Maxim MAX1245BEPP, MAX1245BEAP, MAX1245BCPP, MAX1245AEPP, MAX1245AEAP Datasheet

...

19-1066; Rev 0; 6/96

+2.375V, Low-Power, 8-Channel,

Serial 12-Bit ADC

________________General Description

The MAX1245 12-bit data-acquisition system combines an 8-channel multiplexer, high-bandwidth track/hold, and serial interface with high conversion speed and ultra-low power consumption. It operates from a single +2.375V to +3.3V supply, and its analog inputs are software configurable for unipolar/bipolar and single-ended/differential operation.

The 4-wire serial interface directly connects to SPI™, QSPI™, and Microwire™ devices without external logic. A serial strobe output allows direct connection to TMS320-family digital signal processors. The MAX1245 works with an external reference, and uses either the internal clock or an external serial-interface clock to perform successive-approximation analog-to-digital conversions.

This device provides a hard-wired SHDN pin and a software-selectable power-down, and can be programmed to automatically shut down at the end of a conversion. Accessing the serial interface powers up the MAX1245, and the quick turn-on time allows it to be shut down between conversions. This technique can cut supply current to under 10µA at reduced sampling rates.

The MAX1245 is available in a 20-pin DIP package and an SSOP that occupies 30% less area than an 8-pin DIP. For supply voltages from +2.7V to +5.25V, use the pincompatible MAX147.

________________________Applications

Portable Data Logging Medical Instruments Battery-Powered Instruments Data Acquisition

___________T ypical Operating Circuit

+2.5V

+2.048V

ANALOG

INPUTS

+2.048V

0V to

0.1µF

CH0

CH7

VREF

MAX1245

DGND AGND

COM

SCLK

DIN

DOUT

SSTRB

SHDN

0.1µF

CPU

I/O SCK (SK)*

MOSI (SO) MISO (SI)

____________________________Features

♦ Single +2.375V to +3.3V Operation ♦ 8-Channel Single-Ended or 4-Channel

Differential Analog Inputs

♦ Low Power: 0.8mA (100ksps)

10µA (1ksps) 1µA (power-down mode)

♦ Internal Track/Hold, 100kHz Sampling Rate ♦ SPI/QSPI/Microwire/TMS320-Compatible

4-Wire Serial Interface

♦ Software-Configurable Unipolar or Bipolar Inputs ♦ 20-Pin DIP/SSOP Packages

________________Ordering Information

†

PART

MAX1245ACPP MAX1245BCPP MAX1245ACAP 0°C to +70°C MAX1245BCAP 0°C to +70°C 20 SSOP MAX1245BC/D 0°C to +70°C Dice*

Ordering Information continued at end of data sheet.

†

Contact factory for availability of alternate surface-mount

TEMP. RANGE PIN-PACKAGE

0°C to +70°C 0°C to +70°C

20 Plastic DIP 20 Plastic DIP 20 SSOP

packages.

Contact factory for availability.

INL

(LSB)

±1/2 ±1 ±1/2 ±1 ±1

___________________Pin Configuration

TOP VIEW

CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7

COM



1 2 3 4 5 6 7 8 9

MAX1245

DIP/SSOP

SCLK

DIN

SSTRB DOUT



DGND

14 13

AGND V

VREFSHDN

MAX1245

SPI and QSPI are registered trademarks of Motorola, Inc. Microwire is a registered trademark of National Semiconductor Corp.

________________________________________________________________

Maxim Integrated Products

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

+2.375V, Low-Power, 8-Channel, Serial 12-Bit ADC

ABSOLUTE MAXIMUM RATINGS

VDDto AGND, DGND.............................................. -0.3V to +6V

AGND to DGND.................................................... -0.3V to +0.3V

CH0–CH7, COM to AGND, DGND............ -0.3V to (V

VREF to AGND........................................... -0.3V to (V

Digital Inputs to DGND............................................ -0.3V to +6V

Digital Outputs to DGND........................... -0.3V to (V

Digital Output Sink Current.................................................25mA

Continuous Power Dissipation (T

MAX1245

Plastic DIP (derate 11.11mW/°C above +70°C) ......... 889mW

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

= +70°C)

DD DD

+ 0.3V) + 0.3V)

+ 0.3V)

ELECTRICAL CHARACTERISTICS

(VDD= +2.375V to +3.3V, COM = 0V, f VREF = 2.048V applied to VREF pin, T

DC ACCURACY (Note 1)

Differential Nonlinearity Offset Error

Channel-to-Channel Offset Matching

DYNAMIC SPECIFICATIONS (10kHz sine-wave input, 0Vp-p to 2.048Vp-p, 100ksps, 1.5MHz external clock, bipolar input mode)

CONVERSION RATE

Conversion Time (Note 5)

Track/Hold Acquisition Time External clock = 1.5MHz

Internal Clock Frequency

External Clock Frequency

= 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps),

CLK

= T

to T

INLRelative Accuracy (Note 2)

CONV

ACQ

MIN

, unless otherwise noted.)

MAX

MAX1245A MAX1245B No missing codes over temperature

Up to the 5th harmonic

50kHz, 2V

-3dB rolloff

Internal clock, SHDN = FLOAT Internal clock, SHDN = V External clock = 1.5MHz, 12 clocks/conversion

SHDN = FLOAT SHDN = V

Data transfer only

p-p

(Note 4)

SSOP (derate 8.00mW/°C above +70°C) ................... 640mW

CERDIP (derate 11.11mW/°C above +70°C).............. 889mW

Operating Temperature Ranges

MAX1245_C_P................................................... 0°C to +70°C

MAX1245_E_P ................................................ -40°C to +85°C

Storage Temperature Range............................ -60°C to +150°C

Lead Temperature (soldering, 10sec)............................ +300°C

CONDITIONS

±0.5 ±1.0

5.5 7.5

35 65

1.5

0.225

0.1 1.5 0 1.5

UNITSMIN TYP MAXSYMBOLPARAMETER

ppm/°C±0.25Gain Temperature Coefficient

Bits12Resolution LSB LSB±1DNL

LSB±0.5 ±4 LSBGain Error (Note 3) ±0.5 ±4

LSB±0.2

dB68SINADSignal-to-Noise + Distortion Ratio dB-76THDTotal Harmonic Distortion dB76SFDRSpurious-Free Dynamic Range

dB-85Channel-to-Channel Crosstalk MHz2.25Small-Signal Bandwidth MHz1.0Full-Power Bandwidth

µs

µs2.0t ns40Aperture Delay

ps<50Aperture Jitter MHz

MHz

2 _______________________________________________________________________________________

+2.375V, Low-Power, 8-Channel,

Serial 12-Bit ADC

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +2.375V to +3.3V, COM = 0V, f VREF = 2.048V applied to VREF pin, T

ANALOG/COM INPUTS

Input Voltage Range, SingleEnded and Differential (Note 6)

Multiplexer Leakage Current

EXTERNAL REFERENCE

VREF Input Voltage Range (Note 8)

DIGITAL INPUTS (DIN, SCLK, CS, SHDN) DIN, SCLK, CS Input High Voltage DIN, SCLK, CS Input Low Voltage DIN, SCLK, CS Input Hysteresis DIN, SCLK, CS Input Leakage DIN, SCLK, CS Input Capacitance

SHDN Input High Voltage SHDN Input Low Voltage SHDN Input Current

SHDN Input Mid Voltage SHDN Voltage, Floating

SHDN Maximum Allowed Leakage,

Mid Input

DIGITAL OUTPUTS (DOUT, SSTRB) Output Voltage Low

Output Voltage High Three-State Leakage Current Three-State Output Capacitance

POWER REQUIREMENTS

Positive Supply Voltage Positive Supply Current

= 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps),

CLK

= T

to T

INH

INL

HYST

INH

INL IN

FLT

OUT

MIN

, unless otherwise noted.)

MAX

CONDITIONS

Unipolar, COM = 0V Bipolar, COM = VREF/2 On/off leakage current, VIN= 0V or V (Note 7)

VREF = 2.048V

VIN= 0V or V (Note 7)

SHDN = 0V or V

SHDN = open SHDN = open

SINK

SOURCE

CS = V CS = VDD(Note 7)

Operating mode, full-scale input

VDD= 2.375V to 3.3V, full-scale input, external reference = 2.048V

= 5mA = 16mA

=0.5mA

0 to VREF

±VREF/2

0.5

1.2 10Power-down

50mV

0.4

1.0

VDD/2 VDD/2

- 0.3 + 0.3

MAX1245

UNITSMIN TYP MAXSYMBOLPARAMETER

µA±0.01 ±1

pF16Input Capacitance

µA82 120VREF Input Current kΩ18 25VREF Input Resistance µA0.01 10Shutdown VREF Input Current

V2.0V V0.8V V0.2V

µA±0.01 ±1I

pF15C

VVDD- 0.4V V0.4V

µA±4.0I

V VVDD/2V

nA±80

V VVDD - 0.375V

µA±0.01 ±10I

pF15C

V2.375 3.3V

mA0.8 1.3

µA mV±0.3PSRSupply Rejection (Note 9)

_______________________________________________________________________________________ 3

+2.375V, Low-Power, 8-Channel, Serial 12-Bit ADC

TIMING CHARACTERISTICS

(VDD= +2.375V to +3.3V, COM = 0V, TA= T

PARAMETER

Acquisition Time DIN to SCLK Setup DIN to SCLK Hold SCLK Fall to Output Data Valid

MAX1245

CS Fall to Output Enable CS Rise to Output Disable CS to SCLK Rise Setup CS to SCLK Rise Hold

SCLK Pulse Width Low SCLK Fall to SSTRB ns

CS Fall to SSTRB Output Enable CS Rise to SSTRB Output Disable

SSTRB Rise to SCLK Rise

Note 1: Tested at V Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has

= +2.375V; COM = 0V; unipolar single-ended input mode.

been calibrated.

Note 3: External reference (VREF = +2.048V), offset nulled. Note 4: Ground “on” channel; sine wave applied to all “off” channels. Note 5: Conversion time defined as the number of clock cycles multiplied by the clock period; clock has 50% duty cycle. Note 6: The common-mode range for the analog inputs is from AGND to V Note 7: Guaranteed by design. Not subject to production testing. Note 8: ADC performance is limited by the converter’s noise floor, typically 300µVp-p. Note 9: Measured as

VFS(2.375V) - VFS(3.3V)|.

to T

MIN

, unless otherwise noted.)

MAX

CONDITIONS

ACQ

DS DH

Figure 1 ns20 260

Figure 1

Figure 2

CSS

CSH

CH CL

Figure 1

SSTRB

External clock mode only, Figure 1

SDV

External clock mode only, Figure 2

STR

Internal clock mode only (Note 7)

SCK

300t

260t

UNITSMIN TYP MAXSYMBOL

µs2.0t ns200t ns0t

ns240t ns400t ns200t ns0 ns300SCLK Pulse Width High ns

ns240t ns400t ns

__________________________________________Typical Operating Characteristics

(VDD= 2.5V, VREF = 2.048V, f

SUPPLY CURRENT

1.25

1.00

(mA)

0.75

0.50

vs. SUPPLY VOLTAGE

RL = ∞ CODE = 101010100000

= 50pF

LOAD



2.625

2.375

= 20pF

LOAD



2.875 (V)

4 _______________________________________________________________________________________

= 1.5MHz, C

CLK

3.125

3.375

LOAD

0.90

MAX1245-01

0.85

0.80

(mA)

0.75

0.70

0.65

-55 -30 70

= 20pF, TA = +25°C, unless otherwise noted.)

SUPPLY CURRENT 

vs. TEMPERATURE

RL = ∞ CODE = 101010100000

20 145120-5 45 95

TEMPERATURE (°C)

MAX1245-02

0.50

0.45

0.40

0.35

0.30

0.25

INL (LSB)

0.20

0.15

0.10

0.05

0.00

2.375

INTEGRAL NONLINEARITY

vs. SUPPLY VOLTAGE

2.875

(V)

3.3753.1252.625

MAX1245-03

+2.375V, Low-Power, 8-Channel,

Serial 12-Bit ADC

____________________________Typical Operating Characteristics (continued)

(VDD= 2.5V, VREF = 2.048V, f

INTEGRAL NONLINEARITY

0.50

0.45

0.40

0.35

0.30

0.25

INL (LSB)

0.20

0.15

0.10

0.05 0

-55 -30 45

vs. TEMPERATURE

VDD = 2.375V

20-5 70 95 145120

TEMPERATURE (˚C)

CHANNEL-TO-CHANNEL OFFSET MATCHING 

2.375

vs. SUPPLY VOLTAGE

2.875

(V)

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

OFFSET MATCHING (LSB)

0.10

0.05

GAIN ERROR 

0.50

0.45

0.40

0.35

0.30

0.25

0.20

GAIN ERROR (LSB)

0.15

0.10

0.05 0

vs. TEMPERATURE

-55

-5 45 120

-30 20 TEMPERATURE (˚C)

CLK

3.1252.625

= 1.5MHz, C



MAX1245-04

MAX1245-07

3.375

MAX1245-10

145

= 20pF, TA = +25°C, unless otherwise noted.)

LOAD



OFFSET vs. SUPPLY VOLTAGE

0.50

0.45

0.40

0.35

0.30

0.25

0.20

OFFSET (LSB)

0.15

0.10

0.05 0

2.375

CHANNEL-TO-CHANNEL OFFSET MATCHING 

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

OFFSET MATCHING (LSB)

0.10

0.05 0

-55

-30 45

CHANNEL-TO-CHANNEL GAIN MATCHING 

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

GAIN MATCHING (LSB)

0.10

0.05 0

2.375

2.875

(V)

vs. TEMPERATURE

-5 TEMPERATURE (˚C)

vs. SUPPLY VOLTAGE

2.875

2.625 V

(V)

3.1252.625



MAX1245-05

3.375

MAX1245-08

145120

MAX1245-11

3.3753.125

OFFSET vs. TEMPERATURE

0.50

0.45

0.40

0.35

0.30

0.25

0.20

OFFSET (LSB)

0.15

0.10

0.05 0

-55 -30

20-5 70 14512095

TEMPERATURE (˚C)

GAIN ERROR 



2.375 2.875 3.3753.1252.625

vs. SUPPLY VOLTAGE

(V)

0.50

0.45

0.40

0.35

0.30

0.25

0.20

GAIN ERROR (LSB)

0.15

0.10

0.05

CHANNEL-TO-CHANNEL GAIN MATCHING 

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

GAIN MATCHING (LSB)

0.10

0.05 0

-55

vs. TEMPERATURE

-30

-5 45 TEMPERATURE (˚C)



MAX1245

MAX1245-06

MAX1245-09

MAX1245-12

1451209570

_______________________________________________________________________________________

+2.375V, Low-Power, 8-Channel, Serial 12-Bit ADC

____________________________Typical Operating Characteristics (continued)

(VDD= 2.5V, VREF = 2.048V, f

= 1.5MHz, C

CLK

= 20pF, TA = +25°C, unless otherwise noted.)

LOAD

1000

MAX1245

0.25

0.20

0.15

0.10

0.05 0

INL (BITS)

-0.05



-0.10

-0.15

-0.20

-0.25

100

(µA)

0.1

 

AVERAGE SUPPLY CURRENT 



vs. CONVERSION RATE

VREF = 2.5V

DD =

CODE = 101010100000

= ∞



8 CHANNELS

1 CHANNEL

0.1

CONVERSIONS PER CHANNEL PER SECOND (Hz)

101 1k 10k100 100k

MAX1245-13

INTEGRAL NONLINEARITY

   

2048

DIGITAL CODE



4096

12.0

11.5

11.0

10.5

EFFECTIVE NUMBER OF BITS

10.0 1 10 100

-20

-40

-60

AMPLITUDE (dB)

-80

-100

-120 0

 

EFFECTIVE NUMBER OF BITS

vs. INPUT FREQUENCY

MAX1245-14

INPUT FREQUENCY (kHz)

FFT PLOT

= 10ksps

TONE

= 100ksps

SAMPLE



   

10 20 30 40 50

FREQUENCY (kHz)



6 _______________________________________________________________________________________

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