Analog Devices AD7714 c Datasheet

3 V/5 V, CMOS, 500 ␮A

REF IN(+)

MCLK IN

MCLK OUT

A = 1–128

CHARGE

BALANCING

A/D CONVERTER

REF IN(–)

AD7714

BUFFER

AGND

BUFFER

SERIAL INTERFACE

AGND

DGND

Σ-∆

MODULATOR

SYNC

STANDBY

DIGITAL FILTER

PGA

1mA

AIN1 AIN2 AIN3 AIN4 AIN5 AIN6

SWITCHING

MATRIX

CLOCK

GENERATION

SCLK

DIN DOUT

POL

DRDY

RESET

FEATURES Charge Balancing ADC

24 Bits No Missing Codes

0.0015% Nonlinearity

Five-Channel Programmable Gain Front End

Gains from 1 to 128 Can Be Configured as Three Fully Differential Inputs or Five Pseudo-Differential Inputs

Three-Wire Serial Interface

SPI™, QSPI™, MICROWIRE™ and DSP Compatible 3 V (AD7714-3) or 5 V (AD7714-5) Operation Low Noise (<150 nV rms) Low Current (350␣ ␮A typ) with Power-Down (5 ␮A typ) AD7714Y Grade:

+2.7 V to 3.3 V or +4.75 V to +5.25 V Operation

0.0010% Linearity Error

–40ⴗC to +105ⴗC Temperature Range

Schmitt Trigger on SCLK and DIN

Low Current (226␣ ␮A typ) with Power-Down (4 ␮A typ)

Lower Power Dissipation than Standard AD7714

Available in 24-Lead TSSOP Package Low-Pass Filter with Programmable Filter Cutoffs Ability to Read/Write Calibration Coefficients

APPLICATIONS Portable Industrial Instruments Portable Weigh Scales Loop-Powered Systems Pressure Transducers

GENERAL DESCRIPTION†

The AD7714 is a complete analog front end for low-frequency measurement applications. The device accepts low level signals directly from a transducer and outputs a serial digital word. It employs a sigma-delta conversion technique to realize up to 24 bits of no missing codes performance. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an onchip digital filter. The first notch of this digital filter can be programmed via the on-chip control register allowing adjustment of the filter cutoff and settling time.

The part features three differential analog inputs (which can also be configured as five pseudo-differential analog inputs) as well as a differential reference input. It operates from a single supply (+3␣ V or +5␣ V). The AD7714 thus performs all signal conditioning and conversion for a system consisting of up to five channels.

The AD7714 is ideal for use in smart, microcontroller- or DSPbased systems. It features a serial interface that can be configured

*Protected by U.S. Patent No. 5,134,401. †See page 39 for data sheet index. SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corporation.

REV. C

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Signal Conditioning ADC

AD7714*

FUNCTIONAL BLOCK DIAGRAM

for three-wire operation. Gain settings, signal polarity and channel selection can be configured in software using the serial port. The AD7714 provides self-calibration, system calibration and background calibration options and also allows the user to read and write the on-chip calibration registers.

CMOS construction ensures very low power dissipation, and the power-down mode reduces the standby power consumption to

15␣ µW typ. The part is available in a 24-pin, 0.3 inch-wide, plastic

dual-in-line package (DIP); a 24-lead small outline (SOIC) package, a 28-lead shrink small outline package (SSOP) and a 24-lead thin shrink small outline package (TSSOP).

PRODUCT HIGHLIGHTS

1. The AD7714Y offers the following features in addition to the standard AD7714: wider temperature range, Schmitt trigger on SCLK and DIN, operation down to 2.7 V, lower power consumption, better linearity, and availability in 24-lead TSSOP package.

2. The AD7714 consumes less than 500 µA (f

or 1 mA (f

= 2.5␣ MHz) in total supply current, making

CLK IN

it ideal for use in loop-powered systems.

3. The programmable gain channels allow the AD7714 to accept input signals directly from a strain gage or transducer removing a considerable amount of signal conditioning.

4. The AD7714 is ideal for microcontroller or DSP processor applications with a three-wire serial interface reducing the number of interconnect lines and reducing the number of optocouplers required in isolated systems. The part contains on-chip registers that allow control over filter cutoff, input gain, channel selection, signal polarity and calibration modes.

5. The part features excellent static performance specifications

with 24-bit no missing codes, ±0.0015% accuracy and low

rms noise (140 nV). Endpoint errors and the effects of temperature drift are eliminated by on-chip self-calibration, which removes zero-scale and full-scale errors.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1998

CLK IN

= 1␣ MHz)

AD7714-5–SPECIFICATIONS

= 2.4576␣ MHz unless otherwise noted. All specifications T

CLK IN

Parameter A Versions

(AVDD = +5␣ V, DVDD = +3.3␣ V or +5␣ V, REF IN(+) = +2.5␣ V; REF␣ IN(–) = AGND;

to T

MIN

Units Conditions/Comments

unless otherwise noted.)

MAX

STATIC PERFORMANCE

No Missing Codes 24 Bits min Guaranteed by Design. Bipolar Mode. For Filter Notches ≤ 60 Hz

22 Bits min For Filter Notch = 100 Hz 18 Bits min For Filter Notch = 250 Hz 15 Bits min For Filter Notch = 500 Hz 12 Bits min For Filter Notch = 1 kHz

Output Noise See Tables I to IV Depends on Filter Cutoffs and Selected Gain Integral Nonlinearity ±0.0015 % of FSR max Filter Notches ≤ 60 Hz Unipolar Offset Error See Note 2 Unipolar Offset Drift

0.5 µV/°C typ For Gains of 1, 2, 4

0.3 µV/°C typ For Gains of 8, 16, 32, 64, 128

Bipolar Zero Error See Note 2 Bipolar Zero Drift

Positive Full-Scale Error Full-Scale Drift

Gain Error Gain Drift Bipolar Negative Full-Scale Error ±0.0015 % of FSR max Typically ±0.0004% Bipolar Negative Full-Scale Drift

3, 7

3, 5

0.5 µV/°C typ For Gains of 1, 2, 4

0.3 µV/°C typ For Gains of 8, 16, 32, 64, 128 See Note 2

0.5 µV/°C typ For Gains of 1, 2, 4

0.3 µV/°C typ For Gains of 8, 16, 32, 64, 128 See Note 2

0.5 ppm of FSR/°C typ

1 µV/°C typ For Gains of 1, 2, 4

0.6 µV/°C typ For Gains of 8, 16, 32, 64, 128

ANALOG INPUTS/REFERENCE INPUTS Specifications for AIN and REF IN Unless Noted

Input Common-Mode Rejection (CMR) 90 dB min At DC. Typically 102 dB Normal-Mode 50 Hz Rejection Normal-Mode 60 Hz Rejection Common-Mode 50 Hz Rejection Common-Mode 60 Hz Rejection Common-Mode Voltage Range Absolute AIN/REF IN Voltage

Absolute/Common-Mode AIN Voltage

AIN Input Current

AIN Sampling Capacitance AIN Differential Voltage Range

AIN Input Sampling Rate, f REF IN(+) – REF IN(–) Voltage +2.5 V nom ±1% for Specified Performance. Functional with Lower V

REF IN Input Sampling Rate, f

100 dB min For Filter Notches of 10 100 dB min For Filter Notches of 10 150 dB min For Filter Notches of 10 150 dB min For Filter Notches of 10 AGND to AV

V min to V max AIN for BUFFER = 0 and REF IN

AGND – 30 mV V min AIN for BUFFER = 0 and REF IN AV

+ 30 mV V max

AGND + 50 mV V min BUFFER = 1. A Version AV

– 1.5 V V max

1 nA max A Version 7 pF max 0 to +V ±V GAIN × f f

CLK␣ IN

CLK IN

/GAIN11nom Unipolar Input Range (B/U Bit of Filter High Register = 1)

REF

/GAIN nom Bipolar Input Range (B/U Bit of Filter High Register = 0)

REF

/64 For Gains of 1, 2, 4

CLK␣ IN

/8 For Gains of 8, 16, 32, 64, 128

/64

Hz Hz Hz Hz

, 25

, 50 Hz, ±0.02 × f

, 30

, 60 Hz, ±0.02 × f

, 25

, 50 Hz, ±0.02 × f

, 30

, 60 Hz, ±0.02 × f

NOTCH

REF

LOGIC INPUTS

Input Current ±10 µA max All Inputs Except MCLK IN

, Input Low Voltage 0.8 V max DV

INL

, Input Low Voltage 0.4 V max DVDD = +3.3␣ V

INL

, Input High Voltage 2.4 V min DV

INH

, Input High Voltage 2.0 V min DV

INH

MCLK IN Only

, Input Low Voltage 0.8 V max DVDD = +5␣ V

INL

, Input Low Voltage 0.4 V max DVDD = +3.3␣ V

INL

, Input High Voltage 3.5 V min DVDD = +5␣ V

INH

, Input High Voltage 2.5 V min DVDD = +3.3␣ V

INH

LOGIC OUTPUTS (Including MCLK OUT)

, Output Low Voltage 0.4 V max I

, Output High Voltage 4.0 V min I

, Output High Voltage DV

Floating State Leakage Current ±10 µA max Floating State Output Capacitance

– 0.6 V V min I

9 pF typ

= +5 V

= +3.3 V

= 800␣ µA Except for MCLK OUT.

SINK

= 100␣ µA Except for MCLK OUT.

SINK

= 200 µA Except for MCLK OUT.

SOURCE

= 100 µA Except for MCLK OUT.

SOURCE

DVDD = +5 V

DVDD = +3.3 V

DVDD = +5␣ V

DVDD = +3.3␣ V

Data Output Coding Binary Unipolar Mode

Offset Binary Bipolar Mode

NOTES

Temperature range is as follows: A Versions: –40°C to +85°C.

A calibration is effectively a conversion so these errors will be of the order of the conversion noise shown in Tables I to IV. This applies after calibration at the temperature of interest.

Recalibration at any temperature will remove these drift errors.

Positive Full-Scale Error includes Zero-Scale Errors (Unipolar Offset Error or Bipolar Zero Error) and applies to both unipolar and bipolar input ranges.

Full-Scale Drift includes Zero-Scale Drift (Unipolar Offset Drift or Bipolar Zero Drift) and applies to both unipolar and bipolar input ranges.

Gain Error does not include Zero-Scale Errors. It is calculated as Full-Scale Error—Unipolar Offset Error for unipolar ranges and Full-Scale Error—Bipolar Zero Error for

bipolar ranges.

–2–

REV. C

AD7714

AD7714-3–SPECIFICATIONS

= 2.4576␣ MHz unless otherwise noted. All specifications T

CLK IN

(AVDD = +3.3␣ V, DVDD = +3.3␣ V, REF IN(+) = +1.25␣ V; REF␣ IN(–) = AGND;

to T

MIN

unless otherwise noted.)

MAX

Parameter A Versions Units Conditions/Comments

STATIC PERFORMANCE

No Missing Codes 24 Bits min Guaranteed by Design. Bipolar Mode. For Filter Notches ≤ 60 Hz

22 Bits min For Filter Notch = 100 Hz 18 Bits min For Filter Notch = 250 Hz 15 Bits min For Filter Notch = 500 Hz 12 Bits min For Filter Notch = 1 kHz

Output Noise See Tables I to IV Depends on Filter Cutoffs and Selected Gain

Integral Nonlinearity ±0.0015 % of FSR max Filter Notches ≤ 60 Hz

Unipolar Offset Error See Note 2 Unipolar Offset Drift

0.4 µV/°C typ For Gains of 1, 2, 4

0.1 µV/°C typ For Gains of 8, 16, 32, 64, 128

Bipolar Zero Error See Note 2 Bipolar Zero Drift

Positive Full-Scale Error Full-Scale Drift

Gain Error Gain Drift

Bipolar Negative Full-Scale Error ±0.003 % of FSR max Typically ±0.0004%

Bipolar Negative Full-Scale Drift

3, 7

3, 5

0.4 µV/°C typ For Gains of 1, 2, 4

0.1 µV/°C typ For Gains of 8, 16, 32, 64, 128

See Note 2

0.4 µV/°C typ For Gains of 1, 2, 4

0.1 µV/°C typ For Gains of 8, 16, 32, 64, 128

See Note 2

0.2 ppm of FSR/°C typ

1 µV/°C typ For Gains of 1, 2, 4

0.6 µV/°C typ For Gains of 8, 16, 32, 64, 128

ANALOG INPUTS/REFERENCE INPUTS Specifications for AIN and REF IN Unless Noted

Input Common-Mode Rejection (CMR) 90 dB min At DC. Typically 102 dB. Normal-Mode 50 Hz Rejection Normal-Mode 60 Hz Rejection Common-Mode 50 Hz Rejection Common-Mode 60 Hz Rejection Common-Mode Voltage Range Absolute AIN/REF IN Voltage

100 dB min For Filter Notches of 10 Hz, 25 Hz, 50 Hz, ±0.02 × f 100 dB min For Filter Notches of 10 Hz, 30 Hz, 60 Hz, ±0.02 × f 150 dB min For Filter Notches of 10 Hz, 25 Hz, 50 Hz, ±0.02 × f 150 dB min For Filter Notches of 10 Hz, 30 Hz, 60 Hz, ±0.02 × f

AGND to AV

V min to V max AIN for BUFFER = 0 and REF IN

AGND – 30 mV V min AIN for BUFFER = 0 and REF IN

NOTCH

AVDD + 30 mV V max

Absolute/Common-Mode AIN Voltage9AGND + 50 mV V min BUFFER = 1

AIN Input Current AIN Sampling Capacitance AIN Differential Voltage Range

AIN Input Sampling Rate, f

AVDD – 1.5 V V max 1 nA max 7 pF max 0 to +V

±V GAIN × f

CLK␣ IN

/GAIN11nom Unipolar Input Range (B/U Bit of Filter High Register = 1)

REF

/GAIN nom Bipolar Input Range (B/U Bit of Filter High Register = 0)

REF

/64 For Gains of 1, 2, 4

CLK␣ IN

/8 For Gains of 8, 16, 32, 64, 128

REF IN(+) – REF IN(–) Voltage +1.25 V nom ±1% for Specified Performance. Part Functions with

Lower V

REF IN Input Sampling Rate, f

CLK IN

/64

REF

LOGIC INPUTS

Input Current ±10 µA max

All Inputs Except MCLK IN

, Input Low Voltage 0.4 V max

INL

, Input High Voltage 2.0 V min

INH

MCLK IN Only

, Input Low Voltage 0.4 V max

INL

, Input High Voltage 2.5 V min

INH

LOGIC OUTPUTS (Including MCLK OUT)

VOL, Output Low Voltage 0.4 V max I VOH, Output High Voltage DVDD – 0.6 V min I

Floating State Leakage Current ±10 µA max

Floating State Output Capacitance

9 pF typ

= 100␣ µA Except for MCLK OUT

SINK

= 100 µA Except for MCLK OUT

SOURCE

Data Output Coding Binary Unipolar Mode

Offset Binary Bipolar Mode

NOTES

Gain Error Drift does not include Unipolar Offset Drift/Bipolar Zero Drift. It is effectively the drift of the part if zero-scale calibrations only were performed as is the case with

background calibration.

These numbers are guaranteed by design and/or characterization.

The common-mode voltage range on the input pairs applies provided the absolute input voltage specification is obeyed.

The input voltage range on the analog inputs is given here with respect to the voltage on the respective negative input of its differential or pseudo-differential pair. See Table VII

for which inputs form differential pairs.

= REF IN(+) – REF IN(–).

REF

These logic output levels apply to the MCLK OUT output only when it is loaded with a single CMOS load.

Sample tested at +25°C to ensure compliance.

See Burnout Current section.

REV. C

–3–

AD7714–SPECIFICATIONS

(AD7714-5); REF␣ IN(–) = AGND; MCLK␣ IN = 1␣ MHz to 2.4576␣ MHz unless otherwise noted. All specifications T

(AVDD = + 3.3␣ V to +5␣ V, DVDD = +3.3␣ V to +5␣ V, REF IN(+) = +1.25␣ V (AD7714-3) or +2.5␣ V

to T

MIN

unless otherwise noted.)

MAX

Parameter A Versions Units Conditions/Comments

TRANSDUCER BURNOUT

Current 1 µA nom Initial Tolerance ±10 % typ Drift 0.1 %/°C typ

SYSTEM CALIBRATION

Positive Full-Scale Calibration Limit Negative Full-Scale Calibration Limit Offset Calibration Limit Input Span

(1.05 × V –(1.05 × V –(1.05 × V

0.8 × V

REF

(2.1 × V

REF

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

/GAIN V min GAIN Is the Selected PGA Gain (Between 1 and 128)

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

POWER REQUIREMENTS

Power Supply Voltages

AVDD Voltage (AD7714-3) +3 to +3.6 V For Specified Performance AVDD Voltage (AD7714-5) +4.75 to +5.25 V For Specified Performance DVDD Voltage +3 to +5.25 V For Specified Performance

Power Supply Currents

AVDD Current AVDD = 3.3␣ V or 5␣ V. BST Bit of Filter High Register = 0

0.27 mA max Typically 0.2 mA. BUFFER = 0 V. f

0.6 mA max Typically 0.4 mA. BUFFER = DVDD. f

= 1␣ MHz or 2.4576␣ MHz

CLK IN

= 1␣ MHz or 2.4576␣ MHz

CLK IN

AVDD = 3.3␣ V or 5␣ V. BST Bit of Filter High Register = 1

0.5 mA max Typically 0.3␣ mA. BUFFER = 0␣ V. f

1.1 mA max Typically 0.8␣ mA. BUFFER = DVDD. f Digital I/Ps = 0␣ V or DV

External MCLK IN

DD.

Current

0.23 mA max Typically 0.15␣ mA. DVDD = 3.3␣ V. f

0.4 mA max Typically 0.3␣ mA. DVDD = 5␣ V. f

CLK IN

0.5 mA max Typically 0.4␣ mA. DVDD = 3.3␣ V. f

Power Supply Rejection Normal-Mode Power Dissipation

0.8 mA max Typically 0.6␣ mA. DVDD = 5␣ V. f

See Note 20 dB typ

= DV

= +3.3␣ V. Digital I/Ps = 0␣ V or DVDD. External MCLK IN

CLK IN

1.65 mW max Typically 1.25␣ mW. BUFFER = 0␣ V. f

2.75 mW max Typically 1.8␣ mW. BUFFER = +3.3␣ V. f

2.55 mW max Typically 2␣ mW. BUFFER = 0␣ V. f

3.65 mW max Typically 2.6␣ mW. BUFFER = +3.3␣ V. f

Normal-Mode Power Dissipation AV

= DV

= +5␣ V. Digital I/Ps = 0␣ V or DVDD. External MCLK IN

3.35 mW max Typically 2.5␣ mW. BUFFER = 0␣ V. f

5 mW max Typically 3.5␣ mW. BUFFER = +5␣ V. f

5.35 mW max Typically 4␣ mW. BUFFER = 0␣ V. f

Standby (Power-Down) Current Standby (Power-Down) Current

NOTES

After calibration, if the input voltage exceeds positive full scale, the converter will output all 1s. If the input is less than negative full scale, then the device outputs all 0s.

These calibration and span limits apply provided the absolute voltage on the analog inputs does not exceed AVDD + 30␣ mV or go more negative than AGND␣ –␣ 30␣ mV. The

offset calibration limit applies to both the unipolar zero point and the bipolar zero point.

For higher gains (≥8) at f

When using a crystal or ceramic resonator across the MCLK pins as the clock source for the device, the DVDD current and power dissipation will vary depending on the crystal

or resonator type (see Clocking and Oscillator Circuit section).

Measured at dc and applies in the selected passband. PSRR at 50 Hz will exceed 120 dB with filter notches of 5 Hz, 10 Hz, 25 Hz or 50 Hz. PSRR at 60 Hz will exceed 120 dB

with filter notches of 6 Hz, 10 Hz, 30 Hz or 60 Hz.

PSRR depends on gain. For Gain of 1 : 70 dB typ: For Gain of 2 : 75 dB typ; For Gain of 4 : 80 dB typ; For Gains of 8 to 128 : 85 dB typ.

If the external master clock continues to run in standby mode, the standby current increases to 150 µA typical with 5 V supplies and 75 µA typical with 3.3 V supplies. When

using a crystal or ceramic resonator across the MCLK pins as the clock source for the device, the internal oscillator continues to run in standby mode and the power dissipation depends on the crystal or resonator type (see Standby Mode section).

Specifications subject to change without notice.

CLK␣ IN

= 2.4576␣ MHz, the BST bit of the Filter High Register must be set to 1. For other conditions, it can be set to 0.

7 mW max Typically 5␣ mW. BUFFER = +5␣ V. f

40 µA max External MCLK IN = 0 V or DVDD. Typically 20␣ µA. V 10 µA max External MCLK IN = 0 V or DVDD. Typically 5␣ µA. V

= 2.4576␣ MHz

CLK IN

= 2.4576␣ MHz

CLK IN

= 1␣ MHz

CLK IN

= 1␣ MHz

= 2.4576␣ MHz

CLK IN

= 2.4576␣ MHz

= 1␣ MHz. BST Bit = 0

CLK IN

= 1␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

= 1␣ MHz. BST Bit = 0

CLK IN

= 1␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

= +5 V

= +3.3 V

REV. C–4–

AD7714

AD7714Y–SPECIFICATIONS

and +2.5 V with AVDD = 5 V; REF␣ IN(–) = AGND; MCLK IN = 2.4576␣ MHz unless otherwise noted. All specifications T

Parameter Y Versions

(AVDD = DVDD = +2.7␣ V to +3.3␣ V or 4.75 V to 5.25 V, REF IN(+) = +1.25␣ V; with AVDD = 3 V

to T

unless otherwise noted.)

MAX

Units Conditions/Comments

MIN

STATIC PERFORMANCE

No Missing Codes 24 Bits min Guaranteed by Design. For Filter Notches ≤ 60 Hz

22 Bits min For Filter Notch = 100 Hz 18 Bits min For Filter Notch = 250 Hz 15 Bits min For Filter Notch = 500 Hz 12 Bits min For Filter Notch = 1 kHz

Output Noise See Tables I to IV Depends on Filter Cutoffs and Selected Gain

Integral Nonlinearity ±0.001 % of FSR max Filter Notches ≤ 60 Hz.

Unipolar Offset Error See Note 2 Unipolar Offset Drift

0.4 µV/°C typ For Gains of 1, 2, 4

0.1 µV/°C typ For Gains of 8, 16, 32, 64, 128

Bipolar Zero Error See Note 2 Bipolar Zero Drift

Positive Full-Scale Error Full-Scale Drift

Gain Error Gain Drift

Bipolar Negative Full-Scale Error

Bipolar Negative Full-Scale Drift

3, 7

3, 5

0.4 µV/°C typ For Gains of 1, 2, 4

0.1 µV/°C typ For Gains of 8, 16, 32, 64, 128

See Note 2

0.4 µV/°C typ For Gains of 1, 2, 4

0.1 µV/°C typ For Gains of 8, 16, 32, 64, 128

See Note 2

0.2 ppm of FSR/

±0.0015 % of FSR max AVDD = 5 V. Typically ±0.0004% ±0.003 % of FSR max AVDD = 3 V. Typically ±0.0004% 1 µV/°C typ For Gains of 1 to 4

°C typ

0.6 µV/°C typ For Gains of 8 to 128

ANALOG INPUTS/REFERENCE INPUTS Specifications for AIN and REF IN Unless Noted

Input Common-Mode Rejection (CMR)890 dB min At DC. Typically 102 dB. Normal-Mode 50 Hz Rejection Normal-Mode 60 Hz Rejection Common-Mode 50 Hz Rejection Common-Mode 60 Hz Rejection

Absolute/Common-Mode REF IN Voltage8AGND to AVDDV min to V max Absolute/Common-Mode AIN Voltage8, 9AGND – 30 mV V min BUF Bit of Setup Register = 0

AVDD + 30 mV V max

Absolute/Common-Mode AIN Voltage

AIN DC Input Current AIN Sampling Capacitance

AIN Differential Voltage Range

AIN Input Sampling Rate, f

Reference Input Range

REF IN(+) – REF IN(–) Voltage 1/1.75 V min/max AVDD = 2.7 V to 3.3 V. V REF IN(+) – REF IN(–) Voltage 1/3.5 V min/max AVDD = 4.75 V to 5.25 V. V

REF IN Input Sampling Rate, f

8, 9

AGND + 50 mV V min BUF Bit of Setup Register = 1 AVDD – 1.5 V V max 1 nA max

7 pF max 0 to +V

±V GAIN × f

CLK␣ IN

CLK IN

/GAIN11nom Unipolar Input Range (B/U Bit of Filter High Register = 1)

REF

/GAIN nom Bipolar Input Range (B/U Bit of Filter High Register = 0)

REF

/64 For Gains of 1 to 4

CLK␣ IN

/8 For Gains of 8 to 128

/64

= 1.25 ±1% for Specified Performance

REF

= 2.5 ±1% for Specified Performance

REF

LOGIC INPUTS

Input Current ±10 µA max

All Inputs Except MCLK IN

, Input Low Voltage 0.8 V max DVDD = 5 V

INL

, Input High Voltage 2.4 V min DVDD = 5 V

INH

0.4 V max DVDD = 3 V

2 V min DVDD = 3 V

SCLK & DIN Only (Schmitt Triggered Input) DVDD = 5 V NOMINAL

T+

T–

VT+ – V

SCLK & DIN Only (Schmitt Triggered Input) DVDD = 3 V NOMINAL

MCLK In Only DVDD = 5 V NOMINAL

MCLK In Only DVDD = 3 V NOMINAL

T–

T+

T–

VT+ – V

T–

, Input Low Voltage 0.8 V max

INL

, Input High Voltage 3.5 V min

INH

, Input Low Voltage 0.4 V max

INL

, Input High Voltage 2.5 V min

INH

1.4/3 V min/V max

0.8/1.4 V min/V max

0.4/0.8 V min/V max

1/2.5 V min/V max

0.4/1.1 V min/V max

0.375/0.8 V min/V max

LOGIC OUTPUTS (Including MCLK OUT)

VOL, Output Low Voltage 0.4 V max I VOL, Output Low Voltage 0.4 V max I VOH, Output High Voltage 4 V min I

REV. C

–5–

= 800␣ µA with DV

SINK

= 100␣ µA with DV

SINK

= 200 µA with DV

SOURCE

= 5 V. Except for MCLK OUT

= 3 V. Except for MCLK OUT

= 5 V. Except for MCLK OUT

NOTCH

AD7714Y

Parameter Y Versions Units Conditions/Comments

LOGIC OUTPUTS (Continued))

VOH, Output High Voltage DVDD – 0.6 V min I

Floating State Leakage Current ±10 µA max

Floating State Output Capacitance

ata Output Coding Binary Unipolar Mode

9 pF typ

= 100 µA with DV

SOURCE

= 3 V. Except for MCLK OUT

Offset Binary Bipolar Mode

TRANSDUCER BURNOUT

Current 1 µA nom Initial Tolerance ±10 % typ Drift 0.1 %/°C typ

SYSTEM CALIBRATION

Positive Full-Scale Calibration Limit Negative Full-Scale Calibration Limit Offset Calibration Limit Input Span

(1.05 × V

–(1.05 × V –(1.05 × V

0.8 × V (2.1 × V

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

/GAIN V min GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

)/GAIN V max GAIN Is the Selected PGA Gain (Between 1 and 128)

REF

POWER REQUIREMENTS

Power Supply Voltages

AVDD Voltage +2.7 to +3.3 or V

+4.75 to +5.25 V For Specified Performance

DVDD Voltage +2.7 to +5.25 V For Specified Performance

Power Supply Currents

AVDD Current AVDD = 3 V or 5␣ V. BST Bit of Filter High Register = 017, CLKDIS = 1

0.28 mA max Typically 0.22 mA. BUFFER = 0 V. f

0.6 mA max Typically 0.45 mA. BUFFER = DVDD. f AVDD = 3 V or 5␣ V. BST Bit of Filter High Register = 1

0.5 mA max Typically 0.38␣ mA. BUFFER = 0␣ V. f

Current

Power Supply Rejection Normal-Mode Power Dissipation

1.1 mA max Typically 0.8␣ mA. BUFFER = DVDD. f

0.080 mA max Typically 0.06␣ mA. DVDD = 3 V. f

Digital I/Ps = 0␣ V or DV

0.16 mA max Typically 0.13␣ mA. DVDD = 5␣ V. f

0.18 mA max Typically 0.15␣ mA. DVDD = 3 V. f

0.35 mA max Typically 0.3 mA. DVDD = 5␣ V. f

See Note 20 dB typ

= DV

BST Bit of Filter High Register = 0

= +3 V. Digital I/Ps = 0␣ V or DVDD. External MCLK IN

External MCLK IN, CLKDIS = 1

DD.

CLK IN

1.05 mW max Typically 0.84␣ mW. BUFFER = 0␣ V. f

2.04 mW max Typically 1.53␣ mW. BUFFER = +3 V. f

1.35 mW max Typically 1.11␣ mW. BUFFER = 0␣ V. f

2.34 mW max Typically 1.9␣ mW. BUFFER = +3 V. f

Normal-Mode Power Dissipation AV

2.1 mW max Typically 1.75 mW. BUFFER = 0␣ V. f

= DV

= +5␣ V. Digital I/Ps = 0␣ V or DVDD. External MCLK IN

3.75 mW max Typically 2.9 mW. BUFFER = +5␣ V. f

3.1 mW max Typically 2.6␣ mW. BUFFER = 0␣ V. f

Standby (Power-Down) Current Standby (Power-Down) Current

NOTES

Temperature range is as follows: Y Version: –40°C to +105°C.

A calibration is effectively a conversion so these errors will be of the order of the conversion noise shown in Tables I to IV. This applies after calibration at the temperature of interest.

Recalibration at any temperature will remove these drift errors.

Positive Full-Scale Error includes Zero-Scale Errors (Unipolar Offset Error or Bipolar Zero Error) and applies to both unipolar and bipolar input ranges.

Full-Scale Drift includes Zero-Scale Drift (Unipolar Offset Drift or Bipolar Zero Drift) and applies to both unipolar and bipolar input ranges.

Gain Error does not include Zero-Scale Errors. It is calculated as Full-Scale Error—Unipolar Offset Error for unipolar ranges and Full-Scale Error—Bipolar Zero Error for

bipolar ranges.

Gain Error Drift does not include Unipolar Offset Drift/Bipolar Zero Drift. It is effectively the drift of the part if zero-scale calibrations only were performed as is the case with background calibration.

These numbers are guaranteed by design and/or characterization.

The common-mode voltage range on the input pairs applies provided the absolute input voltage specification is obeyed.

The input voltage range on the analog inputs is given here with respect to the voltage on the respective negative input of its differential or pseudo-differential pair. See Table VII for which

inputs form differential pairs.

= REF IN(+) – REF IN(–).

REF

These logic output levels apply to the MCLK OUT output only when it is loaded with a single CMOS load.

Sample tested at +25°C to ensure compliance.

See Burnout Current section.

After calibration, if the input voltage exceeds positive full scale, the converter will output all 1s. If the input is less than negative full scale, then the device outputs all 0s.

These calibration and span limits apply provided the absolute voltage on the analog inputs does not exceed AVDD + 30␣ mV or go more negative than AGND␣ –␣ 30␣ mV. The offset calibration

limit applies to both the unipolar zero point and the bipolar zero point.

For higher gains (≥8) at f

When using a crystal or ceramic resonator across the MCLK pins as the clock source for the device, the DVDD current and power dissipation will vary depending on the crystal or resonator

type (see Clocking and Oscillator Circuit section).

Measured at dc and applies in the selected passband. PSRR at 50 Hz will exceed 120 dB with filter notches of 5 Hz, 10 Hz, 25 Hz or 50 Hz. PSRR at 60 Hz will exceed 120 dB with filter

notches of 6 Hz, 10 Hz, 30 Hz or 60 Hz.

PSRR depends on gain.

If the external master clock continues to run in standby mode, the standby current increases to 150 µA typical with 5 V supplies and 75 µA typical with 3.3 V supplies. When using a crystal

or ceramic resonator across the MCLK pins as the clock source for the device, the internal oscillator continues to run in standby mode and the power dissipation depends on the crystal or resonator type (see Standby Mode section).

Specifications subject to change without notice.

CLK␣ IN

= 2.4576␣ MHz, the BST bit of the Filter High Register must be set to 1. For other conditions, it can be set to 0.

Gain 1 2 4 8–128

= 3 V 86 dB 78 dB 85 dB 93 dB

AVDD = 5 V 90 dB 78 dB 84 dB 91 dB

4.75 mW max Typically 3.75␣ mW. BUFFER = +5␣ V. f

18 µA max External MCLK IN = 0 V or DVDD. Typically 9␣ µA. V 10 µA max External MCLK IN = 0 V or DVDD. Typically 4␣ µA. V

= 1␣ MHz or 2.4576␣ MHz

CLK IN

= 1␣ MHz or 2.4576␣ MHz

CLK IN

= 2.4576␣ MHz

CLK IN

= 2.4576␣ MHz

CLK IN

= 1␣ MHz = 1␣ MHz = 2.4576␣ MHz

= 2.4576␣ MHz

= 1␣ MHz. BST Bit = 0

CLK IN

= 1␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

= 1␣ MHz. BST Bit = 0

CLK IN

= 1␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

= 2.4576␣ MHz. BST Bit = 0

CLK IN

–6–

= +5 V

= +3 V

REV. C

AD7714

TIMING CHARACTERISTICS

Limit at T

MIN

, T

(AVDD = DVDD = +2.7 V to +5.25 V; AGND = DGND = 0 V; f

1, 2

Logic 1 = DVDD unless otherwise noted.)

MAX

= 2.5␣ MHz; Input Logic 0 = 0 V,

CLKIN

Parameter (A, Y Versions) Units Conditions/Comments

3, 4

CLKIN

400 kHz min Master Clock Frequency: Crystal/Resonator or Externally

Supplied

2.5 MHz max For Specified Performance

CLK IN LO

CLK IN HI

DRDY

0.4 × t

CLK IN

0.4 × t

CLK IN

500 × t

CLK IN

100 ns min SYNC Pulsewidth 100 ns min RESET Pulsewidth

ns min Master Clock Input Low Time. t

CLK IN

ns min Master Clock Input High Time ns nom DRDY High Time

= 1/f

CLK IN

Read Operation t

0 ns min DRDY to CS Setup Time 0 ns min CS Falling Edge to SCLK Active Edge Setup Time 0 ns min SCLK Active Edge to Data Valid Delay

80 ns max DVDD = +5␣ V 100 ns max DV

100 ns min SCLK High Pulsewidth 100 ns min SCLK Low Pulsewidth 0 ns min CS Rising Edge to SCLK Active Edge Hold Time 10 ns min Bus Relinquish Time after SCLK Active Edge 60 ns max DV 100 ns max DV

100 ns max SCLK Active Edge to DRDY High

Write Operation t

NOTES

Sample tested at +25°C to ensure compliance. All input signals are specified with tr = tf = 5 ns (10% to 90% of DV

See Figures 6 and 7. Timing applies for all grades.

CLKIN Duty Cycle range is 45% to 55%. CLKIN must be supplied whenever the AD7714 is not in standby mode. If no clock is present in this case, the device can draw higher current than specified and possibly become uncalibrated.

The AD7714 is production tested with f

SCLK active edge is falling edge of SCLK with POL = 1; SCLK active edge is rising edge of SCLK with POL = 0.

These numbers are measured with the load circuit of Figure 1 and defined as the time required for the output to cross the V

These numbers are derived from the measured time taken by the data output to change 0.5␣ V when loaded with the circuit of Figure 1. The measured number is then extrapolated back to remove effects of charging or discharging the 100 pF capacitor. This means that the times quoted in the timing characteristics are the true bus relinquish times of the part and as such are independent of external bus loading capacitances.

DRDY returns high after the first read from the device after an output update. The same data can be read again, if required, while DRDY is high although care should be taken that subsequent reads do not occur close to the next output update.

Specifications subject to change without notice.

0 ns min CS Falling Edge to SCLK Active Edge Setup Time 30 ns min Data Valid to SCLK Edge Setup Time 20 ns min Data Valid to SCLK Edge Hold Time 100 ns min SCLK High Pulsewidth 100 ns min SCLK Low Pulsewidth 0 ns min CS Rising Edge to SCLK Edge Hold Time

at 2.4576␣ MHz (1␣ MHz for some IDD tests). It is guaranteed by characterization to operate at 400␣ kHz.

CLKIN

= +3␣ V

= +5␣ V

= +3␣ V

5, 8

) and timed from a voltage level of 1.6 V.

or VOH limits.

ORDERING GUIDE

TO OUTPUT

50pF

(800mA AT DV

SINK

100mA AT DV

(200mA AT DVDD = +5V

SOURCE

100mA AT DV

+1.6V

DD DD

= +5V = +3.3V)

= +3.3V)

Figure 1. Load Circuit for Access Time and Bus Relinquish Time

REV. C

Temperature Package

Model Supply Range Option*

AD7714AN-5 5 V –40°C to +85°C N-24 AD7714AR-5 5 V –40°C to +85°C R-24 AD7714ARS-5 5 V –40°C to +85°C RS-28 AD7714AN-3 3 V –40°C to +85°C N-24 AD7714AR-3 3 V –40°C to +85°C R-24 AD7714ARS-3 3 V –40°C to +85°C RS-28 AD7714YN 3 V/5 V –40°C to +105°C N-24 AD7714YR 3 V/5 V –40°C to +105°C R-24 AD7714YRU 3 V/5 V –40°C to +105°C RU-24 AD7714AChips-5 5 V –40°C to +85°CDie AD7714AChips-3 3 V –40°C to +85°CDie

EVAL-AD7714-5EB 5 V Evaluation Board EVAL-AD7714-3EB 3 V Evaluation Board

*N = Plastic DIP; R = SOIC; RS = SSOP; RU = Thin Shrink Small Outline.

–7–

AD7714

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS*

= +25°C unless otherwise noted)

AVDD to AGND . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V

to DGND . . . . . . . . . . . . . . . . . . . . . . . . –0.3␣ V to +7␣ V

to AGND . . . . . . . . . . . . . . . . . . . . . . . . –0.3␣ V to +7␣ V

to DGND . . . . . . . . . . . . . . . . . . . . . . . . –0.3␣ V to +7␣ V

Analog Input Voltage to AGND . . . . . –0.3 V to AV

Reference Input Voltage to AGND . . . –0.3 V to AV

Digital Input Voltage to DGND . . . . . –0.3 V to DV

Digital Output Voltage to DGND . . . . –0.3 V to DV

+ 0.3␣ V

+ 0.3 V

Operating Temperature Range

Commercial (A Version) . . . . . . . . . . . . . . . –40°C to +85°C

Extended (Y Version) . . . . . . . . . . . . . . . . . –40°C to +105°C

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

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

Plastic DIP Package, Power Dissipation . . . . . . . . . . . 450 mW

Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 105°C/W

Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . +260°C

SOIC Package, Power Dissipation . . . . . . . . . . . . . . . . 450 mW

Thermal Impedance . . . . . . . . . . . . . . . . . . . . . . 75°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C

SSOP Package, Power Dissipation . . . . . . . . . . . . . . . . 450 mW

Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 109°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C

TSSOP Package, Power Dissipation . . . . . . . . . . . . . . 450 mW

Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 128°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . +215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C

*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although these devices feature proprietary ESD protection circuitry, permanent damage may still occur on these devices if they are subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

DIP and SOIC/TSSOP

SCLK

MCLK IN

MCLK OUT

POL

SYNC

RESET

AIN1 AIN2 AIN3 AIN5 AIN4

STANDBY

AD7714

TOP VIEW

(Not to Scale)

PIN CONFIGURATIONS

DGND DV

DIN DOUT

DRDY

AGND AIN6

REF IN(+) REF IN(–) BUFFER

MCLK OUT

SCLK

MCLK IN

POL

SYNC

RESET

NC AIN1 AIN2

AIN3 AIN4

STANDBY

SSOP

AD7714

TOP VIEW

(Not to Scale)

NC = NO CONNECT

DGND DV

DIN DOUT

DRDY

NC NC AGND AIN6

AIN5 REF IN(+) REF IN(–) BUFFER

REV. C–8–

AD7714

PIN FUNCTION DESCRIPTION

DIP/SOIC PIN NUMBERS

Pin No. Mnemonic Function

1 SCLK Serial Clock. Logic Input. An external serial clock is applied to this input to access serial data from the

AD7714. This serial clock can be a continuous clock with all data transmitted in a continuous train of pulses. Alternatively, it can be a noncontinuous clock with the information being transmitted to the AD7714 in smaller batches of data.

2 MCLK IN Master Clock signal for the device. This can be provided in the form of a crystal/resonator or external clock. A

crystal/resonator can be tied across the MCLK IN and MCLK OUT pins. Alternatively, the MCLK IN pin can be driven with a CMOS-compatible clock and MCLK OUT left unconnected. The part is specified with clock input frequencies of both 1 MHz and 2.4576 MHz.

3 MCLK OUT When the master clock for the device is a crystal/resonator, the crystal/resonator is connected between MCLK

IN and MCLK␣ OUT. If an external clock is applied to the MCLK IN, MCLK OUT provides an inverted clock signal. This clock can be used to provide a clock source for external circuits.

4 POL Clock Polarity. Logic Input. With this input low, the first transition of the serial clock in a data transfer

operation is from a low to a high. In microcontroller applications, this means that the serial clock should idle low between data transfers. With this input high, the first transition of the serial clock in a data transfer operation is from a high to a low. In microcontroller applications, this means that the serial clock should idle high between data transfers.

5 SYNC Logic Input which allows for synchronization of the digital filters and analog modulators when using a number

of AD7714s. While SYNC is low, the nodes of the digital filter, the filter control logic and the calibration control logic are reset and the analog modulator is also held in its reset state. SYNC does not affect the digital interface and does not reset DRDY if it is low.

6 RESET Logic Input. Active low input which resets the control logic, interface logic, digital filter and analog modulator

of the part to power-on status.

7 AIN1 Analog Input Channel 1. Programmable-gain analog input which can be used as a pseudo-differential input

when used with AIN6 or as the positive input of a differential analog input pair when used with AIN2 (see Communications Register section).

8 AIN2 Analog Input Channel 2. Programmable-gain analog input which can be used as a pseudo-differential input

when used with AIN6 or as the negative input of a differential analog input pair when used with AIN1 (see Communications Register section).

9 AIN3 Analog Input Channel 3. Programmable-gain analog input which can be used as a pseudo-differential input

when used with AIN6 or as the positive input of a differential analog input pair when used with AIN4 (see Communications Register section).

10 AIN4 Analog Input Channel 4. Programmable-gain analog input which can be used as a pseudo-differential input

when used with AIN6 or as the negative input of a differential analog input pair when used with AIN3 (see Communications Register section).

11 STANDBY Logic Input. Taking this pin low shuts down the analog and digital circuitry, reducing current consumption to

typically 5 µA.

12 AV

13 BUFFER Buffer Option Select. Logic Input. With this input low, the on-chip buffer on the analog input (after the

14 REF IN(–) Reference Input. Negative input of the differential reference input to the AD7714. The REF IN(–) can lie

15 REF IN(+) Reference Input. Positive input of the differential reference input to the AD7714. The reference input is

16 AIN5 Analog Input Channel 5. Programmable-gain analog input which is the positive input of a differential analog

17 AIN6 Analog Input Channel 6. Reference point for AIN1 through AIN4 in pseudo-differential mode or as the

18 AGND Ground reference point for analog circuitry.

Analog Positive Supply Voltage, A Grade Versions: +3.3␣ V nominal (AD7714-3) or +5␣ V nominal (AD7714-5); Y Grade Versions: 3 V or 5 V nominal.

multiplexer and before the analog modulator) is shorted out. With the buffer shorted out the current flowing in the AV allowing the inputs to handle higher source impedances.

anywhere between AV

differential with the provision that REF IN(+) must be greater than REF IN(–). REF IN(+) can lie anywhere between AV

input pair when used with AIN6 (see Communications Register section).

negative input of a differential input pair when used with AIN5 (see Communications Register section).

line is reduced to 270 µA. With this input high, the on-chip buffer is in series with the analog input

and AGND provided REF␣ IN(+) is greater than REF IN(–).

and AGND.

REV. C

–9–

AD7714

PIN FUNCTION DESCRIPTION (Continued)

Pin No. Mnemonic Function

19 CS Chip Select. Active low Logic Input used to select the AD7714. With this input hard-wired low, the AD7714

can operate in its three-wire interface mode with SCLK, DIN and DOUT used to interface to the device. CS can be used to select the device in systems with more than one device on the serial bus or as a frame synchronization signal in communicating with the AD7714.

20 DRDY Logic output. A logic low on this output indicates that a new output word is available from the AD7714 data

register. The DRDY pin will return high upon completion of a read operation of a full output word. If no data read has taken place, after an output update, the DRDY line will return high for 500 × t the next output update. This gives an indication of when a read operation should not be attempted to avoid reading from the data register as it is being updated. DRDY is also used to indicate when the AD7714 has completed its on-chip calibration sequence.

21 DOUT Serial Data Output with serial data being read from the output shift register on the part. This output shift

register can contain information from the calibration registers, mode register, communications register, filter selection registers or data register depending on the register selection bits of the Communications Register.

22 DIN Serial Data Input with serial data being written to the input shift register on the part. Data from this input shift

register is transferred to the calibration registers, mode register, communications register or filter selection registers depending on the register selection bits of the Communications Register.

23 DV

Digital Supply Voltage, A Grade Versions: +3.3␣ V or +5 V nominal; Y Grade Versions: 3 V or 5 V nominal.

24 DGND Ground reference point for digital circuitry.

cycles prior to

CLK␣ IN

TERMINOLOGY*

INTEGRAL NONLINEARITY

This is the maximum deviation of any code from a straight line passing through the endpoints of the transfer function. The endpoints of the transfer function are zero scale (not to be confused with bipolar zero), a point 0.5 LSB below the first code transition (000 . . . 000 to 000 . . . 001) and full scale, a point

0.5 LSB above the last code transition (111 . . . 110 to 111 . . . 111). The error is expressed as a percentage of full scale.

POSITIVE FULL-SCALE ERROR

Positive Full-Scale Error is the deviation of the last code transition (111 . . . 110 to 111 . . . 111) from the ideal AIN(+) voltage (AIN(–) + V

/GAIN – 3/2 LSBs). It applies to both unipolar

REF

and bipolar analog input ranges.

UNIPOLAR OFFSET ERROR

Unipolar Offset Error is the deviation of the first code transition from the ideal AIN(+) voltage (AIN(–) + 0.5 LSB) when operating in the unipolar mode.

BIPOLAR ZERO ERROR

This is the deviation of the midscale transition (0111 . . . 111 to 1000 . . . 000) from the ideal AIN(+) voltage (AIN(–) –

0.5 LSB) when operating in the bipolar mode.

GAIN ERROR

This is a measure of the span error of the ADC. It includes fullscale errors but not zero-scale errors. For unipolar input ranges it is defined as (full-scale error – unipolar offset error) while for bipolar input ranges it is defined as (full-scale error – bipolar zero error).

*AIN(–) refers to the negative input of the differential input pairs or to AIN6

when referring to the pseudo-differential input configurations.

BIPOLAR NEGATIVE FULL-SCALE ERROR

This is the deviation of the first code transition from the ideal AIN(+) voltage (AIN(–) – V

/GAIN + 0.5␣ LSB) when operat-

REF

ing in the bipolar mode.

POSITIVE FULL-SCALE OVERRANGE

Positive Full-Scale Overrange is the amount of overhead available to handle input voltages on AIN(+) input greater than AIN(–) + V

/GAIN (for example, noise peaks or excess volt-

REF

ages due to system gain errors in system calibration routines) without introducing errors due to overloading the analog modulator or overflowing the digital filter.

NEGATIVE FULL-SCALE OVERRANGE

This is the amount of overhead available to handle voltages on AIN(+) below AIN(–) – V

/GAIN without overloading the

REF

analog modulator or overflowing the digital filter. Note that the analog input will accept negative voltage peaks even in the unipolar mode provided that AIN(+) is greater than AIN(–) and greater than AGND – 30␣ mV.

OFFSET CALIBRATION RANGE

In the system calibration modes, the AD7714 calibrates its offset with respect to the analog input. The Offset Calibration Range specification defines the range of voltages that the AD7714 can accept and still calibrate offset accurately.

FULL-SCALE CALIBRATION RANGE

This is the range of voltages that the AD7714 can accept in the system calibration mode and still calibrate full scale correctly.

INPUT SPAN

In system calibration schemes, two voltages applied in sequence to the AD7714’s analog input define the analog input range. The input span specification defines the minimum and maximum input voltages from zero to full scale that the AD7714 can accept and still calibrate gain accurately.

REV. C–10–

AD7714

AD7714-5 OUTPUT NOISE

Table Ia shows the output rms noise and effective resolution for some typical notch and –3␣ dB frequencies for the AD7714-5 with

= 2.4576␣ MHz while Table Ib gives the information for f

CLK␣ IN

with a V

of +2.5␣ V and with BUFFER = 0. These numbers are typical and are generated at an analog input voltage of 0␣ V. The

REF

numbers in brackets in each table are for the effective resolution of the part (rounded to the nearest 0.5␣ LSB). The effective resolu-

tion of the device is defined as the ratio of the output rms noise to the input full scale (i.e., 2 × V

it is not calculated using peak-to-peak output noise numbers. Peak-to-peak noise numbers can be up to 6.6 times the rms numbers while effective resolution numbers based on peak-to-peak noise can be 2.5 bits below the effective resolution based on rms noise as quoted in the tables.

The output noise from the part comes from two sources. The first is the electrical noise in the semiconductor devices used in the implementation of the modulator (device noise). Secondly, when the analog input signal is converted into the digital domain, quantization noise is added. The device noise is at a low level and is largely independent of frequency. The quantization noise starts at an even lower level but rises rapidly with increasing frequency to become the dominant noise source. Consequently, lower filter notch settings (below 100␣ Hz approximately for f

= 2.4576␣ MHz and below 40␣ Hz approximately for f

CLK IN

be device noise dominated while higher notch settings are dominated by quantization noise. Changing the filter notch and cutoff frequency in the quantization-noise dominated region results in a more dramatic improvement in noise performance than it does in the device-noise dominated region as shown in Table I. Furthermore, quantization noise is added after the PGA, so effective resolution is largely independent of gain for the higher filter notch frequencies. Meanwhile, device noise is added in the PGA and, therefore, effective resolution reduces at high gains for lower notch frequencies. Additionally, in the device-noise dominated region, the

output noise (in µV) is largely independent of reference voltage while in the quantization-noise dominated region, the noise is pro-

portional to the value of the reference. It is possible to do post-filtering on the device to improve the output data rate for a given –3␣ dB frequency and also to further reduce the output noise.

At the lower filter notch settings (below 60␣ Hz for f

= 2.4576␣ MHz and below 25␣ Hz for f

CLK IN

codes performance of the device is at the 24-bit level. At the higher settings, more codes will be missed until at 1␣ kHz notch setting for f

= 2.4576␣ MHz (400␣ Hz for f

CLK␣ IN

Table Ia. AD7714-5 Output Noise/Resolution vs. Gain and First Notch for f

= 1␣ MHz), no missing codes performance is only guaranteed to the 12-bit level.

CLK IN

= 1␣ MHz. The numbers given are for the bipolar input ranges

CLK IN

/GAIN). It should be noted that

REF

= 1␣ MHz) tend to

CLK IN

= 1␣ MHz), the no missing

CLK IN

= 2.4576␣ MHz, BUFFER = 0

CLK IN

Filter First Notch & O/P –3␣ dB Gain of Gain of Gain of Gain of Gain of Gain of Gain of Gain of Data Rate Frequency 1 2 4 8 16 32 64 128

5␣ Hz 1.31␣ Hz 0.87 (22.5) 0.48 (22.5) 0.24 (22.5) 0.2 (21.5) 0.18 (20.5) 0.17 (20) 0.17 (19) 0.17 (18) 10␣ Hz 2.62␣ Hz 1.0 (22.5) 0.78 (21.5) 0.48 (21.5) 0.33 (21) 0.25 (20.5) 0.25 (19.5) 0.25 (18.5) 0.25 (17.5) 25␣ Hz 6.55␣ Hz 1.8 (21.5) 1.1 (21) 0.63 (21) 0.5 (20) 0.44 (19.5) 0.41 (18.5) 0.38 (17.5) 0.38 (16.5) 30␣ Hz 7.86␣ Hz 2.5 (21) 1.31 (21) 0.84 (20.5) 0.57 (20) 0.46 (19.5) 0.43 (18.5) 0.4 (17.5) 0.4 (16.5) 50␣ Hz 13.1␣ Hz 4.33 (20) 2.06 (20) 1.2 (20) 0.64 (20) 0.54 (19) 0.46 (18.5) 0.46 (17.5) 0.46 (16.5) 60␣ Hz 15.72␣ Hz 5.28 (20) 2.36 (20) 1.33 (20) 0.87 (19.5) 0.63 (19) 0.62 (18) 0.6 (17) 0.56 (16) 100␣ Hz 26.2␣ Hz 12.1 (18.5) 5.9 (18.5) 2.86 (19) 1.91 (18.5) 1.06 (18) 0.83 (17.5) 0.82 (16.5) 0.76 (15.5) 250␣ Hz 65.5␣ Hz 127 (15.5) 58 (15.5) 29 (15.5) 15.9 (15.5) 6.7 (15.5) 3.72 (15.5) 1.96 (15.5) 1.5 (14.5) 500␣ Hz 131␣ Hz 533 (13) 267 (13) 137 (13) 66 (13) 38 (13) 20 (13) 8.6 (13) 4.4 (13) 1␣ kHz 262␣ Hz 2,850 (11) 1,258 (11) 680 (11) 297 (11) 131 (11) 99 (10.5) 53 (10.5) 28 (10.5)

Table Ib. AD7714-5 Output Noise/Resolution vs. Gain and First Notch for f

Filter First Notch & O/P –3␣ dB Gain of Gain of Gain of Gain of Gain of Gain of Gain of Gain of Data Rate Frequency 1 2 4 8 16 32 64 128

2␣ Hz 0.52␣ Hz 0.75 (22.5) 0.56 (22) 0.31 (22) 0.19 (21.5) 0.17 (21) 0.14 (20) 0.14 (19) 0.14 (18) 4␣ Hz 1.05␣ Hz 1.04 (22) 0.88 (21.5) 0.45 (21.5) 0.28 (21) 0.21 (20.5) 0.21 (19.5) 0.21 (18.5) 0.21 (17.5) 10␣ Hz 2.62␣ Hz 1.66 (21.5) 1.01 (21.5) 0.77 (20.5) 0.41 (20.5) 0.37 (19.5) 0.35 (19) 0.35 (18) 0.35 (17) 25 Hz 6.55␣ Hz 5.2 (20) 2.06 (20) 1.4 (20) 0.86 (19.5) 0.63 (19) 0.61 (18) 0.59 (17) 0.59 (16) 30␣ Hz 7.86␣ Hz 7.1 (19.5) 3.28 (19.5) 1.42 (19.5) 1.07 (19) 0.78 (18.5) 0.64 (18) 0.61 (17) 0.61 (16) 50␣ Hz 13.1␣ Hz 19.4 (18) 9.11 (18) 4.2 (18) 2.45 (18) 1.56 (17.5) 1.1 (17) 0.82 (16.5) 0.8 (15.5) 60␣ Hz 15.72␣ Hz 25 (17.5) 16 (17.5) 6.5 (17.5) 2.9 (17.5) 1.93 (17.5) 1.4 (17) 1.1 (16) 0.98 (15.5) 100␣ Hz 26.2␣ Hz 102 (15.5) 58 (15.5) 25 (15.5) 13.5 (15.5) 5.7 (15.5) 3.9 (15.5) 2.1 (15) 1.3 (15) 200␣ Hz 52.4␣ Hz 637 (13) 259 (13) 130 (13) 76 (13) 33 (13) 16 (13) 11 (13) 6 (12.5) 400␣ Hz 104.8␣ Hz 2,830 (11) 1,430 (11) 720 (11) 334 (11) 220 (10.5) 94 (10.5) 54 (10.5) 25 (10.5)

Typical Output RMS Noise in ␮V (Effective Resolution in Bits)

= 1␣ MHz, BUFFER = 0

CLK IN

Typical Output RMS Noise in ␮V (Effective Resolution in Bits)

REV. C

–11–

AD7714

AD7714-3 OUTPUT NOISE

Table IIa shows the output rms noise and effective resolution for some typical notch and –3␣ dB frequencies for the AD7714-3 with

= 2.4576␣ MHz while Table IIb gives the information for f

CLK␣ IN

ranges with a V

of +1.25␣ V and BUFFER = 0. These numbers are typical and are generated at an analog input voltage of 0␣ V.

REF

The numbers in brackets in each table are for the effective resolution of the part (rounded to the nearest 0.5␣ LSB). The effective

resolution of the device is defined as the ratio of the output rms noise to the input full scale (i.e., 2 × V

noted that it is not calculated using peak-to-peak output noise numbers. Peak-to-peak noise numbers can be up to 6.6 times the rms numbers while effective resolution numbers based on peak-to-peak noise can be 2.5 bits below the effective resolution based on rms noise as quoted in the tables.

= 2.4576␣ MHz and below 40␣ Hz approximately for f

CLK IN

be device noise dominated while higher notch settings are dominated by quantization noise. Changing the filter notch and cutoff frequency in the quantization noise dominated region results in a more dramatic improvement in noise performance than it does in the device-noise dominated region as shown in Table II. Furthermore, quantization noise is added after the PGA, so effective resolution is largely independent of gain for the higher filter notch frequencies. Meanwhile, device noise is added in the PGA and, therefore, effective resolution suffers a little at high gains for lower notch frequencies. Additionally, in the device-noise dominated region,

the output noise (in µV) is largely independent of reference voltage while in the quantization-noise dominated region, the noise is

proportional to the value of the reference. It is possible to do post-filtering on the device to improve the output data rate for a given –3␣ dB frequency and also to further reduce the output noise.

At the lower filter notch settings (below 60␣ Hz for f

= 2.4576␣ MHz and below 25␣ Hz for f

CLK IN

codes performance of the device is at the 24-bit level. At the higher settings, more codes will be missed until at 1␣ kHz notch setting for f

= 2.4576␣ MHz (400␣ Hz for f

CLK␣ IN

= 1␣ MHz), no missing codes performance is only guaranteed to the 12-bit level.

CLK IN

= 1␣ MHz. The numbers given are for the bipolar input

CLK IN

/GAIN). It should be

REF

= 1␣ MHz) tend to

CLK IN

= 1␣ MHz), the no missing

CLK IN

Filter First

Table IIa. AD7714-3 Output Noise/Resolution vs. Gain and First Notch for f

Typical Output RMS Noise in ␮V (Effective Resolution in Bits)

= 2.4576␣ MHz, BUFFER = 0

CLK IN

Notch & O/P –3␣ dB Gain of Gain of Gain of Gain of Gain of Gain of Gain of Gain of Data Rate Frequency 1 2 4 8 16 32 64 128

5␣ Hz 1.31␣ Hz 1.07 (21) 0.68 (21) 0.29 (21) 0.24 (20) 0.22 (19.5) 0.22 (18.5) 0.22 (17.5) 0.22 (16.5) 10␣ Hz 2.62␣ Hz 1.69 (20.5) 1.1 (20) 0.56 (20) 0.35 (19.5) 0.33 (19) 0.33 (18) 0.33 (17) 0.33 (16) 25␣ Hz 6.55␣ Hz 3.03 (19.5) 1.7 (19.5) 0.89 (19.5) 0.55 (19) 0.49 (18.5) 0.46 (17.5) 0.46 (16.5) 0.45 (15.5) 30␣ Hz 7.86␣ Hz 3.55 (19.5) 2.1 (19) 1.1 (19) 0.61 (18.5) 0.58 (18) 0.57 (17) 0.55 (16) 0.55 (15) 50␣ Hz 13.1␣ Hz 4.72 (19) 2.3 (19) 1.5 (18.5) 0.84 (18.5) 0.7 (18) 0.68 (17) 0.67 (16) 0.66 (15) 60␣ Hz 15.72␣ Hz 5.12 (19) 3.1 (18.5) 1.6 (18) 0.98 (18) 0.9 (17.5) 0.7 (17) 0.69 (16) 0.68 (15) 100␣ Hz 26.2␣ Hz 9.68 (18) 5.6 (18) 2.4 (18) 1.3 (18) 1.1 (17) 0.95 (16.5) 0.88 (15.5) 0.9 (14.5) 250␣ Hz 65.5␣ Hz 44 (16) 31 (15.5) 15 (15.5) 5.8 (15.5) 3.7 (15.5) 2.4 (15) 1.8 (14.5) 1.8 (13.5) 500␣ Hz 131␣ Hz 304 (13) 129 (13) 76 (13) 33 (13) 20 (13) 11 (13) 6.3 (12.5) 3 (12.5) 1␣ kHz 262␣ Hz 1410 (11) 715 (11) 350 (11) 177 (11) 101 (10.5) 51 (10.5) 31 (10.5) 12 (10.5)

Filter First

Table IIb. AD7714-3 Output Noise/Resolution vs. Gain and First Notch for f

Typical Output RMS Noise in ␮V (Effective Resolution in Bits)

= 1␣ MHz, BUFFER = 0

CLK IN

Notch & O/P –3␣ dB Gain of Gain of Gain of Gain of Gain of Gain of Gain of Gain of Data Rate Frequency 1 2 4 8 16 32 64 128

2␣ Hz 0.52␣ Hz 0.86 (21.5) 0.58 (21) 0.32 (21) 0.21 (20.5) 0.2 (19.5) 0.2 (18.5) 0.2 (17.5) 0.2 (16.5) 4␣ Hz 1.05␣ Hz 1.26 (21) 0.74 (20.5) 0.44 (20.5) 0.35 (20) 0.3 (19) 0.3 (18) 0.3 (17) 0.3 (16) 10␣ Hz 2.62␣ Hz 1.68 (20.5) 1.33 (20) 0.73 (20) 0.5 (19) 0.49 (18.5) 0.49 (17.5) 0.48 (16.5) 0.47 (15.5) 25␣ Hz 6.55␣ Hz 3.82 (19.5) 2.0 (19.5) 1.2 (19) 0.88 (18.5) 0.66 (18) 0.57 (17) 0.55 (16) 0.55 (15) 30␣ Hz 7.86␣ Hz 4.88 (19) 2.1 (19) 1.3 (19) 0.93 (18.5) 0.82 (17.5) 0.69 (17) 0.68 (16) 0.66 (15) 50␣ Hz 13.1␣ Hz 11 (18) 4.8 (18) 2.4 (18) 1.4 (18) 1.4 (17) 0.73 (16.5) 0.71 (15.5) 0.7 (15) 60␣ Hz 15.72␣ Hz 14.7 (17.5) 7.5 (17.5) 3.8 (17.5) 2.6 (17) 1.5 (16.5) 0.95 (16.5) 0.88 (15) 0.9 (14.5) 100␣ Hz 26.2␣ Hz 61 (15.5) 30 (15.5) 12 (15.5) 6.1 (15.5) 2.9 (15.5) 2.4 (15) 1.8 (14.5) 1.8 (13.5) 200␣ Hz 52.4␣ Hz 275 (13) 130 (13) 65 (13) 33 (13) 17 (13) 11 (13) 6.3 (12.5) 3 (12.5) 400 Hz 104.8␣ Hz 1435 (11) 720 (11) 362 (11) 175 (11) 110 (10.5) 51 (10.5) 31 (10.5) 12 (10.5)

REV. C–12–

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Analog Devices AD7714 c Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual