LINEAR TECHNOLOGY LTC2480 Technical data

FEATURES

■

Easy Drive Technology Enables Rail-to-Rail Inputs
with Zero Differential Input Current

■

Directly Digitizes High Impedance Sensors with
Full Accuracy

■

Programmable Gain from 1 to 256

■

Integrated Temperature Sensor

■

GND to VCC Input/Reference Common Mode Range

■

Programmable 50Hz, 60Hz or Simultaneous
50Hz/60Hz Rejection Mode

■

2ppm (0.25LSB) INL, No Missing Codes

■

1ppm Offset and 15ppm Full-Scale Error

■

Selectable 2x Speed Mode (15Hz Using Internal
Oscillator)

■

No Latency: Digital Filter Settles in a Single Cycle

■

Single Supply 2.7V to 5.5V Operation

■

Internal Oscillator

■

Available in a Tiny (3mm × 3mm) 10-Lead
DFN Package

U

APPLICATIO S

■

Direct Sensor Digitizer

■

Weight Scales

■

Direct Temperature Measurement

■

Strain Gauge Transducers

■

Instrumentation

■

Industrial Process Control

■

DVMs and Meters

LTC2480

16-Bit ∆Σ ADC with Easy Drive

Input Current Cancellation

U

DESCRIPTIO

The LTC®2480 combines a 16-bit plus sign No Latency ∆Σ
analog-to-digital converter with patented Easy DriveTM tech­nology. The patented sampling scheme eliminates dynamic
input current errors and the shortcomings of on-chip buff­ering through automatic cancellation of differential input
current. This allows large external source impedances and
input signals, with rail-to-rail input range to be directly digi­tized while maintaining exceptional DC accuracy.

The LTC2480 includes on-chip programmable gain, a
temperature sensor and an oscillator. The LTC2480 can be
configured to provide a programmable gain from 1 to 256
in 8 steps, measure an external signal or internal tempera­ture sensor and reject line frequencies. 50Hz, 60Hz or
simultaneous 50Hz/60Hz line frequency rejection can be
selected as well as a 2x speed-up mode.

The LTC2480 allows a wide common mode input range
(0V to V
reference can be as low as 100mV or can be tied directly
to VCC. The LTC2480 includes an on-chip trimmed oscil­lator eliminating the need for external crystals or oscilla­tors. Absolute accuracy and low drift are automatically
maintained through continuous, transparent, offset and
full-scale calibration.

, LTC and LT are registered trademarks of Linear Technology Corporation.
No Latency ∆Σ and Easy Drive are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Patent Pending.

) independent of the reference voltage. The

CC

TM

TYPICAL APPLICATIO

V

CC

SENSE

10k

10k

I

DIFF

= 0

1µF

V

IN

V

IN

V

REF

+

LTC2480

–

GND F

U

+FS Error vs R

80

VCC = 5V

= 5V

V

REF

60

+

= 3.75V

V

IN

–

= 1.25V

V

IN

40

= GND

1µF

SDI

V

CC

SDO

4-WIRE

SCK

SPI INTERFACE

CS

O

2480 TA01

F

O

= 25°C

T

A

20

0

–20

+FS ERROR (ppm)

–40

–60

–80

10 100 10k

1

R

SOURCE

CIN = 1µF

SOURCE

at IN+ and IN

1k

(Ω)

–

100k

2480 TA04

2480f

1

LTC2480

PACKAGE/ORDER I FOR ATIO

UU

W

WWWU

ABSOLUTE AXI U RATI GS

(Notes 1, 2)

Supply Voltage (VCC) to GND...................... – 0.3V to 6V

Analog Input Voltage to GND ....... –0.3V to (V

+ 0.3V)

CC

Reference Input Voltage to GND .. –0.3V to (VCC + 0.3V)

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

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

+ 0.3V)

CC

+ 0.3V)

CC

Operating Temperature Range

LTC2480C ................................................... 0°C to 70°C

LTC2480I ................................................ –40°C to 85°C

Storage Temperature Range ................ –65°C to 125°C

SDI

V

CC

V

REF

IN

IN

10-LEAD (3mm × 3mm) PLASTIC DFN

Consult LTC Marketing for parts specified with wider operating temperature ranges.
*The temperature grade is identified by a label on the shipping container.

TOP VIEW

1

2

11

3

+

4

–

5

DD PACKAGE

T

= 125°C, θJA = 43°C/ W

JMAX

EXPOSED PAD (PIN 11) IS GND

MUST BE SOLDERED TO PCB

10

9

8

7

6

F

O

SCK

GND

SDO

CS

ORDER PART

NUMBER

LTC2480CDD
LTC2480IDD

DD PART MARKING*

LBJY

UW

ELECTRICAL CHARACTERISTICS ( OR AL SPEED)

over the full operating temperature range, otherwise specifications are TA = 25°C. (Notes 3, 4)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Resolution (No Missing Codes) 0.1 ≤ V
Integral Nonlinearity 5V ≤ VCC ≤ 5.5V, V

2.7V ≤ VCC ≤ 5.5V, V
Offset Error 2.5V ≤ V
Offset Error Drift 2.5V ≤ V
Positive Full-Scale Error 2.5V ≤ V
Positive Full-Scale Error Drift 2.5V ≤ V

Negative Full-Scale Error 2.5V ≤ V
Negative Full-Scale Error Drift 2.5V ≤ V

Total Unadjusted Error 5V ≤ VCC ≤ 5.5V, V

5V ≤ VCC ≤ 5.5V, V

2.7V ≤ VCC ≤ 5.5V, V
Output Noise 5V ≤ VCC ≤ 5.5V, V
Internal PTAT Signal TA = 27°C 420 mV
Internal PTAT Temperature Coefficient 1.4 mV/°C
Programmable Gain ● 1 256

≤ VCC, –FS ≤ VIN ≤ +FS (Note 5) ● 16 Bits

REF

= 5V, V

REF

= 2.5V, V

REF

≤ VCC, GND ≤ IN+ = IN– ≤ VCC (Note 14) ● 0.5 2.5 µV

REF

≤ VCC, GND ≤ IN+ = IN– ≤ V

REF

≤ VCC, IN+ = 0.75V

REF

≤ VCC, IN+ = 0.75V

REF

≤ VCC, IN+ = 0.75V

REF

≤ VCC, IN+ = 0.75V

REF

= 2.5V, V

REF

= 5V, V

REF

= 2.5V, V

REF

= 5V, GND ≤ IN– = IN+ ≤ VCC (Note 13) 0.6 µV

REF

= 2.5V (Note 6) ● 2 10 ppm of V

IN(CM)

IN(CM)

= 1.25V (Note 6) 1 ppm of V

IN(CM)

CC

, IN– = 0.25V

REF

, IN– = 0.25V

REF

, IN– = 0.25V

REF

, IN– = 0.25V

REF

= 1.25V 15 ppm of V

IN(CM)

= 2.5V ppm of V

IN(CM)

REF

REF

REF

REF

= 1.25V ppm of V

The ● denotes specifications which apply

REF
REF

10 nV/°C

● 25 ppm of V

0.1 ppm of

● 25 ppm of V

0.1 ppm of

REF

/°C

V

REF

REF

/°C

V

REF

REF
REF
REF

RMS

2

2480f

LTC2480

ELECTRICAL CHARACTERISTICS (2x SPEED)

The ● denotes specifications which apply over the full

operating temperature range, otherwise specifications are TA = 25°C. (Notes 3, 4)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Resolution (No Missing Codes) 0.1 ≤ V
Integral Nonlinearity 5V ≤ VCC ≤ 5.5V, V

2.7V ≤ VCC ≤ 5.5V, V
Offset Error 2.5V ≤ V
Offset Error Drift 2.5V ≤ V
Positive Full-Scale Error 2.5V ≤ V
Positive Full-Scale Error Drift 2.5V ≤ V

Negative Full-Scale Error 2.5V ≤ V
Negative Full-Scale Error Drift 2.5V ≤ V

Output Noise 5V ≤ VCC ≤ 5.5V, V

≤ VCC, –FS ≤ VIN ≤ +FS (Note 5) ● 16 Bits

REF

= 5V, V

REF

= 2.5V, V

REF

≤ VCC, GND ≤ IN+ = IN– ≤ VCC (Note 14) ● 0.5 2 mV

REF

≤ VCC, GND ≤ IN+ = IN– ≤ V

REF

≤ VCC, IN+ = 0.75V

REF

≤ VCC, IN+ = 0.75V

REF

≤ VCC, IN+ = 0.75V

REF

≤ VCC, IN+ = 0.75V

REF

= 5V, GND ≤ IN– = IN+ ≤ VCC (Note 13) 0.84 µV

REF

= 2.5V (Note 6) ● 2 10 ppm of V

IN(CM)

= 1.25V (Note 6) 1

IN(CM)

CC

, IN– = 0.25V

REF

, IN– = 0.25V

REF

, IN– = 0.25V

REF

, IN– = 0.25V

REF

REF

REF

REF

REF

100 nV/°C

● 25 ppm of V

0.1 ppm of

● 25 ppm of V

0.1 ppm of

REF

REF

/°C

V

REF

REF

/°C

V

REF

RMS

Programmable Gain (Note 15) ● 1 128

U

CO VERTER CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. (Notes 3, 4)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Common Mode Rejection DC 2.5V ≤ V
Input Common Mode Rejection 2.5V ≤ V

50Hz ±2%
Input Common Mode Rejection 2.5V ≤ V

60Hz ±2%
Input Normal Mode Rejection 2.5V ≤ V

50Hz ±2%
Input Normal Mode Rejection 2.5V ≤ V

60Hz ±2%
Input Normal Mode Rejection 2.5V ≤ V

50Hz/60Hz ±2%
Reference Common Mode 2.5V ≤ V

Rejection DC

Power Supply Rejection DC V

Power Supply Rejection, 50Hz ± 2% V

Power Supply Rejection, 60Hz ± 2% V

REF

REF

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

≤ VCC, GND ≤ IN– = IN+ ≤ V

REF

= 2.5V, IN– = IN+ = GND 120 dB

= 2.5V, IN– = IN+ = GND (Notes 7, 9) 120 dB

= 2.5V, IN– = IN+ = GND (Notes 8, 9) 120 dB

The ● denotes specifications which apply over the full operating

(Note 5) ● 140 dB

CC

(Note 5) ● 140 dB

CC

(Note 5) ● 140 dB

CC

(Notes 5, 7) ● 110 120 dB

CC

(Notes 5, 8) ● 110 120 dB

CC

(Notes 5, 9) ● 87 dB

CC

(Note 5) ● 120 140 dB

CC

UUU

A ALOG I PUT AUD REFERE CE

temperature range, otherwise specifications are at TA = 25°C. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

+

IN

–

IN

FS Full Scale of the Differential Input (IN+ – IN–) ● 0.5V

LSB Least Significant Bit of the Output Code ● FS/2

V

IN

V

REF

Absolute/Common Mode IN+ Voltage GND – 0.3V VCC + 0.3V V

Absolute/Common Mode IN– Voltage GND – 0.3V VCC + 0.3V V

Input Differential Voltage Range (IN+ – IN–) ● –FS +FS V

Reference Voltage Range ● 0.1 V

The ● denotes specifications which apply over the full operating

/GAIN V

REF

16

CC

2480f

3

V

LTC2480

UUU

A ALOG I PUT AUD REFERE CE

temperature range, otherwise specifications are at TA = 25°C. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

CS (IN+)IN

CS (IN–)IN

CS (V

)V

REF

I

(IN+)IN+ DC Leakage Current Sleep Mode, IN+ = GND ● –10 1 10 nA

DC_LEAK

I

(IN–)IN– DC Leakage Current Sleep Mode, IN– = GND ● –10 1 10 nA

DC_LEAK

I

DC_LEAK (VREF

+

Sampling Capacitance 11 pF

–

Sampling Capacitance 11 pF

Sampling Capacitance 11 pF

REF

)V

DC Leakage Current Sleep Mode, V

REF

The ● denotes specifications which apply over the full operating

REF

= V

CC

● –100 1 100 nA

UU

DIGITAL I PUTS A D DIGITAL OUTPUTS

operating temperature range, otherwise specifications are at T

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IH

V

IL

V

IH

V

IL

I

IN

I

IN

C

IN

C

IN

V

OH

V

OL

V

OH

V

OL

I

OZ

High Level Input Voltage 2.7V ≤ VCC ≤ 5.5V ● VCC – 0.5 V

, SDI

CS, F

O

Low Level Input Voltage 2.7V ≤ VCC ≤ 5.5V ● 0.5 V

, SDI

CS, F

O

High Level Input Voltage 2.7V ≤ VCC ≤ 5.5V (Note 10) ● VCC – 0.5 V
SCK

Low Level Input Voltage 2.7V ≤ VCC ≤ 5.5V (Note 10) ● 0.5 V
SCK

Digital Input Current 0V ≤ VIN ≤ V

, SDI

CS, F

O

Digital Input Current 0V ≤ VIN ≤ VCC (Note 10) ● –10 10 µA
SCK

Digital Input Capacitance 10 pF
CS, F

, SDI

O

Digital Input Capacitance 10 pF
SCK

High Level Output Voltage IO = –800µA ● VCC – 0.5 V
SDO

Low Level Output Voltage IO = 1.6mA ● 0.4 V
SDO

High Level Output Voltage IO = –800µA ● VCC – 0.5 V
SCK

Low Level Output Voltage IO = 1.6mA ● 0.4 V
SCK

Hi-Z Output Leakage ● –10 10 µA
SDO

= 25°C. (Note 3)

A

CC

The ● denotes specifications which apply over the full

● –10 10 µA

WU

POWER REQUIRE E TS

otherwise specifications are at TA = 25°C. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CC

I

CC

Supply Voltage ● 2.7 5.5 V

Supply Current Conversion Mode (Note 12) ● 160 250 µA

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

Sleep Mode (Note 12)

● 12 µA

2480f

4

LTC2480

WU

TI I G CHARACTERISTICS

range, otherwise specifications are at TA = 25°C. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

f

EOSC

t

HEO

t

LEO

t

CONV_1

t

CONV_2

f

ISCK

D

ISCK

f

ESCK

t

LESCK

t

HESCK

t

DOUT_ISCK

t

DOUT_ESCK

t

1

t

2

t

3

t

4

t

KQMAX

t

KQMIN

t

5

t

6

t

7

t

8

External Oscillator Frequency Range (Note 15) ● 10 4000 kHz

External Oscillator High Period ● 0.125 100 µs

External Oscillator Low Period ● 0.125 100 µs

Conversion Time for 1x Speed Mode 50Hz Mode ● 157.2 160.3 163.5 ms

Conversion Time for 2x Speed Mode 50Hz Mode ● 78.7 80.3 81.9 ms

Internal SCK Frequency Internal Oscillator (Note 10) 38.4 kHz

Internal SCK Duty Cycle (Note 10) ● 45 55 %

External SCK Frequency Range (Note 10) ● 4000 kHz

External SCK Low Period (Note 10) ● 125 ns

External SCK High Period (Note 10) ● 125 ns

Internal SCK 24-Bit Data Output Time Internal Oscillator (Notes 10, 12) ● 0.61 0.625 0.64 ms

External SCK 24-Bit Data Output Time (Note 10) ● 24/f
CS↓ to SDO Low ● 0 200 ns
CS↑ to SDO High Z ● 0 200 ns
CS↓ to SCK↓ Internal SCK Mode ● 0 200 ns
CS↓ to SCK↑ External SCK Mode ● 50 ns
SCK↓ to SDO Valid ● 200 ns
SDO Hold After SCK↓ (Note 5) ● 15 ns
SCK Set-Up Before CS↓ ● 50 ns
SCK Hold After CS↓ ● 50 ns
SDI Setup Before SCK↑ (Note 5) ● 100 ns
SDI Hold After SCK↑ (Note 5) ● 100 ns

The ● denotes specifications which apply over the full operating temperature

60Hz Mode
Simultaneous 50Hz/60Hz Mode
External Oscillator

60Hz Mode
Simultaneous 50Hz/60Hz Mode
External Oscillator

External Oscillator (Notes 10, 11) f

External Oscillator (Notes 10, 11)

● 131.0 133.6 136.3 ms

● 144.1 146.9 149.9 ms

● 41036/f

● 65.6 66.9 68.2 ms

● 72.2 73.6 75.1 ms

● 20556/f

● 192/f

(in kHz) ms

EOSC

(in kHz) ms

EOSC

/8 kHz

EOSC

(in kHz) ms

EOSC

(in kHz) ms

ESCK

Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.

Note 2: All voltage values are with respect to GND.
Note 3: VCC = 2.7V to 5.5V unless otherwise specified.

V

= V

REFCM

/2, FS = 0.5V

REF

VIN = IN+ – IN–, V

IN(CM)

/GAIN

REF

= (IN+ + IN–)/2

Note 4: Use internal conversion clock or external conversion clock source
with f

= 307.2kHz unless otherwise specified.

EOSC

Note 5: Guaranteed by design, not subject to test.
Note 6: 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 7: 50Hz mode (internal oscillator) or f

= 256kHz ±2% (external

EOSC

oscillator).

Note 8: 60Hz mode (internal oscillator) or f

= 307.2kHz ±2% (external

EOSC

oscillator).
Note 9: Simultaneous 50Hz/60Hz mode (internal oscillator) or f

EOSC

=

280kHz ±2% (external oscillator).
Note 10: The SCK can be configured in external SCK mode or internal SCK

mode. In external SCK mode, the SCK pin is used as digital input and the
driving clock is f
output and the output clock signal during the data output is f

Note 11: The external oscillator is connected to the F
oscillator frequency, f

. In internal SCK mode, the SCK pin is used as digital

ESCK

, is expressed in kHz.

EOSC

pin. The external

O

ISCK

.

Note 12: The converter uses the internal oscillator.
Note 13: The output noise includes the contribution of the internal

calibration operations.

Note 14: Guaranteed by design and test correlation.
Note 15: Refer to Applications Information section for performance vs

data rate graphs.

2480f

5

LTC2480

INPUT VOLTAGE (V)

–12

TUE (ppm OF V

REF

)

–4

4

12

–8

0

8

–0.75 –0.25 0.25 0.75

2480 G03

1.25–1.25

VCC = 2.7V
V

REF

= 2.5V

V

IN(CM)

= 1.25V

F

O

= GND

85°C

25°C

–45°C

INPUT VOLTAGE (V)

–3

INL (ppm OF V

REF

)

–1

1

3

–2

0

2

–0.75 –0.25 0.25 0.75

2480 G06

1.25–1.25

VCC = 2.7V
V

REF

= 2.5V

V

IN(CM)

= 1.25V

F

O

= GND

–45°C, 25°C, 90°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Integral Nonlinearity
(VCC = 5V, V

3

VCC = 5V

= 5V

V

REF

2

)

1

REF

0

–1

INL (ppm OF V

–2

–3

= 2.5V

V

IN(CM)

= GND

F

O

–45°C

85°C

–1.5 –0.5 0.5 1.5

INPUT VOLTAGE (V)

Total Unadjusted Error
(VCC = 5V, V

12

VCC = 5V

= 5V

V

REF

8

)

4

REF

0

V

IN(CM)

F

O

= 2.5V

= GND

REF

25°C

REF

= 5V)

= 5V)

25°C

85°C

–45°C

2480 G04

Integral Nonlinearity
(VCC = 5V, V

3

VCC = 5V

= 2.5V

V

REF

2

)

1

REF

0

–1

INL (ppm OF V

–2

2.5–2–2.5 –1 0 1 2

–3

= 1.25V

V

IN(CM)

= GND

F

O

–0.75 –0.25 0.25 0.75

= 2.5V)

REF

–45°C, 25°C, 90°C

INPUT VOLTAGE (V)

1.25–1.25

2480 G05

Total Unadjusted Error
(VCC = 5V, V

12

VCC = 5V
V

8

V
F

)

4

REF

0

REF
IN(CM)

= GND

O

= 5V

= 1.25V

= 2.5V)

REF

85°C

25°C

–45°C

Integral Nonlinearity
(VCC = 2.7V, V

= 2.5V)

REF

Total Unadjusted Error
(VCC = 2.7V, V

= 2.5V)

REF

–4

TUE (ppm OF V

–8

–12

–1.5 –0.5 0.5 1.5

INPUT VOLTAGE (V)

2.5–2–2.5 –1 0 1 2

2480 G01

Noise Histogram (6.8sps) Long-Term ADC Readings

14

10,000 CONSECUTIVE
READINGS

12

= 5V

V

CC

= 5V

V

REF

= 0V

V

10

IN

GAIN = 256

= 25°C

T

A

8

6

4

NUMBER OF READINGS (%)

2

0

–3

–1.8 –0.6

–2.4 1.2

–1.2 0 1.8

OUTPUT READING (µV)

RMS = 0.60µV

AVERAGE = –0.69µV

0.6

2480 G07

–4

TUE (ppm OF V

–8

–12

–0.75 –0.25 0.25 0.75

INPUT VOLTAGE (V)

Noise Histogram (7.5sps)

14

10,000 CONSECUTIVE
READINGS

12

= 2.7V

V

CC

= 2.5V

V

REF

= 0V

V

10

IN

GAIN = 256

= 25°C

T

A

8

6

4

NUMBER OF READINGS (%)

2

0

–3

–1.8 –0.6

–2.4 1.2

–1.2 0 1.8

OUTPUT READING (µV)

2480 G02

RMS = 0.59µV

AVERAGE = –0.19µV

0.6

2480 G08

1.25–1.25

5

–1

ADC READING (µV)

–2

–3

–4

–5

VCC = 5V, V
GAIN = 256, T

4

3

2

1

0

0

= 5V, VIN = 0V, V

REF

= 25°C, RMS NOISE = 0.60µV

A

10

20

TIME (HOURS)

30 40

IN(CM)

= 2.5V

50

60

2480 G09

6

2480f

UW

V

REF

(V)

0

–0.3

OFFSET ERROR (ppm OF V

REF

)

–0.2

–0.1

0

0.1

0.2

0.3

1234

2480 G18

5

VCC = 5V
REF

–

= GND

V

IN

= 0V

V

IN(CM)

= GND
GAIN = 256
T

A

= 25°C

TYPICAL PERFOR A CE CHARACTERISTICS

RMS Noise
vs Input Differential Voltage RMS Noise vs V

)

REF

1.0

0.9

0.8

VCC = 5V

= 5V

V

REF

GAIN = 256

= 2.5V

V

IN(CM)

= 25°C

T

A

1.0

0.9

0.8

VCC = 5V

= 5V

V

REF

= 0V

V

IN

V

IN(CM)

GAIN = 256

= 25°C

T

A

= GND

IN(CM)

LTC2480

RMS Noise vs Temperature (TA)

1.0
VCC = 5V

= 5V

V

REF

0.9

= 0V

V

IN

= GND

V

IN(CM)

GAIN = 256

0.8

0.7

0.6

RMS NOISE (ppm OF V

0.5

0.4
–1.5 –0.5 0.5 1.5

INPUT DIFFERENTIAL VOLTAGE (V)

RMS Noise vs V

1.0

V

= 2.5V

REF

= 0V

V

IN

= GND

V

0.9

IN(CM)

GAIN = 256

= 25°C

T

A

0.8

0.7

RMS NOISE (µV)

0.6

0.5

0.4

2.7

3.1 3.5

CC

4.3 5.1 5.5

3.9 4.7
VCC (V)

2480 G10

2480 G13

0.7

RMS NOISE (µV)

0.6

0.5

2.5–2–2.5 –1 0 1 2

0.4
–1

01

RMS Noise vs V

1.0

VCC = 5V

= 0V

V

IN

0.9

V

IN(CM)

GAIN = 256

= 25°C

T

A

0.8

0.7

RMS NOISE (µV)

0.6

0.5

0.4

0

356

24

V

(V)

IN(CM)

2480 G11

REF

= GND

1234

V

(V)

REF

2480 G14

5

0.7

RMS NOISE (µV)

0.6

0.5

0.4
–45

–30 –15 15

0 304560

TEMPERATURE (°C)

Offset Error vs V

0.3
VCC = 5V

= 5V

V

REF

)

REF

–0.1

OFFSET ERROR (ppm OF V

–0.3

0.2

0.1

–0.2

V
GAIN = 256
T

0

–1

= 0V

IN

= 25°C

A

01

75 90

2480 G12

IN(CM)

356

24

V

(V)

IN(CM)

2480 G15

Offset Error vs Temperature

0.3
VCC = 5V

V

0.2

V

)

V

REF

F

0.1

0

–0.1

OFFSET ERROR (ppm OF V

–0.2

–0.3

–45

= 5V

REF

= 0V

IN

= GND

IN(CM)

= GND

O

–30 0

–15

30 90

45

15

TEMPERATURE (°C)

Offset Error vs V

0.3
REF+ = 2.5V

–

= GND

REF

)

REF

OFFSET ERROR (ppm OF V

60

75

2480 G16

0.2

0.1

–0.1

–0.2

–0.3

V
V
GAIN = 256
T

0

2.7

= 0V

IN
IN(CM)

= 25°C

A

3.1 3.5

= GND

CC

4.3 5.1 5.5

3.9 4.7
VCC (V)

2480 G17

Offset Error vs V

REF

2480f

7

LTC2480

TEMPERATURE (°C)

–45 –30

300

FREQUENCY (kHz)

304

310

–15

30

45

2480 G26

302

308

306

150

60 75

90

VCC = 4.1V
V

REF

= 2.5V

V

IN

= 0V

V

IN(CM)

= GND

F

O

= GND

TEMPERATURE (°C)

–45

0

SLEEP MODE CURRENT (µA)

0.2

0.6

0.8

1.0

2.0

1.4

–15

15

30 90

2480 G32

0.4

1.6

1.8

1.2

–30 0

45

60

75

VCC = 5V

VCC = 2.7V

FO = GND
CS = V

CC

SCK = NC
SDO = NC
SDI = GND

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Temperature Sensor
vs Temperature

0.40
VCC = 5V

= 1.4V

V

REF

= GND

F

O

0.35

(V)

REF

0.30

/V

PTAT

V

0.25

0.20

–60

30090–30 60

TEMPERATURE (°C)

On-Chip Oscillator Frequency
vs V

CC

310

308

306

V

REF

V

IN

V

IN(CM)

F

O

= 2.5V

= 0V

= GND

2480 G24

= GND

120

Temperature Sensor Error
vs Temperature

5

VCC = 5V

4

= GND

F

O

3

2

1

0

–1

–2

TEMPERATURE ERROR (°C)

–3

–4

–5

–30

–60

0

TEMPERATURE (°C)

PSRR vs Frequency at V

0

VCC = 4.1V DC

= 2.5V

V

REF

–20

+

= GND

IN

–

= GND

IN

–40

= GND

F

O

= 25°C

T

A

–60

On-Chip Oscillator Frequency
vs Temperature

V

= 1.4V

REF

30

60

90

120

2480 G25

CC

PSRR vs Frequency at V

0

VCC = 4.1V DC ±1.4V

= 2.5V

V

REF

–20

+

= GND

IN

–

= GND

IN

–40

= GND

F

O

= 25°C

T

A

–60

CC

FREQUENCY (kHz)

REJECTION (dB)

8

–100

–120

–140

304

302

300

2.5

3.5 4.0 4.5

3.0
VCC (V)

PSRR vs Frequency at V

0

VCC = 4.1V DC ±0.7V

= 2.5V

V

REF

–20

+

= GND

IN

–

= GND

IN

–40

= GND

F

O

= 25°C

T

A

–60

–80

30600

30650 30700 30800

FREQUENCY AT VCC (Hz)

CC

30750

5.0 5.5

2480 G27

2480 G30

–80

REJECTION (dB)

–100

–120

–140

1

10 100

FREQUENCY AT VCC (Hz)

Conversion Current
vs Temperature

200

FO = GND
CS = GND
SCK = NC

180

SDO = NC
SDI = GND

160

140

CONVERSION CURRENT (µA)

120

100

–30 0

–15

–45

10k 1M

1k 100k

VCC = 5V

VCC = 2.7V

30 90

45

15

TEMPERATURE (°C)

–80

REJECTION (dB)

–100

–120

2480 G28

–140

100

120 160

140

0

60

80

40

20

FREQUENCY AT VCC (Hz)

180

220200

2480 G29

Sleep Mode Current
vs Temperature

60

75

2480 G31

2480f

UW

INPUT VOLTAGE (V)

–3

INL (ppm OF V

REF

)

–1

1

3

–2

0

2

–0.75 –0.25 0.25 0.75

2480 G35

1.25–1.25

VCC = 5V
V

REF

= 2.5V

V

IN(CM)

= 1.25V

F

O

= GND

90°C

–45°C, 25°C

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2480

Conversion Current
vs Output Data Rate

500

V

= V

REF

CC

IN+ = GND

450

–

= GND

IN
SCK = NC

400

SDO = NC
SDI = GND

350

CS GND

= EXT OSC

F

O

300

= 25°C

T

A

250

SUPPLY CURRENT (µA)

200

150

100

0

20 40 60 1007010 30 50 90

OUTPUT DATA RATE (READINGS/SEC)

VCC = 5V

Integral Nonlinearity (2x Speed
Mode; VCC = 2.7V, V

3

VCC = 2.7V

= 2.5V

V

REF

2

)

1

REF

0

–1

INL (ppm OF V

–2

–3

= 1.25V

V

IN(CM)

= GND

F

O

90°C

–45°C, 25°C

–0.75 –0.25 0.25 0.75

INPUT VOLTAGE (V)

REF

VCC = 3V

80

= 2.5V)

2480 G33

2480 G36

Integral Nonlinearity (2x Speed
Mode; V

3

2

)

1

REF

0

–1

INL (ppm OF V

–2

–3

= 5V, V

CC

–1.5 –0.5 0.5 1.5

INPUT VOLTAGE (V)

= 5V)

REF

VCC = 5V
V

REF

V

IN(CM)

F

O

25°C, 90°C

–45°C

= 5V

= GND

= 2.5V

2.5–2–2.5 –1 0 1 2

2480 G34

Noise Histogram
(2x Speed Mode)

16

10,000 CONSECUTIVE
READINGS

14

= 5V

V

CC

= 5V

V

REF

12

= 0V

V

IN

GAIN = 256

10

= 25°C

T

A

8

6

4

NUMBER OF READINGS (%)

2

1.25–1.25

0

179

181.4 183.8 188.6
OUTPUT READING (µV)

RMS = 0.86µV

AVERAGE = 0.184mV

186.2

2480 G37

Integral Nonlinearity (2x Speed
Mode; V

RMS Noise vs V

= 5V, V

CC

REF

REF

(2x Speed Mode)

1.0

0.8

0.6

0.4

RMS NOISE (µV)

VCC = 5V

= 0V

V

IN

0.2

0

0

V

IN(CM)

F

O

T

A

= GND
= 25°C

= GND

1

3

2

V

(V)

REF

= 2.5V)

4

5

2480 G38

200

198

196

194

192

190

188

186

OFFSET ERROR (µV)

184

182

180

–1

Offset Error vs V
(2x Speed Mode)

VCC = 5V

= 5V

V

REF

= 0V

V

IN

= GND

F

O

= 25°C

T

A

2

1

0

V

IN(CM)

IN(CM)

3

(V)

Offset Error vs Temperature
(2x Speed Mode)

240

VCC = 5V

= 5V

V

REF

230

= 0V

V

IN

= GND

V

IN(CM)

220

= GND

F

O

210

200

190

OFFSET ERROR (µV)

180

170

5

6

2480 G39

4

160

–30 90

–45

–15

15

30

0

TEMPERATURE (°C)

75

45

60

2480 G40

2480f

9

LTC2480

FREQUENCY AT VCC (Hz)

1

0

–20

–40

–60

–80

–100

–120

–140

1k 100k

2480 G43

10 100

10k 1M

REJECTION (dB)

VCC = 4.1V DC
REF

+

= 2.5V

REF

–

= GND

IN

+

= GND

IN

–

= GND

F

O

= GND

T

A

= 25°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Offset Error vs V
(2x Speed Mode)

250

V

= 2.5V

REF

= 0V

V

IN

V

IN(CM)

200

= GND

F

O

= 25°C

T

A

150

100

OFFSET ERROR (µV)

50

0

2 2.5

= GND

3

CC

4

3.5
VCC (V)

4.5

5

2480 G41

PSRR vs Frequency at V
(2x Speed Mode)

0

VCC = 4.1V DC ±1.4V

+

= 2.5V

REF

–20

–

= GND

REF

+

= GND

IN

–

–40

= GND

IN

= GND

F

O

= 25°C

T

A

–60

5.5

Offset Error vs V
(2x Speed Mode)

240

VCC = 5V

= 0V

V

IN

230

V

IN(CM)

= GND

F

O

220

= 25°C

T

A

210

200

190

OFFSET ERROR (µV)

180

170

160

0

CC

REF

= GND

12 4

3

V

(V)

REF

2480 G42

PSRR vs Frequency at V
(2x Speed Mode)

0

VCC = 4.1V DC ±0.7V
REF

–20

REF
IN

–40

IN
F

O

T

A

–60

5

+

= 2.5V

–

= GND

+

= GND

–

= GND
= GND
= 25°C

PSRR vs Frequency at V
(2x Speed Mode)

CC

CC

PI FU CTIO S

SDI (Pin 1): Serial Data Input. This pin is used to select the
GAIN, line frequency rejection, input, temperature sensor
and 2x speed mode. Data is shifted into the SDI pin on the
rising edge of serial clock (SCK).

VCC (Pin 2): Positive Supply Voltage. Bypass to GND
(Pin 8) with a 1µF tantalum capacitor in parallel with 0.1µF
ceramic capacitor as close to the part as possible.

V

pin can have any value between 0.1V and VCC. The negative
reference input is GND (Pin 8).

–80

RREJECTION (dB)

–100

–120

–140

0

U

(Pin 3): Positive Reference Input. The voltage on this

REF

60

80

40

20

FREQUENCY AT VCC (Hz)

UU

100

120 160

140

180

220200

2480 G44

–80

REJECTION (dB)

–100

–120

–140

30600

30650 30700 30800

FREQUENCY AT VCC (Hz)

30750

2480 G45

IN+ (Pin 4), IN– (Pin 5): Differential Analog Inputs. The
voltage on these pins can have any value between GND –

0.3V and VCC + 0.3V. Within these limits the converter
bipolar input range (VIN = IN+ – IN–) extends from –0.5 •
V

/GAIN to 0.5 • V

REF

/GAIN. Outside this input range the

REF

converter produces unique overrange and underrange
output codes.

CS (Pin 6): Active LOW Chip Select. A LOW on this pin
enables the digital input/output and wakes up the ADC.
Following each conversion the ADC automatically enters
the Sleep mode and remains in this low power state as long

2480f

10

LTC2480

U

UU

PI FU CTIO S

as CS is HIGH. A LOW-to-HIGH transition on CS during the
Data Output transfer aborts the data transfer and starts a
new conversion.

SDO (Pin 7): Three-State Digital Output. During the Data
Output period, this pin is used as the serial data output.
When the chip select CS is HIGH (CS = V
is in a high impedance state. During the Conversion and
Sleep periods, this pin is used as the conversion status
output. The conversion status can be observed by pulling
CS LOW.

GND (Pin 8): Ground. Shared pin for analog ground,
digital ground and reference ground. Should be connected
directly to a ground plane through a minimum impedance.

SCK (Pin 9): Bidirectional Digital Clock Pin. In Internal
Serial Clock Operation mode, SCK is used as the digital
output for the internal serial interface clock during the Data

), the SDO pin

CC

Input/Output period. In External Serial Clock Operation
mode, SCK is used as the digital input for the external
serial interface clock during the Data Output period. A weak
internal pull-up is automatically activated in Internal Serial
Clock Operation mode. The Serial Clock Operation mode is
determined by the logic level applied to the SCK pin at
power up or during the most recent falling edge of CS.

F

(Pin 10): Frequency Control Pin. Digital input that

O

controls the conversion clock. When FO is connected to
GND the converter uses its internal oscillator running at

307.2kHz. The conversion clock may also be overridden
by driving the FO pin with an external clock in order to
change the output rate or the digital filter rejection null.

Exposed Pad (Pin 11): This pin is ground and should be
soldered to the PCB ground plane. For prototyping pur­poses, this pin may remain floating.

UU

W

FU CTIO AL BLOCK DIAGRA

V

REF

3

+

IN

4

–

IN

5

TEMP

SENSOR

MUX

TEST CIRCUITS

SDO

1.69k

C

LOAD

= 20pF

+

IN

–

IN

REF

AUTOCALIBRATION

GND

8

+

REF

3RD ORDER

∆Σ ADC

(1-256)

–

AND CONTROL

GAIN

2

V

CC

SDI

1

SCK

SERIAL

INTERFACE

INTERNAL

OSCILLATOR

SDO

9

SD0

7

CS

6

F

O

10

2480 FD

V

CC

1.69k

= 20pF

C

LOAD

Hi-Z TO V
VOL TO V
VOH TO Hi-Z

OH

OH

2480 TA02

Hi-Z TO V
VOH TO V
VOL TO Hi-Z

OL

OL

2480 TA03

2480f

11

LTC2480

WUW

TI I G DIAGRA S

CS

Timing Diagram Using Internal SCK

SDO

SCK

SDI

SDO

SCK

SDI

SLEEP

t

1

t

t

3

t

8

t

7

KQMIN

t

KQMAX

t

2

2480 TD1

CONVERSIONDATA IN/OUT

Timing Diagram Using External SCK

CS

SLEEP

t

1

t

5

t

6

t

4

t

8

t

7

t

KQMIN

t

KQMAX

t

2

2480 TD2

CONVERSIONDATA IN/OUT

WUUU

APPLICATIO S I FOR ATIO

CONVERTER OPERATION

Converter Operation Cycle

The LTC2480 is a low power, delta-sigma analog-to­digital converter with an easy to use 4-wire serial interface
and automatic differential input current cancellation. Its
operation is made up of three states. The converter oper­ating cycle begins with the conversion, followed by the low
power sleep state and ends with the data output (see
Figure 1). The 4-wire interface consists of serial data
output (SDO), serial clock (SCK), chip select (CS) and
serial data input (SDI).

Initially, the LTC2480 performs a conversion. Once the
conversion is complete, the device enters the sleep state.

12

CONVERT

SLEEP

FALSE

CS = LOW

AND

SCK

TRUE

DATA OUTPUT

CONFIGURATION INPUT

2480 F01

Figure 1. LTC2480 State Transition Diagram

2480f