LTC2305HMSXTRPBF_技术文档

LTC2301/LTC2305

1-/2-Channel, 12-Bit ADCs

2

with I C Compatible Interface

FEATURES

DESCRIPTION

The LTC^®2301/LTC2305 are low noise, low power, 1-/2-

n

12-Bit Resolution

2

n

Low Power: 1.5mW at 1ksps, 35μW Sleep Mode

channel,12-bitsuccessiveapproximationADCswithanI C

n

14ksps Throughput Rate

compatibleserialinterface.TheseADCsincludeaninternal

reference and a fully differential sample-and-hold circuit

to reduce common-mode noise. The LTC2301/LTC2305

operate from an internal clock to achieve a fast 1.3μs

conversion time.

n

Internal Reference

n

Low Noise: SNR = 73.5dB

n

Guaranteed No Missing Codes

n

Single 5V Supply

2

n

2-wire I C Compatible Serial Interface with 9

The LTC2301/LTC2305 operate from a single 5V supply

and draw just 300μA at a throughput rate of 1ksps. The

ADC enters nap mode when not converting, reducing the

power dissipation.

Addresses Plus One Global for Synchronization

n

Fast Conversion Time: 1.3ꢀs

n

1-Channel (LTC2301) and 2-Channel (LTC2305)

Versions

n

The LTC2301/LTC2305 are available in small 12-pin

4mm × 3mm DFN and 12-pin MSOP packages. The in-

ternal 2.5V reference further reduces PCB board space

requirements.

Unipolar or Bipolar Input Ranges (Software

Selectable)

Internal Conversion Clock

n

Guaranteed Operation from –40°C to 125°C

(MSOP Package)

The low power consumption and small size make the

LTC2301/LTC2305 ideal for battery operated and portable

n

12-Pin 4mm × 3mm DFN and 12-Pin MSOP

Packages

2

applications,whilethe2-wireI Ccompatibleserialinterface

makes these ADCs a good match for space-constrained

systems.

APPLICATIONS

n

Industrial Process Control

2

12-Bit I C ADC Famly

n

Motor Control

n

Input Channels

Part Number

1

2

8

Accelerometer Measurements

n

LTC2301

LTC2305

LTC2309

Battery Operated Instruments

Isolated and/or Remote Data Acquisition

n

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

All other trademarks are the property of their respective owners.

n

Power Supply Monitoring

BLOCK DIAGRAM

Integral Nonlinearity vs Output Code (LTC2305)

5V

1.00

10μF

V

0.1μF

0.75

AD1

AD0

LTC2301

LTC2305

DD

0.50

0.25

+

–

CH0(IN )

ANALOG

INPUT

MUX

12-BIT

SCL

SDA

2

ANALOG INPUT

0V TO 4.096V UNIPOLAR

2.048V BIPOLAR

I C

0.00

SAR ADC

+

PORT

CH1(IN )

–0.25

–0.50

–0.75

–1.00

V

REF

INTERNAL

2.5V REF

2.2μF

PIN NAMES IN PARENTHESES

REFER TO LTC2301

REFCOMP

10μF

0

1024

2048

3072

4096

GND

0.1μF

OUTPUT CODE

23015 TA01a

23015 TA01b

23015f

1

LTC2301/LTC2305

(Notes 1,2)

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (V ) ................................ –0.3V to 6.0V

Power Dissipation...............................................500mW

Operating Temperature Range

LTC2301C/LTC2305C ............................... 0°C to 70°C

LTC2301I/LTC2305I..............................–40°C to 85°C

LTC2301H/LTC2305H (Note 13).........–40°C to 125°C

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

DD

Analog Input Voltage

+

–

CH0(IN ), CH1(IN ), REF,

REFCOMP .....................(GND – 0.3V) to (V + 0.3V)

DD

Digital Input Voltage..........(GND – 0.3V) to (V + 0.3V)

DD

Digital Output Voltage .......(GND – 0.3V) to (V + 0.3V)

DD

PIN CONFIGURATION

LTC2305

LTC2301

TOP VIEW

GND

SDA

SCL

GND

CH0

CH1

1

2

3

4

5

6

12 AD0

11 AD1

GND

SDA

SCL

GND

1

2

3

4

5

6

12 AD0

11 AD1

10

9

V

10

9

V

DD

13

GND

+

8

REFCOMP

IN

8

REFCOMP

–

7

V

REF

IN

7

V

REF

DE PACKAGE

12-LEAD (4mm × 3mm) PLASTIC DFN

DE PACKAGE

12-LEAD (4mm × 3mm) PLASTIC DFN

T

= 150°C, θ = 43°C/W

T

= 150°C, θ = 43°C/W

JMAX

JA

JMAX JA

EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB

LTC2305

LTC2301

TOP VIEW

1

2

3

4

5

6

GND

SDA

SCL

GND

CH0

CH1

12 AD0

11 AD1

1

2

3

4

5

6

GND

SDA

SCL

GND

12 AD0

11 AD1

10

9

V

GND

10

9

V

GND

DD

+

8

REFCOMP

IN

8

REFCOMP

–

7

V

IN

7

V

REF

MS PACKAGE

12-LEAD PLASTIC MSOP

MS PACKAGE

12-LEAD PLASTIC MSOP

T

= 150°C, θ = 130°C/W

T

= 150°C, θ = 130°C/W

JMAX

JA

JMAX

JA

ORDER INFORMATION

LEAD FREE FINISH

LTC2301CDE#PBF

LTC2301IDE#PBF

LTC2305CDE#PBF

LTC2305IDE#PBF

LTC2301CMS#PBF

LTC2301IMS#PBF

LTC2301HMS#PBF

LTC2305CMS#PBF

TAPE AND REEL

PART MARKING*

PACKAGE DESCRIPTION

TEMPERATURE RANGE

0°C to 70°C

LTC2301CDE#TRPBF

LTC2301IDE#TRPBF

LTC2305CDE#TRPBF

LTC2305IDE#TRPBF

LTC2301CMS#TRPBF

LTC2301IMS#TRPBF

LTC2301HMS#TRPBF

LTC2305CMS#TRPBF

2301

2305

2301

2305

12-Lead (3mm × 4mm) Plastic DFN

12-Lead Plastic MSOP

–40°C to 85°C

0°C to 70°C

–40°C to 85°C

0°C to 70°C

12-Lead Plastic MSOP

–40°C to 85°C

–40°C to 125°C

0°C to 70°C

12-Lead Plastic MSOP

23015f

2

LTC2301/LTC2305

ORDER INFORMATION

LEAD FREE FINISH

LTC2305IMS#PBF

LTC2305HMS#PBF

TAPE AND REEL

PART MARKING*

2305

PACKAGE DESCRIPTION

TEMPERATURE RANGE

–40°C to 85°C

LTC2305IMS#TRPBF

LTC2305HMS#TRPBF

12-Lead Plastic MSOP

2305

–40°C to 125°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is 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/

CONVERTER AND MULTIPLEXER CHARACTERISTICS

The

l

denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at T = 25°C. (Note 4)

A

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Bits

Resolution (No Missing Codes)

Integral Linearity Error

Differential Linearity Error

Bipolar Zero Error

l

12

(Note 5)

0.4

0.3

1

8

LSB

(Note 6)

0.5

LSB

Bipolar Zero Error Drift

Unipolar Zero Error

0.002

0.7

LSB/°C

LSB

l

(Note 6)

6

Unipolar Zero Error Drift

Unipolar Zero Error Match (LTC2305)

Bipolar Full-Scale Error

0.002

0.1

LSB/°C

LSB

1

l

External Reference (Note 7)

REFCOMP = 4.096V (Note 7)

1

0.9

10

9

LSB

Bipolar Full-Scale Error Drift

Unipolar Full-Scale Error

External Reference

0.05

LSB/°C

l

External Reference (Note 7)

REFCOMP = 4.096V (Note 7)

0.5

0.7

10

6

LSB

Unipolar Full-Scale Error Drift

External Reference

0.05

0.1

LSB/°C

LSB

Unipolar Full-Scale Error Match (LTC2305)

2

ANALOG INPUT ^The

l

denotes the speciﬁcations which apply over the full operating temperature range, otherwise

speciﬁcations are at T = 25°C. (Note 4)

A

SYMBOL

V +

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

Absolute Input Range (CH0, CH1, IN+)

Absolute Input Range (CH0, CH1, IN–)

(Note 8)

–0.05

REFCOMP

V

IN

V –

IN

Unipolar (Note 8)

Bipolar (Note 8)

–0.05

0.25 • REFCOMP

0.75 • REFCOMP

V

l

V + – V –

Input Differential Voltage Range

V

= V + – V – (Unipolar)

0 to REFCOMP

REFCOMP/2

V

IN

= V + – V – (Bipolar)

IN

I

IN

Analog Input Leakage Current

Analog Input Capacitance

1

μA

C

IN

Sample Mode

Hold Mode

55

5

pF

CMRR

Input Common Mode Rejection Ratio

70

dB

23015f

3

LTC2301/LTC2305

DYNAMIC ACCURACY

The

l

denotes the speciﬁcations which apply over the full operating temperature range,

otherwise speciﬁcations are at T = 25°C and A = –1dBFS. (Notes 4,9)

A

IN

SYMBOL

SINAD

SNR

PARAMETER

CONDITIONS

MIN

71

TYP

73.4

73.5

–91

92

MAX

UNITS

dB

l

Signal-to-(Noise + Distortion) Ratio

Signal-to-Noise Ratio

f

IN

f

IN

f

IN

f

IN

f

IN

f

IN

= 1kHz

71

dB

THD

Total Harmonic Distortion

Spurious Free Dynamic Range

Channel-to-Channel Isolation

Full Linear Bandwidth

= 1kHz

–77

dB

SFDR

= 1kHz, First 5 Harmonics

79

dB

= 1kHz

–109

700

25

dB

kHz

MHz

ns

–3dB Input Linear Bandwidth

Aperture Delay

(Note 10)

13

Transient Response

Full-Scale Step

240

ns

INTERNAL REFERENCE CHARACTERISTICS

The

l

denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at T = 25°C. (Notes 4)

A

PARAMETER

CONDITIONS

MIN

TYP

2.50

25

MAX

UNITS

V

l

V

Output Voltage

Output Tempco

Output Impedance

I

= 0

2.46

2.54

REF

OUT

I

ppm/°C

kΩ

REF

–0.1mA ≤ I

≤ 0.1mA

8

REF

OUT

Output Voltage

I

= 0

4.096

0.8

V

REFCOMP

OUT

Line Regulation

V

DD

= 4.75V to 5.25V

mV/V

REF

I²C INPUTS AND DIGITAL OUTPUTS

The

l

denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at T = 25°C. (Notes 4)

A

SYMBOL PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

High Level Input Voltage

2.85

V

IH

Low Level Input Voltage

1.5

IL

High Level Input Voltage for Address Pins A1, A0

Low Level Input Voltage for Address Pins A1, A0

4.75

V

IHA

ILA

0.25

10

V

R

Resistance from A1, A0 to V to Set Chip

Address Bit to 1

kꢁ

INH

INL

INF

DD

l

Resistance from A1, A0 to GND to Set Chip

Address Bit to 0

10

kꢁ

Resistance from A1, A0 to GND or V to Set

Chip Address Bit to Float

2

Mꢁ

DD

l

I

Digital Input Current

V

= V

DD

–10

10

ꢀA

V

I

IN

V

Hysteresis of Schmitt Trigger Inputs

Low Level Output Voltage (SDA)

(Note 8)

I = 3mA

0.25

HYS

OL

0.4

250

50

V

t

Output Fall Time V

to V

Bus Load C 10pF to 400pF (Note 11)

20 + 0.1C

B

ns

pF

OF

SP

IN(MIN)

IL(MAX)

B

Input Spike Suppression

C

External Capacitance Load on Chip Address Pins

(A1, A0) for Valid Float

10

CAX

23015f

4

LTC2301/LTC2305

POWER REQUIREMENTS

The

l

denotes the speciﬁcations which apply over the full operating temperature

range, otherwise speciﬁcations are at T = 25°C. (Note 4)

A

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

DD

Supply Voltage

4.75

5

5.25

V

l

I

Supply Current

Nap Mode

Sleep Mode

14ksps Sample Rate

SLP Bit = 0, Conversion Done

SLP Bit = 1, Conversion Done

2.3

225

7

3.5

400

15

mA

μA

DD

l

P

D

Power Dissipation

Nap Mode

Sleep Mode

14ksps Sample Rate

SLP Bit = 0, Conversion Done

SLP Bit = 1, Conversion Done

11.5

1.125

35

17.5

2

75

mW

μW

I²C TIMING CHARACTERISTICS ^The

l

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T = 25°C. (Note 4)

A

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

kHz

μs

l

f

t

SCL Clock Frequency

400

SCL

Hold Time (Repeated) Start Condition

Low Period of the SCL Pin

High Period of the SCL Pin

0.6

1.3

0.6

HD(SDA)

LOW

μs

HIGH

Set-Up Time for a Repeated Start

Condition

μs

SU(STA)

l

t

Data Hold Time

0

100

0.9

μs

ns

μs

HD(DAT)

Data Set-Up Time

SU(DAT)

Rise Time for SDA/SCL Signals

Fall Time for SDA/SCL Signals

Set-Up Time for Stop Condition

(Note 11)

20 + 0.1C

0.6

300

r

B

f

B

SU(STO)

BUF

Bus Free Time Between a Second Start

Condition

1.3

ADC TIMING CHARACTERISTICS ^The

l

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T = 25°C. (Note 4)

A

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

1.3

MAX

14

UNITS

ksps

μs

l

f

t

Throughput Rate (Successive Reads)

Conversion Time

SMPL

CONV

1.6

Acquisition Time

(Note 8)

240

ns

ACQ

REFCOMP Wakeup Time (Note 12)

C

= 10μF, C = 2.2μF

200

ms

REFWAKE

REFCOMP

REF

23015f

5

LTC2301/LTC2305

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.

Note 7: Full-scale bipolar error is the worst-case of –FS or FS untrimmed

deviation from ideal ﬁrst and last code transitions and includes the effect

of offset error. Unipolar full-scale error is the deviation of the last code

transition from ideal and includes the effect of offset error.

Note 2: All voltage values are with respect to ground.

Note 8: Guaranteed by design, not subject to test.

Note 3: When these pin voltages are taken below ground or above V

,

Note 9: All speciﬁcations in dB are referred to a full-scale 2.048V input

with a 2.5V reference voltage.

Note 10: Full linear bandwidth is deﬁned as the full-scale input frequency

DD

they will be clamped by internal diodes. These products can handle input

currents greater than 100mA below ground or above V without latchup.

DD

Note 4: V = 5V, f

= 14kHz, internal reference unless otherwise

at which the SINAD degrades to 60dB or 10 bits of accuracy.

DD

SMPL

noted.

Note 11: C = capacitance of one bus line in pF (10pF ≤ C ≤ 400pF)

B

Note 5: Integral nonlinearity is deﬁned as the deviation of a code from a

straight line passing through the actual endpoints of the transfer curve.

The deviation is measured from the center of the quantization band.

Note 12: REFCOMP wakeup time is the time required for the REFCOMP pin

to settle within 0.5LSB at 12-bit resolution of its ﬁnal value after waking up

from sleep mode.

Note 6: Bipolar zero error is the offset voltage measured from –0.5LSB

when the output code ﬂickers between 0000 0000 0000 and 1111 1111

1111. Unipolar zero error is the offset voltage measured from 0.5LSB

when the output code ﬂickers between 0000 0000 0000 and 0000 0000

0001.

Note 13: High temperatures degrade operating lifetimes. Operating lifetime

is derated at temperatures greater than 105°C.

23015f

6

LTC2301/LTC2305

TYPICAL PERFORMANCE CHARACTERISTICS

(LTC2301) T = 25°C, V = 5V, f

= 14ksps, unless otherwise noted.

A

DD

SMPL

Integral Nonlinearity

vs Output Code

Differential Nonlinearity

vs Output Code

1kHz Sine Wave

8192 Point FFT Plot

1.00

0.75

1.00

0

–10

–20

–30

SNR = 73.2 dB

SINAD = 73.1 dB

THD = –80dB

0.75

0.50

–40

–50

–60

0.25

–70

0.00

–80

–90

–0.25

–0.50

–0.75

–1.00

–0.25

–0.50

–0.75

–1.00

–100

–110

–120

–130

–140

0

1024

2048

3072

4096

0

1024

2048

3072

4096

0

1

2

3

4

5

6

7

OUTPUT CODE

FREQUENCY (kHz)

23015 G01

23015 G02

23015 G03

Supply Current

vs Sampling Frequency

Offset Error vs Temperature

Full-Scale Error vs Temperature

2.5

2.0

1.5

1.0

0.5

0

4

2

1.5

1.0

UNIPOLAR

BIPOLAR

0

0.5

BIPOLAR

–2

–4

–6

0.0

UNIPOLAR

–0.5

–1.0

0.1

1

10

100

–50 –25

0

25

50

75 100 125

–50 –25

0

25

50

75 100 125

SAMPLING FREQUENCY (ksps)

TEMPERATURE (°C)

23015 G04

23015 G06

23015 G05

Analog Input Leakage Current

vs Temperature

Supply Current vs Temperature

Sleep Current vs Temperature

2.4

2.2

1.8

1.6

1.4

10

8

1000

900

800

700

600

500

400

300

200

100

0

6

4

2

0

–50 –25

0

25

50

75 100 125

–50 –25

0

25

50

75 100 125

–50 –25

0

25

50

75 100 125

TEMPERATURE (°C)

23015 G07

23015 G08

23015 G09

23015f

7

LTC2301/LTC2305

TYPICAL PERFORMANCE CHARACTERISTICS

(LTC2305) T = 25°C, V = 5V, f

= 14ksps, unless otherwise noted.

A

DD

SMPL

Integral Nonlinearity

vs Output Code

Differential Nonlinearity

vs Output Code

1kHz Sine Wave

8192 Point FFT Plot

1.00

0.75

0

–10

–20

–30

–40

SNR = 73.2 dB

SINAD = 73.1 dB

THD = –80dB

0.75

0.50

–50

–60

0.25

0.00

–70

0.00

–80

–90

–0.25

–0.50

–0.75

–1.00

–0.25

–0.50

–0.75

–1.00

–100

–110

–120

–130

–140

0

1024

2048

3072

4096

0

1024

2048

3072

4096

0

1

2

3

4

5

6

7

OUTPUT CODE

FREQUENCY (kHz)

23015 G11

23015 G10

23015 G12

Supply Current

vs Sampling Frequency

Offset Error vs Temperature

Full-Scale Error vs Temperature

4

1.0

0.5

2.5

2.0

1.5

1.0

0.5

0

2

0

BIPOLAR

UNIPOLAR

–2

–4

–6

0.0

UNIPOLAR

–0.5

–50 –25

0

25

50

75 100 125

–50 –25

0

25

50

75 100 125

0.1

1

10

100

TEMPERATURE (°C)

SAMPLING FREQUENCY (ksps)

23015 G15

23015 G14

23015 G13

Analog Input Leakage Current

vs Temperature

Supply Current vs Temperature

Sleep Current vs Temperature

2.4

2.2

1.8

1.6

1.4

1000

900

800

700

600

500

400

300

200

100

0

10

8

6

4

CH(ON)

CH(OFF)

2

0

–50 –25

0

25

50

75 100 125

–50 –25

0

25

50

75 100 125

–50 –25

0

25

50

75 100 125

TEMPERATURE (°C)

23015 G16

23015 G18

23015 G17

23015f

8

LTC2301/LTC2305

PIN FUNCTIONS

(LTC2301)

GND (Pins 1, 4, 9): Ground. All GND pins must be con-

REFCOMP (Pin 8): Reference Buffer Output. Bypass to

GND with a 10μF low ESR ceramic or tantalum and 0.1μF

ceramic capacitor in parallel. Nominal output voltage is

4.096V. The internal reference buffer driving this pin is

nected to a solid ground plane.

2

SDA (Pin 2): Bidirectional Serial Data Line of the I C In-

terface. Intransmittermode(Read), theconversionresult

is output at the SDA pin, while in receiver mode (Write),

disabled by grounding V , allowing REFCOMP to be

REF

overdriven by an external source (see Figure 5c).

the D word is input at the SDA pin to conﬁgure the ADC.

IN

The pin is high impedance during the data input mode and

V

(Pin10): 5VAnalogSupply. TherangeofV is4.75V

DD DD

to 5.25V. Bypass V to GND with a 0.1μF ceramic and a

is an open drain output (requires an appropriate pull-up

DD

device to V ) during the data output mode.

10μF low ESR ceramic or tantalum capacitor in parallel.

DD

2

SCL (Pin 3): Serial Clock Pin of the I C Interface. The

AD1 (Pin 11): Chip Address Control Pin. This pin is con-

LTC2301 can only act as a slave and the SCL pin only ac-

cepts an external serial clock. Data is shifted into the SDA

pinontherisingedgesoftheSCLclockandoutputthrough

the SDA pin on the falling edges of the SCL clock.

ﬁgured as a three-state (LOW, HIGH, Floating) address

2

control bit for the device I C address. See Table 2 for

address selection.

AD0 (Pin 12): Chip Address Control Pin. This pin is con-

+

–

IN+, IN– (Pins 5, 6): Positive (IN ) and negative (IN )

ﬁgured as a three-state (LOW, HIGH, Floating) address

2

differential analog inputs.

control bit for the device I C address. See Table 2 for

address selection.

V

REF

(Pin 7): 2.5V Reference Output. Bypass to GND with

a minimum 2.2μF tantalum capacitor or low ESR ceramic

capacitor. The internal reference may be overdriven by an

external 2.5V reference at this pin.

GND (Pin 13 – DFN Package Only): Exposed Pad Ground.

Must be soldered directly to ground plane.

23015f

9

LTC2301/LTC2305

PIN FUNCTIONS

(LTC2305)

GND (Pins 1, 4, 9): Ground. All GND pins must be con-

REFCOMP (Pin 8): Reference Buffer Output. Bypass to

GND with a 10μF low ESR ceramic or tantalum and 0.1μF

ceramic capacitor in parallel. Nominal output voltage is

4.096V. The internal reference buffer driving this pin is

nected to a solid ground plane.

2

SDA (Pin 2): Bidirectional Serial Data Line of the I C In-

terface. In transmitter mode (Read), the conversion result

is output at the SDA pin, while in receiver mode (Write),

disabled by grounding V , allowing REFCOMP to be

REF

overdriven by an external source (see Figure 5c).

the D word is input at the SDA pin to conﬁgure the ADC.

IN

The pin is high impedance during the data input mode and

V

(Pin10): 5VAnalogSupply. TherangeofV is4.75V

DD DD

to 5.25V. Bypass V to GND with a 0.1μF ceramic and a

is an open drain output (requires an appropriate pull-up

DD

device to V ) during the data output mode.

10μF low ESR ceramic or tantalum capacitor in parallel.

DD

2

SCL (Pin 3): Serial Clock Pin of the I C Interface. The

AD1 (Pin 11): Chip Address Control Pin. This pin is con-

LTC2305 can only act as a slave and the SCL pin only ac-

cepts an external serial clock. Data is shifted into the SDA

pinontherisingedgesoftheSCLclockandoutputthrough

the SDA pin on the falling edges of the SCL clock.

ﬁgured as a three-state (LOW, HIGH, Floating) address

2

control bit for the device I C address. See Table 2 for

address selection.

AD0 (Pin 12): Chip Address Control Pin. This pin is con-

CH0-CH1 (Pins 5, 6): Channel 0 and Channel 1 Analog

Inputs. CH0 and CH1 can be conﬁgured as single-ended

or differential input channels. See the Analog Input Multi-

plexer section.

ﬁgured as a three-state (LOW, HIGH, Floating) address

2

control bit for the device I C address. See Table 2 for

address selection.

GND (Pin 13 – DFN Package Only): Exposed Pad Ground.

Must be soldered directly to ground plane.

V

REF

(Pin 7): 2.5V Reference Output. Bypass to GND with

a minimum 2.2μF tantalum capacitor or low ESR ceramic

capacitor. The internal reference may be overdriven by an

external 2.5V reference at this pin.

23015f

10

LTC2301/LTC2305

FUNCTIONAL BLOCK DIAGRAM

V

DD

AD1

AD0

LTC2301

LTC2305

+

–

CH0(IN )

SCL

SDA

2

ANALOG

INPUT

MUX

12-BIT

SAR ADC

I C

PORT

–

CH1(IN )

V

REF

8k

INTERNAL

2.5V REF

GAIN = 1.6384x

PIN NAMES IN PARENTHESES

REFER TO LTC2301

REFCOMP

GND

23015 BD

TIMING DIAGRAM

2

Deﬁnition of Timing for Fast/Standard Mode Devices on the I C Bus

SDA

SCL

t

SU(DAT)

t

BUF

LOW

HD(SDA)

r

t

f

t

SP

t

f

r

t

SU(STO)

HD(SDA)

SU(STA)

t

HIGH

S

Sr

P

S

HD(DAT)

23015 TD

S = START, Sr = REPEATED START, P = STOP

23015f

11

LTC2301/LTC2305

APPLICATIONS INFORMATION

Overview

(a 12-bit data word) that represent the sampled analog

input are loaded into 12 output latches that allow the data

The LTC2301/LTC2305 are low noise, 1-/2-channel, 12-bit

successive approximation register (SAR) A/D converters

2

to be shifted out via the I C interface.

2

with an I C compatible serial interface. The LTC2301/

Programming the LTC2301 and LTC2305

LTC2305 both include a precision internal reference. The

LTC2305 includes a 2-channel analog input multiplexer

(MUX)whiletheLTC2301includesaninputMUXthatallows

the polarity of the differential input to be selected. These

ADCs can operate in either unipolar or bipolar mode. Uni-

polarmodeshouldbeusedforsingle-endedoperationwith

the LTC2305, since single-ended input signals are always

referenced to GND. A sleep mode option is also provided

to further reduce power during inactive periods.

ThesoftwarecompatibleLTC2301/LTC2305/LTC2309fam-

ily features a 6-bit D word to program various modes of

IN

operation. Don’t care bits (X) are ignored. The SDA data

bits are loaded on the rising edge of SCL during a write

operation, with the S/D bit loaded on the ﬁrst rising edge

and the SLP bit on the sixth rising edge (see Figure 7b

2

in the I C Interface section). The input data word for the

LTC2305 is deﬁned as follows:

The LTC2301/LTC2305 communicate through a 2-wire

2

S/D O/S

X

UNI SLP

I C compatible serial interface. Conversions are initiated

by signaling a stop condition after the part has been

successfully addressed for a read/write operation. The

device will not acknowledge an external request until the

conversion is ﬁnished. After a conversion is ﬁnished, the

device is ready to accept a read/write request. Once the

LTC2301/LTC2305 is addressed for a read operation, the

device begins outputting the conversion result under the

control of the serial clock (SCL). There is no latency in the

conversionresult.Thereare12bitsofoutputdatafollowed

by four trailing zeros. Data is updated on the falling edges

of SCL, allowing the user to reliably latch data on the ris-

ing edge of SCL. A write operation may follow the read

operation by using a repeat start or a stop condition may

be given to start a new conversion. By selecting a write

S/D = SINGLE-ENDED/DIFFERENTIAL BIT

O/S = ODD/SIGN BIT

UNI = UNIPOLAR/BIPOLAR BIT

SLP = SLEEP MODE BIT

For the LTC2301, the input word is deﬁned as:

X

O/S

X

UNI SLP

Analog Input Multiplexer

The analog input MUX is programmed by the S/D and

O/S bits of the D word for the LTC2305 and the O/S

IN

operation, these ADCs can be programmed by a 6-bit D

IN

bit of the D word for the LTC2301. Table 1 and Table 2

IN

word. The D word conﬁgures the MUX and programs

IN

list the MUX conﬁgurations for all combinations of the

conﬁguration bits. Figure 1a shows several possible MUX

conﬁgurations and Figure 1b shows how the MUX can be

reconﬁgured from one conversion to the next.

various modes of operation.

Duringaconversion, theinternal12-bitcapacitivecharge-

redistribution DAC output is sequenced through a succes-

siveapproximationalgorithmbytheSARstartingfromthe

mostsigniﬁcantbit(MSB)totheleastsigniﬁcantbit(LSB).

The sampled input is successively compared with binary

weighted charges supplied by the capacitive DAC using

a differential comparator. At the end of a conversion, the

DAC output balances the analog input. The SAR contents

Table 1. Channel Conﬁguration for the LTC2305

S/D

0

O/S

0

CH0

+

CH1

–

0

1

–

+

1

0

+

1

+

23015f

12

LTC2301/LTC2305

APPLICATIONS INFORMATION

Table 2. Channel Conﬁguration for the LTC2301

Driving the Analog Inputs

O/S

0

IN+

+

IN–

–

The analog inputs of the LTC2301/LTC2305 are easy to

drive. Each of the analog inputs of the LTC2305 (CH0 and

CH1) can be used as single-ended input relative to GND

or as a differential pair. The analog inputs of the LTC2301

1

–

+

–

(IN , IN ) are always conﬁgured as a differential pair.

Regardless of the MUX conﬁguration, the “+” and “–“

inputs are sampled at the same instant. Any unwanted

signal that is common to both inputs will be reduced by

the common mode rejection of the sample-and-hold cir-

cuit. The inputs draw only one small current spike while

chargingthesample-and-holdcapacitorsduringtheacquire

mode. In conversion mode, the analog inputs draw only

a small leakage current. If the source impedance of the

drivingcircuitislow, theADCinputscanbedrivendirectly.

Otherwise, more acquisition time should be allowed for a

source with higher impedance.

1 Differential

2 Single-Ended

CH0

CH1

+ (

)

CH0

CH1

+

–

{

(

+

–

LTC2305

GND (

)

–

1 Differential

CH0

CH1

+ (–)

{

– (+)

Input Filtering

The noise and distortion of the input ampliﬁer and other

circuitry must be considered since they will add to the

ADC noise and distortion. Therefore, noisy input circuitry

should be ﬁltered prior to the analog inputs to minimize

noise. A simple 1-pole RC ﬁlter is sufﬁcient for many

applications.

LTC2301

23015 F01a

Figure 1a. Example MUX Conﬁgurations

TheanaloginputsoftheLTC2301/LTC2305canbemodeled

as a 55pF capacitor (C ) in series with a 100Ω resistor

IN

(R ) as shown in Figure 2a. C gets switched to the

ON

IN

selected input once during each conversion. Large ﬁlter

RC time constants will slow the settling of the inputs. It

is important that the overall RC time constants be short

enough to allow the analog inputs to completely settle to

1st Conversion

2nd Conversion

+

CH0

CH1

–

+

CH0

CH1

12-bit resolution within the acquisition time (t ) if DC

{

ACQ

–

accuracy is important.

LTC2305

When using a ﬁlter with a large C

value (e.g. 1μF),

FILTER

GND (

)

–

theinputsdonotcompletelysettleandthecapacitiveinput

23015 F01b

switchingcurrentsareaveragedintoanetDCcurrent(I ).

Inthiscase, theanaloginputcanbemodeledbyanequiva-

DC

Figure 1b. Changing the MUX Assignment “On the Fly”

lent resistance (R = 1/(f

• C )) in series with an

EQ

SMPL

IN

ideal voltage source (V

/2) as shown in Figure 2b.

REFCOMP

23015f

13

LTC2301/LTC2305

APPLICATIONS INFORMATION

ThemagnitudeoftheDCcurrentisthenapproximatelyI

and from damage that may occur during soldering. Metal

ﬁlm surface mount resistors are much less susceptible

to both problems.

DC

=(V –V

IN

/2)/R ,whichisroughlyproportionalto

IN

REFCOMP

EQ

V . To prevent large DC drops across the resistor R

,

FILTER

a ﬁlter with a small resistor and large capacitor should be

Dynamic Performance

chosen. When running at the maximum throughput rate

of 14ksps, the input current equals 1.5μA at V = 4.096V,

IN

Fast Fourier Transform (FFT) test techniques are used to

test the ADC’s frequency response, distortion and noise

at the rated throughput. By applying a low distortion

sine wave and analyzing the digital output using an FFT

algorithm, the ADC’s spectral content can be examined

for frequencies outside the fundamental.

whichamountstoafull-scaleerrorof0.5LSBswhenusing

a ﬁlter resistor (R

) of 333Ω. Applications requiring

FILTER

lower sample rates can tolerate a larger ﬁlter resistor for

the same amount of full-scale error.

Figures 3a and 3b show respective examples of input

ﬁltering for single-ended and differential inputs. For the

single-ended case in Figure 4a, a 50Ω source resistor

and a 2000pF capacitor to ground on the input will limit

the input bandwidth to 1.6MHz. High quality capacitors

and resistors should be used in the RC ﬁlter since these

components can add distortion. NPO and silver mica type

dielectriccapacitorshaveexcellentlinearity.Carbonsurface

mount resistors can generate distortion from self heating

Signal-to-Noise and Distortion Ratio (SINAD)

The signal-to-noise and distortion ratio (SINAD) is the

ratiobetweentheRMSamplitudeofthefundamentalinput

frequency to the RMS amplitude of all other frequency

components at the A/D output. The output is band-limited

tofrequenciesfromaboveDCandbelowhalfthesampling

50ꢁ

ANALOG

INPUT

CH0, CH1

INPUT

2000pF

CH0, CH1,

R

=

LTC2301

LTC2305

ON

+

–

LTC2305

IN , IN

R

SOURCE

100ꢁ

V

IN

C

=

IN

REFCOMP

C

FILTER

55pF

10μF

0.1μF

23015 F03a

23015 F02a

Figure 2a. Analog Input Equivalent Circuit

Figure 3a. Optional RC Input Filtering for Single-Ended Input

1000pF

50ꢁ

INPUT

+

(CH0, CH1,

CH0, IN

I

+

–

DC

C

DIFFERENTIAL

R

FILTER

IN , IN )

LTC2301

ANALOG

INPUTS

1000pF

LTC2301

LTC2305

V

IN

LTC2305

–

50ꢁ

R

=

EQ

CH1, IN

FILTER

1/(f

• C )

IN

SMPL

+

V

/2

REFCOMP

–

REFCOMP

10μF

0.1μF

23015 F02b

23015 F03b

Figure 2b. Analog Input Equivalent

Circuit for Large Filter Capacitances

Figure 3b. Optional RC Input Filtering for Differential Inputs

23015f

14

LTC2301/LTC2305

APPLICATIONS INFORMATION

frequency. Figure 4 shows a typical SINAD of 73.2dB with

a 14kHz sampling rate and a 1kHz input. A SNR of 73.3dB

can be achieved with the LTC2301/LTC2305.

a0.1ꢀFceramiccapacitorforbestnoiseperformance. The

internal reference buffer can also be overdriven from 1V

to V with an external reference at REFCOMP as shown

DD

in Figure 5c. To do so, V must be grounded to disable

REF

0

–10

–20

–30

–40

SNR = 73.2dB

the reference buffer. This will result in an input range of

SINAD = 73.1dB

THD = –80dB

0V to V

in unipolar mode and 0.5 • V

in

REFCOMP

bipolar mode.

REFCOMP

–50

–60

–70

–80

–90

R1

8k

V

REF

BANDGAP

2.5V

REFERENCE

–100

–110

–120

–130

–140

2.2μF

REFCOMP

4.096V

10μF

REFERENCE

AMP

+

0

1

2

3

4

5

6

7

FREQUENCY (kHz)

23015 F04

R2

0.1μF

Figure 4. 1kHz Sine Wave 8192 Point FFT Plot

R3

GND

LTC2301

LTC2305

Total Harmonic Distortion (THD)

23015 F05a

Total Harmonic Distortion (THD) is the ratio of the RMS

sumofallharmonicsoftheinputsignaltothefundamental

itself. The out-of-band harmonics alias into the frequency

Figure 5a. LTC2301/LTC2305 Reference Circuit

bandbetweenDCandhalfthesamplingfrequency(f

THD is expressed as:

/2).

SMPL

5V

0.1μF

V

IN

2

V₂+ V₃+ V₄...+ V_N

LT1790A-2.5

V

THD= 20log

V₁

V

OUT

REF

2.2μF

0.1μF

LTC2301

LTC2305

where V1 is the RMS amplitude of the fundamental fre-

REFCOMP

quencyandV2throughV aretheamplitudesofthesecond

N

+

10μF

through Nth harmonics.

GND

Internal Reference

23015 F05b

The LTC2301/LTC2305 have an on-chip, temperature

compensated bandgap reference that is factory trimmed

to 2.5V (Refer to Figure 5a). It is internally connected

Figure 5b. Using the LT1790A-2.5 as an External Reference

to a reference ampliﬁer and is available at V

(Pin 7).

5V

REF

V

should be bypassed to GND with a 2.2ꢀF tantalum

REF

V

REF

V

IN

capacitor to minimize noise. An 8k resistor is in series

with the output so that it can be easily overdriven by an

external reference if more accuracy and/or lower drift are

required as shown in Figure 5b. The reference ampliﬁer

0.1μF

LTC2301

LTC2305

LT1790A-4.096

V

OUT

REFCOMP

+

0.1μF

10μF

GND

gains the V

voltage by 1.638 to 4.096V at REFCOMP.

REF

23015 F05c

To compensate the reference ampliﬁer, bypass REFCOMP

with a 10ꢀF ceramic or tantalum capacitor in parallel with

Figure 5c. Overdriving REFCOMP Using the LT1790A-4.096

23015f

15

LTC2301/LTC2305

APPLICATIONS INFORMATION

Internal Conversion Clock

Start Condition

Stop Condition

SDA

SCL

The internal conversion clock is factory trimmed to

achieve a typical conversion time (t

) of 1.3ꢀs and a

SDA

SCL

CONV

S

P

maximum conversion time of 1.6ꢀs over the full operating

temperature range.

23015 F06

2

I C Interface

Figure 6. Timing Diagrams of Start and Stop Conditions

2

The LTC2301/LTC2305 communicate through an I C in-

2

terface. The I C interface is a 2-wire open-drain interface

When the bus is in use, it stays busy if a Repeated Start

(Sr)isgeneratedinsteadofaStopcondition.TheRepeated

Start timing is functionally identical to the Start and is

used for writing and reading from the device before the

initiation of a new conversion.

supporting multiple devices and multiple masters on a

single bus. The connected devices can only pull the serial

data line (SDA) low and can never drive it high. SDA is

required to be externally connected to the supply through

a pull-up resistor. When the data line is not being driven

low, it is high. Data on the I C bus can be transferred at

rates up to 100kbits/s in the standard mode and up to

400kbits/s in the fast mode.

2

Data Transferring

2

After the Start condition, the I C bus is busy and data

transfer can begin between the master and the addressed

slave. Data is transferred over the bus in groups of nine

bits, one byte followed by one acknowledge (ACK) bit.

The master releases the SDA line during the ninth SCL

clock cycle. The slave device can issue an ACK by pulling

SDA low or issue a Not Acknowledge (NAK) by leaving

the SDA line high impedance (the external pull-up resistor

will hold the line high). Change of data only occurs while

the SCL line is low.

2

Each device on the I C bus is recognized by a unique

address stored in the device and can only operate either

as a transmitter or receiver, depending on the function of

the device. A device can also be considered as a master

or a slave when performing data transfers. A master is

the device which initiates a data transfer on the bus and

generates the clock signals to permit the transfer. Devices

addressed by the master are considered slaves.

The LTC2301/LTC2305 can only be addressed as slaves.

Data Format

Once addressed, they can receive conﬁguration bits (D

IN

word)ortransmitthelastconversionresult.Theserialclock

line (SCL) is always an input to the LTC2301/LTC2305 and

the serial data line (SDA) is bidirectional. These devices

support the standard mode and the fast mode for data

transfer speeds up to 400kbits/s (see Timing Diagram

After a Start condition, the master sends a 7-bit address

followed by a read/write (R/W) bit. The R/W bit is 1 for

a read request and 0 for a write request. If the 7-bit

address matches one of the LTC2301/LTC2305’s 9 pin-

selectable addresses (see Table 2), the ADC is selected.

When the ADC is addressed during a conversion, it will

not acknowledge R/W requests and will issue a NAK by

leaving the SDA line high. If the conversion is complete,

the LTC2301/LTC2305 issues an ACK by pulling the SDA

line low. The LTC2301/LTC2305 has two registers. The

12-bit wide output register contains the last conversion

result. The 6-bit wide input register conﬁgures the input

MUX and the operating mode of the ADC.

2

section for deﬁnition of the I C timing).

The Start and Stop Conditions

Referring to Figure 6, a Start (S) condition is generated

by transitioning SDA from high to low while SCL is high.

The bus is considered to be busy after the Start condition.

When the data transfer is ﬁnished, a Stop (P) condition

is generated by transitioning SDA from low to high while

SCL is high. The bus is free after a Stop condition is gen-

erated. Start and Stop conditions are always generated

by the master.

23015f

16

LTC2301/LTC2305

APPLICATIONS INFORMATION

Output Data Format

result. The remaining four bits are zero. Figures 13 and 14

arethetransfercharacteristicsforthebipolarandunipolar

modes. Data is output on the SDA line in 2’s complement

format for bipolar readings and in straight binary for

unipolar readings.

The output register contains the last conversion result.

After each conversion is completed, the device automati-

cally enters either nap or sleep mode depending on the

setting of the SLP bit (see Nap Mode and Sleep Mode

sections). When the LTC2301/LTC2305 is addressed for

a read operation, it acknowledges by pulling SDA low and

acts as a transmitter. The master/receiver can read up to

two bytes from the LTC2301/LTC2305. After a complete

read operation of 2 bytes, a Stop condition is needed to

initiate a new conversion. The device will NAK subsequent

read operations while a conversion is being performed.

Input Data Format

When the LTC2301/LTC2305 is addressed for a write

operation, it acknowledges by pulling SDA low during

the low period before the 9th cycle and acts as a receiver.

The master/transmitter can then send 1 byte to program

the device. The input byte consists of the 6-bit D word

IN

followed by two bits that are ignored by the ADC and are

considered don’t cares (X) (see Figure 7b). The input bits

are latched on the rising edge of SCL during the write

operation.

The data output stream is 16 bits long and is shifted out

on the falling edges of SCL (see Figure 7a). The ﬁrst bit

is the MSB and the 12th bit is the LSB of the conversion

1

2

3

4

5

6

7

8

9

1

2

3

4

5

6

7

8

9

• • •

SCL

SDA

A6

A5

A4

A3

A2

A1

A0 R/W

B11 B10 B9

B8

B7

B6

B5 B4

• • •

START BY

MASTER

ACK BY

ADC

ACK BY

MASTER

MOST SIGNIFICANT DATA BYTE

READ 1 BYTE

ADDRESS FRAME

1

2

3

4

5

6

7

8

9

SCL

• • •

(CONTINUED)

CONVERSION

INITIATED

SDA

(CONTINUED)

STOP

BY MASTER

B3

B2

B1

B0

NAK BY

MASTER

LEAST SIGNIFICANT DATA BYTE

READ 1 BYTE

23015 F07a

Figure 7a. Timing Diagram for Reading from the LTC2301/LTC2305

NOTE: S/D BIT IS A DON’T CARE (X) FOR THE LTC2301

1

2

3

4

5

6

7

8

9

1

2

3

4

5

6

7

8

9

SCL

SDA

CONVERSION

INITIATED

A6

A5

A4

A3

A2

A1

A0 R/W

S/D O/S

X

UNI SLP

X

STOP BY

MASTER

START BY

MASTER

ACK BY

ADC

ACK BY

ADC

D

WORD

IN

23015 F07b

ADDRESS FRAME

WRITE 1 BYTE

Figure 7b. Timing Diagram for Writing to the LTC2301/LTC2305

23015f

17

LTC2301/LTC2305

APPLICATIONS INFORMATION

Table 2. Address Assignment

After power-up, the ADC initiates an internal reset cycle

which sets the D word to all 0s (S/D=O/S=UNI=SLP=0).

AD1

LOW

AD0

LOW

ADDRESS

0001000

0001001

0001010

0001011

0011000

0011001

0011010

0011011

0101000

IN

A write operation may be performed if the default state

of the ADC’s conﬁguration is not desired. Otherwise, the

ADC must be properly addressed and followed by a Stop

condition to initiate a conversion.

LOW

FLOAT

HIGH

FLOAT

LOW

FLOAT

HIGH

Initiating a New Conversion

LOW

The LTC2301/LTC2305 awakens from either nap or sleep

when properly addressed for a read/write operation. A

Stop command may then be issued after performing the

read/write operation to trigger a new conversion.

FLOAT

HIGH

Continuous Read

Issuing a Stop command after the 8th SCL clock pulse of

theaddressframeandbeforethecompletionofaread/write

operation will also initiate new conversion, but the output

result may not be valid due to lack of adequate acquisition

time (see Acquisition section).

In applications where the same input channel is sampled

each cycle, conversions can be continuously performed

and read without a write cycle (see Figure 8). The D word

IN

remains unchanged from the last value written into the

device. If the device has not been written to since power-

LTC2301/LTC2305 Address

up, theD worddefaultstoall0s(S/D=O/S=UNI=SLP=0).

IN

At the end of a read operation, a Stop condition may be

given to start a new conversion. At the conclusion of the

conversion cycle, the next result may be read using the

method described above. If the conversion cycle is not

concluded and a valid address selects the device, the

LTC2301/LTC2305 generates a NAK signal indicating the

conversion cycle is in progress.

The LTC2301/LTC2305 have two address pins (AD0 and

AD1) that may be tied high, low or left ﬂoating to enable

one of the 9 possible addresses (see Table 2).

In addition to the conﬁgurable addresses listed in Table 2,

the LTC2301/LTC2305 also contain a global address

(1110111) which may be used for synchronizing multiple

2

LTC2301/LTC2305s or other I C LTC230X SAR ADCs (see

Synchronizing Multiple LTC2301/LTC2305s with Global

Address Call section).

S

7-BIT ADDRESS

NAP

R

ACK

READ

P

S

7-BIT ADDRESS

NAP

R

ACK

READ

P

CONVERSION

DATA OUTPUT

CONVERSION

DATA

OUTPUT

CONVERSION

23015 F08

Figure 8. Consecutive Reading with the Same Conﬁguration

23015f

18

LTC2301/LTC2305

APPLICATIONS INFORMATION

Continuous Read/Write

the request. The master then sends a write byte (optional)

followed by the Stop command. This will update the

channel selection (optional) and simultaneously initiate

a conversion for all ADCs on the bus (see Figure 10).

Inordertosynchronizemultipleconverterswithoutchang-

ing the channel, a Stop command may be issued after

acknowledgement of the global write command. Global

read commands are not allowed and the converters will

NAK a global read request.

Once the conversion cycle is complete, the LTC2301/

LTC2305 can be written to and then read from using the

RepeatedStart(Sr)command.Figure9showsacyclewhich

begins with a data Write, a repeated Start, followed by a

Read and concluded with a Stop command. The following

conversionbeginsafterall16bitsarereadoutofthedevice

or after a Stop command. The following conversion will

be performed using the newly programmed data.

Nap Mode

Synchronizing Multiple LTC2301/LTC2305s with a

Global Address Call

The ADCs enter nap mode after a conversion is complete

(t ) if the SLP bit is set to a logic 0. The supply current

CONV

In applications where several LTC2301/LTC2305s or other

decreases to 225ꢀA in nap mode between conversions,

thereby reducing the average power dissipation as the

sampleratedecreases.Forexample,theLTC2301/LTC2305

draw an average of 300μA at a 1ksps sampling rate. The

2

I C SAR ADCs from Linear Technology Corporation are

2

used on the same I C bus, all converters can be synchro-

nized through the use of a global address call. Prior to

issuing the global address call, all converters must have

completed a conversion cycle. The master then issues a

Start, followed by the global address 1110111, and a write

request. All converters will be selected and acknowledge

LTC2301/LTC2305 keep only the reference (V ) and

REF

reference buffer (REFCOMP) circuitry active when in nap

mode.

S

7-BIT ADDRESS

NAP

W

ACK

WRITE

Sr

7-BIT ADDRESS

CONVERSION

R

ACK

READ

P

CONVERSION

DATA OUTPUT

DATA

OUTPUT

CONVERSION

23015 F09

Figure 9. Write, Read, Start Conversion

SCL

SDA

LTC2301/LTC2305

S

GLOBAL ADDRESS

NAP

W

ACK

WRITE (OPTIONAL)

P

CONVERSION

DATA OUTPUT

CONVERSION OF ALL LTC2301/05s

23015 F10

Figure 10. Synchronize Multiple LTC2301/LTC2305s with a Global Address Call

23015f

19

LTC2301/LTC2305

APPLICATIONS INFORMATION

Sleep Mode

performed, acquisition of the input signal begins on the

rising edge of the 9th clock pulse following the address

frame as shown in Figure 12a.

The ADCs enter sleep mode after a conversion is complete

(t ) if the SLP bit is set to a logic 1. The ADCs draw

CONV

only 7μA in sleep mode, provided that none of the digital

inputs are switching. When the LTC2301/LTC2305 are

properly addressed, the ADCs are released from sleep

If a write operation is being performed, acquisition of the

input signal begins on the falling edge of the sixth clock

cycle after the D word has been shifted in as shown in

IN

modeandrequire200ms(t

)towakeupandcharge

Figure 12b. The LTC2301/LTC2305 will acquire the signal

REFWAKE

the respective 2.2ꢀF and 10ꢀF bypass capacitors on the

fromtheinputchannelthatwasmostrecentlyprogrammed

V

and REFCOMP pins. A new conversion should not

bytheD word.Aminimumof240nsisrequiredtoacquire

REF

IN

be initiated before this time as shown in Figure 11.

the input signal before initiating a new conversion.

Acquisition

Board Layout and Bypassing

The LTC2301/LTC2305 begin acquiring the input signal at

different instances depending on whether a read or write

operation is being performed. If a read operation is being

Toobtainthebestperformance,aprintedcircuitboardwith

a solid ground plane is required. Layout for the printed

board should ensure digital and analog signal lines are

S

7-BIT ADDRESS

SLEEP

R/W

ACK

P

CONVERSION

t

CONVERSION

REFWAKE

23015 F11

Figure 11. Exiting Sleep Mode and Starting a New Conversion

1

2

3

4

5

6

7

8

9

1

2

SCL

SDA

ACQUISITION BEGINS

A6

A5

A4

A3

A2

A1

A0 R/W

B11 B10

23015 F12a

t

ACQ

Figure 12a. Timing Diagram Showing Acquisition During a Read Operation

5

6

7

8

9

1

2

3

4

5

6

7

8

9

SCL

SDA

ACQUISITION BEGINS

A2

A1

A0 R/W

S/D O/S

X

UNI SLP

X

23015 F12b

t

ACQ

Figure 12b. Timing Diagram Showing Acquisition During a Write Operation

23015f

20

LTC2301/LTC2305

APPLICATIONS INFORMATION

separated as much as possible. Care should be taken not

to run any digital signals alongside an analog signal. All

for the common return of these bypass capacitors is es-

sential to the low noise operation of the ADC. These traces

should be as wide as possible. See Figure 15a–15e for a

suggested layout.

analoginputsshouldbeshieldedbyGND.V ,REFCOMP

REF

and V should be bypassed to the ground plane as close

DD

to the pin as possible. Maintaining a low impedance path

011...111

111...111

111...110

BIPOLAR

ZERO

011...110

000...001

000...000

111...111

111...110

100...001

100...000

UNIPOLAR

011...111

ZERO

011...110

FS = 4.096V

1LSB = FS/2

FS = 4.096V

1LSB = FS/2

100...001

100...000

000...001

000...000

n

1LSB = 1mV

–1 0V

1

–FS/2

FS/2 – 1LSB

0V

FS – 1LSB

LSB

INPUT VOLTAGE (V)

23015 F13

23015 F14

Figure 13. Bipolar Transfer Characteristics (2’s Complement)

Figure 14. Unipolar Transfer Characteristics (Straight Binary)

Figure 15a. Top Silkscreen

23015f

21

LTC2301/LTC2305

APPLICATIONS INFORMATION

Figure 15c. Layer 2 Ground Plane

Figure 15b. Topside

Figure 15d. Layer 3 Power Plane

Figure 15e. Bottomside

23015f

22

LTC2301/LTC2305

PACKAGE DESCRIPTION

DE/UE Package

12-Lead Plastic DFN (4mm × 3mm)

(Reference LTC DWG # 05-08-1695)

0.40 ± 0.10

4.00 ±0.10

(2 SIDES)

R = 0.115

TYP

7

12

0.70 ±0.05

R = 0.05

TYP

3.30 ±0.05

1.70 ± 0.05

3.30 ±0.10

3.60 ±0.05

2.20 ±0.05

3.00 ±0.10

(2 SIDES)

1.70 ± 0.10

PIN 1

PIN 1 NOTCH

TOP MARK

(NOTE 6)

R = 0.20 OR

PACKAGE

OUTLINE

0.35 × 45°

CHAMFER

(UE12/DE12) DFN 0806 REV

D

6

1

0.25 ± 0.05

0.75 ±0.05

0.200 REF

0.25 ± 0.05

2.50 REF

0.50 BSC

2.50 REF

BOTTOM VIEW—EXPOSED PAD

0.00 – 0.05

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

NOTE:

1. DRAWING PROPOSED TO BE A VARIATION OF VERSION

(WGED) IN JEDEC PACKAGE OUTLINE M0-229

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION

ON THE TOP AND BOTTOM OF PACKAGE

MS Package

12-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1668 Rev Ø)

0.889 p 0.127

(.035 p .005)

5.23

(.206)

MIN

3.20 – 3.45

(.126 – .136)

4.039 p 0.102

(.159 p .004)

(NOTE 3)

0.65

0.42 p 0.038

(.0165 p .0015)

TYP

(.0256)

0.406 p 0.076

BSC

(.016 p .003)

12 11 10 9 8 7

REF

RECOMMENDED SOLDER PAD LAYOUT

DETAIL “A”

0o – 6o TYP

3.00 p 0.102

(.118 p .004)

(NOTE 4)

4.90 p 0.152

(.193 p .006)

0.254

(.010)

GAUGE PLANE

0.53 p 0.152

(.021 p .006)

1

2 3 4 5 6

0.86

(.034)

REF

1.10

(.043)

MAX

DETAIL “A”

0.18

(.007)

SEATING

PLANE

0.22 – 0.38

(.009 – .015)

TYP

0.1016 p 0.0508

(.004 p .002)

MSOP (MS12) 1107 REV Ø

0.650

(.0256)

BSC

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

23015f

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.

23

LTC2301/LTC2305

TYPICAL APPLICATION

Driving the LTC2305 with 10V Input Signals Using a Precision Attenuator

5V

IN

OUT

1μF

0.1μF

LT1790-2.5

5V

GND

10V

7

10μF

0.1μF

450k

50k

AD1 AD0

V

1.7k 1.7k

DD

8

9

150k

LTC2305

–

+

10

4pF

100ꢁ

47pF

450k

SCL

SDA

CONTROL

LOGIC

(FPGA, CPLD,

DSP, ETC)

6

CH0

CH1

ANALOG

INPUT

MUX

LT1991

+

–

2

12-BIT

SAR ADC

I C

1

2

3

PORT

450k

150k

50k

10V

INPUT

SIGNAL

4pF

INTERNAL

2.5V REF

V

REF

4

5

2.2μF

–10V

REFCOMP

GND

0.1μF

10μF

23015 TA02

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23015f

LT 0808 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

24

●

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


型号：	LTC2305HMSXTRPBF
厂家：	Linear
描述：	1-/2-Channel, 12-Bit ADCs with I2C Compatible Interface 单/双通道， 12位ADC， I2C兼容接口
文件：	总24页 (文件大小：957K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC2305HMSXTRPBF [Linear]

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