Datasheet

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LTC1655/LTC1655L

16-Bit Rail-to-Rail

Micropower DACs in

SO-8 Package

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16-Bit Monotonicity Over Temperature

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Deglitched Rail-to-Rail Voltage Output

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SO-8 Package

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CC(TYP)

: 600µA

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Internal Reference: 2.048V (LTC1655)

1.25V (LTC1655L)

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Maximum DNL Error: ±1LSB

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Settling Time: 20µS to ±1LSB

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750kHz Max Update Rate

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Power-On Reset to Zero Volts

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3-Wire Cascadable Serial Interface

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Low Cost

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Pin Compatible Upgrade for LTC1451 12-Bit DAC

Family

The LTC

1655/LTC1655L are rail-to-rail voltage output,

16-bit digital-to-analog converters in an SO-8 package.

They include an output buffer and a reference. The 3-wire

serial interface is compatible with SPI/QSPI and

MICROWIRE

protocols. The CLK input has a Schmitt

trigger that allows direct optocoupler interface.

The LTC1655 has an onboard 2.048V reference that can be

overdriven to a higher voltage. The output swings from 0V

to 4.096V when using the internal reference. The typical

power dissipation is 3.0mW on a single 5V supply.

The LTC1655L has an onboard 1.25V reference that can be

overdriven to a higher voltage. The output swings from 0V

to 2.5V when using the internal reference. The typical

power dissipation is 1.8mW on a single 3V supply.

The LTC1655/LTC1655L are pin compatible with Linear

Technology’s 12-bit V

OUT

DAC family, allowing an easy

upgrade path. They are the only buffered 16-bit DACs in

an SO-8 package and they include an onboard reference

for standalone performance.

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Digital Calibration

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Industrial Process Control

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Automatic Test Equipment

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Cellular Telephones

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

MICROWIRE is a trademark of National Semiconductor Corporation.

–

16-BIT

DAC

LTC1655: 4.5V TO 5.5V

LTC1655L: 2.7V TO 5.5V

LTC1655: 2.048V

LTC1655L: 1.25V

GND

POWER-ON

RESET

OTHER

DACS

16-BIT

SHIFT

REG

AND

DAC

LATCH

µP

REF

OUT

1655/55L TA01

CLK1

CS/LD3

OUT

REF

Functional Block Diagram: 16-Bit Rail-to-Rail DAC

Differential Nonlinearity

vs Input Code

CODE

–1.0

–0.2

–0.4

–0.6

–0.8

0.2

0.4

0.6

0.8

1.0

DNL ERROR (LSB)

16384 32768

1655/55L TA02

49152

65535

APPLICATIO S

FEATURES

DESCRIPTIO

FU CTIO AL BLOCK DIAGRA

Summary of content (16 pages)

PAGE 1
LTC1655/LTC1655L 16-Bit Rail-to-Rail Micropower DACs in SO-8 Package U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LTC®1655/LTC1655L are rail-to-rail voltage output, 16-bit digital-to-analog converters in an SO-8 package. They include an output buffer and a reference. The 3-wire serial interface is compatible with SPI/QSPI and MICROWIRETM protocols. The CLK input has a Schmitt trigger that allows direct optocoupler interface.
PAGE 2
LTC1655/LTC1655L W U U W W U W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER I FOR ATIO (Note 1) VCC to GND .............................................. – 0.5V to 7.5V TTL Input Voltage .................................... – 0.5V to 7.5V VOUT, REF ....................................... – 0.5V to VCC + 0.5V Maximum Junction Temperature ......................... 125°C Operating Temperature Range LTC1655C/LTC1655LC ........................... 0°C to 70°C LTC1655I/LTC1655LI ........................
PAGE 3
LTC1655/LTC1655L ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V (LTC1655), VCC = 2.7V to 5.5V (LTC1655L); VOUT unloaded, REF unloaded, unless otherwise noted.
PAGE 4
LTC1655/LTC1655L ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 4.5V to 5.5V (LTC1655), VCC = 2.7V to 5.5V (LTC1655L); VOUT unloaded, REF unloaded, unless otherwise noted.
PAGE 5
LTC1655/LTC1655L U W TYPICAL PERFORMANCE CHARACTERISTICS VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted. LTC1655L Differential Nonlinearity 1.0 1.0 0.8 0.8 DIFFERENTIAL NONLINEARITY (LSB) DIFFERENTIAL NONLINEARITY (LSB) TC1655 Differential Nonlinearity 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 0 16,384 49,152 32,768 DIGITAL INPUT CODE 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.
PAGE 6
LTC1655/LTC1655L U W TYPICAL PERFORMANCE CHARACTERISTICS VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted. LTC1655 Minimum Output Voltage vs Output Sink Current LTC1655L Minimum Output Voltage vs Output Sink Current 1.0 0.8 CODE: ALL 0s OUTPUT PULL-DOWN VOLTAGE (V) OUTPUT PULL-DOWN VOLTAGE (V) CODE: ALL 0s 0.8 0.6 125°C 0.4 25°C –55°C 0.2 0 0 10 5 OUTPUT SINK CURRENT (mA) 0.6 25°C –55°C 0.4 0.
PAGE 7
LTC1655/LTC1655L U W TYPICAL PERFORMANCE CHARACTERISTICS VCC = 5V (LTC1655), VCC = 3V (LTC1655L) unless otherwise noted. LTC1655 Supply Current vs Logic Input Voltage LTC1655L Supply Current vs Logic Input Voltage 1.0 3.0 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 2.6 2.2 1.8 1.4 0.8 0.6 1.0 0.4 0.
PAGE 8
LTC1655/LTC1655L U U U PIN FUNCTIONS CLK (Pin 1): The TTL Level Input for the Serial Interface Clock. GND (Pin 5): Ground. REF (Pin 6): Reference. Output of the internal reference is 2.048V (LTC1655), 1.25V (LTC1655L). There is a gain of two from this pin to the output. The reference can be overdriven from 2.2V to VCC/2 (LTC1655) and 1.3V to VCC/2 (LTC1655L). When tied to VCC/2, the output will swing from GND to VCC.
PAGE 9
LTC1655/LTC1655L U U DEFI ITIO S Differential Nonlinearity (DNL): The difference between the measured change and the ideal 1LSB change for any two adjacent codes. The DNL error between any two codes is calculated as follows: DNL = (∆VOUT – LSB)/LSB Where ∆VOUT is the measured voltage difference between two adjacent codes. Digital Feedthrough: The glitch that appears at the analog output caused by AC coupling from the digital inputs when they change state. The area of the glitch is specified in (nV)(sec).
PAGE 10
LTC1655/LTC1655L U W U U APPLICATIONS INFORMATION Rail-to-Rail Output Considerations In any rail-to-rail DAC, the output swing is limited to voltages within the supply range. If the DAC offset is negative, the output for the lowest codes limits at 0V as shown in Figure 1b. error (FSE) is positive, the output for the highest codes limits at VCC as shown in Figure 1c. No full-scale limiting can occur if VREF is less than (VCC – FSE)/2.
PAGE 11
LTC1655/LTC1655L U TYPICAL APPLICATIONS This circuit shows how to use an LTC1655 to make an optoisolated digitally controlled 4mA to 20mA process controller. The controller circuitry, including the optoisolation, is powered by the loop voltage that can have a wide range of 6V to 30V. The 2.048V reference output of the LTC1655 is used for the 4mA offset current and VOUT is used for the digitally controlled 0mA to 16mA current.
PAGE 12
LTC1655/LTC1655L U TYPICAL APPLICATIONS the onboard reference is always sourcing current and never has to sink any current even when VOUT is at full scale. The LT1077 output will have a wide bipolar output swing of – 4.096V to 4.096V as shown in the figure below. With this output swing 1LSB = 125µV. This circuit shows how to make a bipolar output 16-bit DAC with a wide output swing using an LTC1655 and an LT1077.
PAGE 13
LTC1655/LTC1655L U TYPICAL APPLICATIONS This circuit shows a digitally programmable current source from an external voltage source using an external op amp, an LT1218 and an NPN transistor (2N3440). Any digital word from 0 to 65535 is loaded into the LTC1655 and its output correspondingly swings from 0V to 4.096V. This voltage will be forced across the resistor RA. If RA is chosen to be 412Ω, the output current will range from 0mA at zero scale to 10mA at full scale.
PAGE 14
LTC1655/LTC1655L U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.100 (2.54) BSC *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
PAGE 15
LTC1655/LTC1655L U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH.
PAGE 16
LTC1655/LTC1655L U TYPICAL APPLICATION This circuit shows how to measure negative offset. Since LTC1655/LTC1655L operate on a single supply, if its offset is negative, the output for code 0 limits to 0V. To measure this negative offset, a negative supply is needed. Connect resistor R1 as shown in the figure below. The output voltage is the offset when code 0 is loaded in. Negative Offset Measurement 5V 0.