LT6656AIS6-2.048TRPBF

LT6656

1µA Precision Series

Voltage Reference

FeaTures

DescripTion

The LT^®6656 is a small precision voltage reference that

draws less than 1µA of supply current and can operate

with a supply voltage within 10mV of the output voltage.

The LT6656 offers an initial accuracy of 0.05% and tem-

perature drift of 10ppm/°C. The combined low power and

precision characteristics are ideal for portable and battery

powered instrumentation.

n

Low Drift

A Grade: 10 ppm/°C Max

B Grade: 20 ppm/°C Max

High Accuracy

n

A Grade: 0.05% Max

B Grade: 0.1% Max

n

Ultralow Supply Current: 850nA

High Output Drive Current: 5mA Min

Low Dropout Voltage: 10mV Max

Fully Speciﬁed from –40°C to 85°C

Operational from –55°C to 125°C

Wide Supply Range to 18V

The LT6656 can supply up to 5mA of output drive with

65ppm/mA of load regulation, allowing it to be used as

the supply voltage and the reference input to a low power

ADC. The LT6656 can accept a supply voltage up to 18V

and withstand the reversal of the input connections.

Reverse Input/Output Protection

Available Output Voltage Options:

1.25V, 2.048V, 2.5V, 3V, 3.3V, 4.096V and 5V

Thermal Hysteresis: 25ppm

The LT6656 output is stable with 1µF or larger output

capacitance and operates with a wide range of output

capacitor ESR.

n

Low Proﬁle (1mm) ThinSOT™ Package

This reference is fully speciﬁed for operation from –40°C

to 85°C, and is functional over the extreme temperature

range of –55°C to 125°C. Low hysteresis and a consistent

temperature drift are obtained through advanced design,

processing and packaging techniques.

applicaTions

n

Precision A/D and D/A Converters

n

Portable Gas Monitors

n

The LT6656 is offered in the 6-lead SOT-23 package.

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is

a trademark of Linear Technology Corporation. All other trademarks are the property of their

respective owners.

Battery- or Solar-Powered Systems

n

Precision Regulators

n

Low Voltage Signal Processing

n

Micropower Remote Sensing

Typical applicaTion

Output Voltage Temperature Drift

LT6656-2.5

2.503

38 TYPICAL UNITS

Basic Connection

2.502

2.501

2.500

2.499

2.498

LT6656-2.5

V

OUT

2.51V ≤ V ≤ 18V

V

OUT

IN

2.5V

GND

0.1µF

1µF

6656 TA01a

–40 –20

0

20

40

60

80

TEMPERATURE (°C)

6652 TA01b

6656fa

ꢀ

LT6656

absoluTe MaxiMuM raTings

pin conFiguraTion

(Note 1)

TOP VIEW

Input Voltage........................................................... 20V

Output Voltage........................................... –0.3V to 20V

Output Voltage Above Input Voltage .........................20V

Speciﬁed Temperature Range

GND* 1

GND 2

NC 3

6 V

OUT

5 NC

4 V

IN

S6 PACKAGE

6-LEAD PLASTIC TSOT-23

= 150°C, θ = 230°C/W

Commercial ............................................. 0°C to 70°C

Industrial .............................................–40°C to 85°C

Operating Temperature Range ............... –55°C to 125°C

Output Short Circuit Duration ......................... Indeﬁnite

Junction Temperature .......................................... 150°C

Storage Temperature Range (Note 2)..... –65°C to 150°C

Lead Temperature (Soldering, 10 sec.)

T

JMAX

JA

*CONNECT PIN TO DEVICE GND (PIN 2)

(Note 3).................................................................300°C

orDer inForMaTion

LEAD FREE FINISH

TAPE AND REEL

PART MARKING*

LTFNK

PACKAGE DESCRIPTION

SPECIFIED TEMPERATURE RANGE

LT6656ACS6-1.25#PBF

LT6656BCS6-1.25#PBF

LT6656AIS6-1.25#PBF

LT6656BIS6-1.25#PBF

LT6656ACS6-2.048#PBF

LT6656BCS6-2.048#PBF

LT6656AIS6-2.048#PBF

LT6656BIS6-2.048#PBF

LT6656ACS6-2.5#PBF

LT6656BCS6-2.5#PBF

LT6656AIS6-2.5#PBF

LT6656BIS6-2.5#PBF

LT6656ACS6-3#PBF

LT6656BCS6-3#PBF

LT6656AIS6-3#PBF

LT6656ACS6-1.25#TRPBF

LT6656BCS6-1.25#TRPBF

LT6656AIS6-1.25#TRPBF

LT6656BIS6-1.25#TRPBF

LT6656ACS6-2.048#TRPBF

LT6656BCS6-2.048#TRPBF

LT6656AIS6-2.048#TRPBF

LT6656BIS6-2.048#TRPBF

LT6656ACS6-2.5#TRPBF

LT6656BCS6-2.5#TRPBF

LT6656AIS6-2.5#TRPBF

LT6656BIS6-2.5#TRPBF

LT6656ACS6-3#TRPBF

LT6656BCS6-3#TRPBF

LT6656AIS6-3#TRPBF

6-Lead Plastic TSOT-23

0°C to 70°C

LTFNK

0°C to 70°C

LTFNK

–40°C to 85°C

0°C to 70°C

LTFNK

LTFNN

LTFGW

LTFNQ

LTFNS

0°C to 70°C

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

LT6656BIS6-3#PBF

LT6656BIS6-3#TRPBF

LT6656ACS6-3.3#PBF

LT6656BCS6-3.3#PBF

LT6656AIS6-3.3#PBF

LT6656BIS6-3.3#PBF

LT6656ACS6-3.3#TRPBF

LT6656BCS6-3.3#TRPBF

LT6656AIS6-3.3#TRPBF

LT6656BIS6-3.3#TRPBF

LTFNS

0°C to 70°C

LTFNS

–40°C to 85°C

LTFNS

6656fa

ꢁ

LT6656

orDer inForMaTion

LEAD FREE FINISH

TAPE AND REEL

PART MARKING*

LTFNV

PACKAGE DESCRIPTION

6-Lead Plastic TSOT-23

SPECIFIED TEMPERATURE RANGE

0°C to 70°C

LT6656ACS6-4.096#PBF

LT6656BCS6-4.096#PBF

LT6656AIS6-4.096#PBF

LT6656BIS6-4.096#PBF

LT6656ACS6-5#PBF

LT6656BCS6-5#PBF

LT6656AIS6-5#PBF

LT6656ACS6-4.096#TRPBF

LT6656BCS6-4.096#TRPBF

LT6656AIS6-4.096#TRPBF

LT6656BIS6-4.096#TRPBF

LT6656ACS6-5#TRPBF

LT6656BCS6-5#TRPBF

LT6656AIS6-5#TRPBF

LT6656BIS6-5#TRPBF

LTFNV

0°C to 70°C

LTFNV

–40°C to 85°C

0°C to 70°C

LTFNV

LTFNX

0°C to 70°C

LTFNX

–40°C to 85°C

LT6656BIS6-5#PBF

LTFNX

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

*The temperature and performance grades are identiﬁed by a label on the shipping container.

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

available opTions

SPECIFIED TEMPERATURE RANGE

0°C to 70°C

–40°C to 85°C

TEMPERATURE

COEFFICIENT

OUTPUT VOLTAGE

INITIAL ACCURACY

ORDER PART NUMBER**

1.250V

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-1.25

LT6656BCS6-1.25

LT6656AIS6-1.25

LT6656BIS6-1.25

2.048V

2.500V

3.000V

3.300V

4.096V

5.000V

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-2.048

LT6656BCS6-2.048

LT6656AIS6-2.048

LT6656BIS6-2.048

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-2.5

LT6656BCS6-2.5

LT6656AIS6-2.5

LT6656BIS6-2.5

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-3

LT6656BCS6-3

LT6656AIS6-3

LT6656BIS6-3

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-3.3

LT6656BCS6-3.3

LT6656AIS6-3.3

LT6656BIS6-3.3

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-4.096

LT6656BCS6-4.096

LT6656AIS6-4.096

LT6656BIS6-4.096

0.05%

0.1%

10ppm/°C

20ppm/°C

LT6656ACS6-5

LT6656BCS6-5

LT6656AIS6-5

LT6656BIS6-5

**See Order Information section for complete part number listing.

6656fa

ꢂ

LT6656

elecTrical characTerisTics ^Thel denotes the speciﬁcations which apply over the speciﬁed

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_IN= V_OUT+ 0.5V (for LT6656-1.25, V_IN= 2.2V), C_L= 1μF, I_L= 0,unless

otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Output Voltage Error

LT6656A

LT6656B

–0.05

–0.10

0.05

0.10

%

l

Output Voltage Temperature Coefﬁcient (Note 4)

Line Regulation

LT6656A

LT6656B

5

10

20

ppm/°C

12

V

IN

= (V

+ 0.5V) to 18V

2

25

40

ppm/V

OUT

l

LT6656-2.048, LT6656-2.5, LT6656-3,

LT6656-3.3, LT6656-4.096, LT6656-5

V

= 2.2V to 18V

2

25

40

ppm/V

IN

l

LT6656-1.25

Load Regulation (Note 5)

Dropout Voltage (Note 6)

I = 5mA, Sourcing

65

150

375

ppm/mA

L

LT6656-2.048, LT6656-2.5, LT6656-3,

LT6656-3.3, LT6656-4.096, LT6656-5

I = 5mA, Sourcing

80

3

175

425

ppm/mA

L

l

LT6656-1.25

V

L

– V , ∆V

Error ≤ 0.1%

OUT

IN

OUT

I = 0

10

40

mV

LT6656-2.048, LT6656-2.5, LT6656-3,

LT6656-3.3, LT6656-4.096, LT6656-5

I = 5mA, Sourcing

250

370

500

mV

L

LT6656-2.048, LT6656-2.5, LT6656-3,

LT6656-3.3, LT6656-4.096, LT6656-5

Minimum Input Voltage

I = 0, ∆V

Error ≤ 0.1%

L

OUT

LT6656-1.25

0°C ≤ T ≤ 70°C

1.35

0.85

1.5

1.6

1.8

V

l

A

–40°C ≤ T ≤ 85°C

A

Supply Current

1.0

1.5

µA

l

Output Short Circuit Current

Short V

to GND

18

4

mA

OUT

to V

IN

Input Reverse Leakage Current

Reverse Output Current

V

IN

V

IN

= –18V, V

= GND, V

= GND

80

30

µA

OUT

= 18V

Output Voltage Noise (Note 7)

0.1Hz to 10Hz

30

50

ppm

P-P

RMS

10Hz to 1kHz, LT6656-1.25

10Hz to 1kHz, LT6656-2.5

10Hz to 1kHz, LT6656-5

µV

80

140

Turn-On Time

LT6656-1.25, 0.1% Settling

LT6656-2.5, 0.1% Settling

LT6656-5, 0.1% Settling

15

30

60

ms

Long Term Drift of Output Voltage (Note 8)

Hysteresis (Note 9)

50

ppm/√kHr

∆T = 0°C to 70°C

∆T = –40°C to 85°C

25

70

ppm

6656fa

ꢃ

LT6656

elecTrical characTerisTics

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

environment to eliminate thermocouple effects on the leads. The test

time is 10 seconds. RMS noise is measured on a spectrum analyzer in a

shielded environment.

Note 8: Long term stability typically has a logarithmic characteristic and

therefore, changes after 1000 hours tend to be much smaller than before

that time. Total drift in the second thousand hours is normally less than

one third that of the ﬁrst thousand hours with a continuing trend toward

reduced drift with time. Long-term stability will also be affected by

differential stresses between the IC and the board material created during

board assembly.

Note 2: If the parts are stored outside of the speciﬁed temperature range,

the output may shift due to hysteresis.

Note 3: The stated temperature is typical for soldering of the leads during

manual rework. For detailed IR reﬂow recommendations, refer to the

Applications section.

Note 4: Temperature coefﬁcient is measured by dividing the maximum

Note 9: Hysteresis in output voltage is created by mechanical stress

that differs depending on whether the IC was previously at a higher or

lower temperature. Output voltage is always measured at 25°C, but

the IC is cycled to the hot or cold temperature limit before successive

measurements. For instruments that are stored at well controlled

temperatures (within 20 or 30 degrees of operational temperature)

hysteresis is usually not a dominant error source.

change in output voltage by the speciﬁed temperature range.

Note 5: Load regulation is measured with a pulse from no load to the

speciﬁed load current. Output changes due to die temperature change

must be taken into account separately.

Note 6: Excludes load regulation errors.

Note 7: Peak-to-peak noise is measured with a 3-pole highpass ﬁlter at

0.1Hz and a 4-pole lowpass ﬁlter at 10Hz. The unit is enclosed in a still-air

Typical perForMance characTerisTics

Output Voltage Temperature Drift

Typical V_OUTDistribution

Supply Current vs Input Voltage

100

10

1

200

180

160

140

120

100

80

10000

9000

8000

7000

6000

5000

4000

3000

2000

1000

0

T

= 125°C

= 85°C

1.25V OPTION

ALL OPTIONS

25 TYPICAL UNITS

NORMALIZED AT 25°C

ALL OPTIONS

A

C

L

= 1µF

L

= 25°C

I

= 0

= –40°C

= –55°C

C

I

= 1µF

= 0

T

= 25°C

A

L

60

40

20

0.1

–1000

0

2

4

6

8

10 12 14 16 18 20

–0.10

–0.06

–0.02 0 0.02

0.06

0.10

–60 –40 –20

0

20 40 60 80 100 120

INPUT VOLTAGE (V)

TEMPERATURE (°C)

OUTPUT VOLTAGE ERROR (%)

6652 G01

6656 G17

6656 G02

6656fa

ꢄ

LT6656

Typical perForMance characTerisTics

Minimum Supply Voltage

vs Load Current

Dropout Voltage vs Load Current

Supply Current vs Input Voltage

100

10

1

2.0

1.8

1.6

1.4

1.2

1.0

0.8

1000

100

10

T

= 125°C

= 85°C

= 25°C

= –55°C

2.048V TO 5V OPTIONS

1.25V OPTION

2.048V TO 5V OPTIONS

A

INITIAL V = 2.2V

V

– V

IN

= 0.1%

IN OUT

∆V

INITIAL V = V

+ 0.5V

OUT

IN

∆V

= 0.1%

OUT

V

ON

T

= 125°C

= 85°C

A

T

= 125°C

= 85°C

= 25°C

= –55°C

A

2.5V OPTION SHOWN

MOVES WITH VOLTAGE OPTION

= 25°C

V

= –40°C

= –55°C

ON

0.1

1

0

2

4

6

8

10 12 14 16 18 20

0.1µ

1µ

10µ

100µ

1m

10m

0.1µ

1µ

10µ

100µ

1m

10m

INPUT VOLTAGE (V)

LOAD CURRENT (A)

6656 G03

6656 G18

6656 G04

Load Regulation (Sourcing)

Load Regulation (Sinking)

500

250

750

500

250

0

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

1.25V OPTION

2.048V TO 5V OPTIONS

ALL OPTIONS

V

C

= 1.75V

V

C

= V

+ 0.5V

V

C

= V + 0.5V

IN

L

IN

L

OUT

IN

OUT

= 1µF

L

0

T

= 85°C, 125°C

= 25°C

A

–250

–500

–750

–1000

= –40°C

= –55°C

–250

–500

–750

T

= 125°C

= 85°C

A

T

= 125°C

= 85°C

= 25°C

= –55°C

A

= 25°C

= –40°C

= –55°C

–0.5

0.1µ

1µ

10µ

100µ

1m

10m

0.1µ

1µ

10µ

100µ

1m

10m

10µ

100µ

1m

LOAD CURRENT (A)

6656 G19

6656 G05

6656 G06

Power Supply Rejection Ratio

vs Frequency

Power Supply Rejection Ratio

vs Frequency

Line Regulation

1000

900

800

700

600

500

400

300

200

100

0

90

80

70

60

50

40

30

20

10

0

90

80

70

60

50

40

30

20

10

0

ALL OPTIONS

T

= 125°C

= 85°C

= 25°C

= –55°C

V

C

I

= V + 0.5V

OUT

2.5V OPTION

V = 3V

IN

A

IN

L

I

= 0

L

= 1µF

L

C

= 1µF

= 0

2.5V OPTION SHOWN

MOVES WITH

V

ON

VOLTAGE OPTION

V

ON

I

L

I

L

I

L

I

L

= 0, C = 1µF

L

= 0, C = 10µF

L

1.25V OPTION

2.5V OPTION

5V OPTION

= 1mA, C = 1µF

L

= 1mA, C = 10µF

L

–100

–200

–10

0

2

4

6

8

10 12 14 16 18 20

10

100

1k

10k

10

100

1k

10k

INPUT VOLTAGE (V)

FREQUENCY (Hz)

6656 G08

6656 G09

6656 G20

6656fa

ꢅ

LT6656

Typical perForMance characTerisTics

Ground Current vs Load Current

Output Impedance vs Frequency

10k

1k

10k

1k

1000

100

10

V

C

I

= V

+ 0.5V

OUT

2.5V OPTION

ALL OPTIONS

IN

L

= 1µF

V

= 3V

V

C

= V

+ 0.5V

IN

L

OUT

= 0

= 1µF

100

10

1

100

10

1

I

L

I

L

I

L

I

L

= 0, C = 1µF

L

T

= 125°C

= 85°C

= 25°C

= –55°C

A

= 0, C = 10µF

L

1.25V OPTION

2.5V OPTION

5V OPTION

= 100µA, C = 1µF

L

= 100µA, C = 10µF

L

1

10

100

1k

10k

10

100

1k

10k

10µ

100µ

1m

10m

FREQUENCY (Hz)

LOAD CURRENT (A)

6656 G21

6656 G22

6656 G07

Reverse Output Current

Output Noise 0.1Hz to 10Hz

Reverse Input Current

1000

100

10

100

10

1

ALL OPTIONS

V

= GND

V

= GND

V

C

L

= V

+ 0.5V

OUT

IN

L

OUT

= 1µF

I

= 0

1

T

= 125°C

= 85°C

= 25°C

= –55°C

T

= 125°C

= 85°C

= 25°C

= –55°C

A

0

–2 –4 –6 –8 –10 –12 –14 –16 –18 –20

0

5

10

15

20

TIME (1s/DIV)

6656 G13

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

6656 G11

6656 G12

Output Voltage Noise Spectrum

vs Load Current

Output Noise Voltage Spectrum

vs Load Capacitance

Output Voltage Noise Spectrum

30

25

20

15

10

5

16

14

12

10

8

40

35

30

25

20

15

10

5

V

C

I

= V

+ 5V

OUT

2.5V OPTION

I

L

I

L

I

L

I

L

= 0

IN

L

= 1µF

V

C

= 3V

V

I

= 3V

= 10µA

= 250µA

= 1mA

IN

L

IN

L

C = 47µF

L

= 0

= 1µF

= 0

5V OPTION

C

= 4.7µF

C

L

6

= 0.47µF

4

L

2.5V OPTION

2

1.25V OPTION

1k

0

10

100

10k

10

100

1k

10k

1

10

100

1k

FREQUENCY (Hz)

6656 G24

6656 G14

6656 G15

6656fa

ꢆ

LT6656

Typical perForMance characTerisTics

Integrated 10Hz to 1kHz Noise

vs Load Current

Integrated 10Hz to 1kHz Noise

vs Load Current

Long-Term Drift

500

400

300

200

100

0

250

200

150

100

50

200

150

100

50

V

C

= V

+ 0.5V

OUT

2.5V OPTION

ALL OPTIONS

IN

L

= 1µF

C = 1µF

L

I

= 0

0

5V OPTION

–50

–100

–150

–200

2.5V OPTION

C

= 0.47µF

= 1µF

= 10µF

= 47µF

L

1.25V OPTION

5 TYPICAL PARTS

SOLDERED ONTO PCB

0

0.1µ

1µ

10µ

100µ

1m

10m

0.1µ

1µ

10µ

100µ

1m

10m

0

100 200 300 400 500 600 700 800 900 1000

LOAD CURRENT (A)

HOURS

6656 G25

6656 G23

6656 G16

pin FuncTions

GND* (Pin 1): Internal Function. This pin must be tied

to ground.

NC (Pin 5): Not internally connected. May be tied to V ,

OUT

IN

V

, GND or ﬂoated.

GND (Pin 2): Device Ground.

V

(Pin 6): Output Voltage. An output capacitor of 1µF

OUT

minimum is required for stable operation.

NC (Pin 3): Not internally connected. May be tied to V ,

IN

V , GND or ﬂoated.

OUT

V

(Pin 4): Power Supply. Bypass V with a 0.1µF

IN

capacitor to ground.

block DiagraM

V

IN

NC

V

OUT

ERROR

AMP

BANDGAP

NC

GND

6656 BD

6656fa

ꢇ

LT6656

applicaTions inForMaTion

Long Battery Life

Output Voltage Options

Series references have a large advantage over shunt style

references. Shunt references require a resistor from the

power supply to operate. This resistor must be chosen

to supply the maximum current that can be demanded by

the load. When the load is not operating at this maximum

current, theshuntreferencemustalwayssinkthiscurrent,

resulting in high dissipation and shortened battery life.

TheperformanceoftheLT6656isconsistentforthe2.048V

to 5V options. The 1.25V option has slightly reduced load

regulation, and unlike the higher voltage options, the

minimum operating supply voltage is limited by internal

circuitry rather than the output voltage.

Parametersthatarebasedonchangesintheoutputvoltage,

suchasloadregulationandhysteresis,remainproportional

to the output voltage and are speciﬁed in relative units,

for example, parts per million (ppm). Parameters that

are not based on changes in the output voltage, such as

supply current and reverse input current, are the same

for all options.

The LT6656 series reference does not require a current

setting resistor and is speciﬁed to operate with any supply

from 1.5V to 18V, depending on the output voltage option,

load current and operating temperature (see Dropout

Voltage and Minimum Input Voltage in the Typical Perfor-

mance Characteristics). When the load does not demand

current, the LT6656 reduces its dissipation and battery life

is extended. If the reference is not delivering load current,

it dissipates only a few µW, yet the same connection can

deliver 5mA of load current when required.

ThebandwidthoftheLT6656decreaseswithhigheroutput

voltage. This causes parameters that are affected by both

bandwidth and output voltage, such as wideband noise

and output impedance, to increase less with higher output

voltage.

Start-Up

Bypass and Load Capacitance

To ensure proper start-up, the output voltage should be

between –0.3V and the rated output voltage. If the output

load may be driven more than 0.3V below ground, a low

forward voltage schottky diode from the output to ground

is required. The turn-on characteristics can be seen in

Figure 1.

The LT6656 voltage reference needs a 0.1μF input bypass

capacitor placed within an inch of the input pin. An ad-

ditional 2.2μF capacitor should be used when the source

impedance of the input supply is high or when driving

heavy loads. The bypassing of other local devices may

serve as the required components. The output of the

LT6656requiresacapacitanceof1µForlarger. TheLT6656

is stable with a wide variety of capacitor types including

ceramic,tantalumandelectrolyticduetoitslowsensitivity

to ESR (5Ω or less).

V

IN

1V/DIV

The test circuit in Figure 2 was used to test the response

and stability of the LT6656 to various load currents. The

resultant transient responses can be seen in Figure 3 and

Figure4.Thelargescaleoutputresponsetoa500mVinput

step is shown in Figure 5 with a more detailed photo and

description in the Output Settling section.

V

OUT

6656 F01

1ms/DIV

Figure 1. LT6656-2.5 Turn-On Characteristics, C_L= 1µF

R2

V

IN

LT6656-2.5

3V

V

GEN

3V

C

IN

C

L

1µF

R1

0.1µF

2N7000

6656 F02

Figure 2. Transient Load Test Circuit

6656fa

ꢈ

LT6656

applicaTions inForMaTion

Thesettlingtimeistypicallylessthan8msforoutputloads

up to 5mA, however the time required to settle when the

loadisturnedofforinresponsetoaninputtransientcanbe

signiﬁcantly longer due to the dead band (shown in Figure

7). Duringthisintervaltheoutputstageisneithersourcing

nor sinking current so the settling time is dominated by

the ability of the application circuit to discharge the output

capacitor to the voltage at which the sourcing circuitry

in the output stage reactivates. Larger load currents will

decrease the settling time and higher output capacitance

will increase the settling time.

0µA

I

OUT

100µA

2.52V

2.50V

2.48V

V

OUT

6656 F03

5ms/DIV

Figure 3. Transient Response, 0µA to 100µA Load Step

(R2 = 24.9k, R1 = Open)

In application circuits where the LT6656 is experiencing

a load step greater than 5µA, such as an ADC reference

and supply implementation, the settling time will typically

remain less than 8ms, regardless of the output settling

from a previous load step.

1mA

I

OUT

2mA

The settling time can be estimated by the following

equation:

2.52V

2.50V

2.48V

V

OUT

2(Deadband)(C_L)

Settling time≈

+(V_OUT)(0.8ms/V)

I_L

6656 F04

5ms/DIV

The deadband is ≈7mV for the 2.5V option, is proportional

to the voltage option (i.e., ≈14mV for the 5V option) and

can double due to variations in processing.

Figure 4. Transient Response, 1mA to 2mA Load Step

(R1 = R2 = 2.49k)

The graph in Figure 6 shows the settling time versus load

step with no load and with a constant 2µA load applied.

Note the settling time can be longer with load steps that

are not large enough to activate the sinking side of the

output stage.

3.25V

V

IN

2.75V

2.7V

2.5V

2.3V

30

2.5V OPTION

V

OUT

V

C

= 3V

IN

L

= 1µF

25

20

15

10

5

∆I = LOAD

L

STEP TO ZERO

6656 F05

5ms/DIV

Figure 5. Output Response to 0.5V_P-PStep on V_IN, C_L= 1µF, I_L= 0

∆I = LOAD

L

STEP TO 2µA

Output Settling

The output of the LT6656 is primarily designed to source

current into a load, but is capable of sinking current to

aid in output transient recovery. The output stage uses a

class B architecture to minimize quiescent current and

has a crossover dead band as the output transitions from

sourcing to sinking current.

∆I = ZERO TO

L

LOAD STEP

0

0.001

0.01

0.1

LOAD STEP (mA)

1

10

6656 F06

Figure 6. Output Settling Time to 0.05% vs Load Step

6656fa

ꢀ0

LT6656

applicaTions inForMaTion

input pulled to ground, the reverse output protection of

the LT6656 limits the output current to typically less than

30µA. The current versus reverse voltage is shown in the

Typical Performance Characteristics section.

3.25V

V

IN

2.75V

I

= 0

L

V

Long-Term Drift

OUT

10mV/DIV

I

= 5µA

Long-term drift cannot be extrapolated from accelerated

high temperature testing. This erroneous technique gives

drift numbers that are wildly optimistic. A more realistic

way to determine long-term drift is to measure it over the

time interval of interest. The LT6656 drift data was taken

over 100 parts that were soldered onto PC boards in a

typical application conﬁguration. The boards were then

L

6656 F07

5ms/DIV

Figure 7. Detailed Output Response to a 0.5V Input Step,

C_IN= C_L= 1µF

The photo in Figure 7 shows the output response to a 0.5V

input step in both a no-load and 5µA load condition. In

the no-load condition only the bias current of the internal

bandgapreference(about400nA)isavailabletodischarge

the output capacitor.

= 30°C,

placed into a constant temperature oven with T

A

their outputs scanned regularly and measured with an

8.5 digit DVM. The parts chosen in the Long Term Drift

curves in the Typical Performance Characteristics section

represent high, low and typical units.

Output Noise

Hysteresis

Low frequency noise is proportional to the output voltage

and is insensitive to output current and moderate levels

of output capacitance.

Hysteresis on the LT6656 is measured in two steps, for

example, from 25°C to –40°C to 25°C, then from 25°C to

85°C to 25°C, for the industrial temperature range. This

two-stepcycleisrepeatedseveraltimesandthemaximum

hysteresis from all the partial cycles is noted. Unlike other

commonly used methods for specifying hysteresis, this

ensures the worst-case hysteresis is included, whether it

occurs in the ﬁrst temperature excursion or the last.

Wideband noise increases less with higher output voltage

and is proportional to the bandwidth of the output stage,

increasing with higher load current and lower output

capacitance.

Peaking in the noise response is another factor contribut-

ing to the output noise level for a given frequency range.

Noise peaking can be reduced by increasing the size of the

outputcapacitorwhendrivingheavierloads,orconversely,

reducing the size of the output capacitor when driving

lighterloads.NoiseplotsintheTypicalPerformanceCurves

section show noise spectrum with various load currents

and output capacitances.

Results over both commercial and industrial temperature

rangesareshowninFigure8andFigure9.Thepartscycled

overthehighertemperaturerangehaveahigherhysteresis

than those cycled over the lower range.

Power Dissipation

The LT6656 will not exceed the maximum junction tem-

perature when operating within its speciﬁed temperature

range of –40°C to 85°C, maximum input voltage of 18V

and speciﬁed load current of 5mA.

Internal Protection

The LT6656 incorporates several internal protection

features that make it ideal for use in battery powered

systems. Reverse input protection limits the input cur-

rent to typically less than 40µA when either the LT6656

or the battery is installed backwards. In systems where

the output can be held up by a backup battery with the

IR Reﬂow Shift

The different expansion and contraction rates of the mate-

rials that make up the LT6656 package may induce small

stressesonthediethatcancausetheoutputtoshiftduring

6656fa

ꢀꢀ

LT6656

applicaTions inForMaTion

30

300

225

150

75

380s

2.5V OPTION

0°C TO 25°C

70°C TO 25°C

T

= 260°C

P

V

C

= 3V

IN

RAMP

DOWN

= 1µF

25

20

15

10

5

L

= 0

T = 217°C

L

I

L

T

= 200°C

S(MAX)

t

T

= 190°C

P

S

30s

T = 150°C

t

L

RAMP TO

150°C

130s

40s

120s

4

0

–60 –40 –20

0

20

40

60

0

2

6

8

10

MINUTES

HYSTERESIS (ppm)

6656 F10

6656 F08

Figure 10. Lead Free Reﬂow Proﬁle Due to IR Reﬂow

Figure 8. 0°C to 70°C Hysteresis

7

20

18

16

14

12

10

8

2.5V OPTION

3 CYCLES

1 CYCLE

2.5V OPTION

–40°C TO 25°C

85°C TO 25°C

V

C

I

= 3V

V

C

I

= 3V

IN

6

5

4

3

2

1

0

= 1µF

L

= 0

L

= 0

L

6

4

2

0

20

60

100

140

180

220

–160 –120 –80 –40

0

40 80 120 160

CHANGE IN OUTPUT VOLTAGE (ppm)

HYSTERESIS (ppm)

6656 F11

6656 F09

Figure 9. –40°C to 85°C Hysteresis

Figure 11. Output Voltage Shift Due to IR Reﬂow,

Peak Temperature = 260°C

IR reﬂow. Common lead free IR reﬂow proﬁles reach over

250°C, considerably more than lead solder proﬁles. The

higherreﬂowtemperatureoftheleadfreepartsexacerbates

the issue of thermal expansion and contraction causing

the output shift to generally be greater than with a leaded

reﬂow process.

PC Board Layout

The mechanical stress of soldering a surface mount volt-

age reference to a PC board can cause the output voltage

to shift and temperature coefﬁcient to change.

To reduce the effects of stress-related shifts, position

the reference near the short edge of the PC board or in a

corner. In addition, slots can be cut into the board on two

sides of the device. See Application Note AN82 for more

information. http://www.linear.com

The lead free IR reﬂow proﬁle used to experimentally

measure the output voltage shift in the LT6656-2.5 is

shown in Figure 10. Similar results can be expected using

a convection reﬂow oven. Figure 11 shows the change

in output voltage that was measured for parts that were

run through the reﬂow process for 1 cycle and also 3

cycles. The results indicate that the standard deviation

of the output voltage increases with a positive mean shift

of 120ppm. While there can be up to 220ppm of output

voltage shift, additional drift of the LT6656 after IR reﬂow

does not vary signiﬁcantly.

The input and output capacitors should be mounted close

to the package. The GND and V

short as possible to minimize the voltage drops caused

by load and ground currents. Excessive trace resistance

directly impacts load regulation.

traces should be as

OUT

6656fa

ꢀꢁ

LT6656

Typical applicaTions

Regulator Reference

Low Power ADC Reference

The robust input and output of the LT6656 along with its

high output current make it an excellent precision low

power regulator as well as a reference. The LT6656 would

be a good match with a small, low power microcontroller.

Using the LT6656 as a regulator reduces power consump-

tion, decreases solution size and increases the accuracy

of the microcontroller’s on board ADC.

Low power ADCs draw only a few µAs during their idle

period and well over 100µA during conversions. Despite

these surges of current, the ADC in reality can have very

low power consumption. Figure 13 shows the LTC2480, a

low power delta sigma ADC. When the ADC is disabled its

quiescentcurrent(I )isroughly1µA,duringconversionthe

Q

I jumps up to 160µA. In reality, the power consumption

Q

is not only based on the I during conversion, but the real

Q

LT6656-2.5

power consumption of the ADC is set by the conversion

timeandthesamplerate. TheLTC2480showninFigure13

has a conversion time of 160ms which sets the maximum

samplerateof6samplespersecond.Themaximumsample

ratealsosetsthemaximumcurrentconsumptionto160µA,

but at slower sample rates the ADC will have signiﬁcantly

lower average current draw. If the ADC is sampled at 1

sample per second the average current drawn by the ADC

during a 1 second interval would only be 26.4µA. When

taking into consideration the current drawn by the refer-

ence, the total current draw is only 27.4µA. This system is

greatlysimpliﬁedbecausetheprecisionreferencedoesnot

need to be cycled on and off to save power. Furthermore,

leaving the reference on continuously eliminates concern

for turn-on settling time.

3V ≤ V ≤ 18V

IN

OUT

IN

MCU

V /V

CC REF

0.1µF

10µF

5

6

7

2

3

1

PB0/AIN0/A /MOSI

REF

PB1/INT0/A /MISO/OC1A

IN1

PB2/ADC1/SCK/T0/INT0

PB3/ADC2

PB4/ADC3

PB5/RESET/ADC0

GND

6656 TA02

Figure 12. Microcontroller Reference and Regulator

LT6656-5

5.1V ≤ V ≤ 18V

IN

OUT

IN

4.7µF

0.1µF

REF

V

CC

+

–

IN

CS

SCK

SDO

DIFFERENTIAL INPUT

±V • 0.5 (±±.5Vꢀ

LTC±480

REF

AT 1sps, I = ±7.4µA

Q

6656 TA05

Figure 13. Low Power ADC Reference

6656fa

ꢀꢂ

LT6656

Typical applicaTions

Extended Supply Range Reference

V

CC

UP TO 160V

330k

MMBT5551

IN

BZX584C12

0.1µF

V

OUT

LT6656-2.5

2.2µF

1µF

6656 TA03

Boosted Output Current Reference

3.6V ≤ V ≤ 18V

CC

+

2207

10µF

2N2905

1µF

0.1µF

IN

V

OUT

LT6656-2.5

40mA MAX

6656 TA04

Micropower Regulator, I_Q= 2µA, Sink Up to 8mA

3V ≤ V ≤ 18V

CC

LT6656-2.5

IN

OUT

+

–

0.1µF

1µF

LT6003

2.5V

6656 TA06

ADC Reference and Bridge Excitation Supply

3.3V ≤ V ≤ 5.5V

CC

LT6656-3.3

3.8V ≤ V ≤ 18V

IN

OUT

IN

0.1µF

1µF

0.1µF

10µF

10k

V

CC

REF

–

+

IN

CS

SCK

SDO

0.1µF

LTC2452

IN

6656fa

ꢀꢃ

LT6656

Typical applicaTions

Low Power Precision High Voltage Supply Monitor, I_Q= 1.4µA, High Voltage Supply Load = 10µA

100V

105V OVERVOLTAGE THRESHOLD

V

CC

9.53M

3

4

7

+

6.5V ≤ V ≤ 10V

CC

OVERVOLTAGE FLAG

LTC1540

LT6656-5

6

IN

OUT

–

5

0.1µF

1µF 475k

1, 2

6656 TA08

2-Terminal Current Source

+

–

LT6003

R3

V

REF

R1

1µF

LT6656-1.25

GND

IN

OUT

0.1µF

R2

–

6656 TA09

V_REFR2

¥

´

¶

I_OUT

ꢀ

ꢁ1

µ

¦

§

R1 R3

Precision Current and Boosted Reference, I_Q= 5.5µA

249k

V

CC

+

–

+

–

1k

2.75V

200k

2N5086

LT6004

1µA OUT

3V ≤ V ≤ 16V

CC

2M

LT6656-2.5

IN

OUT

2.5V

0.1µF

1µF

6656 TA10

6656fa

ꢀꢄ

LT6656

package DescripTion

S6 Package

6-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1636)

2.90 BSC

(NOTE 4)

0.62

MAX

0.95

REF

1.22 REF

1.4 MIN

1.50 – 1.75

2.80 BSC

3.85 MAX 2.62 REF

(NOTE 4)

PIN ONE ID

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

0.30 – 0.45

6 PLCS (NOTE 3)

0.95 BSC

0.80 – 0.90

0.20 BSC

DATUM ‘A’

0.01 – 0.10

1.00 MAX

0.30 – 0.50 REF

1.90 BSC

0.09 – 0.20

(NOTE 3)

S6 TSOT-23 0302 REV B

NOTE:

1. DIMENSIONS ARE IN MILLIMETERS

2. DRAWING NOT TO SCALE

3. DIMENSIONS ARE INCLUSIVE OF PLATING

4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

5. MOLD FLASH SHALL NOT EXCEED 0.254mm

6. JEDEC PACKAGE REFERENCE IS MO-193

6656fa

ꢀꢅ

LT6656

revision hisTory

REV

DATE

DESCRIPTION

PAGE NUMBER

A

7/10

Voltage options added (1.25, 2.048, 3, 3.3), reﬂected throughout the data sheet

1 to 18

6656fa

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 representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

ꢀꢆ

LT6656

Typical applicaTion

Reference Regulator for Micropower DAC, Total I_Q= 4.8µA

LT6656-5

5V

5.1V ≤ V ≤ 18V

IN

OUT

IN

0.1µF

10µF

V

CC

REF

0V TO 5V OUTPUT

DAC A

DAC B

CS

SCK LTC1662

SDI

GND

6656 TA07

relaTeD parTs

PART NUMBER DESCRIPTION

COMMENTS

LT1389

LTC1440

LT1460

Nanopower Precision Shunt Voltage Reference 0.05% Max 10ppm/°C Max, 800nA Supply

Micropower Comparator with Reference

Micropower Series Reference

3.7µA Max Supply Current, 1% 1.182V Reference, MSOP, PDIP and SO-8 Packages

0.075% Max, 10ppm/°C Max Drift, 2.5V, 5V and 10V Versions,MSOP, PDIP, SO-8,

SOT-23 and TO-92 Packages

LT1461

LT1495

LTC1540

LT1634

Micropower Precision LDO Series Reference

1.5µA Precision Rail-to-Rail Dual Op Amp

Nanopower Comparator with Reference

3ppm/°C Max Drift, 0°C to 70°C, –40°C to 85°C, –40°C to 125°C Options in SO-8

1.5µA Max Supply Current, 100pA Max IOS

600nA Max Supply Current, 2% 1.182V Reference, MSOP and SO-8 Packages

Micropower Precision Shunt Voltage

Reference

0.05% Max, 10ppm/°C Max Drift, 1.25V, 2.5V, 4.096V, 5V, 10µA Maximum Supply

Current

LT1790

LTC1798

LT6003

LT6650

LT6660

LT6700

Micropower Precision Series Reference

6µA Low Dropout Series Reference

1.6V, 1µA Precision Rail-to-Rail Op Amp

Micropower Reference with Buffer Ampliﬁer

Tiny Micropower Series Reference

0.05% Max, 10ppm/°C Max, 60µA Supply, SOT23 Package

Available in Adjustable, 2.5V, 3V, 4.096V and 5V

1µA Max Supply Current, 1.6V Minimum Operating Voltage, SOT-23 Package

0.05% Max, 5.6µA Supply, SOT-23 Package

0.2% Max, 20ppm/°C Max, 20mA Output Current, 2mm × 2mm DFN

6.5µA Supply Current, 1.4V Minimum Operating Voltage

Micropower, Low Voltage Dual Comparator

with 40mV Reference

6656fa

LT 0710 REV A • PRINTED IN USA

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

ꢀꢇ

●

 LINEAR TECHNOLOGY CORPORATION 2010

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


型号：	LT6656AIS6-2.048TRPBF
厂家：	Linear
描述：	1Î¼A Precision Series Voltage Reference 1Î¼A精准串联电压基准
文件：	总18页 (文件大小：558K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT6656AIS6-2.048TRPBF [Linear]

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