LTC1655LCN8应用文章市场行情现货热卖使用介绍供应商报价-中国IC网-芯三七

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

MICROWIRE^TMprotocols. The CLK input has a Schmitt

trigger that allows direct optocoupler interface.

■

16-Bit Monotonicity Over Temperature

■

Deglitched Rail-to-Rail Voltage Output

■

SO-8 Package

I_CC(TYP): 600µA

Internal Reference: 2.048V (LTC1655)

■

1.25V (LTC1655L)

■

Maximum DNL Error: ±1LSB

TheLTC1655hasanonboard2.048Vreferencethatcanbe

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.

■

Settling Time: 20µS to ±1LSB

■

750kHz Max Update Rate

Power-On Reset to Zero Volts

3-Wire Cascadable Serial Interface

Low Cost

Pin Compatible Upgrade for LTC1451 12-Bit DAC

Family

■

TheLTC1655Lhasanonboard1.25Vreferencethatcanbe

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.

■

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The LTC1655/LTC1655L are pin compatible with Linear

Technology’s 12-bit V_OUTDAC 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.

APPLICATIO S

■

Digital Calibration

■

Industrial Process Control

■

Automatic Test Equipment

Cellular Telephones

■

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

MICROWIRE is a trademark of National Semiconductor Corporation.

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FU CTIO AL BLOCK DIAGRA

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

Differential Nonlinearity

vs Input Code

LTC1655: 4.5V TO 5.5V

LTC1655L: 2.7V TO 5.5V

LTC1655: 2.048V

LTC1655L: 1.25V

1.0

0.8

8

6

V

CC

REF

0.6

REF

2

1

D

IN

0.4

CLK

16-BIT

SHIFT

REG

0.2

16

µP

16-BIT

DAC

0

+

–

3

CS/LD

V

OUT

7

AND

–0.2

–0.4

–0.6

–0.8

–1.0

DAC

LATCH

4

D

OUT

POWER-ON

RESET

TO

OTHER

DACS

0

16384

32768

CODE

49152

65535

GND

5

1655/55L TA01

1655/55L TA02

1

LTC1655/LTC1655L

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W

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/O

ABSOLUTE MAXIMUM RATINGS

PACKAGE RDER I FOR ATIO

(Note 1)

ORDER PART

NUMBER

V_CCto GND .............................................. –0.5V to 7.5V

TTL Input Voltage .................................... –0.5V to 7.5V

V_OUT, REF ....................................... –0.5V to V_CC+ 0.5V

Maximum Junction Temperature ......................... 125°C

Operating Temperature Range

LTC1655C/LTC1655LC ........................... 0°C to 70°C

LTC1655I/LTC1655LI ........................ –40°C to 85°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

TOP VIEW

LTC1655CN8

CLK

1

2

3

4

8

7

6

5

V

CC

LTC1655IN8

LTC1655CS8

LTC1655IS8

LTC1655LCN8

LTC1655LIN8

LTC1655LCS8

LTC1655LIS8

D

IN

OUT

CS/LD

REF

D

GND

OUT

N8 PACKAGE

8-LEAD PDIP

S8 PACKAGE

8-LEAD PLASTIC SO

T_JMAX= 125°C, θ_JA= 100°C/W (N8)

_JMAX= 125°C, θ_JA= 150°C/W (S8)

T

S8 PART MARKING

1655

1655I

1655L

1655LI

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at T_A= 25°C.

V_CC= 4.5V to 5.5V (LTC1655), V_CC= 2.7V to 5.5V (LTC1655L); V_OUTunloaded, REF unloaded, unless otherwise noted.

SYMBOL PARAMETER

DAC

CONDITIONS

MIN

TYP

MAX

UNITS

Resolution

●

16

Bits

Monotonicity

DNL

Differential Nonlinearity

Guaranteed Monotonic (Note 2)

LTC1655, REF = 2.2V, V = 5V (Note 8) (External)

●

±0.3

±0.5

±1.0

LSB

CC

LTC1655L, REF = 2.2V, V = 5V (Note 8) (External)

CC

INL

Integral Nonlinearity

Zero Scale Error

Offset Error

LTC1655, REF = 2.2V, V = 5V (Note 8) (External)

●

±8

±20

LSB

CC

LTC1655L, REF = 2.2V, V = 5V (Note 8) (External)

CC

ZSE

LTC1655

LTC1655L

●

0

3.0

3.5

mV

V

Measured at Code 200

OS

LTC1655, REF = 2.2V, V = 5V (Note 8) (External)

●

±0.5

±3.0

±3.5

mV

CC

LTC1655L, REF = 1.3V, V = 2.7V (Note 8) (External)

CC

TC

Offset Error Tempco

Gain Error

±5

0.5

µV/°C

LSB

OS

REF = 2.2V (External), V = 5V (Note 8)

●

±16

CC

Gain Error Drift

ppm/°C

Power Supply

V

Positive Supply Voltage

For Specified Performance

LTC1655

LTC1655L

CC

●

4.5

2.7

5.5

V

I

Supply Current

(Note 3)

●

600

1200

µA

CC

2

LTC1655/LTC1655L

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at T_A= 25°C.

_CC= 4.5V to 5.5V (LTC1655), V_CC= 2.7V to 5.5V (LTC1655L); V_OUTunloaded, REF unloaded, unless otherwise noted.

V

SYMBOL PARAMETER

Op Amp DC Performance

CONDITIONS

MIN

TYP

MAX

UNITS

Short-Circuit Current Low

V

Shorted to GND

OUT

LTC1655

LTC1655L

●

70

120

140

mA

Short-Circuit Current High

Output Impedance to GND

Output Line Regulation

V

Shorted to V

OUT CC

LTC1655

LTC1655L

●

80

70

140

150

mA

Input Code = 0

LTC1655

LTC1655L

●

40

70

120

160

Ω

Input Code = 65535, with Internal Reference

±3

mV/V

AC Performance

Voltage Output Slew Rate

(Note 4)

●

±0.3

±0.7

V/µs

Voltage Output Settling Time

(Note 4) to 0.0015% (16-Bit Settling Time), V = 5V

20

10

µs

CC

(Note 4) to 0.012% (13-Bit Settling Time), V = 5V

CC

Digital Feedthrough

(Note 5)

0.3

12

nV-s

Midscale Glitch Impulse

DAC Switched Between 8000 and 7FFF

H

Output Voltage Noise

Spectral Density

LTC1655, At 1kHz

LTC1655L, At 1kHz

280

220

nV√Hz

Reference Output

Reference Output Voltage

LTC1655

LTC1655L

●

2.036

1.240

2.048

1.250

2.060

1.260

V

Reference Input Range

(Notes 6, 7) LTC1655

LTC1655L

2.2

1.3

V

CC

V

CC

/2

V

Reference Output Tempco

Reference Input Resistance

LTC1655

LTC1655L

5

10

ppm/°C

LTC1655, REF Overdriven to 2.2V

LTC1655L, REF Overdriven to 1.3V

●

8.5

7.0

13

kΩ

Reference Short-Circuit Current

Reference Output Line Regulation

Reference Load Regulation

●

40

100

±1.5

5

mA

mV/V

mV/A

I

= 100µA

●

OUT

Reference Output Voltage Noise

Spectral Density

LTC1655, At 1kHz

LTC1655L, At 1kHz

150

115

nV√Hz

Digital I/O

V

Digital Input High Voltage

Digital Input Low Voltage

Digital Output High Voltage

Digital Output Low Voltage

LTC1655

LTC1655L

●

2.4

2.0

V

IH

LTC1655

LTC1655L

●

0.8

0.6

V

IL

LTC1655, I

LTC1655L, I

= –1mA

●

V

– 1.0

V

OH

OL

OUT

CC

= –1mA

– 0.7

OUT

LTC1655, I

LTC1655L, I

= 1mA

●

0.4

V

OUT

= 1mA

OUT

3

LTC1655/LTC1655L

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at T_A= 25°C.

V_CC= 4.5V to 5.5V (LTC1655), V_CC= 2.7V to 5.5V (LTC1655L); V_OUTunloaded, REF unloaded, unless otherwise noted.

SYMBOL PARAMETER

CONDITIONS

= GND to V

CC

MIN

TYP

MAX

±10

10

UNITS

µA

I

Digital Input Leakage

V

●

LEAK

IN

C

Digital Input Capacitance

(Note 7)

pF

IN

Switching

t

D

Valid to CLK Setup

Valid to CLK Hold

LTC1655

LTC1655L

●

40

60

ns

1

2

3

4

5

6

7

8

9

IN

LTC1655

LTC1655L

●

0

ns

IN

CLK High Time

LTC1655

LTC1655L

●

40

60

ns

CLK Low Time

LTC1655

LTC1655L

●

40

60

ns

CS/LD Pulse Width

LSB CLK to CS/LD

CS/LD Low to CLK

LTC1655

LTC1655L

●

50

80

ns

LTC1655

LTC1655L

●

40

60

ns

LTC1655

LTC1655L

●

20

30

ns

D

OUT

Output Delay

LTC1655, C

LTC1655L, C

= 15pF

LOAD

●

20

120

300

ns

= 15pF

LOAD

CLK Low to CS/LD Low

LTC1655

LTC1655L

●

20

30

ns

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: Nonlinearity is defined from code 128 to code 65535 (full scale).

See Applications Information.

Note 5: Part is clocked with pin toggling between 1s and 0s, CS/LD is low.

Note 6: Reference can be overdriven (see Applications Information).

Note 7: Guaranteed by design. Not subject to test.

Note 8: Guaranteed by correlation for other reference and supply

conditions.

Note 3: DAC switched between all 1s and all 0s. V = 4.096V.

FS

Note 4: Digital inputs at 0V or V

.

CC

4

LTC1655/LTC1655L

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TYPICAL PERFORMANCE CHARACTERISTICS

V_CC= 5V (LTC1655), V_CC= 3V (LTC1655L) unless otherwise noted.

TC1655 Differential Nonlinearity

LTC1655L Differential Nonlinearity

1.0

0.8

1.0

0.8

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

–0.8

–1.0

–0.2

–0.4

–0.6

–0.8

–1.0

0

16,384

32,768

49,152

65,535

15

0

16,384

32,768

49,152

65,535

DIGITAL INPUT CODE

1655/55L G01

1655/55L G01a

LTC1655 Integral Nonlinearity

LTC1655L Integral Nonlinearity

10

8

10

8

6

4

2

0

–2

–4

–6

–8

–10

–2

–4

–6

–8

–10

128

16,480

32,832

49,184

65,535

0

16,384

32,768

49,152

DIGITAL INPUT CODE

1655/55L G02a

1655/55L G02

LTC1655 Minimum Supply

Headroom for Full Output Swing

vs Load Current

LTC1655L Minimum Supply

Headroom for Full Output Swing

vs Load Current

1.2

1.0

0.8

0.6

0.4

0.2

0

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

∆V

OUT

< 1LSB

∆V

OUT

< 1LSB

OUT

V

= 4.096V

V

= 2.5V

CODE: ALL 1’s

125°C

25°C

125°C

25°C

–55°C

10

5

LOAD CURRENT (mA)

15

10

5

LOAD CURRENT (mA)

0

1655/55L G03a

1655/55L G03

5

LTC1655/LTC1655L

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TYPICAL PERFORMANCE CHARACTERISTICS

V_CC= 5V (LTC1655), V_CC= 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

0.6

0.4

0.2

0

CODE: ALL 0s

0.8

125°C

25°C

–55°C

0.6

125°C

0.4

25°C

–55°C

0.2

0

10

OUTPUT SINK CURRENT (mA)

15

10

15

0

5

OUTPUT SINK CURRENT (mA)

1655/55L G04

1655/55L G04a

LTC1655L Full-Scale Voltage vs

Temperature

LTC1655 Full-Scale Voltage vs

Temperature

4.10

4.09

4.08

4.07

2.510

2.505

2.500

2.495

2.490

–55

5

35

65

95

125

–55

5

35

65

95

125

–25

TEMPERATURE (°C)

1655/55L G05

1655/55L G05a

LTC1655 Offset vs Temperature

LTC1655L Offset vs Temperature

1.0

0.8

0.6

0.5

0.4

0.3

0.2

0.1

0

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

–0.8

–1.0

–55

–10

35

80

125

–55

–10

35

80

125

TEMPERATURE (°C)

1655/55L G06

1655/55L G06a

6

LTC1655/LTC1655L

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TYPICAL PERFORMANCE CHARACTERISTICS

V_CC= 5V (LTC1655), V_CC= 3V (LTC1655L) unless otherwise noted.

LTC1655 Supply Current vs

Logic Input Voltage

LTC1655L Supply Current vs

Logic Input Voltage

1.0

0.8

0.6

0.4

3.0

2.6

2.2

1.8

1.4

1.0

0.6

0

1

2

3

0

1

2

3

4

5

LOGIC INPUT VOLTAGE (V)

1655/55L G07a

1655/55L G07

LTC1655 Supply Current vs

Temperature

LTC1655L Supply Current vs

Temperature

700

680

660

640

620

600

580

560

540

520

500

480

460

V

CC

= 5.5V

V

CC

= 3.3V

V

CC

= 5V

V

= 3V

CC

V

CC

= 4.5V

= 2.7V

CC

–55 –35 –15

5

25 45 65 85 105 125

–55 –35 –15

5

25 45 65 85 105 125

TEMPERATURE (°C)

1655/55L G08

1655/55L G08a

LTC1655 Large-Signal Transient

Response

LTC1655L Large-Signal Transient

Response

5

4

3

2

1

0

3

2

1

0

V

A

UNLOADED

V

UNLOADED

OUT

T

= 25°C

T = 25°C

A

TIME (5µs/DIV)

1655/55L G09

1655/55L G10

7

LTC1655/LTC1655L

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 V_CC/2 (LTC1655) and 1.3V to

V_CC/2 (LTC1655L). When tied to V_CC/2, the output will

swing from GND to V_CC. The output can only swing to

within its offset specification of V_CC(see Applications

Information).

D_IN(Pin 2): The TTL Level Input for the Serial Interface

Data. Data on the D_INpin is latched into the shift register

on the rising edge of the serial clock and is loaded MSB

first. The LTC1655/LTC1655L requires a 16-bit word.

CS/LD (Pin 3): The TTL Level Input for the Serial Inter-

face Enable and Load Control. When CS/LD is low, the

CLK signal is enabled, so the data can be clocked in.

When CS/LD is pulled high, data is loaded from the shift

register into the DAC register, updating the DAC output.

V_OUT(Pin7):DeglitchedRail-to-RailVoltageOutput. V_OUT

clears to 0V on power-up.

D_OUT(Pin 4): Output of the Shift Register. Becomes valid

on the rising edge of the serial clock and swings from GND

to V_CC.

V_CC(Pin 8): Positive Supply Input. 4.5V ≤ V_CC≤ 5.5V

(LTC1655), 2.7V ≤ V_CC≤ 5.5V (LTC1655L). Requires a

0.1µF bypass capacitor to ground.

W U

W

TI I G DIAGRA

t

1

9

t

6

t

3

t

2

4

7

CLK

1

2

3

15

16

D15

MSB

D0

LSB

D

D14

D13

D1

IN

t

5

CS/LD

t

8

D15

PREVIOUS WORD

D14

D13

D0

PREVIOUS WORD

D15

D

OUT

PREVIOUS WORD PREVIOUS WORD

CURRENT WORD

1655/55L TD

8

LTC1655/LTC1655L

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DEFI ITIO S

Differential Nonlinearity (DNL): The difference between

the measured change and the ideal 1LSB change for any

twoadjacentcodes. TheDNLerrorbetweenanytwocodes

is calculated as follows:

lowestcodethatguaranteestheoutputwillbegreaterthan

zero. The INL error at a given input code is calculated as

follows:

INL = [V_OUT– V_OS– (V_FS– V_OS)(code/65535)]/LSB

DNL = (∆V_OUT– LSB)/LSB

Where V_OUTis the output voltage of the DAC measured at

the given input code.

Where ∆V_OUTis the measured voltage difference between

two adjacent codes.

Least Significant Bit (LSB): The ideal voltage difference

between two successive codes.

DigitalFeedthrough: Theglitchthatappearsattheanalog

outputcausedbyACcouplingfromthedigitalinputswhen

they change state. The area of the glitch is specified in

(nV)(sec).

LSB = 2V_REF/65536

Resolution (n): Defines the number of DAC output states

(2ⁿ) that divide the full-scale range. Resolution does not

imply linearity.

Full-Scale Error (FSE): The deviation of the actual full-

scale voltage from ideal. FSE includes the effects of offset

and gain errors (see Applications Information).

Voltage Offset Error (V_OS): Nominally, the voltage at the

output when the DAC is loaded with all zeros. A single

supply DAC can have a true negative offset, but the output

cannot go below zero (see Applications Information).

Gain Error (GE): The difference between the full-scale

output of a DAC from its ideal full-scale value after offset

error has been adjusted.

For this reason, single supply DAC offset is measured at

the lowest code that guarantees the output will be greater

than zero.

Integral Nonlinearity (INL): The deviation from a straight

line passing through the endpoints of the DAC transfer

curve(EndpointINL).Becausetheoutputcannotgobelow

zero, the linearity is measured between full scale and the

U

OPERATIO

Serial Interface

of the chips, then the CS/LD signal is pulled high to update

all of them simultaneously. The shift register and DAC

register are cleared to all 0s on power-up.

The data on the D_INinput is loaded into the shift register

ontherisingedgeoftheclock.TheMSBisloadedfirst.The

DAC register loads the data from the shift register when

CS/LD is pulled high. The clock is disabled internally when

CS/LD is high. Note: CLK must be low before CS/LD is

pulled low to avoid an extra internal clock pulse. The input

word must be 16 bits wide.

Voltage Output

The LTC1655/LTC1655L rail-to-rail buffered output can

source or sink 5mA over the entire operating temperature

range while pulling to within 600mV of the positive supply

voltage or ground. The output stage is equipped with a

deglitcherthatgivesamidscaleglitchof12nV-s.Atpower-

up, the output clears to 0V.

The buffered output of the 16-bit shift register is available

on the D_OUTpin which swings from GND to V_CC.

Multiple LTC1655s/LTC1655Ls may be daisy-chained to-

getherbyconnectingtheD_OUTpintotheD_INpinofthenext

chip while the clock and CS/LD signals remain common to

all chips in the daisy chain. The serial data is clocked to all

The output swings to within a few millivolts of either sup-

ply rail when unloaded and has an equivalent output resis-

tance of 40Ω (70Ω for the LTC1655L) when driving a load

totherails.Theoutputcandrive1000pFwithoutgoinginto

oscillation.

9

LTC1655/LTC1655L

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APPLICATIONS INFORMATION

Rail-to-Rail Output Considerations

error (FSE) is positive, the output for the highest codes

limits at V_CCas shown in Figure 1c. No full-scale limiting

can occur if V_REFis less than (V_CC– FSE)/2.

In any rail-to-rail DAC, the output swing is limited to

voltages within the supply range.

Offset and linearity are defined and tested over the region

of the DAC transfer function where no output limiting can

occur.

If the DAC offset is negative, the output for the lowest

codes limits at 0V as shown in Figure 1b.

Similarly, limiting can occur near full-scale when the REF

pin is tied to V_CC/2. If V_REF= V_CC/2 and the DAC full-scale

POSITIVE

FSE

V

CC

V

= V /2

CC

OUTPUT

VOLTAGE

REF

INPUT CODE

(1c)

V

CC

V

= V /2

CC

OUTPUT

VOLTAGE

REF

0

32768

65535

INPUT CODE

(1a)

OUTPUT

VOLTAGE

0V

NEGATIVE

OFFSET

INPUT CODE

1655/55L F01

(1b)

Figure 1. Effects of Rail-to-Rail Operation On a DAC Transfer Curve. (a) Overall Transfer Function (b) Effect of Negative

Offset for Codes Near Zero Scale (c) Effect of Positive Full-Scale Error for Input Codes Near Full Scale When V_REF= V_CC/2

10

LTC1655/LTC1655L

U

TYPICAL APPLICATIONS

This circuit shows how to use an LTC1655 to make an is used for the digitally controlled 0mA to 16mA current.

optoisolated digitally controlled 4mA to 20mA process R_Sis a sense resistor and the op amp modulates the

controller. The controller circuitry, including the transistor Q1 to provide the 4mA to 20mA current through

optoisolation, ispoweredbytheloopvoltagethatcanhave this resistor. The potentiometers allow for offset and full-

a wide range of 6V to 30V. The 2.048V reference output of scale adjustment. The control circuitry dissipates well

the LTC1655 is used for the 4mA offset current and V_OUTunder the 4mA budget at zero scale.

An Isolated 4mA to 20mA Process Controller

V

LOOP

6V TO 30V

150k

1%

LT^®1121-5

IN OUT

20k

5k

8

6

1µF

V

REF

CC

1

2

3

75k

1%

CLK

FROM

7

3

2

7

V

OUT

LTC1655

D

IN

+

OPTOISOLATED

INPUTS

1k

6

Q1

2N3440

LT^®1077

CS/LD

GND

3k

–

4

5

R

S

5V

10Ω

OPTOISOLATORS

I

OUT

10k

CLK

IN

1655/55L TA03

D

CS/LD

CLK

IN

CS/LD

500Ω

4N28

D

11

LTC1655/LTC1655L

U

TYPICAL APPLICATIONS

the onboard reference is always sourcing current and

never has to sink any current even when V_OUTis 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. R1 and R2 resistively divide down the LTC1655

output and an offset is summed in using the LTC1655

onboard2.048VreferenceandR3andR4. R5ensuresthat

A Wide Swing, Bipolar Output 16-Bit DAC

5V

0.1µF

8

V

CC

1

2

3

CLK

7

µP

V

OUT

LTC1655

D

IN

R1

5V

CS/LD

100k

GND

5

V

REF

6

1%

3

2

7

LT1077

4

+

–

6

(2)(D )(4.096)

IN

R2

200k

1%

V

OUT

:

– 4.096V

TRANSFER CURVE

32768

65536

4.096

R3

100k

1%

R4

200k

1%

–5V

65535

0

1655/55L TA05

V

OUT

D

IN

R5

100k

1%

–4.096

12

LTC1655/LTC1655L

U

TYPICAL APPLICATIONS

Thiscircuitshowsadigitallyprogrammablecurrentsource

fromanexternalvoltagesourceusinganexternalopamp,

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 R_A. If R_Ais

chosen to be 412Ω, the output current will range from

0mA at zero scale to 10mA at full scale. The minimum

voltage for V_Sis determined by the load resistor R_Land

Q1’s V_CESATvoltage. With a load resistor of 50Ω, the

voltage source can be 5V.

Digitally Programmable Current Source

5V

5V < V < 100V

S

FOR R ≤ 50Ω

8

L

0.1µF

V

CC

1

2

3

(D )(4.096)

IN

CLK

R

L

I

=

OUT

(65536)(R )

7

3

2

7

A

V

LTC1655

µP

+

D

OUT

IN

≈ 0mA TO 10mA

6

Q1

2N3440

LT1218

CS/LD

–

GND

5

4

R

A

412Ω

1%

1655/55L TA04

13

LTC1655/LTC1655L

U

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTION

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

0.400*

(10.160)

MAX

8

7

6

5

4

0.255 ± 0.015*

(6.477 ± 0.381)

1

2

3

0.130 ± 0.005

0.300 – 0.325

0.045 – 0.065

(3.302 ± 0.127)

(1.143 – 1.651)

(7.620 – 8.255)

0.065

(1.651)

TYP

0.009 – 0.015

(0.229 – 0.381)

0.125

0.020

(0.508)

MIN

(3.175)

MIN

+0.035

0.325

–0.015

0.018 ± 0.003

(0.457 ± 0.076)

0.100

(2.54)

BSC

+0.889

8.255

(

)

N8 1098

–0.381

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

14

LTC1655/LTC1655L

U

Dimensions in inches (millimeters) unless otherwise noted.

PACKAGE DESCRIPTION

S8 Package

8-Lead Plastic Small Outline (Narrow 0.150)

(LTC DWG # 05-08-1610)

0.189 – 0.197*

(4.801 – 5.004)

7

5

8

6

0.150 – 0.157**

(3.810 – 3.988)

0.228 – 0.244

(5.791 – 6.197)

1

3

4

2

0.010 – 0.020

(0.254 – 0.508)

× 45°

0.053 – 0.069

(1.346 – 1.752)

0.004 – 0.010

(0.101 – 0.254)

0.008 – 0.010

(0.203 – 0.254)

0°– 8° TYP

0.016 – 0.050

(0.406 – 1.270)

0.050

(1.270)

BSC

0.014 – 0.019

(0.355 – 0.483)

TYP

*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

SO8 1298

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

15

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

0.1µF

8

V

CC

1

2

3

CLK

LTC1655/

LTC1655L

7

µP

V

OUT

D

IN

R1

100k

CS/LD

GND

5

–5V

1655/55L TA06

RELATED PARTS

PART

NUMBER

DESCRIPTION

COMMENTS

5V to 15V Single Supply, Complete V

LTC1257

Single 12-Bit V

DAC, Full Scale: 2.048V, V : 4.75V to 15.75V,

DAC SO-8 Package

OUT

CC

in Reference Can Be Overdriven Up to 12V, i.e., FS

= 12V

MAX

LTC1446/ Dual 12-Bit V

LTC1446L

DACs in SO-8 Package

LTC1446: V = 4.5V to 5.5V, V

= 0V to 4.095V

OUT

CC

OUT

LTC1446L: V = 2.7V to 5.5V, V

= 0V to 2.5V

CC

OUT

LTC1448

Dual 12-Bit V

DAC, V : 2.7V to 5.5V

Output Swings from GND to REF. REF Input Can Be Tied to V

CC

OUT

CC

LTC1450/ Single 12-Bit V

LTC1450L

DACs with Parallel Interface

LTC1450: V = 4.5V to 5.5V, V

= 0V to 4.095V

OUT

CC

OUT

LTC1450L: V = 2.7V to 5.5V, V

= 0V to 2.5V

CC

OUT

LTC1451

LTC1452

LTC1453

Single Rail-to-Rail 12-Bit DAC, Full Scale: 4.095V, V : 4.5V to 5.5V,

Internal 2.048V Reference Brought Out to Pin

5V, Low Power Complete V

DAC in SO-8 Package

CC

OUT

Single Rail-to-Rail 12-Bit V

Multiplying DAC, V : 2.7V to 5.5V

Low Power, Multiplying V

DAC with Rail-to-Rail

OUT

CC

OUT

Buffer Amplifier in SO-8 Package

Single Rail-to-Rail 12-Bit V

DAC, Full Scale: 2.5V, V : 2.7V to 5.5V 3V, Low Power, Complete V DAC in SO-8 Package

OUT

CC

OUT

LTC1454/ Dual 12-Bit V

LTC1454L

DACs in SO-16 Package with Added Functionality

LTC1454: V = 4.5V to 5.5V, V

= 0V to 4.095V

OUT

CC

OUT

LTC1454L: V = 2.7V to 5.5V, V

= 0V to 2.5V

CC

OUT

LTC1456

Single Rail-to-Rail Output 12-Bit DAC with Clear Pin,

Full Scale: 4.095V, V : 4.5V to 5.5V

Low Power, Complete V

Package with Clear Pin

DAC in SO-8

OUT

CC

LTC1458/ Quad 12 Bit Rail-to-Rail Output DACs with Added Functionality

LTC1458L

LTC1458: V = 4.5V to 5.5V, V

= 0V to 4.095V

CC

OUT

LTC1458L: V = 2.7V to 5.5V, V

= 0V to 2.5V

CC

OUT

LTC1650

Single 16-Bit V

Industrial DAC in 16-Pin SO, V = ±5V

Low Power, Deglitched, 4-Quadrant Mulitplying V

Output Swing ±4.5V

DAC,

OUT

CC

OUT

LTC1654

Dual 14-Bit DAC

1LSB DNL, 2 DACs in SO-8 Footprint

LTC1657/ Single 16-Bit V

LTC1657L

DAC with Parallel Interface

LTC1657: V = 5V, Low Power, Deglitched, V

= 0V to 4.096V

OUT

CC

OUT

LTC1657L: V = 3V, Low Power, Deglitched, V

= 0V to 2.5V

CC

OUT

LTC1658

Single Rail-to-Rail 14-Bit V

DAC in 8-Pin MSOP,

Low Power, Multiplying V

Swings from GND to REF. REF Input Can Be Tied to V

DAC in MS8 Package. Output

OUT

V

= 2.7V to 5.5V

CC

LTC1659

Single Rail-to-Rail 12-Bit V

= 2.7V to 5.5V

Low Power, Multiplying V

DAC in MS8 Package. Output

OUT

V

Swings from GND to REF. REF Input Can Be Tied to V

CC

16555lf LT/TP 0800 4K • PRINTED IN USA

LINEAR TECHNOLOGY CORPORATION 1998

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

(408)432-1900 FAX:(408)434-0507 www.linear-tech.com

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