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LTC1654

1654fb

Dual 14-Bit Rail-to-Rail DAC

in 16-Lead SSOP Package

■

14-Bit Monotonic Over Temperature

■

Individually Programmable Speed/Power:

3µs Settling Time at 930µA

8.5µs Settling Time at 540µA

■

3V to 5V Single Supply Operation

■

Maximum Update Rate: 0.9MHz

■

Buffered True Rail-to-Rail Voltage Outputs

■

User Selectable Gain

■

Power-On Reset and Clear Function

■

Schmitt Trigger On Clock Input Allows Direct

Optocoupler Interface

■

Smallest Dual 14-Bit DAC: 16-Lead Narrow

SSOP Package

The LTC

1654 is a dual, rail-to-rail voltage output, 14-bit

digital-to-analog converter (DAC). It is available in a

16-lead narrow SSOP package, making it the smallest dual

14-bit DAC available. It includes output buffer amplifiers

and a flexible serial interface.

The LTC1654 has REFHI pins for each DAC that can be

driven up to V

. The output will swing from 0V to V

a gain of 1 configuration or V

/2 in a gain of 1/2 configu-

ration. It operates from a single 2.7V to 5.5V supply.

The LTC1654 has two programmable speeds: a FAST and

SLOW mode with ±1LSB settling times of 3µs or 8.5µs

respectively and supply currents of 930µA and 540µA in

the two modes. The LTC1654 also has shutdown capabil-

ity, power-on reset and a clear function to 0V.

■

Digital Calibration

■

Industrial Process Control

■

Automatic Test Equipment

■

Offset/Gain Adjustment

■

Multiplying DAC

DAC B

1654 BD

OUT B

REFHI B

OUT A

1/2

REFHI A

–

POWER-ON

RESET

DAC A

REFLO AREFLO B

1/2

–

INPUT

LATCH

CONTROL

LOGIC

CS/LD

SCK

SDO

CLR

SDI

INPUT

LATCH

DAC

32-BIT

SHIFT

DAC

FEATURES

DESCRIPTIO

APPLICATIO S

BLOCK DIAGRA

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

All other trademarks are the property of their respective owners.

Protected by U.S. Patents, including 5396245.

Summary of content (16 pages)

PAGE 1
LTC1654 Dual 14-Bit Rail-to-Rail DAC in 16-Lead SSOP Package U FEATURES DESCRIPTIO ■ The LTC®1654 is a dual, rail-to-rail voltage output, 14-bit digital-to-analog converter (DAC). It is available in a 16-lead narrow SSOP package, making it the smallest dual 14-bit DAC available. It includes output buffer amplifiers and a flexible serial interface. ■ ■ ■ ■ ■ ■ ■ ■ 14-Bit Monotonic Over Temperature Individually Programmable Speed/Power: 3µs Settling Time at 930µA 8.
PAGE 2
LTC1654 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) VCC to GND .............................................. – 0.5V to 7.5V TTL Input Voltage, REFHI, REFLO, X1/X1/2 ........................................ – 0.5V to 7.5V VOUT, SDO .................................. – 0.5V to (VCC + 0.5V) Operating Temperature Range LTC1654C ............................................. 0°C to 70°C LTC1654I ........................................
PAGE 3
LTC1654 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Unless otherwise noted, VCC = 2.7V to 5.5V, VOUT A, VOUT B unloaded, REFHI A, REFHI B = 4.096V (VCC = 5V), REFHI A, REFHI B = 2.048V (VCC = 2.7V), REFLO = 0V, X1/X1/2 = 0V. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 0.20 1.25 0.9 3.8 V/µs V/µs 8.5 3.
PAGE 4
LTC1654 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. Unless otherwise noted, VCC = 2.7V to 5.5V, VOUT A, VOUT B unloaded, REFHI A, REFHI B = 4.096V (VCC = 5V), REFHI A, REFHI B = 2.048V (VCC = 2.7V), REFLO = 0V, X1/X1/2 = 0V. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 150 ns Switching Characteristics (VCC = 2.7V to 5.
PAGE 5
LTC1654 U W TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Logic Input Voltage Large-Signal Settling—Slow Mode Large-Signal Settling—Fast Mode SUPPLY CURRENT (mA) 3.0 VOUT 1V/DIV VOUT 1V/DIV CS/LD 2V/DIV CS/LD 2V/DIV 1.5 0 0 1 3 4 2 LOGIC INPUT VOLTAGE (V) 5 TIME (2µs/DIV) TIME (2µs/DIV) 1654 G08 1654 G09 1654 G07 Midscale Glitch—Fast Mode Midscale Glitch—Slow Mode VOUT Glitch at Power-Up VCC 0.
PAGE 6
LTC1654 U U U PI FU CTIO S X1/X1/2 B, X1/X1/2 A (Pins 1, 8): The Gain of 1 or Gain of 1/2 Pin. When this pin is tied to VOUT, the output range will be REFLO to (REFLO + REFHI)/2 (0V to REFHI/2 when REFLO = 0V). When this pin is tied to REFLO, the output range will be REFLO to REFHI (0V to REFHI when REFLO = 0V). These pins should not be left floating. CS/LD (Pin 5): The TTL Level Input for the Serial Interface Enable and Load Control.
PAGE 7
X X SDI SDO SCK CS/LD 1 X X 2 X X X 4 X X X DON’T CARE 5 C3 SDI 3 1 SCK CS/LD C1 3 X X 6 X X 7 X X CONTROL BITS C2 2 8 A1 7 ADDRESS BITS A2 6 A0 8 B13 9 B12 10 B11 11 B10 12 B9 13 B8 14 B7 15 B5 17 DATA WORD B6 16 B4 18 B3 19 C3 C3 9 C1 11 C2 C1 CONTROL BITS C2 10 C0 C0 12 A3 A3 A2 14 A1 15 A1 16 A0 A0 PREVIOUS STREAM A2 ADDRESS BITS 13 B13 B13 17 B12 B12 18 32-BIT DATA STREAM B10 B10 20 B13 t1 B9 B9 21 22 t8 t
PAGE 8
LTC1654 U OPERATIO Serial Interface The data on the SDI input is loaded into the shift register on the rising edge of SCK. The MSB is loaded first. The Clock is disabled internally when CS/LD is high. Note: SCK must be low before CS/LD is pulled low to avoid an extra internal clock pulse. If no daisy-chaining is required, the input word can be 24-bit wide, as shown in the timing diagrams. The 8 MSBs, which are loaded first, are the control and address bits followed by a 16-bit data word.
PAGE 9
LTC1654 U OPERATIO Voltage Output The LTC1654 comes complete with rail-to-rail voltage output buffer amplifiers. These amplifiers will swing to within a few millivolts of either supply rail when unloaded and to within a 450mV of either supply rail when sinking or sourcing 5mA.
PAGE 10
LTC1654 U OPERATIO Table 1.
PAGE 11
LTC1654 U W U U APPLICATIO S I FOR ATIO Rail-to-Rail Output Considerations Rail-to-rail DACs take full advantage of the supply range available to them, but cannot produce output voltages above VCC or below ground. See Figure 2a. The offset, gain error and linearity of the LTC1654 are defined and tested in output ranges that avoid limiting. The low code kL used in these measurements is defined as the code which gives a nominal output of 32mV above ground; see Table 2.
PAGE 12
LTC1654 U U DEFI ITIO S Resolution (n): Resolution is defined as the number of digital input bits (n). It is also the number of DAC output states (2n) that divide the full-scale range. Resolution does not imply linearity. Least Significant Bit (LSB): One LSB is the ideal voltage difference between two successive codes. Full-Scale Voltage (VFS): This is the output of the DAC when all bits are set to 1.
PAGE 13
LTC1654 U TYPICAL APPLICATIO S This circuit shows how to use an LTC1654 and an LT®1077 to make a wide bipolar output swing 14-bit DAC with an offset that can be digitally programmed. VOUTA, which can be set by loading the appropriate code for DAC A, sets the offset. As this value changes, the transfer curve for the output moves up and down as illustrated in the graph below. A Wide Swing, Bipolar Output 14-Bit DAC with Digitally Controlled Offset 5V 0.
PAGE 14
LTC1654 U TYPICAL APPLICATIO S Dual 14-Bit Voltage Output DAC 2.7V TO 5.5V 0.
PAGE 15
LTC1654 U PACKAGE DESCRIPTION GN Package 16-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641) .189 – .196* (4.801 – 4.978) .045 ± .005 16 15 14 13 12 11 10 9 .254 MIN .009 (0.229) REF .150 – .165 .229 – .244 (5.817 – 6.198) .0165 ± .0015 .150 – .157** (3.810 – 3.988) .0250 TYP RECOMMENDED SOLDER PAD LAYOUT 1 .015 ± .004 × 45° (0.38 ± 0.10) .007 – .0098 (0.178 – 0.249) 2 3 4 5 6 7 .053 – .068 (1.351 – 1.727) 8 .004 – .0098 (0.102 – 0.249) 0° – 8° TYP .016 – .050 (0.
PAGE 16
LTC1654 U TYPICAL APPLICATIO A Wide Swing, Bipolar Output 14-Bit DAC with Digitally Controlled Offset 5V 0.1µF LTC1654 1 2 3 µP 4 5 6 7 8 X1/X1/2 B VCC CLR VOUT B SCK REFHI B SDI CS/LD REFLO B AGND DGND REFLO A SDO REFHI A X1/X1/2 A VOUT A 16 15 14 13 49.9k 1% 15V + 12 11 VOUT 2 (VOUTB – VOUTA) LT1077 100k 1% – 10 –15V 9 49.9k 1% 100k 1% 1654 TA02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1257 Single 12-Bit VOUT DAC, Full Scale: 2.048V, VCC: 4.75V to 15.