19-5323; Rev 3; 10/11
KIT ATION EVALU ILABLE AVA
12-Bit, 300ksps ADCs with FIFO and Internal Reference
General Description Features
o Analog Multiplexer with Track/Hold 16 Channels (MAX11632/MAX11633) 8 Channels (MAX11628/MAX11629) 4 Channels (MAX11626/MAX11627) o Single Supply 2.7V to 3.6V (MAX11627/MAX11629/MAX11633) 4.75V to 5.25V (MAX11626/MAX11628/MAX11632) o Internal Reference 2.5V (MAX11627/MAX11629/MAX11633) 4.096V (MAX11626/MAX11628/MAX11632) o External Reference: 1V to VDD o 16-Entry First-In/First-Out (FIFO) o Scan Mode, Internal Averaging, and Internal Clock o Accuracy: ±1 LSB INL, ±1 LSB DNL, No Missing Codes Over Temperature o 10MHz 3-Wire SPI-/QSPI-/MICROWIRE-Compatible Interface o Small Packages 16-Pin QSOP (MAX11626–MAX11629) 24-Pin QSOP (MAX11632/MAX11633)
MAX11626–MAX11629/MAX11632/MAX11633
The MAX11626–MAX11629/MAX11632/MAX11633 are serial 12-bit analog-to-digital converters (ADCs) with an internal reference. These devices feature on-chip FIFO, scan mode, internal clock mode, internal averaging, and AutoShutdown™. The maximum sampling rate is 300ksps using an external clock. The MAX11632/ MAX11633 have 16 input channels; the MAX11628/ MAX11629 have 8 input channels; and the MAX11626/ MAX11627 have 4 input channels. These six devices operate from either a +3V supply or a +5V supply, and contain a 10MHz SPI™-/QSPI™-/MICROWIRE™-compatible serial port. The MAX11626–MAX11629 are available in 16-pin QSOP packages. The MAX11632/MAX11633 are available in 24-pin QSOP packages. All six devices are specified over the extended -40°C to +85°C temperature range.
________________________Applications
System Supervision Data-Acquisition Systems Industrial Control Systems Patient Monitoring Data Logging Instrumentation
Ordering Information
PART NUMBER OF INPUTS 4 4 8 8 8 16 SUPPLY VOLTAGE RANGE (V) 4.75 to 5.25 2.7 to 3.6 4.75 to 5.25 4.75 to 5.25 2.7 to 3.6 4.75 to 5.25 PIN PACKAGE 16 QSOP 16 QSOP 16 QSOP 16 QSOP 16 QSOP 24 QSOP
AutoShutdown is a trademark of Maxim Integrated Products, Inc. SPI/QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp.
MAX11626EEE+ MAX11627EEE+ MAX11628EEE+ MAX11628EEE/V+ MAX11629EEE+
AIN0 1 AIN1 2 AIN2 3 AIN3 4 AIN4 (N.C.) 5 AIN5 (N.C.) 6 AIN6 (N.C.) 7 AIN7/(CNVST) 8
Pin Configurations
TOP VIEW
+
16 EOC 15 DOUT 14 DIN
MAX11632EEG+
MAX11633EEG+ 16 2.7 to 3.6 24 QSOP Note: All devices are specified over the -40°C to +85°C operating temperature range.
MAX11626– MAX11629
13 SCLK 12 CS 11 VDD 10 GND 9 REF
+Denotes a lead(Pb)-free/RoHS-compliant package. /V denotes an automotive qualified part.
QSOP
() MAX11626/MAX11627 ONLY
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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.
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
ABSOLUTE MAXIMUM RATINGS
VDD to GND ..............................................................-0.3V to +6V CS, SCLK, DIN, EOC, DOUT to GND.........-0.3V to (VDD + 0.3V) AIN0–AIN13, AIN_, CNVST/AIN_, REF to GND ...........................................-0.3V to (VDD + 0.3V) Maximum Current into Any Pin............................................50mA Continuous Power Dissipation (TA = +70°C) 16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW 24-Pin QSOP (derate 9.5mW/°C above +70°C)...........762mW Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-60°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering, 10s) .................................+300°C Soldering Temperature (reflow) .......................................+260°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 = +2.7V to +3.6V (MAX11627/MAX11629/MAX11633); VDD = +4.75V to +5.25V (MAX11626/MAX11628/MAX11632), fSAMPLE = 300kHz, fSCLK = 4.8MHz (50% duty cycle), VREF = 2.5V (MAX11627//MAX11629/MAX11633); VREF = 4.096V (MAX11626/MAX11628/ MAX11632), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER DC ACCURACY (Note 1) Resolution Integral Nonlinearity D ifferential Nonlinearity Offset Error Gain Error Offset Error Temperature Coefficient Gain Temperature Coefficient Channel-to-Channel Offset Matching D YNAMIC SPECIFICATIONS (30kHz sine-wave input, 2.5VP-P, 300ksps, fSCLK = 4.8MHz) Signal-to-Noise Plus Distortion SINAD MAX11627/MAX11629/MAX11633 MAX11626/MAX11628/MAX11632 Up to the 5th harmonic M AX11627/MAX11629/ MAX11633 MAX11626/MAX11628/ MAX11632 71 73 -80 dBc -88 81 89 76 1 100 dBc dBc MHz kHz dB (Note 2) RES INL DNL No missing codes over temperature ±0.5 ±0.5 ±2 ±0.8 ±0.1 12 ±1.0 ±1.0 ±4.0 ±4.0 Bits LSB LSB LSB LSB ppm/°C FSR ppm/°C LSB SYMBOL CONDITIONS MIN TYP MAX UNITS
Total Harmonic Distortion
THD
Spurious-Free Dynamic Range Intermodulation Distortion Full-Power Bandwidth Full-Linear Bandwidth
SFDR IMD
M AX11627/MAX11629/MAX11633 MAX11626/MAX11628/MAX11632 fIN1 = 29.9kHz, fIN2 = 30.2kHz -3dB point S/(N + D) > 68dB
2
_______________________________________________________________________________________
12-Bit, 300ksps ADCs with FIFO and Internal Reference
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +2.7V to +3.6V (MAX11627/MAX11629/MAX11633); VDD = +4.75V to +5.25V (MAX11626/MAX11628/MAX11632), fSAMPLE = 300kHz, fSCLK = 4.8MHz (50% duty cycle), VREF = 2.5V (MAX11627//MAX11629/MAX11633); VREF = 4.096V (MAX11626/MAX11628/ MAX11632), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONVERSION RATE Power-Up Time Acquisition Time Conversion Time External Clock Frequency Aperture Delay Aperture Jitter ANALOG INPUT Input Voltage Range Input Leakage Current Input Capacitance INTERNAL REFERENCE REF Output Voltage REF Temperature Coefficient Output Resistance REF Output Noise REF Power-Supply Rejection E XTERNAL REFERENCE INPUT REF Input Voltage Range VREF VREF = 2.5V (MAX11627/MAX11629/ MAX11633); VREF = 4 .096V (MAX11626/MAX11628/MAX11632), f SAMPLE = 3 00ksps VREF = 2.5V (MAX11627/MAX11629/ MAX11633); VREF = 4 .096V (MAX11626/MAX11628/MAX11632), f SAMPLE = 0 1.0 VDD + 50mV V PSRR TCREF MAX11626/MAX11628/MAX11632 MAX11627/MAX11629/MAX11633 MAX11626/MAX11628/MAX11632 MAX11627/MAX11629/MAX11633 4.024 2.48 4.096 2.50 ±20 ±30 6.5 200 -70 4.168 2.52 V ppm/°C k µVRMS dB Unipolar VIN = VDD During acquisition time (Note 5) 0 ± 0.01 24 VREF ±1 V µA pF t PU tACQ tCONV f SCLK Internally clocked Externally clocked (Note 4) Externally clocked conversion Data I/O 30 < 50 2.7 0.1 4.8 10 3.5 External reference Internal reference (Note 3) 0.8 65 0.6 µs µs µs MHz ns ps SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX11626–MAX11629/MAX11632/MAX11633
40
100 µA
REF Input Current
IREF
± 0.1
±5
_______________________________________________________________________________________
3
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +2.7V to +3.6V (MAX11627/MAX11629/MAX11633); VDD = +4.75V to +5.25V (MAX11626/MAX11628/MAX11632), fSAMPLE = 300kHz, fSCLK = 4.8MHz (50% duty cycle), VREF = 2.5V (MAX11627//MAX11629/MAX11633); VREF = 4.096V (MAX11626/MAX11628/ MAX11632), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MAX11626/MAX11628/MAX11632 MAX11627/MAX11629/MAX11633 MAX11626/MAX11628/MAX11632 MAX11627/MAX11629/MAX11633 VIN = 0V or VDD 2.0 VDD x 0.7 200 ±0.01 15 I SINK = 2 mA I SINK = 4 mA I SOURCE = 1.5mA CS = VDD CS = VDD MAX11626/MAX11628/MAX11632 MAX11627/MAX11629/MAX11633 Internal reference IDD External reference Internal reference IDD External reference Power-Supply Rejection PSR f SAMPLE = 3 00ksps f SAMPLE = 0, REF on Shutdown f SAMPLE = 3 00ksps Shutdown f SAMPLE = 3 00ksps f SAMPLE = 0 , REF on Shutdown f SAMPLE = 3 00ksps Shutdown 4.75 2.7 1750 1000 0.2 1050 0.2 2300 1050 0.2 1550 0.2 ±0.2 ±0.2 VDD - 0.5 ± 0.05 15 5.25 3.6 2000 1200 5 1200 5 2550 1350 5 1700 5 ±1 ±1.2 mV µA µA ±1 0.4 0.8 ±1.0 MIN TYP MAX 0.8 VDD x 0.3 UNITS DIGITAL INPUTS (SCLK, DIN, CS, CNVST) Input Voltage Low Input Voltage High Input Hysteresis Input Leakage Current Input Capacitance DIGITAL OUTPUTS (DOUT, EOC) Output Voltage Low Output Voltage High Three-State Leakage Current Three-State Output Capacitance POWER REQUIREMENTS Supply Voltage VDD V VOL VOH IL C OUT V V µA pF VIL VIH VHYST I IN CIN V V mV µA pF
MAX11627/MAX11629/MAX11633 Supply Current (Note 6)
MAX11626/MAX11628/MAX11632 Supply Current (Note 6)
VDD = 2.7V to 3.6V; full-scale input VDD = 4.75V to 5.25V; full-scale input
Note 1: Note 2: Note 3: Note 4: Note 5:
MAX11627/MAX11629/MAX11633 tested at VDD = +3V. MAX11626/MAX11628/MAX11632 tested at VDD = +5V. Offset nulled. Time for reference to power up and settle to within 1 LSB. Conversion time is defined as the number of clock cycles multiplied by the clock period; clock has 50% duty cycle. See Figure 3 (Equivalent Input Circuit) and the Sampling Error vs. Source Impedance curve in the Typical Operating Characteristics section. Note 6: Supply current is specified depending on whether an internal or external reference is used for voltage conversions.
4
_______________________________________________________________________________________
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
TIMING CHARACTERISTICS (Figure 1)
(VDD = +2.7V to +3.6V (MAX11627/MAX11629/MAX11633); VDD = +4.75V to +5.25V (MAX11626/MAX11628/MAX11632), fSAMPLE = 300kHz, f SCLK = 4.8MHz (50% duty cycle), V REF = 2.5V (MAX11627//MAX11629/MAX11633); V REF = 4.096V (MAX11626/ MAX11628/MAX11632), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER SCLK Clock Period SCLK Pulse Width High SCLK Pulse Width Low SCLK Fall to DOUT Transition CS Rise to DOUT Disable CS Fall to DOUT Enable DIN to SCLK Rise Setup SCLK Rise to DIN Hold CS Low to SCLK Setup CS H igh to SCLK Setup CS H igh After SCLK Hold CS Low After SCLK Hold CNVST Pulse Width Low CS or CNVST Rise to EOC Low (Note 7) SYMBOL tCP tCH tCL tDOT tDOD tDOE tDS tDH tCSS0 tCSS1 tCSH1 tCSH0 tCSPW C KSEL = 00 CKSEL = 01 Voltage conversion Reference power-up CLOAD = 30pF CLOAD = 30pF CLOAD = 30pF 40 0 40 40 0 0 40 1.4 7 65 4 Data I/O CONDITIONS Externally clocked conversion MIN 208 100 40 40 40 40 40 TYP MAX UNITS ns ns ns ns ns ns ns ns ns ns ns µs ns µs µs
Note 7: This time is defined as the number of clock cycles needed for conversion multiplied by the clock period. If the internal reference needs to be powered up, the total time is additive.
Typical Operating Characteristics
(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA = +25°C, unless otherwise noted.)
INTEGRAL NONLINEARITY vs. OUTPUT CODE
MAX11626 toc01
INTEGRAL NONLINEARITY vs. OUTPUT CODE
MAX11626 toc02
DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE
0.8 0.6 0.4 DNL (LSB) 0.2 0 -0.2 -0.4
MAX11626 toc03
1.0 0.8 0.6 0.4 INL (LSB) 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 1024 2048 3072 MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps
1.0 0.8 0.6 0.4 INL (LSB) 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 MAX11627/MAX11629/MAX11633 fSAMPLE = 300ksps 1024 2048 3072
1.0
-0.6 -0.8 -1.0 0
MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps 1024 2048 3072 4096
4096
4096
OUTPUT CODE (DECIMAL)
OUTPUT CODE (DECIMAL)
OUTPUT CODE (DECIMAL)
_______________________________________________________________________________________
5
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Typical Operating Characteristics (continued)
(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA = +25°C, unless otherwise noted.)
DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE
MAX11626 toc04
SINAD vs. FREQUENCY
MAX11626 toc05
SFDR vs. FREQUENCY
MAX11626/MAX11628/ MAX11632 90
MAX11626 toc06
1.0 0.8 0.6 0.4 DNL (LSB) 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 1024 2048 3072 MAX11627/MAX11629/MAX11633 fSAMPLE = 300ksps
80 MAX11626/MAX11628/MAX11632 75 70 65 60 55 50 MAX11627/MAX11629/MAX11633
100
SINAD (dB)
SFDR (dB)
80 MAX11627/MAX11629/MAX11633 70
60
4096
1
10
100
1000
50 1 10 100 1000 FREQUENCY (kHz)
OUTPUT CODE (DECIMAL)
FREQUENCY (kHz)
THD vs. FREQUENCY
MAX11626 toc07
SUPPLY CURRENT vs. SAMPLING RATE
MAX11626/MAX11628/MAX11632 VDD = 5V
MAX11626 toc08
-50
3000 2500 2000 IVDD (µA) 1500 1000
-60 MAX11627/MAX11629/MAX11633 THD (dB) -70
INTERNAL REFERENCE
-80 EXTERNAL REFERENCE -90 MAX11626/MAX11628/MAX11632 -100 1 10 100 1000 FREQUENCY (kHz) 0 1 10 100 1000 SAMPLING RATE (ksps) 500
SUPPLY CURRENT vs. SAMPLING RATE
1600 1400 1200 IVDD (µA) 1000 800 600 400 200 0 1 10 100 1000 SAMPLING RATE (ksps) EXTERNAL REFERENCE INTERNAL REFERENCE MAX11627/MAX11629/MAX11633 VDD = 3V
MAX11626 toc09
SUPPLY CURRENT vs. SUPPLY VOLTAGE
2400 2200 IDD (µA) 2000 1800 1600 1400 1200 1000 4.75 4.85 4.95 5.05 5.15 5.25
VDD (V)
INTERNAL REFERENCE
EXTERNAL REFERENCE
MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps
6
_______________________________________________________________________________________
MAX11626 toc10
1800
2600
12-Bit 300ksps ADCs with FIFO, Temp Sensor, Internal Reference
Typical Operating Characteristics (continued)
(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA = +25°C, unless otherwise noted.)
MAX11626–MAX11629/MAX11632/MAX11633
SUPPLY CURRENT vs. SUPPLY VOLTAGE
1800 1600 1400 IDD (µA) EXTERNAL REFERENCE IDD (µA) 1200 1000 800 600 400 200 0 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 VDD (V) MAX11627/MAX11629/MAX11633 fSAMPLE = 300ksps INTERNAL REFERENCE
MAX11626 toc11
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 4.75 4.85 4.95 5.05 5.15 5.25 VDD (V) MAX11626/MAX11628/MAX11632 VDD = 5V
MAX11626 toc12
2000
0.8
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX11626 toc13
SUPPLY CURRENT vs. TEMPERATURE
MAX11626 toc14
0.5
2500 INTERNAL REFERENCE
0.4
2200
IDD (µA)
IDD (µA)
0.3
1900
0.2
1600 EXTERNAL REFERENCE
0.1 MAX11627/MAX11629/MAX11633 VDD = 3V 0 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 VDD (V)
1300
1000 -40 -15
MAX11626/MAX11628/MAX11632 VDD = 5V fSAMPLE = 300ksps 10 35 60 85
TEMPERATURE (°C)
SUPPLY CURRENT vs. TEMPERATURE
MAX11626 toc15
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX11626/MAX11628/MAX11632 VDD = 5V
MAX11626 toc16
1800 INTERNAL REFERENCE 1600 1400 1200 1000 800 600 -40 -15 10 35 60 EXTERNAL REFERENCE MAX11627/MAX11629/MAX11633 VDD = 3V fSAMPLE = 300ksps IDD (µA)
2.5
2.0
IDD (µA) 85
1.5
1.0
0.5
0 -40 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C)
_______________________________________________________________________________________
7
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Typical Operating Characteristics (continued)
(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA = +25°C, unless otherwise noted.)
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX11626 toc17
INTERNAL REFERENCE VOLTAGE vs. SUPPLY VOLTAGE
MAX11626 toc18
INTERNAL REFERENCE VOLTAGE vs. SUPPLY VOLTAGE
MAX11626 toc19
1.0
MAX11627/MAX11629/MAX11633 VDD = 3V
4.099
2.502
0.8
4.098
2.501
IDD (µA)
VREF (V)
0.4
4.096
VREF (V)
0.6
4.097
2.500
2.499
0.2
4.095 MAX11626/MAX11628/MAX11632 VDD = 5V 4.094 -40 -15 10 35 60 85 4.75 4.85 4.95 5.05 5.15 5.25 TEMPERATURE (°C) VDD (V)
2.498
MAX11627/MAX11629/MAX11633 VDD = 3V 2.7 3.0 VDD (V) 3.3 3.6
0
2.497
INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE
MAX11626 toc20
INTERNAL REFERENCE VOLTAGE vs. TEMPERATURE
MAX11626 toc21
OFFSET ERROR vs. SUPPLY VOLTAGE
MAX11626 toc22
4.12
2.52
0.6 0.4 OFFSET ERROR (LSB) 0.2 0 -0.2 -0.4 -0.6 MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps 4.75 4.85 4.95 5.05 5.15
4.11
2.51
VREF (V)
4.09
VREF (V) MAX11626/MAX11628/MAX11632 VDD = 5V -40 -15 10 35 60 85
4.10
2.50
2.49
4.08
2.48
MAX11627/MAX11629/MAX11633 VDD = 3V -40 -15 10 35 60 85
4.07 TEMPARATURE (°C)
2.47 TEMPARATURE (°C)
5.25
VDD (V)
OFFSET ERROR vs. SUPPLY VOLTAGE
MAX11626 toc23
OFFSET ERROR vs. TEMPERATURE
MAX11626 toc24
OFFSET ERROR vs. TEMPERATURE
MAX11626 toc25
1.08 1.07 OFFSET ERROR (LSB) 1.06 1.05 1.04 1.03 1.02 1.01 1.00 2.7 3.0 VDD (V) 3.3 MAX11627/MAX11629/MAX11633 fSAMPLE = 300ksps
1.0
1.5
0.6 OFFSET ERROR (LSB)
1.3 OFFSET ERROR (LSB)
0.2
1.1
-0.2
0.9
-0.6
MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps -40 -15 10 35 60 85
0.7
MAX11627/MAX11629/MAX11633 fSAMPLE = 300ksps -40 -15 10 35 60 85
-1.0 3.6 TEMPERATURE (°C)
0.5 TEMPERATURE (°C)
8
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12-Bit, 300ksps ADCs with FIFO and Internal Reference
Typical Operating Characteristics (continued)
(VDD = +3V, VREF = +2.5V, fSCLK = 4.8MHz, CLOAD = 30pF, TA = +25°C, unless otherwise noted.)
MAX11626–MAX11629/MAX11632/MAX11633
GAIN ERROR vs. SUPPLY VOLTAGE
MAX11626 toc26
GAIN ERROR vs. SUPPLY VOLTAGE
MAX11626 toc27
0.7 0.6 GAIN ERROR (LSB) 0.5 0.4 0.3 0.2 0.1 0 4.75 4.85 4.95 5.05 5.15 MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps
0
-0.1 GAIN ERROR (LSB)
-0.2
-0.3
-0.4
MAX11627/MAX11629/MAX11633
-0.5 5.25 2.7 3.0 VDD (V) 3.3 3.6 VDD (V)
GAIN ERROR vs. TEMPERATURE
MAX11626 toc28
GAIN ERROR vs. TEMPERATURE
MAX11627/MAX11629/MAX11633 fSAMPLE = 300ksps
MAX11626 toc29
SAMPLING ERROR vs. SOURCE IMPEDANCE
MAX11626 toc30
1.0
0.5
2 0 SAMPLING ERROR (LSB) -2 -4 -6 -8 -10
0.6 GAIN ERROR (LSB)
0.3 GAIN ERROR (LSB)
0.2
0.1
-0.2
-0.1
-0.6
MAX11626/MAX11628/MAX11632 fSAMPLE = 300ksps -40 -15 10 35 60 85
-0.3
-1.0 TEMPERATURE (°C)
-0.5 -40 -15 10 35 60 85 TEMPERATURE (°C)
0
2
4
6
8
10
SOURCE IMPEDANCE (kΩ)
_______________________________________________________________________________________
9
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Pin Description
MAX11626 MAX11627 (4 CHANNELS) 5, 6, 7 — — 1–4 — MAX11628 MAX11629 (8 CHANNELS) — — 1–7 — — MAX11632 MAX11633 (16 CHANNELS) — 1–15 — — 16 NAME N.C. AIN0–AIN14 AIN0–AIN6 AIN0–AIN3 CNVST/AIN15 FUNCTION No Connection. Not internally connected. Analog Inputs Analog Inputs Analog Inputs Active-Low Conversion Start Input/Analog Input 15. See Table 3 for details on programming the setup register. Active-Low Conversion Start Input/Analog Input 7. See Table 3 for details on programming the setup register. Active-Low Conversion Start Input. See Table 3 for details on programming the setup register. Reference Input. Bypass to GND with a 0.1µF capacitor. Ground Power Input. Bypass to GND with a 0.1µF capacitor. Active-Low Chip-Select Input. When CS is low, the serial interface is enabled. When CS is high, DOUT is high impedance. Serial Clock Input. Clocks data in and out of the serial interface. (Duty cycle must be 40% to 60%.) See Table 3 for details on programming the clock mode. Serial Data Input. DIN data is latched into the serial interface on the rising edge of SCLK. Serial Data Output. Data is clocked out on the falling edge of SCLK. High impedance when CS is connected to VDD. End of Conversion Output. Data is valid after EOC pulls low.
—
8
—
CNVST/AIN7
8 9 10 11
— 9 10 11
— 17 18 19
CNVST REF GND VDD
12
12
20
CS
13
13
21
SCLK
14
14
22
DIN
15
15
23
DOUT
16
16
24
EOC
10
______________________________________________________________________________________
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
CS
tCSS0 tCL
tCH
tCP
tCSH1
tCSH0 tCSS1
SCLK tDH tDS DIN tDOT tDOE DOUT tDOD
Figure 1. Detailed Serial-Interface Timing Diagram
CS DIN SCLK
SERIAL INTERFACE
DOUT
OSCILLATOR CNVST
CONTROL
EOC
AIN1 AIN2 AIN15 T/H 12-BIT SAR ADC FIFO AND ACCUMULATOR
REF MAX11626–MAX11629/MAX11632/MAX11633
INTERNAL REFERENCE
Figure 2. Functional Diagram
Detailed Description
The MAX11626–MAX11629/MAX11632/MAX11633 are low-power, serial-output, multichannel ADCs with FIFO capability for system monitoring, process-control, and instrumentation applications. These 12-bit ADCs have internal track and hold (T/H) circuitry supporting singleended inputs. Data is converted from analog voltage sources in a variety of channel and data-acquisition configurations. Microprocessor (µP) control is made easy
through a 3-wire SPI-/QSPI-/MICROWIRE-compatible serial interface. Figure 2 shows a simplified functional diagram of the MAX11626–MAX11629/MAX11632/MAX11633 internal architecture. The MAX11632/MAX11633 have 16 single-ended analog input channels. The MAX11628/ MAX11629 have 8 single-ended analog input channels. The MAX11626/MAX11627 have 4 single-ended analog input channels.
11
______________________________________________________________________________________
12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Converter Operation
The MAX11626–MAX11629/MAX11632/MAX11633 ADCs use a successive-approximation register (SAR) conversion technique and an on-chip T/H block to convert voltage signals into a 12-bit digital result. This single-ended configuration supports unipolar signal ranges. bus. In clock mode 01, use CNVST to request conversions one channel at a time, controlling the sampling speed without tying up the serial bus. Request and start internally timed conversions through the serial interface by writing to the conversion register in the default clock mode 10. Use clock mode 11 with SCLK up to 4.8MHz for externally timed acquisitions to achieve sampling rates up to 300ksps. Clock mode 11 disables scanning and averaging. See Figures 4–7 for timing specifications and how to begin a conversion. These devices feature an active-low, end-of-conversion output. EOC goes low when the ADC completes the last requested operation and is waiting for the next input data byte (for clock modes 00 and 10). In clock mode 01, E OC goes low after the ADC completes each requested operation. E OC goes high when C S or CNVST goes low. EOC is always high in clock mode 11.
Input Bandwidth
The ADC’s input-tracking circuitry has a 1MHz smallsignal bandwidth, so it is possible to digitize high-speed transient events and measure periodic signals with bandwidths exceeding the ADC’s sampling rate by using undersampling techniques. Anti-alias prefiltering of the input signals is necessary to avoid high-frequency signals aliasing into the frequency band of interest.
Analog Input Protection
Internal ESD protection diodes clamp all pins to VDD and GND, allowing the inputs to swing from (GND 0.3V) to (VDD + 0.3V) without damage. However, for accurate conversions near full scale, the inputs must not exceed VDD by more than 50mV or be lower than GND by 50mV. If an off-channel analog input voltage exceeds the supplies, limit the input current to 2mA.
Single-Ended Inputs
The single-ended analog input conversion modes can be configured by writing to the setup register (see Table 3). Single-ended conversions are internally referenced to GND (see Figure 3). AIN0–AIN3 are available on the MAX11626–MAX11629/ MAX11632/MAX11633. AIN4–AIN7 are only available on the MAX11628–MAX11633. AIN8–AIN15 are only available on the MAX11632/MAX11633. See Tables 2–5 for more details on configuring the inputs. For the inputs that can be configured as CNVST or an analog input, only one can be used at a time.
3-Wire Serial Interface
The MAX11626–MAX11629/MAX11632/MAX11633 feature a serial interface compatible with SPI/QSPI and MICROWIRE devices. For SPI/QSPI, ensure the CPU serial interface runs in master mode so it generates the serial clock signal. Select the SCLK frequency of 10MHz or less, and set clock polarity (CPOL) and phase (CPHA) in the µP control registers to the same value. The MAX11626–MAX11629/MAX11632/MAX11633 operate with SCLK idling high or low, and thus operate with CPOL = CPHA = 0 or CPOL = CPHA = 1. Set CS low to latch input data at DIN on the rising edge of SCLK. Output data at DOUT is updated on the falling edge of SCLK. Results are output in binary format. Serial communication always begins with an 8-bit input data byte (MSB first) loaded from DIN. A high-to-low transition on CS initiates the data input operation. The input data byte and the subsequent data bytes are clocked from DIN into the serial interface on the rising edge of SCLK. Tables 1–5 detail the register descriptions. Bits 5 and 4, CKSEL1 and CKSEL0, respectively, control the clock modes in the setup register (see Table 3). Choose between four different clock modes for various ways to start a conversion and determine whether the acquisitions are internally or externally timed. Select clock mode 00 to configure CNVST/AIN_ to act as a conversion start and use it to request the programmed, internally timed conversions without tying up the serial
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Unipolar
The MAX11626–MAX11629/MAX11632/MAX11633 always operate in unipolar mode. The analog inputs are internally referenced to GND with a full-scale input range from 0 to VREF.
REF GND AIN0-AIN15 CIN+ HOLD
DAC
COMPARATOR + -
CINGND HOLD VDD/2 HOLD
Figure 3. Equivalent Input Circuit
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12-Bit, 300ksps ADCs with FIFO and Internal Reference
True Differential Analog Input T/H
The equivalent circuit of Figure 3 shows the MAX11626–MAX11629/MAX11632/MAX11633’s input architecture. In track mode, a positive input capacitor is connected to AIN0–AIN15. A negative input capacitor is connected to GND. For external T/H timing, use clock mode 01. After the T/H enters hold mode, the difference between the sampled positive and negative input voltages is converted. The time required for the T/H to acquire an input signal is determined by how quickly its input capacitance is charged. If the input signal’s source impedance is high, the required acquisition time lengthens. The acquisition time, tACQ, is the maximum time needed for a signal to be acquired, plus the power-up time. It is calculated by the following equation: tACQ = 9 x (RS + RIN) x 24pF + tPWR where RIN = 1.5kΩ, RS is the source impedance of the input signal, and tPWR = 1µs, the power-up time of the device. The varying power-up times are detailed in the explanation of the clock mode conversions. tACQ is never less than 1.4µs, and any source impedance below 300Ω does not significantly affect the ADC’s AC performance. A high-impedance source can be accommodated either by lengthening t ACQ or by placing a 1µF capacitor between the positive and negative analog inputs. oscillator is active in clock modes 00, 01, and 10. Read out the data at clock speeds up to 10MHz. See Figures 4–7 for details on timing specifications and starting a conversion.
MAX11626–MAX11629/MAX11632/MAX11633
Applications Information
Register Descriptions
The MAX11626–MAX11629/MAX11632/MAX11633 communicate between the internal registers and the external circuitry through the SPI-/QSPI-compatible serial interface. Table 1 details the registers and the bit names. Tables 2–5 show the various functions within the conversion register, setup register, averaging register, and reset register.
Conversion Time Calculations The conversion time for each scan is based on a number of different factors: conversion time per sample, samples per result, results per scan, and if the external reference is in use.
Use the following formula to calculate the total conversion time for an internally timed conversion in clock modes 00 and 10 (see the Electrical Characteristics section as applicable): Total Conversion Time = tCNV x nAVG x nRESULT + tRP where tCNV = tACQ (max) + tCONV (max). nAVG = samples per result (amount of averaging). nRESULT = number of FIFO results requested; determined by the number of channels being scanned or by NSCAN1, NSCAN0. tRP = internal reference wake-up; set to zero if internal reference is already powered up or external reference is being used . In clock mode 01, the total conversion time depends on how long CNVST is held low or high, including any time required to turn on the internal reference. Conversion time in externally clocked mode (CKSEL1, CKSEL0 = 11) depends on the SCLK period and how long CS is held high between each set of eight SCLK cycles. In clock mode 01, the total conversion time does not include the time required to turn on the internal reference.
BIT 4 CHSEL1 CKSEL0 AVGON 1 BIT 3 CHSEL0 REFSEL1 NAVG1 RESET BIT 2 SCAN1 REFSEL0 NAVG0 X BIT 1 SCAN0 X NSCAN1 X BIT 0 X X NSCAN0 X
Internal FIFO
The MAX11626–MAX11629/MAX11632/MAX11633 contain a FIFO buffer that can hold up to 16 ADC results. This allows the ADC to handle multiple internally clocked conversions, without tying up the serial bus. If the FIFO is filled and further conversions are requested without reading from the FIFO, the oldest ADC results are overwritten by the new ADC results. Each result contains 2 bytes, with the MSB preceded by four leading zeros. After each falling edge of CS, the oldest available byte of data is available at DOUT, MSB first. When the FIFO is empty, DOUT is zero.
Internal Clock
The MAX11626–MAX11629/MAX11632/MAX11633 operate from an internal oscillator, which is accurate within 10% of the 4.4MHz nominal clock rate. The internal
Table 1. Input Data Byte (MSB First)
REGISTER NAME Conversion Setup Averaging Reset BIT 7 1 0 0 0 BIT 6 CHSEL3 1 0 0 BIT 5 CHSEL2 CKSEL1 1 0
X = Don’t care.
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12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Conversion Register Select active analog input channels per scan and scan modes by writing to the conversion register. Table 2 details channel selection and the four scan modes. Request a scan by writing to the conversion register when in clock mode 10 or 11, or by applying a low pulse to the CNVST pin when in clock mode 00 or 01. A conversion is not performed if it is requested on a channel that has been configured as CNVST. Do not request conversions on channels 8–15 on the MAX11626–MAX11629. Set CHSEL3:CHSEL0 to the lower channel’s binary values. Select scan mode 00 or 01 to return one result per single-ended channel within the requested range. Select scan mode 10 to scan a single input channel numerous times, depending on NSCAN1 and NSCAN0 in the averaging register (Table 4). Select scan mode 11 to return only one result from a single channel. Setup Register Write a byte to the setup register to configure the clock, reference, and power-down modes. Table 3 details the bits in the setup register. Bits 5 and 4 (CKSEL1 and CKSEL0) control the clock mode, acquisition and sampling, and the conversion start. Bits 3 and 2 (REFSEL1 and REFSEL0) control internal or external reference use. Averaging Register Write to the averaging register to configure the ADC to average up to 32 samples for each requested result, and to independently control the number of results requested for single-channel scans. Table 2 details the four scan modes available in the conversion register. All four scan modes allow averaging as long as the AVGON bit, bit 4 in the averaging register, is set to 1. Select scan mode 10 to scan the same channel multiple times. Clock mode 11 disables averaging. Reset Register Write to the reset register (as shown in Table 5) to clear the FIFO or to reset all registers to their default states. Set the RESET bit to 1 to reset the FIFO. Set the reset bit to zero to return the MAX11626–MAX11629/ MAX11632/MAX11633 to the default power-up state.
Table 2. Conversion Register*
BIT NAME — CHSEL3 CHSEL2 CHSEL1 CHSEL0 SCAN1 SCAN0 — BIT FUNCTION
7 (MSB) Set to 1 to select conversion register. 6 5 4 3 2 1 Analog input channel select. Analog input channel select. Analog input channel select. Analog input channel select. Scan mode select. Scan mode select.
0 (LSB) Don’t care.
*See below for bit details.
CHSEL3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 CHSEL2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 CHSEL1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 CHSEL0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 SELECTED CHANNEL (N) AIN0 AIN1 AIN2 AIN3 AIN4 AIN5 AIN6 AIN7 AIN8 AIN9 AIN10 AIN11 AIN12 AIN13 AIN14 AIN15
SCAN1 SCAN0 0 0 1 1 0 1 0 1
SCAN MODE (CHANNEL N IS SELECTED BY BITS CHSEL3–CHSEL0) Scans channels 0 through N. Scans channels N through the highest numbered channel. Scans channel N repeatedly. The averaging register sets the number of results. No scan. Converts channel N once only.
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12-Bit, 300ksps ADCs with FIFO and Internal Reference
Table 3. Setup Register*
BIT NAME — — CKSEL1 CKSEL0 REFSEL1 REFSEL0 — — BIT 7 (MSB) 6 5 4 3 2 1 0 (LSB) Set to 0 to select setup register. Set to 1 to select setup register. Clock mode and CNVST configuration. Resets to 1 at power-up. Clock mode and CNVST configuration. Reference mode configuration. Reference mode configuration. Don’t care. Don’t care. FUNCTION
MAX11626–MAX11629/MAX11632/MAX11633
*See below for bit details.
CKSEL1 0 0 1 1
CKSEL0 0 1 0 1
CONVERSION CLOCK Internal Internal Internal External (4.8MHz max)
ACQUISITION/SAMPLING Internally timed Externally timed through CNVST Internally timed Externally timed through SCLK
CNVST CONFIGURATION CNVST CNVST AIN15/AIN11/AIN7* AIN15/AIN11/AIN7*
*For the MAX11626/MAX11627, CNVST has its own dedicated pin.
REFSEL1 0 0 1 1
REFSEL0 0 1 0 1
VOLTAGE REFERENCE Internal External Internal Reserved
AutoShutdown Reference off after scan; need wake-up delay. Reference off; no wake-up delay. Reference always on; no wake-up delay. Reserved. Do not use.
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12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Table 4. Averaging Register*
BIT NAME — — — AVGON NAVG1 NAVG0 NSCAN1 NSCAN0 BIT 7 (MSB) 6 5 4 3 2 1 0 (LSB) Set to 0 to select averaging register. Set to 0 to select averaging register. Set to 1 to select averaging register. Set to 1 to turn averaging on. Set to 0 to turn averaging off. Configures the number of conversions for single-channel scans. Configures the number of conversions for single-channel scans. Single-channel scan count. (Scan mode 10 only.) Single-channel scan count. (Scan mode 10 only.) FUNCTION
*See below for bit details.
AVGON 0 1 1 1 1 NAVG1 x 0 0 1 1 NAVG0 x 0 1 0 1 FUNCTION Performs one conversion for each requested result. Performs four conversions and returns the average for each requested result. Performs eight conversions and returns the average for each requested result. Performs 16 conversions and returns the average for each requested result. Performs 32 conversions and returns the average for each requested result.
NSCAN1 0 0 1 1
NSCAN0 0 1 0 1
FUNCTION (APPLIES ONLY IF SCAN MODE 10 IS SELECTED) Scans channel N and returns four results. Scans channel N and returns eight results. Scans channel N and returns 12 results. Scans channel N and returns 16 results.
Table 5. Reset Register
BIT NAME — — — — RESET x x x BIT 7 (MSB) 6 5 4 3 2 1 0 (LSB) Set to 0 to select reset register. Set to 0 to select reset register. Set to 0 to select reset register. Set to 1 to select reset register. Set to 0 to reset all registers. Set to 1 to clear the FIFO only. Reserved. Don’t care. Reserved. Don’t care. Reserved. Don’t care. FUNCTION
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12-Bit, 300ksps ADCs with FIFO and Internal Reference
Power-Up Default State
The MAX11626–MAX11629/MAX11632/MAX11633 power up with all blocks in shutdown, including the reference. All registers power up in state 00000000, except for the setup register, which powers up in clock mode 10 (CKSEL1 = 1) goes low before pulling CS low to communicate with the serial interface. EOC stays low until CS or CNVST is pulled low again. Do not initiate a second CNVST before EOC goes low; otherwise, the FIFO can become corrupted.
MAX11626–MAX11629/MAX11632/MAX11633
Output Data Format
Figures 4–7 illustrate the conversion timing for the MAX11626–MAX11629/MAX11632/MAX11633. The 12-bit conversion result is output in MSB-first format with four leading zeros. DIN data is latched into the serial interface on the rising edge of SCLK. Data on DOUT transitions on the falling edge of SCLK. Conversions in clock modes 00 and 01 are initiated by C NVST . Conversions in clock modes 10 and 11 are initiated by writing an input data byte to the conversion register. Data output is binary.
Externally Timed Acquisitions and Internally Timed Conversions with CNVST
Performing Conversions in Clock Mode 01 In clock mode 01, conversions are requested one at a time using CNVST and performed automatically using the internal oscillator. See Figure 5 for clock mode 01 timing. Setting CNVST low begins an acquisition, wakes up the ADC, and places it in track mode. Hold CNVST low for at least 1.4µs to complete the acquisition. If the internal reference needs to wake up, an additional 65µs is required for the internal reference to power up.
Set CNVST high to begin a conversion. After the conversion is complete, the ADC shuts down and pulls EOC low. EOC stays low until CS or CNVST is pulled low again. Wait until EOC goes low before pulling CS or CNVST low. If averaging is turned on, multiple CNVST pulses need to be performed before a result is written to the FIFO. Once the proper number of conversions has been performed to generate an averaged FIFO result, as specified by the averaging register, the scan logic automatically switches the analog input multiplexer to the next-requested channel. The result is available on DOUT once EOC has been pulled low.
Internally Timed Acquisitions and Conversions Using CNVST
Performing Conversions in Clock Mode 00 In clock mode 00, the wake-up, acquisition, conversion, and shutdown sequences are initiated through CNVST and performed automatically using the internal oscillator. Results are added to the internal FIFO to be read out later. See Figure 4 for clock mode 00 timing. Initiate a scan by setting CNVST low for at least 40ns before pulling it high again. The MAX11626–MAX11629/ MAX11632/MAX11633 then wake up, scan all requested channels, store the results in the FIFO, and shut down. After the scan is complete, EOC is pulled low and the results are available in the FIFO. Wait until EOC
CNVST (UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS) CS SCLK
DOUT MSB1 LSB1 MSB2
EOC SET CNVST LOW FOR AT LEAST 40ns TO BEGIN A CONVERSION.
Figure 4. Clock Mode 00 Timing
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12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
CNVST (CONVERSION2) (ACQUISITION1) CS (CONVERSION1) SCLK (ACQUISITION2)
DOUT MSB1 LSB1 MSB2
EOC REQUEST MULTIPLE CONVERSIONS BY SETTING CNVST LOW FOR EACH CONVERSION.
Figure 5. Clock Mode 01 Timing
DIN
(CONVERSION BYTE) (UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)
CS SCLK
DOUT MSB1 LSB1 MSB2
EOC THE CONVERSION BYTE BEGINS THE ACQUISITION. CNVST IS NOT REQUIRED.
Figure 6. Clock Mode 10 Timing
Internally Timed Acquisitions and Conversions Using the Serial Interface
Performing Conversions in Clock Mode 10 In clock mode 10, the wake-up, acquisition, conversion, and shutdown sequences are initiated by writing an input data byte to the conversion register, and are performed automatically using the internal oscillator. This is the default clock mode upon power-up. See Figure 6 for clock mode 10 timing. Initiate a scan by writing a byte to the conversion register. The MAX11626–MAX11629/MAX11632/MAX11633 then power up, scan all requested channels, store the results in the FIFO, and shut down. After the scan is
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complete, EOC is pulled low and the results are available in the FIFO. EOC stays low until CS is pulled low again.
Externally Clocked Acquisitions and Conversions Using the Serial Interface
Performing Conversions in Clock Mode 11 In clock mode 11, acquisitions and conversions are initiated by writing to the conversion register and are performed one at a time using the SCLK as the conversion clock. Scanning and averaging are disabled, and the conversion result is available at DOUT during the conversion. See Figure 7 for clock mode 11 timing.
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12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
DIN (ACQUISITION1) CS SCLK (CONVERSION BYTE) (CONVERSION1) (ACQUISITION2)
DOUT MSB1 LSB1 MSB2
EOC EXTERNALLY TIMED ACQUISITION, SAMPLING AND CONVERSION WITHOUT CNVST.
Figure 7. Clock Mode 11 Timing
Initiate a conversion by writing a byte to the conversion register followed by 16 SCLK cycles. If CS is pulsed high between the eight and ninth cycles, the pulse width must be less than 100µs. To continuously convert at 16 cycles per conversion, alternate 1 byte of zeros between each conversion byte. If reference mode 00 is requested, wait 65µs with CS high after writing the conversion byte to extend the acquisition and allow the internal reference to power up.
OUTPUT CODE FULL-SCALE TRANSITION
11 . . . 111 11 . . . 110 11 . . . 101
FS = VREF + VCOM ZS = VCOM V 1 LSB = REF 4096
Partial Reads and Partial Writes
If the first byte of an entry in the FIFO is partially read (CS is pulled high after fewer than eight SCLK cycles), the second byte of data that is read out contains the next 8 bits (not b7–b0). The remaining bits are lost for that entry. If the first byte of an entry in the FIFO is read out fully, but the second byte is read out partially, the rest of the entry is lost. The remaining data in the FIFO is uncorrupted and can be read out normally after taking CS low again, as long as the 4 leading bits (normally zeros) are ignored. Internal registers that are written partially through the SPI contain new values, starting at the MSB up to the point that the partial write is stopped. The part of the register that is not written contains previously written values. If CS is pulled low before EOC goes low, a conversion cannot be completed and the FIFO is corrupted.
00 . . . 011 00 . . . 010 00 . . . 001 00 . . . 000 01 (COM) 2 3 INPUT VOLTAGE (LSB)
FS FS - 3/2 LSB
Figure 8. Unipolar Transfer Function, Full Scale (FS) = VREF
Layout, Grounding, and Bypassing
For best performance, use PCBs. Do not use wire wrap boards. Board layout should ensure that digital and analog signal lines are separated from each other. Do not run analog and digital (especially clock) signals parallel to one another or run digital lines underneath the MAX11626–MAX11629/MAX11632/MAX11633 package. High-frequency noise in the V DD power supply can affect performance. Bypass the VDD supply with a 0.1µF capacitor to GND, close to the VDD pin. Minimize capacitor lead lengths for best supply-noise rejection. If the power supply is very noisy, connect a 10Ω resistor in series with the supply to improve power-supply filtering.
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Transfer Function
Figure 8 shows the unipolar transfer function. Code transitions occur halfway between successive-integer LSB values. Output coding is binary, with 1 LSB = VREF/2.5V (MAX11627/MAX11629/MAX11633) and 1 LSB = VREF/ 4.096V (MAX11626/MAX11628/MAX11632).
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12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values on an actual transfer function from a straight line. This straight line can be either a best-straight-line fit or a line drawn between the end points of the transfer function, once offset and gain errors have been nullified. INL for the MAX11626–MAX11629/MAX11632/MAX11633 is measured using the end-point method.
Signal-to-Noise Plus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio of the fundamental input frequency’s RMS amplitude to the RMS equivalent of all other ADC output signals: SINAD (dB) = 20 x log (SignalRMS/NoiseRMS)
Effective Number of Bits
Effective number of bits (ENOB) indicates the global accuracy of an ADC at a specific input frequency and sampling rate. An ideal ADC error consists of quantization noise only. With an input range equal to the fullscale range of the ADC, calculate the effective number of bits as follows: ENOB = (SINAD - 1.76)/6.02
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between an actual step width and the ideal value of 1 LSB. A DNL error specification of less than 1 LSB guarantees no missing codes and a monotonic transfer function.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS sum of the first five harmonics of the input signal to the fundamental itself. This is expressed as: ⎛ ⎞ THD = 20 x log ⎜ ⎛ V22 + V32 + V4 2 + V52 ⎞ /V1⎟ ⎝ ⎠⎠ ⎝ where V1 is the fundamental amplitude, and V2–V5 are the amplitudes of the first five harmonics.
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in the time between the samples.
Aperture Delay
Aperture delay (t AD ) is the time between the rising edge of the sampling clock and the instant when an actual sample is taken.
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital samples, signal-to-noise ratio (SNR) is the ratio of the full-scale analog input (RMS value) to the RMS quantization error (residual error). The ideal, theoretical minimum analog-to-digital noise is caused by quantization error only and results directly from the ADC’s resolution (N bits): 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 calculated 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.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of the RMS amplitude of the fundamental (maximum signal component) to the RMS value of the next-largest distortion component.
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12-Bit, 300ksps ADCs with FIFO and Internal Reference
Pin Configurations (continued)
PROCESS: BiCMOS
TOP VIEW
MAX11626–MAX11629/MAX11632/MAX11633
Chip Information
+
AIN0 1 AIN1 2 AIN2 3 AIN3 4 AIN4 5 AIN5 6 AIN6 7 AIN7 8 AIN8 9 AIN9 10 AIN10 11 AIN11 12 24 EOC 23 DOUT 22 DIN 21 SCLK
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
PACKAGE TYPE 16 QSOP 24 QSOP PACKAGE CODE E16+5 E24+1 OUTLINE NO. 21-0055 21-0055 LAND PATTERN NO. 90-0167 90-0172
MAX11632 MAX11633
20 CS 19 VDD 18 GND 17 REF 16 CNVST/AIN15 15 AIN14 14 AIN13 13 AIN12
QSOP
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12-Bit, 300ksps ADCs with FIFO and Internal Reference MAX11626–MAX11629/MAX11632/MAX11633
Revision History
REVISION NUMBER 0 1 2 3 REVISION DATE 6/10 8/10 3/11 10/11 Initial release Initial release of MAX11628/MAX11629 and changed internal reference voltage Added MAX11628 automotive qualified part to data sheet Initial release of MAX11626/MAX11627 DESCRIPTION PAGES CHANGED — 1 1 1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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