LINEAR TECHNOLOGY LTC2435, LTC2435-1 Technical data

查询LTC2435-1CGN供应商

LTC2435/LTC2435-1

ADCs with Differential Input and

FEATURES

■

××

2

× Speed Up Version of the LTC2430: 15Hz Output

××

Rate, 60Hz Notch—LTC2435; 13.75Hz Output Rate,
Simultaneous 50Hz/60Hz Notch—LTC2435-1

■

Differential Input and Differential Reference with
GND to VCC Common Mode Range

■

3ppm INL, No Missing Codes

■

10ppm Gain Error

■

0.8ppm Noise

■

Single Conversion Settling Time for Multiplexed
Applications

■

Internal Oscillator—No External Components
Required

■

Single Supply 2.7V to 5.5V Operation

■

Low Supply Current (200µA,4µA in Auto Sleep)

■

20-Bit ADC in Narrow SSOP-16 Package
(SO-8 Footprint)

U

APPLICATIO S

■

Direct Sensor Digitizer

■

Weight Scales

■

Direct Temperature Measurement

■

Gas Analyzers

■

Strain Gage Transducers

■

Instrumentation

■

Data Acquisition

■

Industrial Process Control

■

6-Digit DVMs

20-Bit No Latency ∆Σ

TM

Differential Reference

U

DESCRIPTIO

The LTC®2435/2435-1 are 2.7V to 5.5V micropower
20-bit differential ∆Σ analog to digital converters with
integrated oscillator, 3ppm INL and 0.8ppm RMS noise.
They use delta-sigma technology and provide single cycle
settling time for multiplexed applications. Through a
single pin, the LTC2435 can be configured for better than
110dB input differential mode rejection at 50Hz or 60Hz
±2%, or it can be driven by an external oscillator for a user
defined rejection frequency. The LTC2435-1 can be con­figured for better than 87dB input differential mode rejec­tion over the range of 49Hz to 61.2Hz (50Hz and 60Hz
±2% simultaneously). The internal oscillator requires no
external frequency setting components.

The converters accept any external differential reference
voltage from 0.1V to VCC for flexible ratiometric and
remote sensing measurement configurations. The full­scale differential input range is from –0.5V
The reference common mode voltage, V
input common mode voltage, V

, may be indepen-

INCM

dently set anywhere within the GND to VCC range of the
LTC2435/LTC2435-1. The DC common mode input rejec­tion is better than 120dB.

The LTC2435/LTC2435-1 communicate through a flexible
3-wire digital interface which is compatible with SPI and
MICROWIRETM protocols.

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

No Latency ∆Σ is a trademark of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
Protected by U.S. Patents including 6140950, 6169506.

to 0.5V

REF

REFCM

REF

, and the

.

U

TYPICAL APPLICATIO S

2.7V TO 5.5V

1µF

214

V

F

CC

O

LTC2435/

LTC2435-1

3

+

REFERENCE

VOLTAGE

0.1V TO V

ANALOG INPUT RANGE

TO 0.5V

–0.5V

REF

1, 7, 8, 9, 10, 15, 16

REF

4

REF

CC

5

+

IN

REF

6

–

IN

GND

13

SCK

–

12

SDO

11

CS

V

CC

= INTERNAL OSC/50Hz REJECTION (LTC2435)
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION (LTC2435)
= INTERNAL 50Hz/60Hz REJECTION (LTC2435-1)

3-WIRE
SPI INTERFACE

2435 TA01

Integral Nonlinearity vs Input

10

8

6

4

)

REF

2

0

–2

INL (ppm OF V

–4

FO = GND

–6

= 5V

V

CC

= 5V

V

REF

–8

= V

V

INCM

–10

–2.5 –1.5 – 0.5 0.5 1.5

INCM

TA = 25°C

TA = 85°C

TA = –45°C

= 2.5V

INPUT VOLTAGE (V)

2435 G04

2.5

24351fa

1

LTC2435/LTC2435-1

WW

W

ABSOLUTE AXI U RATI GS

U

UUW

PACKAGE/ORDER I FOR ATIO

(Notes 1, 2)

Supply Voltage (VCC) to GND....................... –0.3V to 7V

Analog Input Pins Voltage

to GND .................................... –0.3V to (V

+ 0.3V)

CC

Reference Input Pins Voltage

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

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

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

Operating Temperature Range

LTC2435C/LTC2435-1C........................... 0°C to 70°C

LTC2435I/LTC2435-1I ........................ –40°C to 85°C

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

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

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

TOP VIEW

1

GND

2

V

CC

+

3

REF

–

4

REF

+

5

IN

–

6

IN

7

GND

8

GND

GN PACKAGE

16-LEAD PLASTIC SSOP

T

= 125°C, θJA = 95°C/W

JMAX

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

16

GND

15

GND

14

F

O

13

SCK

12

SDO

11

CS

10

GND

9

GND

ORDER PART NUMBER

LTC2435CGN
LTC2435IGN
LTC2435-1CGN
LTC2435-1IGN

GN PART MARKING

2435
2435I
24351
24351I

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

PARAMETER CONDITIONS MIN TYP MAX UNITS

Resolution (No Missing Codes) 0.1V ≤ V

Integral Nonlinearity 5V ≤ VCC ≤ 5.5V, REF+ = 2.5V, REF– = GND, V

5V ≤ VCC ≤ 5.5V, REF+ = 5V, REF– = GND, V

2.7V ≤ VCC ≤ 5.5V, REF+ = 2.5V, REF– = GND, V

Offset Error 2.5V ≤ REF+ ≤ VCC, REF– = GND, ● 25 mV

GND ≤ IN

Offset Error Drift 2.5V ≤ REF+ ≤ VCC, REF– = GND, 100 nV/°C

GND ≤ IN

Positive Gain Error 2.5V ≤ REF+ ≤ VCC, REF– = GND, ● 10 25 ppm of V

IN+ = 0.75REF+, IN– = 0.25 • REF

Positive Gain Error Drift 2.5V ≤ REF+ ≤ VCC, REF– = GND, 0.1 ppm of V

Negative Gain Error 2.5V ≤ REF+ ≤ VCC, REF– = GND, ● 10 25 ppm of V

Negative Gain Error Drift 2.5V ≤ REF+ ≤ VCC, REF– = GND, 0.1 ppm of V

Output Noise 5V ≤ VCC ≤ 5.5V, REF+ = 5V, REF– = GND, 4 µV

+

IN

IN+ = 0.25 • REF+, IN– = 0.75 • REF

+

IN

GND ≤ IN– = IN+ ≤ VCC, (Note 13)

≤ VCC, –0.5 • V

REF

+

= IN– ≤ VCC, (Note 14)

+

= IN– ≤ V

= 0.75REF+, IN– = 0.25 • REF

= 0.25 • REF+, IN– = 0.75 • REF

CC

≤ VIN ≤ 0.5 • V

REF

+

+

, (Note 5) ● 20 Bits

REF

= 1.25V, (Note 6) 2 ppm of V

INCM

= 2.5V, (Note 6) ● 3 20 ppm of V

INCM

= 1.25V, (Note 6) 10 ppm of V

INCM

+

+

REF

REF

REF
REF
REF

REF

/°C

REF

/°C

RMS

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 ≤ REF+ ≤ VCC, REF– = GND, ● 110 120 dB

GND ≤ IN

–

= IN+ ≤ VCC (Note 5)

The ● denotes specifications which apply over the full operating

24351fa

2

LTC2435/LTC2435-1

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 2.5V ≤ REF+ ≤ VCC, REF– = GND, ● 140 dB
60Hz ±2% (LTC2435) GND ≤ IN

Input Common Mode Rejection 2.5V ≤ REF+ ≤ VCC, REF– = GND, ● 140 dB
50Hz ±2% (LTC2435) GND ≤ IN

Input Normal Mode Rejection (Notes 5, 7) ● 110 120 dB
60Hz ±2% (LTC2435)

Input Normal Mode Rejection (Notes 5, 8) ● 110 120 dB
50Hz ±2% (LTC2435)

Input Common Mode Rejection 2.5V ≤ REF+ ≤ VCC, REF– = GND, ● 120 dB
49Hz to 61.2Hz (LTC2435-1) GND ≤ IN

Input Normal Mode Rejection FO = GND (Note 5) ● 87 dB
49Hz to 61.2Hz (LTC2435-1)

Input Normal Mode Rejection External Oscillator (Note 5) ● 87 dB
External Clock f

Input Normal Mode Rejection External Oscillator (Note 5) ● 110 120 dB
External Clock f

Reference Common Mode 2.5V ≤ REF+ ≤ VCC, GND ≤ REF– ≤ 2.5V, ● 130 140 dB
Rejection DC V

Power Supply Rejection, DC REF+ = VCC, REF– = GND, IN– = IN+ = GND 100 dB

Power Supply Rejection, 60Hz ±2% REF+ = 2.5V, REF– = GND, IN– = IN+ = GND, (Note 7) 120 dB

Power Supply Rejection, 50Hz ±2% REF+ = 2.5V, REF– = GND, IN– = IN+ = GND, (Note 8) 120 dB

/2560 ±14%

EOSC

/2560 ±4%

EOSC

–

= IN+ ≤ VCC, (Notes 5, 7)

–

= IN+ ≤ VCC, (Notes 5, 8)

–

= IN+ ≤ VCC, (Notes 5, 7)

= 2.5V, IN– = IN+ = GND (Note 5)

REF

The ● denotes specifications which apply over the full operating

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

V

IN

+

REF

–

REF

V

REF

CS (IN+)IN

CS (IN–)IN

CS (REF+)REF

CS (REF–)REF

I

I

I

I

(IN+)IN+ DC Leakage Current CS = VCC, IN+ = GND ● –10 1 10 nA

DC_LEAK

(IN–)IN– DC Leakage Current CS = VCC, IN– = V

DC_LEAK

(REF+)REF+ DC Leakage Current CS = VCC, REF+ = V

DC_LEAK

(REF–)REF– DC Leakage Current CS = VCC, REF– = GND ● –10 1 10 nA

DC_LEAK

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 ● –V

+

(IN

– IN–)

Absolute/Common Mode REF+ Voltage ● 0.1 V

Absolute/Common Mode REF– Voltage ● GND VCC – 0.1V V

Reference Differential Voltage Range ● 0.1 V

+

(REF

– REF–)

+

Sampling Capacitance 1.5 pF

–

Sampling Capacitance 1.5 pF

+

Sampling Capacitance 1.5 pF

–

Sampling Capacitance 1.5 pF

The ● denotes specifications which apply over the full operating

CC

CC

/2 V

REF

● –10 1 10 nA

● –10 1 10 nA

/2 V

REF

CC

CC

V

V

24351fa

3

LTC2435/LTC2435-1

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 ● 2.5 V
CS, F

O

Low Level Input Voltage 4.5V ≤ VCC ≤ 5.5V ● 0.8 V
CS, F

O

High Level Input Voltage 2.7V ≤ VCC ≤ 5.5V (Note 9) ● 2.5 V
SCK 2.7V ≤ V

Low Level Input Voltage 4.5V ≤ VCC ≤ 5.5V (Note 9) ● 0.8 V
SCK 2.7V ≤ V

Digital Input Current 0V ≤ VIN ≤ V
CS, F

O

Digital Input Current 0V ≤ VIN ≤ VCC (Note 9) ● –10 10 µA
SCK

Digital Input Capacitance 10 pF
CS, F

O

Digital Input Capacitance (Note 9) 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 (Note 10) ● VCC – 0.5 V
SCK

Low Level Output Voltage IO = 1.6mA (Note 10) ● 0.4 V
SCK

Hi-Z Output Leakage ● –10 10 µA
SDO

2.7V ≤ VCC ≤ 3.3V 2.0 V

2.7V ≤ VCC ≤ 5.5V 0.6 V

= 25°C. (Note 3)

A

≤ 3.3V (Note 9) 2.0 V

CC

≤ 5.5V (Note 9) 0.6 V

CC

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 CS = 0V (Note 12)
Sleep Mode CS = V
Sleep Mode CS = V

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

● 200 300 µA

(Note 12) ● 410 µA

CC

, 2.7V ≤ VCC ≤ 3.3V (Note 12) ● 2 µA

CC

24351fa

4

LTC2435/LTC2435-1

WU

TI I G CHARACTERISTICS

range, otherwise specifications are at T

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

f

EOSC

t

HEO

t

LEO

t

CONV

f

ISCK

D

ISCK

f

ESCK

t

LESCK

t

HESCK

t

DOUT_ISCK

t

DOUT_ESCK

t

1

t2 CS ↑ to SDO High Z ● 0 200 ns

t3 CS ↓ to SCK ↓ (Note 10) ● 0 200 ns

t4 CS ↓ to SCK ↑ (Note 9) ● 50 ns

t

KQMAX

t

KQMIN

t

5

t

6

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 = 2.7 to 5.5V unless otherwise specified.

V

= REF+ – REF–, V

REF

= IN+ – IN–, V

V

IN

Note 4: FO pin tied to GND or to VCC or to external conversion clock
source with f

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: FO = 0V (internal oscillator) or f
(external oscillator) for the LTC2435 or f
LTC2435-1.

External Oscillator Frequency Range ● 5 2000 kHz

External Oscillator High Period ● 0.25 200 µs

External Oscillator Low Period ● 0.25 200 µs

Conversion Time (LTC2435) FO = 0V ● 65.6 66.9 68.3 ms

Conversion Time (LTC2435-1) FO = 0V ● 72 73.5 75 ms

Internal SCK Frequency Internal Oscillator (Note 10), LTC2435 19.2 kHz

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

External SCK Frequency Range (Note 9) ● 2000 kHz

External SCK Low Period (Note 9) ● 250 ns

External SCK High Period (Note 9) ● 250 ns

Internal SCK 24-Bit Data Output Time Internal Oscillator (Notes 10, 12), LTC2435 ● 1.22 1.25 1.28 ms

External SCK 24-Bit Data Output Time (Note 9) ● 24/f

CS ↓ to SDO Low Z ● 0 200 ns

SCK ↓ to SDO Valid ● 220 ns

SDO Hold After SCK ↓ (Note 5) ● 15 ns

SCK Set-Up Before CS ↓ ● 50 ns

SCK Hold After CS ↓ ● 50 ns

= (REF+ + REF–)/2;

REFCM

= (IN+ + IN–)/2.

INCM

= 153600Hz unless otherwise specified.

EOSC

= 25°C. (Note 3)

A

= 153600Hz ±2%

EOSC

= 139800Hz ±2% for the

EOSC

The ● denotes specifications which apply over the full operating temperature

F

= V

O

CC

External Oscillator (Note 11)

External Oscillator (Note 11)

Internal Oscillator (Note 10), LTC2435-1 17.5 kHz
External Oscillator (Notes 10, 11) f

Internal Oscillator (Notes 10, 12), LTC2435-1
External Oscillator (Notes 10, 11)

Note 8: FO = VCC (internal oscillator) or f
(external oscillator).

Note 9: The converter is in external SCK mode of operation such that
the SCK pin is used as digital input. The frequency of the clock signal
driving SCK during the data output is f

Note 10: The converter is in internal SCK mode of operation such that
the SCK pin is used as digital output. In this mode of operation the
SCK pin has a total equivalent load capacitance C

Note 11: The external oscillator is connected to the FO pin. The external
oscillator frequency, f

Note 12: The converter uses the internal oscillator.

= 0V or FO = VCC.

F

O

Note 13: The output noise includes the contribution of the internal
calibration operations.

Note 14: Refer to Offset Accuracy and Drift in the Applications
Information section.

● 78.7 80.3 81.9 ms

● 10278/f

● 10278/f

● 1.34 1.37 1.40 ms

● 192/f

ESCK

, is expressed in kHz.

EOSC

(in kHz) ms

EOSC

(in kHz) ms

EOSC

/8 kHz

EOSC

(in kHz) ms

EOSC

(in kHz) ms

ESCK

= 128000Hz ±2%

EOSC

and is expressed in kHz.

= 20pF.

LOAD

24351fa

5

LTC2435/LTC2435-1

–320

–330

–340

–350

–360

TUE (ppm OF V

REF

)

FO = GND
V

CC

= 2.7V

V

REF

= 2.5V

V

INCM

= V

INCM

= 1.25V

INPUT VOLTAGE (V)

–1.25 – 0.75 –0.25 0.25 0.75

2435 G03

1.25

TA = –45°C

TA = 25°C

TA = 85°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Total Unadjusted Error (V
V

= 5V)

REF

–340

FO = GND
V

= 5V

CC

= 5V

V

REF

= V

V

INCM

–345

)

REF

–350

TUE (ppm OF V

–355

–360

–2.5

= 2.5V

INCM

TA = 85°C

–1.5

–0.5

INPUT VOLTAGE (V)

Integral Nonlinearity (V
V

= 5V)

REF

10

8

6

4

)

REF

2

0

–2

INL (ppm OF V

–4

FO = GND

–6

= 5V

V

CC

= 5V

V

REF

–8

–10

= V

V

INCM

–2.5 –1.5 –0.5 0.5 1.5

= 2.5V

INCM

INPUT VOLTAGE (V)

30

25

20

15

10

NUMBER OF READINGS (%)

5

0

–330

= 5V,

CC

–680

–685

)

–690

REF

–695

–700

TUE (ppm OF V

–705

–710

–1.25

Integral Nonlinearity (V

TA = 25°C

0.5

TA = –45°C

1.5

= 5V,

CC

2.5

2435 G01

V

3

2

)

TA = 25°C

TA = 85°C

TA = –45°C

2.5

2435 G04

1

REF

0

–1

INL (ppm OF V

–2

–3

–1.25 –0.75 –0.25 0.25 0.75

Noise Histogram (Output Rate =
15Hz, VCC = 5V, V

10,000 CONSECUTIVE READINGS

= 5V

V

CC

= 5V

V

REF

= 0V

V

IN

= 2.5V

V

INCM

= GND

F

O

= 25°C

T

A

–329 –327

–328

OUTPUT CODE(ppm OF V

= 5V)

REF

GAUSSIAN
DISTRIBUTION
m = –325.4ppm
σ = 0.79ppm

–324

–323

REF

–325 –321

–326

–322

)

2435 G07

Total Unadjusted Error (V
V

= 2.5V)

REF

FO = GND

= 5V

V

CC

= 2.5V

V

REF

= V

V

INCM

REF

FO = GND

= 5V

V

CC

V

REF

V

INCM

= 1.25V

INCM

TA = 25°C

TA = 85°C

–0.75 –0.25 0.25 0.75

INPUT VOLTAGE (V)

CC

= 2.5V)

TA = –45°C

TA = 85°C

TA = 25°C

= 2.5V

= V

= 1.25V

INCM

INPUT VOLTAGE (V)

NUMBER OF READINGS (%)

= 5V,

CC

TA = –45°C

2435 G02

= 5V,

2435 G05

1.25

1.25

Total Unadjusted Error (V
V

= 2.5V)

REF

Integral Nonlinearity (V
V

= 2.5V)

REF

10

FO = GND

= 2.7V

V

8

CC

= 2.5V

V

REF

6

= V

V

INCM

4

)

REF

2

0

–2

INL (ppm of V

–4

–6

–8

–10

–1.25 – 0.75 –0.25 0.25 0.75

INCM

Noise Histogram (Output Rate =
15Hz, VCC = 2.7V, V

14

10,000 CONSECUTIVE READINGS

= 2.7V

V

CC

12

= 2.5V

V

REF

= 0V

V

IN

= 2.5V

V

10

INCM

= GND

F

O

= 25°C

T

A

8

6

4

2

0

–372 –370 –368 –366 –364 –362 –360 –358

OUTPUT CODE (ppm OF V

= 2.5V)

REF

GAUSSIAN
DISTRIBUTION
m = –365ppm
σ = 1.55ppm

= 1.25V

TA = –45°C

INPUT VOLTAGE (V)

)

REF

2435 G08

CC

= 2.7V,

CC

TA = 25°C

= 2.7V,

TA = 85°C

1.25

2435 G06

24351fa

6

UW

TEMPERATURE (°C)

–50

RMS NOISE (µV)

5.0

4.8

4.6

4.4

4.2

4.0

3.8

3.6

3.4

3.2

3.0
0

50

75

2435 G12

–25

25

100

FO = GND
V

CC

= 5V

V

REF

= 5V

V

IN

= 0V

V

INCM

= GND

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2435/LTC2435-1

RMS Noise vs Input Differential
Voltage

1.5
VCC = 5V

= 5V

V

1.4

REF

V

= 2.5V

INCM

1.3

)

RMS NOISE (ppm OF V

= GND

F

O

REF

= 25°C

T

A

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

–2.5 –2 –1.5 –1

INPUT DIFFERENTIAL VOLTAGE (V)

RMS Noise vs V

5.0
FO = GND

+

4.8

= V

REF
REF– = GND

4.6

= 25°C

T

A

= 0V

V

IN

4.4

4.2

4.0

3.8

RMS NOISE (µV)

3.6

3.4

3.2

3.0

2.7

V

INCM

= GND

3.1

–0.5

0.5 1 1.5 2 2.5

0

= V

CC

CC

4.3

3.9

3.5
VCC (V)

REF

4.7

5.1

2435 G10

2435 G13

5.5

RMS Noise vs V

5.0
FO = GND

+

4.8

= 5V

REF

–

= GND

REF

4.6

= 25°C

T

A

= 5V

V

CC

4.4
V

= 0V

IN

4.2

V

INCM

4.0

3.8

RMS NOISE (µV)

3.6

3.4

3.2

3.0

–1

0

RMS Noise vs V

5.0
FO = GND

–

4.8

REF

= 25°C

T

A

4.6

= 5V

V

CC

= 0V

V

IN

4.4
V

INCM

4.2

4.0

3.8

RMS NOISE (µV)

3.6

3.4

3.2

3.0

0

= GND

= GND

= GND

1

INCM

1

V

INCM

4

(V)

3

2

5

6

2435 G11

REF

4

3

2

V

(V)

REF

5

2435 G14

RMS Noise vs Temperature (TA)

Offset Error vs V

–320

–322

)

–324

REF

–326

–328

–330

–332

VCC = 5V

–1

REF
REF
V
F
T

IN
O
A

+

= 5V

–

= GND

= 0V
= GND
= 25°C

0

–334

–336

OFFSET ERROR (ppm OF V

–338

–340

INCM

3

2

1

V

(V)

INCM

5

6

2435 G15

4

Offset Error vs Temperature Offset Error vs V

–320

–322

)

–324

REF

–326

–328

–330

–332

–334

–336

OFFSET ERROR (ppm OF V

–338

–340

–45 –15

–30 0

TEMPERATURE (°C)

15

VCC = 5V

= 5V

V

REF

= 0V

V

IN

= GND

V

INCM

= GND

F

O

60

30 90

45

75

2435 G16

–320

REF+ = V

–322

)

–324

REF

–326

–328

–330

–332

–334

–336

OFFSET ERROR (ppm OF V

–338

–340

2.7

CC

REF– = GND

= 0V

V

IN

= GND

V

INCM

= GND

F

O

= 25°C

T

A

3.1

3.5

= V

CC

REF

4.7

3.9 5.5

4.3

V

(V)

CC

5.1

2435 G17

Offset Error vs V

–1.60

–1.61

–1.62

–1.63

–1.64

–1.65

–1.66

FO = GND

0

REF
T
V
V
V

A

CC
IN
INCM

–

= GND

= 25°C

= 5V

= 0V

= GND

1

–1.67

OFFSET ERROR (mV)

–1.68

–1.69

–1.70

REF

2

V

(V)

REF

5

2435 G18

24351fa

4

3

7

LTC2435/LTC2435-1

REJECTION (dB)

0

–20

–40

–60

–80

–100

–120

–140

FREQUENCY AT V

CC

(Hz)

13800 13950

2435 G24

13850 13900 14000

VCC = 4.1V

DC

±0.7V
REF+ = 2.5V
REF

–

= GND

IN

+

= GND

IN

–

= GND

F

O

= GND

T

A

= 25°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Full-Scale Error vs Temperature Full-Scale Error vs V

–330

)

REF

–340

–350

–360

FULL-SCALE ERROR (ppm OF V

–370

–60 100

PSRR vs Frequency at V

FO = GND

= 5V

V

CC

= 5V

V

REF

= 2.5V

V

INCM

–20

20

TEMPERATURE (°C)

+FS ERROR

–FS ERROR

60–40 0 40

CC

(LTC2435-1)

0

–20

–40

–60

VCC = 4.1V
REF
REF

+

IN

–

IN

= GND

F

O

= 25°C

T

A

+

= 2.5V

–

= GND
= GND
= GND

DC

±1.4V

80

2435 G19

–300

)

–400

REF

–500

–600

–700

–800

FULL-SCALE ERROR(ppm OF V

–900

+FS ERROR

–FS ERROR

2.7

3.1 3.5

PSRR vs Frequency at V
(LTC2435-1)

0

VCC = 4.1V

DC

REF+ = 2.5V

–

–20

–40

–60

REF
IN
IN
F

O

T

+
–

A

= GND
= GND
= GND

= GND
= 25°C

CC

V

REF

–

REF
V

INCM

FO = GND

= 25°C

T

A

4.3 5.1 5.5

3.9 4.7
VCC (V)

= 2.5V

= GND

= 0.5V

CC

REF

2435 G20

+Full-Scale Gain Error vs V

20

V

= 2.5V

REF

–

= GND

REF

)

REF

+FS GAIN ERROR (ppm OF V

15

10

5

0

–5

V

INCM

FO = GND
T

A

2.7

= 0.5V

= 25°C

3.1

REF

3.9 5.5

3.5
V

CC

PSRR vs Frequency at V
(LTC2435-1)

(V)

4.3

4.7

CC

5.1

2435 G21

CC

REJECTION (dB)

REJECTION (dB)

–80

–100

–120

–140

0

60 80

40

20

FREQUENCY AT VCC (Hz)

PSRR vs Frequency at V
(LTC2435)

0

–20

–40

–60

–80

–100

–120

–140

VCC = 4.1V
REF
REF

+

IN

–

IN

= GND

F

O

= 25°C

T

A

0

±1.4V

DC

+

= 2.5V

–

= GND
= GND
= GND

80 120 160 200 240

40

FREQUENCY AT V

–80

REJECTION (dB)

–100

–120

–140

200 220180160140120100

2435 G22

CC

1

PSRR vs Frequency at V
(LTC2435)

0

VCC = 4.1V
REF+ = 2.5V

–20

REF
IN
IN

–40

F

O

T

A

–60

–80

REJECTION (dB)

–100

–120

–140

1

(Hz)

CC

2435 G25

100 1000 10000 1000001000000

10

FREQUENCY AT VCC (Hz)

DC

–

= GND

+

= GND

–

= GND
= GND
= 25°C

100 1000 10000 1000001000000

10

FREQUENCY AT VCC (Hz)

CC

2435 G23

2435 G26

PSRR vs Frequency at V
(LTC2435)

0

VCC = 4.1V
REF+ = 2.5V

–20

REF

+

IN

–

IN

–40

= GND

F

O

= 25°C

T

A

–60

–80

REJECTION (dB)

–100

–120

–140

15250 15400

±0.7V

DC

–

= GND
= GND
= GND

15300 15350 15450

FREQUENCY AT V

CC

(Hz)

CC

2435 G27

24351fa

8

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC2435/LTC2435-1

Conversion Current vs
Temperature

240

230

220

210

FO = GND
CS = GND

200

SCK = NC
SDO = NC

190

180

CONVERSION CURRENT (µA)

170

160

–45

–30 –15

TEMPERATURE (°C)

Offset Change* vs Output Data
Rate

50

V

= V

INCM

REFCM

VIN = 0V

40

)

REF

OFFSET CHANGE* (ppm OF V

–

= GND

REF

30

= EXT OSC

F

O

= 25°C

T

A

20

10

0

–10

–20

–30

* RELATIVE TO OFFSET AT

–40

NORMAL OUTPUT RATE

–50

0 204060

OUTPUT DATA RATE (READINGS/SEC)

80

VCC = V

120 140 160 180 200

100

VCC = 5.5V

VCC = 5V

VCC = 3V

VCC = 2.7V

45 60 75 9030150

REF

VCC = 2.7V

= 2.5V

V

REF

= 5V

2435 G28

2435 G31

Conversion Current vs
Output Data Rate

1000

V

= V

REF

CC

IN+ = GND

900

–

= GND

IN
SCK = NC

800

SDO = NC

700

SDI = GND
CS = GND

600

= EXT OSC

F

O

= 25°C

T

A

500

400

SUPPLY CURRENT (µA)

300

200

100

0102030

OUTPUT DATA RATE (READINGS/SEC)

Resolution (Noise
Output Data Rate

22

21

20

19

18

V

= V

INCM

RESOLUTION (BITS)

17

16

15

0 204060

REFCM

VIN = 0V

–

= GND

REF

= EXT OSC

F

O

= 25°C

T

A

RES = LOG

2

OUTPUT DATA RATE (READINGS/SEC)

Sleep-Mode Current vs
Temperature

40

60 70 80 90 100

50

RMS

VCC = 5V

VCC = 3V

2435 G29

≤ 1LSB) vs

6

5

4

3

2

SLEEP-MODE CURRENT (µA)

1

0

–45

–30 –15

Resolution (INL

TEMPERATURE (°C)

MAX

FO = GND
CS = V
SCK = NC
SDO = NC

VCC = 5.5V

VCC = 5V

VCC = 3V

VCC = 2.7V

45 60 75 9030150

≤ 1LSB) vs

CC

2435 G30

Output Data Rate

21

VCC = V

(V

/NOISE

REF

80

100

= 5V

REF

VCC = 2.7V

= 2.5V

V

REF

)

RMS

120 140 160 180 200

2435 G32

20

19

18

17

V

RESOLUTION (BITS)

VIN = 0V

16

REF
F

15

T
RES = LOG

14

0 204060

VCC = V

VCC = 2.7V

= 2.5V

V

REF

= V

INCM

REFCM

–

= GND

= EXT OSC

O

= 25°C

A

(V

/INL

2

REF

80

OUTPUT DATA RATE (READINGS/SEC)

= 5V

REF

)

MAX

120 140 160 180 200

100

2435 G33

24351fa

9

LTC2435/LTC2435-1

UUU

PI FU CTIO S

GND (Pins 1, 7, 8, 9, 10, 15, 16): Ground. Multiple ground
pins internally connected for optimum ground current flow
and V
ground plane through a low impedance connection. All seven
pins must be connected to ground for proper operation.

VCC (Pin 2): Positive Supply Voltage. Bypass to GND
(Pin 1) with a 10µF tantalum capacitor in parallel with

0.1µF ceramic capacitor as close to the part as possible.

REF+ (Pin 3), REF– (Pin 4): Differential Reference Input.
The voltage on these pins can have any value between GND
and V
maintained more positive than the reference negative
input, REF–, by at least 0.1V.

IN+ (Pin 5), IN– (Pin 6): Differential Analog Input. 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
the converter produces unique overrange and underrange
output codes.

CS (Pin 11): Active LOW Digital Input. A LOW on this pin
enables the SDO digital 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 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.

decoupling. Connect each one of these pins to a

CC

as long as the reference positive input, REF+, is

CC

) to 0.5 • (V

REF

). Outside this input range

REF

SDO (Pin 12): Three-State Digital Output. During the Data
Output period, this pin is used as serial data output. When
the chip select CS is HIGH (CS = V
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.

SCK (Pin 13): Bidirectional Digital Clock Pin. In Internal
Serial Clock Operation mode, SCK is used as digital output
for the internal serial interface clock during the Data
Output period. In External Serial Clock Operation mode,
SCK is used as digital input for the external serial interface
clock during the Data Output period. A weak internal pull­up 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 14): Frequency Control Pin. Digital input that

O

controls the ADC’s notch frequencies and conversion
time. When the FO pin is connected to VCC (LTC2435 only),
the converter uses its internal oscillator and the digital
filter first null is located at 50Hz. When the FO pin is
connected to GND (FO = OV), the converter uses its internal
oscillator and the digital filter first null is located at 60Hz
(LTC2435) or simultaneous 50Hz/60Hz (LTC2435-1).
When FO is driven by an external clock signal with a
frequency f
system clock and the digital filter first null is located at a
frequency f

, the converter uses this signal as its

EOSC

/2560.

EOSC

) the SDO pin is in a

CC

10

24351fa

LTC2435/LTC2435-1

1.69k

SDO

2435 TA04

Hi-Z TO V

OL

VOH TO V

OL

VOL TO Hi-Z

C

LOAD

= 20pF

V

CC

UU

W

FU CTIO AL BLOCK DIAGRA

V

CC

GND

+

REF
REF

IN

–

IN

+
–

+
–

∫∫∫

∑

–+

DAC

ADC

AUTOCALIBRATION

AND CONTROL

DECIMATING FIR

INTERNAL

OSCILLATOR

SERIAL

INTERFACE

(INT/EXT)

F

O

SDO

SCK

CS

2435 F01

TEST CIRCUITS

SDO

1.69k

Hi-Z TO V
VOL TO V

OH

VOH TO Hi-Z

Figure 1. Functional Block Diagram

= 20pF

C

LOAD

OH

2435 TA03

24351fa

11

LTC2435/LTC2435-1

U

WUU

APPLICATIO S I FOR ATIO

CONVERTER OPERATION

Converter Operation Cycle

The LTC2435/LTC2435-1 are low power, delta-sigma ana­log-to-digital converters with an easy to use 3-wire serial
interface (see Figure 1). Their operation is made up of
three states. The converter operating cycle begins with the
conversion, followed by the sleep state and ends with the
data output (see Figure 2). The 3-wire interface consists of
serial data output (SDO), serial clock (SCK) and chip select
(CS).

CONVERT

SLEEP

There is no latency in the conversion result. The data
output corresponds to the conversion just performed.
This result is shifted out on the serial data out pin (SDO)
under the control of the serial clock (SCK). Data is updated
on the falling edge of SCK allowing the user to reliably latch
data on the rising edge of SCK (see Figure 3). The data
output state is concluded once 24 bits are read out of the
ADC or when CS is brought HIGH. The device automati­cally initiates a new conversion and the cycle repeats.

Through timing control of the CS and SCK pins, the
LTC2435/LTC2435-1 offer several flexible modes of op­eration (internal or external SCK and free-running conver­sion modes). These various modes do not require pro­gramming configuration registers; moreover, they do not
disturb the cyclic operation described above. These modes
of operation are described in detail in the Serial Interface
Timing Modes section.

FALSE

CS = LOW

AND

SCK

TRUE

DATA OUTPUT

2435 F02

Figure 2. LTC2435 State Transition Diagram

Initially, the LTC2435/LTC2435-1 perform a conversion.
Once the conversion is complete, the device enters the
sleep state. While in this sleep state, power consumption
is reduced by an order of magnitude if CS is HIGH. The part
remains in the sleep state as long as CS is HIGH. The
conversion result is held indefinitely in a static shift
register while the converter is in the sleep state.

Once CS is pulled LOW, the device exits the low power
sleep mode and enters the data output state. If CS is pulled
HIGH before the first rising edge of SCK, the device returns
to the sleep mode and the conversion result is still held in
the internal static shift register. If CS remains LOW after
the first rising edge of SCK, the device begins outputting
the conversion result. Taking CS HIGH at this point will
terminate the data output state and start a new conversion.

Conversion Clock

A major advantage the delta-sigma converter offers over
conventional type converters is an on-chip digital filter
(commonly implemented as a Sinc or Comb filter). For
high resolution, low frequency applications, this filter is
typically designed to reject line frequencies of 50Hz or
60Hz plus their harmonics. The filter rejection perfor­mance is directly related to the accuracy of the converter
system clock. The LTC2435/LTC2435-1 incorporate a
highly accurate on-chip oscillator. This eliminates the
need for external frequency setting components such as
crystals or oscillators. Clocked by the on-chip oscillator,
the LTC2435 achieves a minimum of 110dB rejection at
the line frequency (50Hz or 60Hz ±2%), while the
LTC2435-1 achieves a minimum of 87db rejection at 50Hz
±2% and 60Hz ±2% simultaneously.

Ease of Use

The

LTC2435/LTC2435-1

data output has no latency,
filter settling delay or redundant data associated with the
conversion cycle. There is a one-to-one correspondence
between the conversion and the output data. Therefore,
multiplexing multiple analog voltages is easy.

12

24351fa