基于Delta-Alfa的24位ADCLTC2449数据手册资源-CSDN文库

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### 基于Delta-Alfa的24位ADC LTC2449数据手册知识点解析 #### 一、产品概述 LTC2449是一款基于Delta-Alfa（ΔΣ）架构的24位高精度模数转换器(ADC)，具备高速多路复用功能。该器件适用于多种应用场合，如重量秤、自动量程六位半数字电压表(DVM)、直接温度测量等。其特点包括但不限于：支持高达8个差分通道或16个单端输入通道、可选的速度/分辨率模式、低噪声性能以及卓越的稳定性和线性度。 #### 二、主要特性与技术参数 - **高速多路复用**：支持最高达8个差分或16个单端输入通道的快速切换。 - **低噪声性能**： - 在1.76kHz输出率时，噪声水平仅为2μV RMS。 - 在13.8Hz输出率时，同时具有50/60Hz的抑制能力，噪声为200nV RMS。 - **可选择的速度/分辨率**：通过简单的4线串行接口可以实现多种速度/分辨率组合的选择，范围从6.9Hz/280nV RMS到3.5kHz/25μV RMS (使用外部振荡器时可达4kHz)。 - **稳定性与抗干扰能力**：保证了调制器在任何输入和参考条件下的稳定性及锁止免疫。 - **高精度指标**：非线性度(INL)达到0.0005%，无缺失码。 - **节能特性**：自动睡眠模式下功耗仅为20μA，在6.9Hz输出频率工作时。 - **偏移电压**：偏移电压小于5μV，在4.5V至5.5V供电电压范围内，温度范围从-40°C到85°C。 - **差分输入与参考**：支持差分输入和差分参考，且具有地至VCC的共模输入范围。 - **无延迟模式**：每个转换结果均准确，即使在选择新通道后也是如此。 - **内部振荡器**：无需外接元件即可工作。 - **外部缓冲或增益控制**：LTC2445/LTC2449型号包含MUXOUT/ADCIN引脚，便于实现外部缓冲或增益控制。 - **紧凑封装**：采用5mm x 7mm TinyQFN封装。 #### 三、应用场景 - **重量秤**：利用其高精度和低噪声特性，提高秤重系统的准确性和可靠性。 - **自动量程六位半数字电压表(DVM)**：自动调整量程以适应不同的输入电压范围，确保测量精度。 - **直接温度测量**：适用于需要直接温度读数的应用，例如热电偶的温度转换。 - **高速数据采集系统**：适用于需要高速采集和处理模拟信号的应用场景，如工业自动化设备、科研仪器等。 #### 四、操作模式 - **1X速度模式**：在这种模式下，新的速度、分辨率或通道选择后的第一次转换即为有效结果，无需等待额外的时间来稳定。 - **2X速度模式**：提供更高的输出率，最高可达7kHz (使用外部振荡器时可达8kHz)，但有一个周期的延迟。 #### 五、工作原理 LTC2449采用了专有的Delta-Alfa架构，该架构允许用户根据实际需求选择不同的速度/分辨率设置，从而在保持较高精度的同时实现高速转换。此外，其内部设计还包括一个用于消除连续转换间记忆效应的内部重置机制，确保了每次转换结果的准确性与稳定性。 LTC2449作为一款高精度、多功能的24位ADC，不仅提供了广泛的适用性和灵活性，还拥有出色的性能指标，适用于各种精密测量和控制应用。

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LTC2444/LTC2445/

LTC2448/LTC2449

2444589fb

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

■

High Speed Multiplexing

■

Weight Scales

■

Auto Ranging 6-Digit DVMs

■

Direct Temperature Measurement

■

High Speed Data Acquisition

■

Up to 8 Differential or 16 Single-Ended Input

Channels

■

Up to 8kHz Output Rate

■

Up to 4kHz Multiplexing Rate

■

Selectable Speed/Resolution

■

2µV

RMS

Noise at 1.76kHz Output Rate

■

200nV

RMS

Noise at 13.8Hz Output Rate with

Simultaneous 50/60Hz Rejection

■

Guaranteed Modulator Stability and Lock-Up

Immunity for any Input and Reference Conditions

■

0.0005% INL, No Missing Codes

■

Autosleep Enables 20µA Operation at 6.9Hz

■

<5µV Offset (4.5V < V

< 5.5V, – 40°C to 85°C)

■

Differential Input and Differential Reference with

GND to V

Common Mode Range

■

No Latency Mode, Each Conversion is Accurate Even

After a New Channel is Selected

■

Internal Oscillator—No External Components

■

LTC2445/LTC2449 Include MUXOUT/ADCIN for

External Buffering or Gain

■

Tiny QFN 5mm x 7mm Package

24-Bit High Speed

8-/16-Channel ∆Σ ADCs with

Selectable Speed/Resolution

The LTC

2444/LTC2445/LTC2448/LTC2449 are 8-/16-

channel (4-/8-differential) high speed 24-bit No Latency

∆Σ

ADCs. They use a proprietary delta-sigma architec-

ture enabling variable speed/resolution. Through a simple

4-wire serial interface, ten speed/resolution combinations

6.9Hz/280nV

RMS

to 3.5kHz/25µV

RMS

(4kHz with external

oscillator) can be selected with no latency between con-

version results or shift in DC accuracy (offset, full-scale,

linearity, drift). Additionally, a 2X speed mode can be

selected enabling output rates up to 7kHz (8kHz if an

external oscillator is used) with one cycle latency.

Any combination of single-ended or differential inputs can

be selected with a common mode input range from ground

to V

, independent of V

REF

. While operating in the 1X

speed mode the first conversion following a new speed,

resolution, or channel selection is valid. Since there is no

settling time between conversions, all 8 differential chan-

nels can be scanned at a rate of 500Hz. At the conclusion

of each conversion, the converter is internally reset elimi-

nating any memory effects between successive conver-

sions and assuring stability of the high order delta-sigma

modulator.

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

LTC2444/LTC2448

Speed vs RMS Noise

Simple 24-Bit Variable Speed Data Acquisition System

SDI

SCK

SDO

REF

4.5V TO 5.5V

1µF

COM

REF

–

GND

THERMOCOUPLE

VARIABLE SPEED/

RESOLUTION

DIFFERENTIAL

24-BIT ∆Σ ADC

16-CHANNEL

MUX

–

2444 TA01

4-WIRE

SPI INTERFACE

LTC2448

= EXTERNAL OSCILLATOR

= INTERNAL OSCILLATOR

(SIMULTANEOUS 50Hz/60Hz

REJECTION AT 6.9Hz OUTPUT RATE)

CH0

CH1

•

CH7

CH8

CH15

CONVERSION RATE (Hz)

0.1

RMS NOISE (µV)

100

10 100

2440 TA02

1000 10000

2.8µV AT 880Hz

280nV AT 6.9Hz

(50/60Hz REJECTION)

= 5V

REF

= 5V

= V

–

= 0V

2X SPEED MODE

NO LATENCY MODE

No Latency ∆Σ is a trademark of Linear Technology Corporation.

LTC2444/LTC2445/

LTC2448/LTC2449

2444589fb

ORDER PART

NUMBER

ORDER PART

NUMBER

ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

UUW

(Notes 1, 2)

Supply Voltage (V

) to GND.......................–0.3V to 6V

Analog Input Pins Voltage

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

+ 0.3V)

Reference Input Pins Voltage

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

+ 0.3V)

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

+ 0.3V)

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

+ 0.3V)

JMAX

= 125°C, θ

= 34°C/W

EXPOSED PAD (PIN 39) IS GND

MUST BE SOLDERED TO PCB

LTC2444CUHF

LTC2444IUHF

QFN PART MARKING*

2444

Operating Temperature Range

LTC2444C/LTC2445C/

LTC2448C/LTC2449C .............................. 0°C to 70°C

LTC2444I/LTC2445I/

LTC2448I/LTC2449I ........................... – 40°C to 85°C

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

LTC2448CUHF

LTC2448IUHF

QFN PART MARKING*

2448

13 14 15 16

TOP VIEW

UHF PACKAGE

38-LEAD (5mm × 7mm) PLASTIC QFN

17 18 19

38 37 36 35 34 33 32

1GND

BUSY

EXT

GND

COM

CH0

CH1

GND

REF

–

REF

CH7

CH6

SCK

SDO

SDI

GND

CH2

CH3

CH4

CH5

ORDER PART

NUMBER

ORDER PART

NUMBER

JMAX

= 125°C, θ

= 34°C/W

EXPOSED PAD (PIN 39) IS GND

MUST BE SOLDERED TO PCB

LTC2445CUHF

LTC2445IUHF

QFN PART MARKING*

2445

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

LTC2449CUHF

LTC2449IUHF

QFN PART MARKING*

2449

JMAX

= 125°C, θ

= 34°C/W

EXPOSED PAD (PIN 39) IS GND

MUST BE SOLDERED TO PCB

13 14 15 16

TOP VIEW

UHF PACKAGE

38-LEAD (5mm × 7mm) PLASTIC QFN

17 18 19

38 37 36 35 34 33 32

1GND

BUSY

EXT

GND

COM

CH0

CH1

GND

REF

–

REF

MUXOUTN

ADCINN

ADCINP

MUXOUTP

CH7

CH6

SCK

SDO

SDI

GND

CH2

CH3

CH4

CH5

TOP VIEW

UHF PACKAGE

38-LEAD (5mm × 7mm) PLASTIC QFN

1GND

BUSY

EXT

GND

COM

CH0

CH1

CH2

CH3

CH4

GND

REF

–

REF

CH15

CH14

CH13

CH12

SCK

SDO

SDI

GND

CH5

CH6

CH7

CH8

CH9

CH10

CH11

TOP VIEW

UHF PACKAGE

38-LEAD (5mm × 7mm) PLASTIC QFN

1GND

BUSY

EXT

GND

COM

CH0

CH1

CH2

CH3

CH4

GND

REF

–

REF

MUXOUTN

ADCINN

ADCINP

MUXOUTP

CH15

CH14

CH13

CH12

SCK

SDO

SDI

GND

CH5

CH6

CH7

CH8

CH9

CH10

CH11

JMAX

= 125°C, θ

= 34°C/W

EXPOSED PAD (PIN 39) IS GND

MUST BE SOLDERED TO PCB

Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF

Lead Free Part Marking: http://www.linear.com/leadfree/

LTC2444/LTC2445/

LTC2448/LTC2449

2444589fb

ELECTRICAL CHARACTERISTICS

PARAMETER CONDITIONS MIN TYP MAX UNITS

Resolution (No Missing Codes) 0.1V ≤ V

REF

≤ V

, –0.5 • V

REF

≤ V

≤ 0.5 • V

REF

, (Note 5) ● 24 Bits

Integral Nonlinearity V

= 5V, REF

–

= GND, V

INCM

= 2.5V, (Note 6) ● 5 15 ppm of V

REF

= 2.5V, REF

–

= GND, V

INCM

= 1.25V, (Note 6) 3 ppm of V

REF

Offset Error 2.5V ≤ REF

≤ V

, REF

–

= GND, ● 2.5 5 µV

GND ≤ IN

= IN

–

≤ V

(Note 12)

Offset Error Drift 2.5V ≤ REF

≤ V

, REF

–

= GND, 20 nV/°C

GND ≤ IN

= IN

–

≤ V

Positive Full-Scale Error REF

= 5V, REF

–

= GND, IN

= 3.75V, IN

–

= 1.25V ● 10 50 ppm of V

REF

= 2.5V, REF

–

= GND, IN

= 1.875V, IN

–

= 0.625V ● 10 50 ppm of V

REF

Positive Full-Scale Error Drift 2.5V ≤ REF

≤ V

, REF

–

= GND, 0.2 ppm of V

REF

/°C

= 0.75 • REF

, IN

–

= 0.25 • REF

Negative Full-Scale Error REF

= 5V, REF

–

= GND, IN

= 1.25V, IN

–

= 3.75V ● 10 50 ppm of V

REF

= 2.5V, REF

–

= GND, IN

= 0.625V, IN

–

= 1.875V ● 10 50 ppm of V

REF

Negative Full-Scale Error Drift 2.5V ≤ REF

≤ V

, REF

–

= GND, 0.2 ppm of V

REF

/°C

= 0.25 • REF

, IN

–

= 0.75 • REF

Total Unadjusted Error 5V ≤ V

≤ 5.5V, REF

= 2.5V, REF

–

= GND, V

INCM

= 1.25V 15 ppm of V

REF

5V ≤ V

≤ 5.5V, REF

= 5V, REF

–

= GND, V

INCM

= 2.5V 15 ppm of V

REF

= 2.5V, REF

–

= GND, V

INCM

= 1.25V, (Note 6) 15 ppm of V

REF

Input Common Mode Rejection DC 2.5V ≤ REF

≤ V

, REF

–

= GND, 120 dB

GND ≤ IN

–

= IN

≤ V

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at T

= 25°C. (Notes 3, 4)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Absolute/Common Mode IN

Voltage ● GND – 0.3V V

+ 0.3V V

–

Absolute/Common Mode IN

–

Voltage ● GND – 0.3V V

+ 0.3V V

Input Differential Voltage Range ● –V

REF

/2 V

REF

/2 V

(IN

– IN

–

)

REF

Absolute/Common Mode REF

Voltage ● 0.1 V

REF

–

Absolute/Common Mode REF

–

Voltage ● GND V

– 0.1V V

REF

Reference Differential Voltage Range ● 0.1 V

(REF

– REF

–

)

S(IN+)

Sampling Capacitance 2 pF

S(IN–)

–

Sampling Capacitance 2 pF

S(REF+)

REF

Sampling Capacitance 2 pF

S(REF–)

REF

–

Sampling Capacitance 2 pF

DC_LEAK(IN+, IN–,

Leakage Current, Inputs and Reference CS = V

, IN

= GND, IN

–

= GND, ● –15 1 15 nA

REF+, REF–)

REF

= 5V, REF

–

= GND

SAMPLE(IN+, IN–,

Average Input/Reference Current Varies, See Applications Section nA

REF+, REF–)

During Sampling

OPEN

MUX Break-Before-Make 50 ns

QIRR MUX Off Isolation V

= 2V

P-P

DC to 1.8MHz 120 dB

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at T

= 25°C. (Note 3)

A ALOG I PUT A

D REFERE CE

UUU

LTC2444/LTC2445/

LTC2448/LTC2449

2444589fb

TI I G CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Supply Voltage ● 4.5 5.5 V

Supply Current

Conversion Mode CS = 0V (Note 7)

● 811 mA

Sleep Mode CS = V

(Note 7) ● 830 µA

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

otherwise specifications are at T

= 25°C. (Note 3)

POWER REQUIRE E TS

The ● denotes specifications which apply over the full

operating temperature range, otherwise specifications are at T

= 25°C. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

High Level Input Voltage 4.5V ≤ V

≤ 5.5V ● 2.5 V

CS, F

Low Level Input Voltage 4.5V ≤ V

≤ 5.5V ● 0.8 V

CS, F

High Level Input Voltage 4.5V ≤ V

≤ 5.5V (Note 8) ● 2.5 V

SCK

Low Level Input Voltage 4.5V ≤ V

≤ 5.5V (Note 8) ● 0.8 V

SCK

Digital Input Current 0V ≤ V

≤ V

● –10 10 µA

CS, F

, EXT, SOI

Digital Input Current 0V ≤ V

≤ V

(Note 8) ● –10 10 µA

SCK

Digital Input Capacitance 10 pF

CS, F

Digital Input Capacitance (Note 8) 10 pF

SCK

High Level Output Voltage I

= –800µA ● V

– 0.5V V

SDO, BUSY

Low Level Output Voltage I

= 1.6mA ● 0.4V V

SDO, BUSY

High Level Output Voltage I

= –800µA (Note 9) ● V

– 0.5V V

SCK

Low Level Output Voltage I

= 1.6mA (Note 9) ● 0.4V V

SCK

Hi-Z Output Leakage ● –10 10 µA

SDO

DIGITAL I PUTS A D DIGITAL OUTPUTS

The ● denotes specifications which apply over the full operating temperature

range, otherwise specifications are at T

= 25°C. (Note 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

EOSC

External Oscillator Frequency Range ● 0.1 20 MHz

HEO

External Oscillator High Period ● 25 10000 ns

LEO

External Oscillator Low Period ● 25 10000 ns

CONV

Conversion Time OSR = 256 (SDI = 0) ● 0.99 1.13 1.33 ms

OSR = 32768 (SDI = 1)

● 126 145 170 ms

External Oscillator (Notes 10, 13) ●

40 • OSR +170

EOSC

(kHz)

ISCK

Internal SCK Frequency Internal Oscillator (Note 9) ● 0.8 0.9 1 MHz

External Oscillator (Notes 9, 10) f

EOSC

/10 Hz

LTC2444/LTC2445/

LTC2448/LTC2449

2444589fb

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

ISCK

Internal SCK Duty Cycle (Note 9) ● 45 55 %

ESCK

External SCK Frequency Range (Note 8) ● 20 MHz

LESCK

External SCK Low Period (Note 8) ● 25 ns

HESCK

External SCK High Period (Note 8) ● 25 ns

DOUT_ISCK

Internal SCK 32-Bit Data Output Time Internal Oscillator (Notes 9, 11) ● 41.6 35.3 30.9 µs

External Oscillator (Notes 9, 10)

● 320/f

EOSC

DOUT_ESCK

External SCK 32-Bit Data Output Time (Note 8) ● 32/f

ESCK

CS ↓ to SDO Low Z (Note 12) ● 025ns

CS ↑ to SDO High Z (Note 12) ● 025ns

CS ↓ to SCK ↓ (Note 9) 5 µs

CS ↓ to SCK ↑ (Notes 8, 12) ● 25 ns

KQMAX

SCK ↓ to SDO Valid ● 25 ns

KQMIN

SDO Hold After SCK ↓ (Note 5) ● 15 ns

SCK Set-Up Before CS ↓ ● 50 ns

SCK Hold After CS ↓ ● 50 ns

SDI Set-Up Before SCK ↑ (Note 5) ● 10 ns

SDI Hold After SCK ↑ (Note 5) ● 10 ns

The ● denotes specifications which apply over the full operating temperature

range, otherwise specifications are at T

= 25°C. (Note 3)

TI I G CHARACTERISTICS

GND (Pins 1, 4, 5, 6, 31, 32, 33): Ground. Multiple

ground pins internally connected for optimum ground

current flow and V

decoupling. Connect each one of

these pins to a common ground plane through a low

impedance connection. All 7 pins must be connected to

ground for proper operation.

BUSY (Pin 2): Conversion in Progress Indicator. This pin

is HIGH while the conversion is in progress and goes LOW

indicating the conversion is complete and data is ready. It

remains LOW during the sleep and data output states. At

the conclusion of the data output state, it goes HIGH

indicating a new conversion has begun.

EXT (Pin 3): Internal/External SCK Selection Pin. This pin

is used to select internal or external SCK for outputting/

inputting data. If EXT is tied low, the device is in the

external SCK mode and data is shifted out of the device

under the control of a user applied serial clock. If EXT is

tied high, the internal serial clock mode is selected. The

device generates its own SCK signal and outputs this on

the SCK pin. A framing signal BUSY (Pin 2) goes low

indicating data is being output.

COM (Pin 7): The common negative input (IN

–

) for all

single ended multiplexer configurations. The voltage on

CH0-CH15 and COM pins can have any value between

PI FU CTIO S

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: V

= 4.5V to 5.5V unless otherwise specified.

REF

= REF

– REF

–

, V

REFCM

= (REF

+ REF

–

)/2;

= IN

– IN

–

, V

INCM

= (IN

+ IN

–

)/2.

Note 4: F

pin tied to GND or to external conversion clock source with

EOSC

= 10MHz unless otherwise specified.

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: The converter uses the internal oscillator.

Note 8: The converter is in external SCK mode of operation such that the

SCK pin is used as a digital input. The frequency of the clock signal driving

SCK during the data output is f

ESCK

and is expressed in Hz.

Note 9: The converter is in internal SCK mode of operation such that the

SCK pin is used as a digital output. In this mode of operation, the SCK pin

has a total equivalent load capacitance of C

LOAD

= 20pF.

Note 10: The external oscillator is connected to the F

pin. The external

oscillator frequency, f

EOSC

, is expressed in Hz.

Note 11: The converter uses the internal oscillator. F

= 0V.

Note 12: Guaranteed by design and test correlation.

Note 13: There is an internal reset that adds an additional 1µs (typ) to the

conversion time.

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