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 |
___________Typical Operating Circuit
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+2.5V |
0V to |
CH0 |
VDD |
VDD |
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0.1μF |
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+2.048V |
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DGND |
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ANALOG |
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AGND |
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INPUTS |
CH7 |
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COM |
CPU |
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MAX1245 |
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CS |
I/O |
+2.048V |
VREF |
SCLK |
SCK (SK)* |
DIN |
MOSI (SO) |
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0.1μF |
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DOUT |
MISO (SI) |
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SSTRB |
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SHDN |
VSS |
____________________________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† |
TEMP. RANGE |
PIN-PACKAGE |
INL |
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(LSB) |
MAX1245ACPP |
0°C to +70°C |
20 Plastic DIP |
±1/2 |
MAX1245BCPP |
0°C to +70°C |
20 Plastic DIP |
±1 |
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MAX1245ACAP |
0°C to +70°C |
20 SSOP |
±1/2 |
MAX1245BCAP |
0°C to +70°C |
20 SSOP |
±1 |
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MAX1245BC/D |
0°C to +70°C |
Dice* |
±1 |
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Ordering Information continued at end of data sheet.
†Contact factory for availability of alternate surface-mount packages.
* Contact factory for availability.
___________________Pin Configuration
TOP VIEW
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CH0 |
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1 |
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20 |
VDD |
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CH1 |
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2 |
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19 |
SCLK |
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CH2 |
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3 |
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18 |
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CS |
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CH3 |
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MAX1245 |
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4 |
17 |
DIN |
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CH4 |
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5 |
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16 |
SSTRB |
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CH5 |
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6 |
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15 |
DOUT |
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CH6 |
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DGND |
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7 |
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14 |
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CH7 |
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8 |
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13 |
AGND |
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VDD |
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COM |
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9 |
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12 |
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SHDN |
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10 |
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11 |
VREF |
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DIP/SSOP
SPI and QSPI are registered trademarks of Motorola, Inc. Microwire is a registered trademark of National Semiconductor Corp.
________________________________________________________________ Maxim Integrated Products 1
MAX1245
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
ABSOLUTE MAXIMUM RATINGS
VDD to AGND, DGND .............................................. |
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-0.3V to +6V |
AGND to DGND.................................................... |
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-0.3V to +0.3V |
CH0–CH7, COM to AGND, DGND ............ |
-0.3V to (VDD + 0.3V) |
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VREF to AGND........................................... |
-0.3V to (VDD + 0.3V) |
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Digital Inputs to DGND............................................ |
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-0.3V to +6V |
Digital Outputs to DGND ........................... |
-0.3V to (VDD + 0.3V) |
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Digital Output Sink Current ................................................. |
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25mA |
Continuous Power Dissipation (TA = +70°C) |
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Plastic DIP (derate 11.11mW/°C above +70°C) |
......... 889mW |
SSOP (derate 8.00mW/°C above +70°C) ................... |
640mW |
CERDIP (derate 11.11mW/°C above +70°C).............. |
889mW |
Operating Temperature Ranges |
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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 |
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.
ELECTRICAL CHARACTERISTICS
(VDD = +2.375V to +3.3V, COM = 0V, fCLK = 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps), VREF = 2.048V applied to VREF pin, TA = TMIN to TMAX, unless otherwise noted.)
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PARAMETER |
SYMBOL |
CONDITIONS |
MIN |
TYP |
MAX |
UNITS |
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DC ACCURACY (Note 1) |
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Resolution |
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12 |
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Bits |
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Relative Accuracy (Note 2) |
INL |
MAX1245A |
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±0.5 |
LSB |
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MAX1245B |
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±1.0 |
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Differential Nonlinearity |
DNL |
No missing codes over temperature |
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±1 |
LSB |
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Offset Error |
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±0.5 |
±4 |
LSB |
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Gain Error (Note 3) |
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±0.5 |
±4 |
LSB |
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Gain Temperature Coefficient |
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±0.25 |
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ppm/°C |
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Channel-to-Channel Offset |
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±0.2 |
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LSB |
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Matching |
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DYNAMIC SPECIFICATIONS (10kHz sine-wave input, 0Vp-p to 2.048Vp-p, 100ksps, 1.5MHz external clock, bipolar input mode)
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Signal-to-Noise + Distortion Ratio |
SINAD |
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68 |
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dB |
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Total Harmonic Distortion |
THD |
Up to the 5th harmonic |
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-76 |
dB |
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Spurious-Free Dynamic Range |
SFDR |
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76 |
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dB |
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Channel-to-Channel Crosstalk |
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50kHz, 2Vp-p (Note 4) |
-85 |
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dB |
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Small-Signal Bandwidth |
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-3dB rolloff |
2.25 |
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MHz |
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Full-Power Bandwidth |
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1.0 |
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MHz |
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CONVERSION RATE |
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Internal clock, SHDN = FLOAT |
5.5 |
7.5 |
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Conversion Time (Note 5) |
tCONV |
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µs |
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Internal clock, SHDN = VDD |
35 |
65 |
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External clock = 1.5MHz, 12 clocks/conversion |
8 |
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Track/Hold Acquisition Time |
tACQ |
External clock = 1.5MHz |
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2.0 |
µs |
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Aperture Delay |
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40 |
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ns |
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Aperture Jitter |
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<50 |
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ps |
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Internal Clock Frequency |
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SHDN = FLOAT |
1.5 |
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MHz |
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SHDN = VDD |
0.225 |
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External Clock Frequency |
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0.1 |
1.5 |
MHz |
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Data transfer only |
0 |
1.5 |
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2 _______________________________________________________________________________________
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +2.375V to +3.3V, COM = 0V, fCLK = 1.5MHz, external clock (50% duty cycle), 15 clocks/conversion cycle (100ksps), VREF = 2.048V applied to VREF pin, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER |
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SYMBOL |
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CONDITIONS |
MIN |
TYP |
MAX |
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UNITS |
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ANALOG/COM INPUTS |
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Input Voltage Range, Single- |
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Unipolar, COM = 0V |
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0 to VREF |
V |
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Ended and Differential (Note 6) |
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Bipolar, COM = VREF/2 |
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±VREF/2 |
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Multiplexer Leakage Current |
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On/off leakage current, VIN = 0V or VDD |
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±0.01 |
±1 |
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µA |
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Input Capacitance |
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(Note 7) |
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16 |
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pF |
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EXTERNAL REFERENCE |
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VREF Input Voltage Range |
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1.0 |
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VDD + |
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V |
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(Note 8) |
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50mV |
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VREF Input Current |
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VREF = 2.048V |
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82 |
120 |
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µA |
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VREF Input Resistance |
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18 |
25 |
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kΩ |
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Shutdown VREF Input Current |
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0.01 |
10 |
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µA |
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DIGITAL INPUTS (DIN, SCLK, |
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CS, |
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SHDN) |
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DIN, SCLK, CS Input High Voltage |
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VINH |
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2.0 |
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V |
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DIN, SCLK, CS Input Low Voltage |
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VINL |
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0.8 |
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V |
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DIN, SCLK, CS Input Hysteresis |
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VHYST |
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0.2 |
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V |
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DIN, SCLK, CS Input Leakage |
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IIN |
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VIN = 0V or VDD |
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±0.01 |
±1 |
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µA |
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DIN, SCLK, CS Input Capacitance |
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CIN |
(Note 7) |
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15 |
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pF |
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SHDN Input High Voltage |
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VINH |
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VDD - 0.4 |
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V |
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SHDN Input Low Voltage |
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VINL |
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0.4 |
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V |
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SHDN Input Current |
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IIN |
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SHDN |
= 0V or VDD |
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±4.0 |
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µA |
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SHDN Input Mid Voltage |
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VIM |
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VDD/2 |
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VDD/2 |
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V |
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- 0.3 |
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+ 0.3 |
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SHDN Voltage, Floating |
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VFLT |
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= open |
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VDD/2 |
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V |
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SHDN |
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SHDN Maximum Allowed Leakage, |
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SHDN = open |
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±80 |
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nA |
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Mid Input |
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DIGITAL OUTPUTS (DOUT, SSTRB) |
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Output Voltage Low |
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VOL |
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ISINK = 5mA |
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0.4 |
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V |
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ISINK = 16mA |
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0.5 |
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Output Voltage High |
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VOH |
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ISOURCE =0.5mA |
VDD - 0.375 |
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V |
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Three-State Leakage Current |
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IL |
CS = VDD |
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±0.01 |
±10 |
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µA |
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Three-State Output Capacitance |
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COUT |
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CS = VDD (Note 7) |
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15 |
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pF |
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POWER REQUIREMENTS |
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Positive Supply Voltage |
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VDD |
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2.375 |
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3.3 |
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V |
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Positive Supply Current |
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IDD |
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Operating mode, full-scale input |
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0.8 |
1.3 |
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mA |
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Power-down |
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1.2 |
10 |
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µA |
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Supply Rejection (Note 9) |
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PSR |
VDD = 2.375V to 3.3V, full-scale input, |
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±0.3 |
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mV |
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external reference = 2.048V |
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MAX1245
_______________________________________________________________________________________ 3
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
TIMING CHARACTERISTICS
(VDD = +2.375V to +3.3V, COM = 0V, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER |
SYMBOL |
CONDITIONS |
MIN |
TYP |
MAX |
UNITS |
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Acquisition Time |
tACQ |
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2.0 |
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µs |
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DIN to SCLK Setup |
tDS |
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200 |
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ns |
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DIN to SCLK Hold |
tDH |
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0 |
ns |
SCLK Fall to Output Data Valid |
tDO |
Figure 1 |
20 |
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260 |
ns |
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CS Fall to Output Enable |
tDV |
Figure 1 |
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240 |
ns |
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CS Rise to Output Disable |
tTR |
Figure 2 |
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400 |
ns |
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CS to SCLK Rise Setup |
tCSS |
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200 |
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ns |
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CS to SCLK Rise Hold |
tCSH |
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0 |
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ns |
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SCLK Pulse Width High |
tCH |
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300 |
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ns |
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SCLK Pulse Width Low |
tCL |
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300 |
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ns |
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SCLK Fall to SSTRB |
tSSTRB |
Figure 1 |
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260 |
ns |
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CS Fall to SSTRB Output Enable |
tSDV |
External clock mode only, Figure 1 |
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240 |
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CS Rise to SSTRB Output Disable |
tSTR |
External clock mode only, Figure 2 |
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SSTRB Rise to SCLK Rise |
tSCK |
Internal clock mode only (Note 7) |
0 |
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Note 1: Tested at VDD = +2.375V; COM = 0V; unipolar single-ended input mode.
Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has 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 VDD.
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)|.
__________________________________________Typical Operating Characteristics
(VDD = 2.5V, VREF = 2.048V, fCLK = 1.5MHz, CLOAD = 20pF, TA = +25°C, unless otherwise noted.)
IDD (mA)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
1.25
RL = ∞
CODE = 101010100000
1.00
CLOAD = 50pF
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0.75 |
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0.50 |
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VDD (V) |
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MAX1245-01
IDD (mA)
3.375
SUPPLY CURRENT vs. TEMPERATURE
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RL = ∞ |
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MAX1245 |
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CODE = 101010100000 |
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0.85 |
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0.80 |
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0.75 |
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0.65 -55 -30 -5 20 45 70 95 120 145
TEMPERATURE (°C)
INL (LSB)
INTEGRAL NONLINEARITY vs. SUPPLY VOLTAGE
0.50 |
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-03 |
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MAX1245 |
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0.40 |
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0.35 |
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0.30 |
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0.25 |
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0.20 |
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0.15 |
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0.10 |
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0.05 |
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0.00 |
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2.625 |
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VDD (V) |
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4 _______________________________________________________________________________________
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
____________________________Typical Operating Characteristics (continued)
(VDD = 2.5V, VREF = 2.048V, fCLK = 1.5MHz, CLOAD = 20pF, TA = +25°C, unless otherwise noted.)
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INTEGRAL NONLINEARITY |
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0.50 |
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vs. TEMPERATURE |
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0.50 |
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OFFSET vs. SUPPLY VOLTAGE |
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OFFSET vs. TEMPERATURE |
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MAX1245-04 |
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MAX1245-05 |
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MAX1245-06 |
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VDD |
= 2.375V |
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0.45 |
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0.45 |
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0.40 |
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0.40 |
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0.40 |
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INL(LSB) |
0.35 |
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OFFSET(LSB) |
0.35 |
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OFFSET(LSB) |
0.35 |
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0.20 |
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0.20 |
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0.20 |
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0.30 |
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0.30 |
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0.30 |
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0.25 |
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0.25 |
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0.25 |
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0.15 |
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0.15 |
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0.15 |
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0.10 |
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0.10 |
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0.10 |
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0.05 |
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0.05 |
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0.05 |
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0 |
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0 |
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3.375 |
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-55 |
-30 |
-5 |
20 |
45 |
70 |
95 |
120 |
145 |
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2.375 |
2.625 |
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2.875 |
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3.125 |
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-55 |
-30 |
-5 |
20 45 70 95 120 |
145 |
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TEMPERATURE (˚C) |
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VDD (V) |
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TEMPERATURE (˚C) |
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CHANNEL-TO-CHANNEL OFFSET MATCHING |
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CHANNEL-TO-CHANNEL OFFSET MATCHING |
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GAIN ERROR |
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vs. SUPPLY VOLTAGE |
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vs. TEMPERATURE |
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0.50 |
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vs. SUPPLY VOLTAGE |
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0.50 |
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MAX1245-07 |
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0.50 |
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MAX1245-08 |
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MAX1245-09 |
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0.45 |
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0.45 |
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0.45 |
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(LSB)MATCHINGOFFSET |
0.40 |
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(LSB)MATCHINGOFFSET |
0.40 |
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(LSB)ERRORGAIN |
0.40 |
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0.35 |
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0.35 |
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0.35 |
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0.30 |
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0.30 |
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0.30 |
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0.25 |
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0.25 |
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0.25 |
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0.20 |
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0.20 |
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0.20 |
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0.15 |
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0.15 |
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0.15 |
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0.10 |
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0.10 |
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0.10 |
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0.05 |
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0.05 |
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0.05 |
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0 |
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0 |
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0 |
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2.375 |
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2.625 |
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2.875 |
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3.125 |
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3.375 |
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-55 |
-30 -5 20 |
45 70 |
95 120 |
145 |
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2.375 |
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2.625 |
2.875 |
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3.125 |
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3.375 |
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VDD (V) |
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TEMPERATURE (˚C) |
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VDD (V) |
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GAIN ERROR |
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CHANNEL-TO-CHANNEL GAIN MATCHING |
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CHANNEL-TO-CHANNEL GAIN MATCHING |
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0.50 |
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vs. TEMPERATURE |
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vs. SUPPLY VOLTAGE |
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vs. TEMPERATURE |
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MAX1245-10 |
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0.50 |
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MAX1245-11 |
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0.50 |
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MAX1245-12 |
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0.45 |
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0.45 |
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0.45 |
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ERRORGAIN(LSB) |
0.40 |
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MATCHINGGAIN (LSB) |
0.40 |
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MATCHINGGAIN (LSB) |
0.40 |
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0.15 |
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0.15 |
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0.15 |
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0.35 |
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0.35 |
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0.35 |
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0.30 |
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0.30 |
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0.30 |
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0.25 |
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0.25 |
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0.25 |
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0.20 |
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0.20 |
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0.20 |
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0.10 |
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0.10 |
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0.10 |
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0.05 |
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0.05 |
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0.05 |
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0 |
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0 |
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0 |
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-55 |
-30 |
-5 |
20 |
45 |
70 |
95 |
120 |
145 |
|
2.375 |
2.625 |
|
2.875 |
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3.125 |
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3.375 |
|
-55 |
-30 |
-5 |
20 45 70 |
95 120 |
145 |
||||||||||||||||||||||||||
|
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|
TEMPERATURE (˚C) |
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VDD (V) |
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TEMPERATURE (˚C) |
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|
MAX1245
_______________________________________________________________________________________ 5
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
____________________________Typical Operating Characteristics (continued)
(VDD = 2.5V, VREF = 2.048V, fCLK = 1.5MHz, CLOAD = 20pF, TA = +25°C, unless otherwise noted.)
IDD (µA)
AVERAGE SUPPLY CURRENT vs. CONVERSION RATE
1000 |
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VDD |
= VREF |
= 2.5V |
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|
-13 |
|||
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MAX1245 |
|||||
|
|
CODE = |
101010100000 |
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|||||
100 |
|
RL = ∞ |
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10 |
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8 CHANNELS |
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1 |
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1 CHANNEL |
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0.1 |
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0.1 |
1 |
10 |
100 |
1k |
10k |
100k |
CONVERSIONS PER CHANNEL PER SECOND (Hz)
EFFECTIVE NUMBER OF BITS
12.0
11.5
11.0
10.5
10.0
EFFECTIVE NUMBER OF BITS vs. INPUT FREQUENCY
MAX1245-14
1 |
10 |
100 |
INPUT FREQUENCY (kHz)
|
|
|
INTEGRAL NONLINEARITY |
|
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|
FFT PLOT |
|
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|||
|
0.25 |
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20 |
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0.20 |
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|
fTONE = 10ksps |
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0 |
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|
fSAMPLE = 100ksps |
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||||
|
0.15 |
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-20 |
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||
|
0.10 |
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(BITS)INL |
0.05 |
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AMPLITUDE(dB) |
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|||
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-40 |
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0 |
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-60 |
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|
-0.05 |
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-0.10 |
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-80 |
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|||
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-0.15 |
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-100 |
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-0.20 |
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-120 |
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-0.25 |
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|
0 |
2048 |
|
4096 |
0 |
10 |
20 |
30 |
40 |
50 |
||||||
|
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DIGITAL CODE |
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FREQUENCY (kHz) |
|
|
|
6 _______________________________________________________________________________________