Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsData collecting ICsData acquisition IC - AD converter (ADC) External TQFN 12

General Description

The MAX1274/MAX1275 low-power, high-speed, serial-

output, 12-bit, analog-to-digital converters (ADCs) oper-

ate at up to 1.8Msps. These devices feature true-differen-

tial inputs, offering better noise immunity, distortion

improvements, and a wider dynamic range over single-

ended inputs. A standard SPI™/QSPI™/MICROWIRE™

interface provides the clock necessary for conversion.

These devices easily interface with standard digital signal

processor (DSP) synchronous serial interfaces.

The MAX1274/MAX1275 operate from a single +4.75V to

+5.25V supply voltage and require an external reference.

The MAX1274 has a unipolar analog input, while the

MAX1275 has a bipolar analog input. These devices fea-

ture a partial power-down mode and a full power-down

mode for use between conversions, which lower the sup-

ply current to 1mA (typ) and 1µA (max), respectively. Also

featured is a separate power-supply input (V

), which

allows direct interfacing to +1.8V to V

digital logic. The

fast conversion speed, low-power dissipation, excellent

AC performance, and DC accuracy (±1 LSB INL) make

the MAX1274/MAX1275 ideal for industrial process con-

trol, motor control, and base-station applications.

The MAX1274/MAX1275 come in a 12-pin TQFN pack-

age, and are available in the extended (-40°C to +85°C)

temperature range.

Applications

Data Acquisition Communications

Bill Validation Portable Instruments

Motor Control

Features

♦ 1.8Msps Sampling Rate

♦ Only 45mW (typ) Power Dissipation

♦ Only 1µA (max) Shutdown Current

♦ High-Speed, SPI-Compatible, 3-Wire Serial Interface

♦ 70dB S/(N + D) at 525kHz Input Frequency

♦ Internal True-Differential Track/Hold (T/H)

♦ External Reference

♦ No Pipeline Delays

♦ Small 12-Pin TQFN Package

MAX1274/MAX1275

1.8Msps, Single-Supply, Low-Power,

True-Differential, 12-Bit ADCs

________________________________________________________________

Maxim Integrated Products

AIN+

N.C.

SCLK

N.C.

GND

2REF

7RGND

CNVST

DOUT

MAX1274

MAX1275

AIN-

TQFN

TOP VIEW

PART TEMP RANGE

PIN-

PACKAGE

INPUT

MAX1274AETC+T -40°C to +85°C 12 TQFN Unipolar

MAX1274BETC+T -40°C to +85°C 12 TQFN Unipolar

MAX1275AETC+T -40°C to +85°C 12 TQFN Bipolar

MAX1275BETC+T -40°C to +85°C 12 TQFN Bipolar

Pin Configuration

Ordering Information

MAX1274

MAX1275

DOUT

AIN+

REF

4.7μF

10μF10μF

+4.75V TO +5.25V

0.01μF

+1.8V TO V

AIN-

REF

DIFFERENTIAL

INPUT

VOLTAGE

RGND

GND

CNVST

SCLK

μC/DSP

Typical Operating Circuit

19-3158; Rev 1; 4/09

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

SPI/QSPI are trademarks of Motorola, Inc.

MICROWIRE is a trademark of National Semiconductor Corp.

Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

Summary of content (18 pages)

PAGE 1
9-3158; Rev 1; 4/09 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs The MAX1274/MAX1275 low-power, high-speed, serialoutput, 12-bit, analog-to-digital converters (ADCs) operate at up to 1.8Msps. These devices feature true-differential inputs, offering better noise immunity, distortion improvements, and a wider dynamic range over singleended inputs. A standard SPI™/QSPI™/MICROWIRE™ interface provides the clock necessary for conversion.
PAGE 2
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V VL to GND ...................-0.3V to the lower of (VDD + 0.3V) or +6V Digital Inputs to GND ....................-0.3V to the lower of (VDD + 0.3V) or +6V Digital Output to GND .......................-0.3V to the lower of (VL + 0.3V) or +6V Analog Inputs and REF to GND.............-0.3V to the lower of (VDD + 0.
PAGE 3
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs (VDD = +5V ±5%, VL = VDD, VREF = 4.096V, fSCLK = 28.8MHz, 50% duty cycle, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs TIMING CHARACTERISTICS (VDD = +5V ±5%, VL = VDD, VREF = 4.096V, fSCLK = 28.8MHz, 50% duty cycle, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SCLK Pulse-Width High tCH VL = 1.8V to VDD 15.6 ns SCLK Pulse-Width Low tCL VL = 1.8V to VDD 15.6 ns SCLK Rise to DOUT Transition tDOUT CL = 30pF, VL = 4.
PAGE 5
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs 0.6 0.2 0 0 -0.2 -0.2 -0.2 -0.4 -0.4 -0.4 -0.6 -0.6 -0.6 -0.8 -0.8 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 0 5000 1000 2000 3000 4000 DIGITAL OUTPUT CODE DIGITAL OUTPUT CODE DIGITAL OUTPUT CODE DIFFERENTIAL NONLINEARITY vs. DIGITAL OUTPUT CODE (MAX1275) OFFSET ERROR vs. TEMPERATURE (MAX1274) OFFSET ERROR vs. TEMPERATURE (MAX1275) OFFSET ERROR (LSB) 0.4 0.2 0 -0.2 0.2 0.1 0 -0.1 0.75 0.50 0.
PAGE 6
Typical Operating Characteristics (continued) (VDD = +5V, VL = VDD, VREF = 4.096V, fSCLK = 28.8MHz, TA = -40°C to +85°C, unless otherwise noted. Typical values are measured at TA = +25°C) FFT PLOT (MAX1275) -40 -60 -80 -40 -60 -80 -100 -100 -120 -120 -140 -140 200 400 600 800 1000 0 ANALOG INPUT FREQUENCY (kHz) -60 800 1000 -80 fSAMPLE = 2Msps fSCLK = 32MHz fIN = 500kHz SINAD = 70.84dB SNR = 71.11dB THD = -83.05dB SFDR = 84.
PAGE 7
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs fIN2 -60 -80 -120 -140 200 400 600 800 1000 0 200 400 600 800 1000 ANALOG INPUT FREQUENCY (kHz) ANALOG INPUT FREQUENCY (kHz) VDD/VL FULL POWER-DOWN SUPPLY CURRENT vs. TEMPERATURE VL PARTIAL/FULL POWER-DOWN SUPPLY CURRENT vs. TEMPERATURE 0.6 VDD, fSCLK = 28.8MHz 0.4 VDD, fSCLK = 0 0.2 VL = 5V, fSCLK = 28.8MHz VL SUPPLY CURRENT (μA) 0.8 MAX1274 toc19 200 MAX1274 toc18 1.0 150 100 VL = 3V, fSCLK = 28.
PAGE 8
Typical Operating Characteristics (continued) (VDD = +5V, VL = VDD, VREF = 4.096V, fSCLK = 28.8MHz, TA = -40°C to +85°C, unless otherwise noted. Typical values are measured at TA = +25°C) VL SUPPLY CURRENT vs. TEMPERATURE VL SUPPLY CURRENT vs. CONVERSION RATE VL SUPPLY CURRENT (mA) 0.6 FULL/PARTIAL POWER-DOWN fSCLK = 28.8MHz 0.4 0.2 0 -40 MAX1274 toc23 CONVERTING fSCLK = 28.8MHz 0.8 1.0 MAX1274 toc22 1.0 VL SUPPLY CURRENT (mA) MAX1274/MAX1275 1.
PAGE 9
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs VL MAX1274/MAX1275 VDD CAPACITIVE DAC REF CIN+ RIN+ AIN+ AIN+ 12-BIT SAR ADC T/H AIN- OUTPUT BUFFER VAZ DOUT COMP CONTROL LOGIC AINCINCONTROL LOGIC AND TIMING RIN- ACQUISITION MODE CAPACITIVE DAC CNVST SCLK CIN+ RIN+ AIN+ MAX1274 MAX1275 VAZ RGND GND Figure 3.
PAGE 10
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs Serial Interface A CNVST falling edge initiates a conversion sequence; the T/H stage holds the input voltage, the ADC begins to convert, and DOUT changes from high impedance to logic low. SCLK is used to drive the conversion process, and it shifts data out as each bit of the conversion is determined.
PAGE 11
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs External Reference Power consumption can be reduced significantly by placing the MAX1274/MAX1275 in either partial power-down mode or full power-down mode. Partial power-down mode is ideal for infrequent data sampling and fast wakeup time applications. Pull CNVST high after the 3rd SCLK rising edge and before the 14th SCLK rising edge to enter and stay in partial power-down mode (see Figure 6). This reduces the supply current to 1mA.
PAGE 12
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs Connection to Standard Interfaces OUTPUT CODE The MAX1274/MAX1275 serial interface is fully compatible with SPI/QSPI and MICROWIRE (see Figure 11). If a serial interface is available, set the CPU’s serial interface in master mode so the CPU generates the serial clock. Choose a clock frequency up to 28.8MHz. FULL-SCALE TRANSITION 111...111 111...110 111...101 SPI and MICROWIRE FS = VREF ZS = 0 V 1 LSB = REF 4096 000...
PAGE 13
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs MAX1274/MAX1275 CNVST SCLK 1 14 16 1 DOUT 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 Figure 10. Continuous Conversion with Burst/Continuous Clock I/O SCK MISO +3V TO +5V CNVST SCLK DOUT MAX1274 MAX1275 SS A) SPI CS SCK MISO +3V TO +5V CNVST SCLK DOUT MAX1274 MAX1275 SS B) QSPI I/O SK SI CNVST SCLK DOUT MAX1274 MAX1275 C) MICROWIRE Figure 11.
PAGE 14
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs CNVST 8 1 9 16 SCLK DOUT HIGH-Z D11 D10 D7 D8 D9 D6 D5 D4 D3 D1 D2 HIGH-Z D0 Figure 12. SPI/MICROWIRE Serial-Interface Timing—Single Conversion (CPOL = CPHA = 0), (CPOL = CPHA = 1) CNVST SCLK 14 1 0 DOUT 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 16 D1 D0 1 0 0 Figure 13.
PAGE 15
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs FSM = 1, burst mode FO = 0, data transmitted/received as 16-bit words This setup allows continuous conversion, provided that the DRR is serviced before the next conversion.
PAGE 16
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs CNVST SCLK 1 DOUT 1 0 0 0 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 Figure 18. DSP Interface—Single-Conversion, Continuous/Burst Clock VL VDDINT MAX1274 SCLK MAX1275 TCLK ADSP21_ _ _ RCLK CNVST TFS RFS DOUT DR Figure 19. Interfacing to the ADSP21_ _ _ Figure 20 shows the recommended system ground connections.
PAGE 17
1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs SNR = (6.02 x N + 1.76)dB In reality, there are other noise sources besides quantization noise, including thermal noise, reference noise, clock jitter, etc. Therefore, SNR is computed by taking the ratio of the RMS signal to the RMS noise, which includes all spectral components minus the fundamental, the first five harmonics, and the DC offset.
PAGE 18
MAX1274/MAX1275 1.8Msps, Single-Supply, Low-Power, True-Differential, 12-Bit ADCs Revision History REVISION NUMBER REVISION DATE 0 1/04 Initial release 1 4/09 Removed commercial temperature grade parts from data sheet DESCRIPTION PAGES CHANGED — 1–8 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.