 5V 0.
PAGE 11
LTC1590 U TYPICAL APPLICATIONS Dual Programmable Gain Amplifier with Input Attenuation VIN B ±10V 1k 15k 5V 15k 1k 15V 0.1µF DATA IN SERIAL CLOCK CHIP SELECT/DAC LOAD DATA OUT CLEAR 16 2 1 14 CLK 0.01µF RFB B VREF B 13 DIN 33pF OUT1 B 3 2 OUT2 B 4 3 1/2 LT1358 DAC B 11 CS/LD 12 DOUT 15 CLR 24-BIT SHIFT REG AND LATCH 10 1 VOUT B + VOUT = –VIN LTC1590 OUT2 A 5 5 OUT1 A 6 6 AGND VREF A 7 1/2 LT1358 – 9 8 VOUT A 0.
PAGE 12
LTC1590 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S Package 16-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.386 – 0.394* (9.804 – 10.008) 0.010 – 0.020 × 45° (0.254 – 0.508) 16 0.053 – 0.069 (1.346 – 1.752) 0.008 – 0.010 (0.203 – 0.254) 0° – 8° TYP 12 11 10 9 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 0.050 (1.270) TYP 0.014 – 0.019 (0.355 – 0.483) 0.016 – 0.050 0.406 – 1.270 13 14 15 0.004 – 0.010 (0.