MAX1228BEEP [MAXIM]
A/D Converter, 12-Bit, 1 Func, BICMOS, PDSO20;
| 型号： | MAX1228BEEP |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | A/D Converter, 12-Bit, 1 Func, BICMOS, PDSO20 传感器 温度传感器 先进先出芯片 |
| 文件： | 总24页 (文件大小：541K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2852; Rev 1; 7/03
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
General Description
Features
The MAX1226/MAX1228/MAX1230 are serial 12-bit ana-
log-to-digital converters (ADCs) with an internal reference
and an internal temperature sensor. These devices fea-
ture on-chip FIFO, scan mode, internal clock mode, inter-
nal averaging, and AutoShutdown™. The maximum
sampling rate is 300ksps using an external clock. The
MAX1230 has 16 input channels, the MAX1228 has 12
input channels, and the MAX1226 has 8 input channels.
All input channels are configurable for single-ended or
differential inputs in unipolar or bipolar mode. All three
devices operate from a +5V supply and contain a 10MHz
SPI™/QSPI™/MICROWIRE™-compatible serial port.
o Internal Temperature Sensor ( 1°C Accuracy)
o 16-Entry First-In/First-Out (FIFO)
o Analog Multiplexer with True Differential
Track/Hold
16-, 12-, 8-Channel Single Ended
8-, 6-, 4-Channel True Differential
(Unipolar or Bipolar)
o Accuracy: 1 LSB INL, 1 LSB DNL, No Missing
Codes Over Temperature
o Scan Mode, Internal Averaging, and Internal Clock
o Low-Power Single +5V Operation
1.9mA at 300ksps
The MAX1230 is available in 28-pin 5mm x 5mm QFN
with exposed pad and 24-pin QSOP packages. The
MAX1226/MAX1228 are only available in QSOP pack-
ages. All three devices are specified over the extended
-40°C to +85°C temperature range.
o Internal 4.096V Reference or External Differential
Reference
o 10MHz 3-Wire SPI/QSPI/MICROWIRE-Compatible
Interface
o Space-Saving 28-Pin 5mm x 5mm QFN Package
________________________Applications
System Supervision
Data-Acquisition Systems
Industrial Control Systems
Patient Monitoring
Data Logging
Ordering Information
PART
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
MAX1226ACEE-T*
MAX1226AEEE-T*
16 QSOP
Instrumentation
*Future product—contact factory for availability.
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
SPI/QSPI are trademarks of Motorola, Inc.
Ordering Information continued at end of data sheet.
MICROWIRE is a trademark of National Semiconductor Corp.
Pin Configurations
TOP VIEW
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
1
2
3
4
5
6
7
8
9
20 EOC
19 DOUT
18 DIN
17 CS
AIN0
1
2
3
4
5
6
7
8
16 EOC
15 DOUT
14 DIN
13 CS
AIN1
AIN2
MAX1228
16 SCLK
AIN3
MAX1226
15
14
V
DD
AIN4
12 SCLK
GND
AIN5
11
10 GND
REF+
V
DD
13 REF+
REF-/AIN6
CNVST/AIN7
12 CNVST/AIN11
11 REF-/AIN10
9
AIN9 10
QSOP
QSOP
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
ABSOLUTE MAXIMUM RATINGS
DD
V
to GND..............................................................-0.3V to +6V
Operating Temperature Ranges
CS% SCLK% DIN% EOC% DOUT to GND.........-0.3V to (V
AIN0–AIN13% REF-/AIN_% CNVST/AIN_%
REF+ to GND.........................................-0.3V to (V
Maximum Current into Any Pin............................................50mA
+ 0.3V)
MAX12__C__.......................................................0°C to +70°C
MAX12__E__....................................................-40°C to +85°C
Storage Temperature Range.............................-60°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering% 10s) .................................+300°C
DD
+ 0.3V)
DD
Continuous Power Dissipation (T = +70°C)
A
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
24-Pin QSOP (derate 9.5mW/°C above +70°C)...........762mW
28-Pin QFN 5mm x 5mm
(derate 20.8mW/°C above +70°C)........................1667mW
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
(V
= +5V 5ꢀ% ꢁ
= 300kHz% ꢁ
= 4.8MHz (50ꢀ duty cycle)% V
= 4.096V% T = T
to T
% unless otherwise noted.
MAX
DD
SAMPLE
SCLK
REF
A
MIN
Typical values are at T = +25°C.)
A
PARAMETER
DC ACCURACY (Note 1)
Resolution
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
RES
INL
12
Bits
LSB
LSB
LSB
LSB
Integral Nonlinearity
Diꢁꢁerential Nonlinearity
Oꢁꢁset Error
1.0
1.0
4.0
4.0
DNL
No missing codes over temperature
(Note 2)
0.5
0.5
Gain Error
Oꢁꢁset Error Temperature
Coeꢁꢁicient
ppm/°C
FSR
2
Gain Temperature Coeꢁꢁicient
0.8
0.1
ppm/°C
Channel-to-Channel Oꢁꢁset
Matching
LSB
DYNAMIC SPECIFICATIONS (10kHz sine wave input, 4.096V , 300ksps, f
= 4.8MHz)
P-P
SCLK
Signal-to-Noise Plus Distortion
Total Harmonic Distortion
Spurious-Free Dynamic Range
Intermodulation Distortion
Full-Power Bandwidth
SINAD
THD
70
-82
80
76
1
dB
dBc
dBc
dBc
MHz
kHz
Up to the 5th harmonic
SFDR
IMD
ꢁ
= 9.9kHz% ꢁ = 10.2kHz
in2
in1
-3dB point
Full-Linear Bandwidth
S / (N + D) > 68dB
25
2
_______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
ELECTRICAL CHARACTERISTICS (continued)
(V
= +5V 5ꢀ% ꢁ
= 300kHz% ꢁ
= 4.8MHz (50ꢀ duty cycle)% V
= 4.096V% T = T
to T
% unless otherwise noted.
MAX
DD
SAMPLE
SCLK
REF
A
MIN
Typical values are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CONVERSION RATE
External reꢁerence
0.8
65
Power-Up Time
Acquisition Time
Conversion Time
t
µs
µs
µs
PU
Internal reꢁerence (Note 3)
t
0.6
ACQ
Internally clocked
3.5
t
CONV
Externally clocked (Note 4)
Externally clocked conversion
Data I/O
2.7
0.1
4.8
10
60
External Clock Frequency
ꢁ
MHz
SCLK
SCLK Duty Cycle
Aperture Delay
Aperture Jitter
40
ꢀ
ns
ps
30
<50
ANALOG INPUT
Unipolar
0
V
REF
Input Voltage Range
V
Bipolar (Note 5)
-V
/ 2
V
REF
/ 2
REF
Input Leakage Current
Input Capacitance
V
= V
0.01
24
1
µA
pF
IN
DD
During acquisition time (Note 6)
INTERNAL TEMPERATURE SENSOR
Grade A% T = +25°C
0.3
0.5
A
Grade A =% T = -20°C to +85°C
1
A
Measurement Error (Note 7)
Grade A% T = T
to T
0.75
0.7
1.5
°C
A
MIN
MAX
Grade B% T = +25°C
A
Grade B% T = T
A
to T
1.2
3.0
MIN
MAX
Temperature Measurement Noise
0.1
°C
RMS
Temperature Resolution
Power-Supply Rejection
INTERNAL REFERENCE
REF Output Voltage
1/8
0.3
°C
°C/V
4.024
4.096
8
4.168
V
Grade A
Grade B
REF Temperature Coeꢁꢁicient
TC
ppm/°C
kΩ
REF
30
Output Resistance
6.5
200
-70
REF Output Noise
µV
RMS
REF Power-Supply Rejection
EXTERNAL REFERENCE INPUT
REF- Input Voltage Range
REF+ Input Voltage Range
PSRR
dB
V
0
500
+ 50mV
100
mV
V
REF-
V
1.0
V
DD
REF+
V
V
= 4.096V% ꢁ
= 4.096V% ꢁ
= 300ksps
= 0
40
REF+
REF+
SAMPLE
SAMPLE
REF+ Input Current
I
µA
REF+
0.1
5
_______________________________________________________________________________________
3
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
ELECTRICAL CHARACTERISTICS (continued)
(V
= +5V 5ꢀ% ꢁ
= 300kHz% ꢁ
= 4.8MHz (50ꢀ duty cycle)% V
= 4.096V% T = T
to T
% unless otherwise noted.
MAX
DD
SAMPLE
SCLK
REF
A
MIN
Typical values are at T = +25°C.)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL INPUTS (SCLK, DIN, CS, CNVST)
Input Voltage Low
V
0.8
V
V
IL
Input Voltage High
V
2.0
IH
Input Hysteresis
V
200
0.01
15
mV
µA
pF
HYST
Input Leakage Current
Input Capacitance
I
V
= 0 or V
DD
1.0
IN
IN
C
IN
DIGITAL OUTPUTS (DOUT, EOC)
I
I
I
= 2mA
= 4mA
0.4
0.8
SINK
Output Voltage Low
V
V
OL
SINK
Output Voltage High
V
= 1.5mA
V - 0.5
DD
V
OH
SOURCE
Tri-State Leakage Current
Tri-State Output Capacitance
POWER REQUIREMENTS
Supply Voltage
I
CS = V
CS = V
0.05
15
1
µA
pF
L
DD
DD
C
OUT
V
4.75
5.25
3100
2300
1350
5
V
DD
DD
During temp sense
2400
1950
1000
0.2
ꢁ
ꢁ
= 300ksps
= 0%REFon
SAMPLE
SAMPLE
Internal
reꢁerence
Supply Current (Note 8)
I
Shutdown
µA
mV
During temp sense
1650
1250
0.2
2300
1500
5
External
reꢁerence
ꢁ
= 300ksps
SAMPLE
Shutdown
Power-Supply Rejection
PSR
V
= 4.75V to 5.25V; ꢁull-scale input
0.2
1.2
DD
Note 1: Tested at V
= +5V% unipolar input mode.
DD
Note 2: Oꢁꢁset nulled.
Note 3: Time ꢁor reꢁerence to power up and settle to within 1 LSB.
Note 4: Conversion time is deꢁined as the number oꢁ clock cycles multiplied by the clock period; clock has 50ꢀ duty cycle.
Note 5: The operational input voltage range ꢁor each individual input oꢁ a diꢁꢁerentially conꢁigured pair is ꢁrom GND to V . The
DD
operational input voltage diꢁꢁerence is ꢁrom -V
/ 2 to +V
/ 2.
REF
REF
Note 6: See Figure 3 (Input Equivalent Circuit) and the Sampling Error vs. Source Impedance curve in the Typical Operating
Characterisitcs section.
Note 7: Fast automated test% excludes selꢁ-heating eꢁꢁects.
Note 8: Supply current is speciꢁied depending on whether an internal or external reꢁerence is used ꢁor voltage conversions.
Temperature measurements always use the internal reꢁerence.
4
_______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
TIMING CHARACTERISTICS (Figure 1)
PARAMETER
SYMBOL
CONDITIONS
Externally clocked conversion
Data I/O
MIN
208
100
40
TYP
MAX
UNITS
SCLK Clock Period
t
ns
CP
SCLK Duty Cycle
t
60
40
40
40
40
ꢀ
ns
ns
ns
ns
ns
ns
ns
ns
µs
CH
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 to SCLK Rise Setup
SCLK Rise to CS Hold
t
C
C
C
= 30pF
= 30pF
= 30pF
DOT
LOAD
LOAD
LOAD
t
DOD
t
DOE
t
DS
DH
t
0
t
40
CSS
CSH
t
0
t
CKSEL = 00% CKSEL = 01 (temp sense)
CKSEL = 01 (voltage conversion)
Temp sense
40
1.4
CSW
CNVST Pulse Width
t
t
55
7
TS
RP
CS or CNVST Rise to EOC
Low (Note 9)
Voltage conversion
µs
Reꢁerence power-up
65
Note 9: This time is deꢁined as the number oꢁ clock cycles needed ꢁor conversion multiplied by the clock period. Iꢁ the internal reꢁer-
ence needs to be powered up% the total time is additive. The internal reꢁerence is always used ꢁor temperature measurements.
Typical Operating Characteristics
(V
= +5V% V
= +4.096V% ꢁ
= 4.8MHz% C
= 30pF% T = +25°C% unless otherwise noted.)
DD
REF
SCLK
LOAD
A
DIFFERENTIAL NONLINEARITY
INTEGRAL NONLINEARITY
vs. OUTPUT CODE
vs. OUTPUT CODE
SINAD vs. FREQUENCY
100
1.0
0.8
1.0
0.8
90
80
70
60
50
40
30
20
10
0
0.6
0.4
0.6
0.4
0.2
0.2
0
0
-0.2
-0.4
-0.6
-0.8
-0.2
-0.4
-0.6
-0.8
-1.0
-1.0
0
1024
2048
3072
4096
0
1024
2048
3072
4096
0.1
1
10
100
1000
OUTPUT CODE
OUTPUT CODE
FREQUENCY (kHz)
_______________________________________________________________________________________
5
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Typical Operating Characteristics (continued)
(V
= +5V% V
= +4.096V% ꢁ
= 4.8MHz% C
= 30pF% T = +25°C% unless otherwise noted.)
DD
REF
SCLK
LOAD A
SFDR vs. FREQUENCY
SUPPLY CURRENT vs. SAMPLING RATE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
120
1200
1200
1150
1100
1050
1000
100
80
60
40
20
0
1000
800
600
400
200
0.1
1
10
100
1000
1
10
100
1000
4.75
4.85
4.95
5.05
5.15
5.25
FREQUENCY (kHz)
SAMPLING RATE (ksps)
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT vs. TEMPERATURE
1300
1250
1200
1150
1100
1050
1000
0.6
0.5
0.4
0.3
0.2
0.1
0
f
S
= 300ksps
4.75
4.85
4.95
5.05
5.15
5.25
-40
-15
10
35
60
85
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
INTERNAL REFERENCE VOLTAGE
vs. SUPPLY VOLTAGE
0.6
0.5
0.4
0.3
0.2
0.1
0
4.0500
4.0499
4.0498
4.0497
4.0496
4.0495
4.0494
-40
-15
10
35
60
85
4.75
4.85
4.95
5.05
5.15
5.25
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
6
_______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Typical Operating Characteristics (continued)
(V
= +5V% V
= +4.096V% ꢁ
= 4.8MHz% C
= 30pF% T = +25°C% unless otherwise noted.)
DD
REF
SCLK
LOAD
A
INTERNAL REFERENCE VOLTAGE
vs. TEMPERATURE
OFFSET ERROR
vs. TEMPERATURE
OFFSET ERROR
vs. SUPPLY VOLTAGE
0.3
4.051
0.3
0.2
0.1
0
0.2
0.1
0
4.050
4.049
4.048
4.047
-0.1
-0.2
-0.3
-0.1
-0.2
-0.3
4.75
-40
-15
10
35
60
85
-40
-15
10
35
60
85
4.85
4.95
5.05
5.15
5.25
TEMPERATURE (°C)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
GAIN ERROR vs. TEMPERATURE
GAIN ERROR vs. SUPPLY VOLTAGE
0.5
0.5
0
0
-0.5
-1.0
-1.5
-0.5
-1.0
-1.5
-40
-15
10
35
60
85
4.75
4.85
4.95
5.05
5.15
5.25
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
SAMPLING ERROR
vs. SOURCE IMPEDANCE
TEMPERATURE SENSOR ERROR
vs. TEMPERATURE
2
1.00
0.75
0
-2
0.50
0.25
GRADE A
-4
0
-0.25
-6
GRADE B
-0.50
-0.75
-1.00
-8
-10
0
2
4
6
8
10
-40
-15
10
35
60
85
SOURCE IMPEDANCE (kΩ)
TEMPERATURE (°C)
_______________________________________________________________________________________
7
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Pin Description
MAX1230 MAX1230
MAX1228 MAX1226
NAME
N.C.
FUNCTION
QFN
QSOP
1% 17%
19% 25
—
—
—
—
—
No Connection. Not internally connected.
Analog Inputs
2–12% 26%
27% 28
1–14
AIN0–13
—
—
—
—
1–10
—
AIN0–9
AIN0–5
Analog Inputs
Analog Inputs
—
1–6
Negative Input ꢁor External Diꢁꢁerential Reꢁerence/Analog Input 14.
See Table 3 ꢁor details on programming the setup register.
13
—
—
14
—
—
15
—
—
16
—
—
—
11
—
—
12
—
—
—
7
REF-/AIN14
REF-/AIN10
REF-/AIN6
Negative Input ꢁor External Diꢁꢁerential Reꢁerence/Analog Input 10.
See Table 3 ꢁor details on programming the setup register.
Negative Input ꢁor External Diꢁꢁerential Reꢁerence/Analog Input 6.
See Table 3 ꢁor details on programming the setup register.
CNVST/
AIN15
Active-Low Conversion Start Input/Analog Input 15. See Table 3
ꢁor details on programming the setup register.
—
—
8
CNVST/
AIN11
Active-Low Conversion Start Input/Analog Input 11. See Table 3
ꢁor details on programming the setup register.
CNVST/
AIN7
Active-Low Conversion Start Input/Analog Input 7. See Table 3 ꢁor
details on programming the setup register.
15
16
18
17
18
19
13
14
15
9
REF+
GND
Positive Reꢁerence Input. Bypass to GND with a 0.1µF capacitor.
Ground
10
11
V
Power Input. Bypass to GND with a 0.1µF capacitor.
DD
Serial Clock Input. Clocks data in and out oꢁ the serial interꢁace.
(Duty cycle must be 40ꢀ to 60ꢀ.) See Table 3 ꢁor details on
programming the clock mode.
20
20
16
12
SCLK
Active-Low Chip-Select Input. When CS is low% the serial interꢁace
is enabled. When CS is high% DOUT is high impedance.
21
22
21
22
17
18
13
14
CS
Serial Data Input. DIN data is latched into the serial interꢁace on
the rising edge oꢁ SCLK.
DIN
Serial Data Output. Data is clocked out on the ꢁalling edge oꢁ
23
24
23
24
19
20
15
16
DOUT
SCLK. High impedance when CS is connected to V
.
DD
EOC
End oꢁ Conversion Output. Data is valid aꢁter EOC pulls low.
8
_______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
CS
t
CSH
t
t
CH
t
t
CP
CSH
CSS
t
CSS
SCLK
DIN
t
DH
t
DS
t
t
DOT
DOD
t
DOE
DOUT
Figure 1. Detailed Serial-Interface Timing Diagram
CS
DIN
SCLK
SERIAL INTERFACE
DOUT
EOC
OSCILLATOR
CONTROL
CNVST
AIN1
AIN2
12-BIT
SAR
ADC
FIFO AND
ACCUMULATOR
T/H
AIN15
TEMP
SENSE
REF-
REF+
INTERNAL
REFERENCE
MAX1226
MAX1228
MAX1230
Figure 2. Functional Diagram
conꢁigurations. Microprocessor (µP) control is made
easy through a 3-wire SPI/QSPI/MICROWIRE-compati-
ble serial interꢁace.
Detailed Description
The MAX1226/MAX1228/MAX1230 are low-power% seri-
al-output% multichannel ADCs with temperature-sensing
capability ꢁor temperature-control% process-control% and
monitoring applications. These 12-bit ADCs have inter-
nal track and hold (T/H) circuitry that supports single-
ended and ꢁully diꢁꢁerential inputs. Data is converted
ꢁrom an internal temperature sensor or analog voltage
sources in a variety oꢁ channel and data-acquisition
Figure 2 shows a simpliꢁied ꢁunctional diagram oꢁ the
MAX1226/MAX1228/MAX1230 internal architecture.
The MAX1226 has eight single-ended analog input
channels or ꢁour diꢁꢁerential channels. The MAX1228
has 12 single-ended analog input channels or six diꢁꢁer-
ential channels. The MAX1230 has 16 single-ended
analog input channels or eight diꢁꢁerential channels.
_______________________________________________________________________________________
9
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Tables 1–7 detail the register descriptions. Bits 5 and 4%
Converter Operation
The MAX1226/MAX1228/MAX1230 ADCs use a ꢁully diꢁ-
ꢁerential% successive-approximation register (SAR) con-
version technique and an on-chip T/H block to convert
temperature and voltage signals into a 12-bit digital
result. Both single-ended and diꢁꢁerential conꢁigurations
are supported% with a unipolar signal range ꢁor single-
ended mode and bipolar or unipolar ranges ꢁor diꢁꢁer-
ential mode.
CKSEL1 and CKSEL0% respectively% control the clock
modes in the setup register (see Table 3). Choose
between ꢁour diꢁꢁerent clock modes ꢁor various ways to
start a conversion and determine whether the acquisi-
tions are internally or externally timed. Select clock
mode 00 to conꢁigure CNVST/AIN_ to act as a conver-
sion start and use it to request the programmed inter-
nally timed conversions without tying up the serial 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 inter-
nally timed conversions through the serial interꢁace by
writing to the conversion register in the deꢁault clock
mode% 10. Use clock mode 11 with SCLK up to 4.8MHz
ꢁor externally timed acquisitions to achieve sampling
rates up to 300ksps. Clock mode 11 disables scanning
and averaging. See Figures 4–7 ꢁor timing speciꢁica-
tions and how to begin a conversion.
Input Bandwidth
The ADC’s input-tracking circuitry has a 1MHz small-
signal 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 preꢁiltering
oꢁ the input signals is necessary to avoid high-ꢁrequen-
cy signals aliasing into the ꢁrequency band oꢁ interest.
Analog Input Protection
These devices ꢁeature an active-low% end-oꢁ-conversion
output. EOC goes low when the ADC completes the
last-requested operation and is waiting ꢁor the next input
data byte (ꢁor clock modes 00 and 10). In clock mode
01% EOC goes low aꢁter the ADC completes each
requested operation. EOC goes high when CS or
CNVST goes low. EOC is always high in clock mode 11.
Internal ESD protection diodes clamp all pins to V
DD
and GND% allowing the inputs to swing ꢁrom (GND -
0.3V) to (V + 0.3V) without damage. However% ꢁor
DD
accurate conversions near ꢁull scale% the inputs must
not exceed V by more than 50mV or be lower than
DD
GND by 50mV. Iꢁ an oꢁꢁ-channel analog input voltage
exceeds the supplies% limit the input current to 2mA.
Single-Ended/Differential Input
The MAX1226/MAX1228/MAX1230 use a ꢁully diꢁꢁeren-
tial ADC ꢁor all conversions. The analog inputs can be
conꢁigured ꢁor either diꢁꢁerential or single-ended con-
versions by writing to the setup register (see Table 3).
Single-ended conversions are internally reꢁerenced to
GND (Figure 3).
3-Wire Serial Interface
The MAX1226/MAX1228/MAX1230 ꢁeature a serial
interꢁace compatible with SPI/QSPI and MICROWIRE
devices. For SPI/QSPI% ensure the CPU serial interꢁace
runs in master mode so it generates the serial clock
signal. Select the SCLK ꢁrequency oꢁ 10MHz or less%
and set clock polarity (CPOL) and phase (CPHA) in the
µP control registers to the same value. The MAX1226/
MAX1228/MAX1230 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 oꢁ SCLK. Output data at DOUT is
updated on the ꢁalling edge oꢁ SCLK. Bipolar true diꢁ-
ꢁerential results and temperature sensor results are
available in two’s complement ꢁormat% while all others
are in binary.
In diꢁꢁerential mode% the T/H samples the diꢁꢁerence
between two analog inputs% eliminating common-mode
DC oꢁꢁsets and noise. IN+ and IN- are selected ꢁrom
the ꢁollowing pairs: AIN0/AIN1% AIN2/AIN3% AIN4/AIN5%
AIN6/AIN7% AIN8/AIN9% AIN10/AIN11% AIN12/AIN13%
and AIN14/AIN15. AIN0–AIN7 are available on the
MAX1226% MAX1228% and MAX1230. AIN8–AIN11 are
only available on the MAX1228 and MAX1230.
AIN12–AIN15 are only available on the MAX1230. See
Tables 2–5 ꢁor more details on conꢁiguring the inputs.
For the inputs that can be conꢁigured as CNVST or an
analog input% only one can be used at a time. For the
inputs that can be conꢁigured as REF- or an analog
input% the REF- conꢁiguration excludes the analog input.
Serial communication always begins with an 8-bit input
data byte (MSB ꢁirst) loaded ꢁrom DIN. Use a second
byte% immediately ꢁollowing the setup byte% to write to
the unipolar mode or bipolar mode registers (see
Tables 1% 3% 4% and 5). A high-to-low transition on CS ini-
tiates the data input operation. The input data byte and
the subsequent data bytes are clocked ꢁrom DIN into
the serial interꢁace on the rising edge oꢁ SCLK.
Unipolar/Bipolar
Address the unipolar and bipolar registers through the
setup register (bits 1 and 0). Program a pair oꢁ analog
channels ꢁor diꢁꢁerential operation by writing a 1 to the
10 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
where R = 1.5kΩ% R is the source impedance oꢁ the
IN
S
PWR
input signal% and t
= 1µs% the power-up time oꢁ the
device. The varying power-up times are detailed in the
REF
GND
AIN0-AIN15
(SINGLE ENDED);
AIN0, AIN2,
DAC
explanation oꢁ the clock mode conversions.
t
is never less than 1.4µs% and any source imped-
ACQ
AIN4…AIN14
(DIFFERENTIAL)
CIN+
ance below 300Ω does not signiꢁicantly aꢁꢁect the
COMPARATOR
+
ADC’s AC perꢁormance. A high-impedance source can
HOLD
be accommodated either by lengthening t
or by
ACQ
-
placing a 1µF capacitor between the positive and neg-
GND
(SINGLE ENDED);
AIN1, AIN3,
AIN5…AIN15
(DIFFERENTIAL)
ative analog inputs.
CIN-
Internal FIFO
The MAX1226/MAX1228/MAX1230 contain a FIFO
buꢁꢁer that can hold up to 16 ADC results plus one tem-
perature result. This allows the ADC to handle multiple
internally clocked conversions and a temperature mea-
surement% without tying up the serial bus.
HOLD
HOLD
V /2
DD
Figure 3. Equivalent Input Circuit
Iꢁ the FIFO is ꢁilled and ꢁurther conversions are request-
ed without reading ꢁrom the FIFO% the oldest ADC
results are overwritten by the new ADC results. Each
result contains 2 bytes% with the MSB preceded by 4
leading zeros. Aꢁter each ꢁalling edge oꢁ CS% the oldest
available byte oꢁ data is available at DOUT% MSB ꢁirst.
When the FIFO is empty% DOUT is zero.
appropriate bit oꢁ the bipolar or unipolar register.
Unipolar mode sets the diꢁꢁerential input range ꢁrom 0 to
REF
mode causes the digital output code to be zero.
Selecting bipolar mode sets the diꢁꢁerential input range
V
. A negative diꢁꢁerential analog input in unipolar
to
V
/ 2. The digital output code is binary in unipo-
REF
The ꢁirst 2 bytes oꢁ data read out aꢁter a temperature mea-
surement always contain the temperature result preceded
by 4 leading zeros% MSB ꢁirst. Iꢁ another temperature mea-
surement is perꢁormed beꢁore the ꢁirst temperature result
is read out% the old measurement is overwritten by the
new result. Temperature results are in degrees Celsius
(two’s complement) at a resolution oꢁ 1/8 oꢁ degree. See
the Temperature Measurements section ꢁor details on
converting the digital code to a temperature.
lar mode and two’s complement in bipolar mode. (See
the transꢁer ꢁunction graphs% Figures 8 and 9.)
In single-ended mode% the MAX1226/MAX1228/
MAX1230 always operate in unipolar mode. The analog
inputs are internally reꢁerenced to GND with a ꢁull-scale
input range ꢁrom 0 to V
.
REF
True Differential Analog Input T/H
The equivalent circuit oꢁ Figure 3 shows the
MAX1226/MAX1228/MAX1230s’ input architecture. In
track mode% a positive input capacitor is connected to
AIN0–AIN15 in single-ended mode (and AIN0% AIN2%
AIN4…AIN14 in diꢁꢁerential mode). A negative input
capacitor is connected to GND in single-ended mode
(or AIN1% AIN3% AIN5…AIN15 in diꢁꢁerential mode). For
external track-and-hold timing% use clock mode 01.
Aꢁter the T/H enters hold mode% the diꢁꢁerence between
the sampled positive and negative input voltages is
converted. The time required ꢁor the T/H to acquire an
input signal is determined by how quickly its input
capacitance is charged. Iꢁ the input signal’s source
impedance is high% the required acquisition time length-
Internal Clock
The MAX1226/MAX1228/MAX1230 operate ꢁrom an inter-
nal oscillator% which is accurate within 10ꢀ oꢁ the 4.4MHz
nominal clock rate. The internal oscillator is active in clock
modes 00% 01% and 10. Read out the data at clock speeds
up to 10MHz. See Figures 4–7 ꢁor details on timing speci-
ꢁications and starting a conversion.
Applications Information
Register Descriptions
The MAX1226/MAX1228/MAX1230 communicate
between the internal registers and the external circuitry
through the SPI-/QSPI-compatible serial interꢁace.
Table 1 details the registers and the bit names. Tables
2–7 show the various ꢁunctions within the conversion
register% setup register% averaging register% reset regis-
ter% unipolar register% and bipolar register.
ens. The acquisition time% t
% is the maximum time
ACQ
needed ꢁor a signal to be acquired% plus the power-up
time. It is calculated by the ꢁollowing equation:
t
= 9 x R + R
x 24pF + t
PWR
(
)
AQC
S
IN
______________________________________________________________________________________ 11
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Conversion Time Calculations
The conversion time ꢁor each scan is based on a num-
ber oꢁ diꢁꢁerent ꢁactors: conversion time per sample%
samples per result% results per scan% iꢁ a temperature
measurement is requested% and iꢁ the external reꢁer-
ence is in use.
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 reꢁerence. Conversion
time in externally clocked mode (CKSEL1% CKSEL0 = 11)
depends on the SCLK period and how long CS is held
high between each set oꢁ eight SCLK cycles.
Use the ꢁollowing ꢁormula to calculate the total conver-
sion time ꢁor an internally timed conversion in clock
modes 00 and 10 (see the Electrical Characteristics
section as applicable):
Conversion Register
Select active analog input channels% scan modes% and
a single temperature measurement per scan by writing
to the conversion register. Table 2 details channel
selection% the ꢁour scan modes% and how to request a
temperature measurement. 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.
total conversion time = t
where:
✕ n
avg
x n + t + t
result TS RP
cnv
t
= t
(max) + t
(max)
conv
cnv
acq
n
n
= samples per result (amount oꢁ averaging)
avg
= number oꢁ FIFO results requested; determined
result
A conversion is not perꢁormed iꢁ it is requested on a
channel that has been conꢁigured as CNVST or REF-.
Do not request conversions on channels 8–15 on the
MAX1226 and channels 12–15 on the MAX1228. Set
CHSEL3:CHSEL0 to the lower channel’s binary value. Iꢁ
the last two channels are conꢁigured as a diꢁꢁerential
pair and one oꢁ them has been reconꢁigured as CNVST
or REF-% the pair is ignored.
by number oꢁ channels being scanned by NSCAN1%
NSCAN0
t
= time required ꢁor temperature measurement; set
TS
to zero iꢁ temp measurement is not requested
t
= internal reꢁerence wake-up; set to zero iꢁ internal
RP
reꢁerence is already powered up or external reꢁerence is
being used
Table 1. Input Data Byte (MSB First)
REGISTER NAME
Conversion
BIT 7
BIT 6
BIT 5
CHSEL2
CKSEL1
1
BIT 4
CHSEL1
CKSEL0
AVGON
1
BIT 3
CHSEL0
REFSEL1
NAVG1
RESET
BIT 2
SCAN1
REFSEL0
NAVG0
X
BIT 1
SCAN0
DIFFSEL1
NSCAN1
X
BIT 0
TEMP
1
CHSEL3
Setup
0
0
1
0
DIFFSEL0
NSCAN0
X
Averaging
Reset
0
0
0
Unipolar mode (setup)
Bipolar mode (setup)
UCH0/1
BCH0/1
UCH2/3
BCH1/2
UCH4/5
BCH4/5
UCH6/7
BCH6/7
UCH8/9*
BCH8/9*
UCH10/11*
BCH10/11*
UCH12/13** UCH14/15**
BCH12/13** BCH14/15**
*Unipolar/bipolar channels 8–15 are only valid on the MAX1228 and MAX1230.
**Unipolar/bipolar channels 12–15 are only valid on the MAX1230.
X = Don’t care.
12 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Select scan mode 00 or 01 to return one result per sin-
Table 2. Conversion Register*
gle-ended channel and one result per diꢁꢁerential pair
within the requested range% plus one temperature result iꢁ
selected. Select scan mode 10 to scan a single input
channel numerous times% depending on NSCAN1 and
NSCAN0 in the averaging register (Table 6). Select scan
mode 11 to return only one result ꢁrom a single channel.
BIT
NAME
BIT
FUNCTION
—
7 (MSB) Set to 1 to select conversion register.
CHSEL3
CHSEL2
CHSEL1
CHSEL0
SCAN1
SCAN0
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.
Setup Register
Write a byte to the setup register to conꢁigure the clock%
reꢁerence% 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 sam-
pling% and the conversion start. Bits 3 and 2 (REFSEL1
and REFSEL0) control internal or external reꢁerence use.
Bits 1 and 0 (DIFFSEL1 and DIFFSEL0) address the
unipolar mode and bipolar mode registers and conꢁigure
the analog input channels ꢁor diꢁꢁerential operation.
Scan mode select.
Set to 1 to take a single temperature
TEMP 0 (LSB) measurement. The ꢁirst conversion result
oꢁ a scan contains temperature inꢁormation.
*See below for bit details.
Unipolar/Bipolar Registers
The ꢁinal 2 bits (LSBs) oꢁ the setup register control the
unipolar/bipolar mode address registers. Set bits 1 and
0 (DIFFSEL1 and DIFFSEL0) to 10 to write to the unipo-
lar mode register. Set bits 1 and 0 to 11 to write to the
bipolar mode register. In both cases% the setup byte
must be ꢁollowed immediately by 1 byte oꢁ data written
to the unipolar register or bipolar register. Hold CS low
and run 16 SCLK cycles beꢁore pulling CS high. Iꢁ the
last 2 bits oꢁ the setup register are 00 or 01% neither the
unipolar mode register nor the bipolar mode register is
written. Any subsequent byte is recognized as a new
input data byte. See Tables 4 and 5 to program the
unipolar and bipolar mode registers.
SELECTED
CHSEL3 CHSEL2 CHSEL1 CHSEL0
CHANNEL (N)
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
AIN9
Iꢁ a channel is conꢁigured as both unipolar and bipolar%
the unipolar setting takes precedence. In unipolar
AIN10
AIN11
AIN12
AIN13
AIN14
AIN15
mode% AIN+ can exceed AIN- by up to V
. The out-
REF
put ꢁormat in unipolar mode is binary. In bipolar mode%
either input can exceed the other by up to V
output ꢁormat in bipolar mode is two's complement.
/ 2. The
REF
Averaging Register
Write to the averaging register to conꢁigure the ADC to
average up to 32 samples ꢁor each requested result%
and to independently control the number oꢁ results
requested ꢁor single-channel scans.
SCAN MODE (CHANNEL N IS
SELECTED BY BITS CHSEL3–CHSEL0)
SCAN1 SCAN0
Table 2 details the ꢁour scan modes available in the con-
version register. All ꢁour 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.
0
0
0
1
Scans channels 0 through N.
Scans channels N through the highest
numbered channel.
Scans channel N repeatedly. The averaging
register sets the number oꢁ results.
1
1
0
1
No scan. Converts channel N once only.
______________________________________________________________________________________ 13
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Table 3. Setup Register*
BIT NAME
—
BIT
FUNCTION
7 (MSB) Set to zero to select setup register.
—
6
Set to 1 to select setup register.
CKSEL1
CKSEL0
REFSEL1
REFSEL0
DIFFSEL1
DIFFSEL0
5
Clock mode and CNVST conꢁiguration. Resets to 1 at power-up.
Clock mode and CNVST conꢁiguration.
4
3
Reꢁerence mode conꢁiguration.
2
1
Reꢁerence mode conꢁiguration.
Unipolar/bipolar mode register conꢁiguration ꢁor diꢁꢁerential mode.
Unipolar/bipolar mode register conꢁiguration ꢁor diꢁꢁerential mode.
0 (LSB)
*See below for bit details.
CKSEL1
CKSEL0
CONVERSION CLOCK
Internal
ACQUISITION/SAMPLING
Internally timed
CNVST CONFIGURATION
CNVST
0
0
1
1
0
1
0
1
Internal
Externally timed through CNVST
Internally timed
CNVST
Internal
AIN15/11/7
AIN15/11/7
External (4.8MHz max)
Externally timed through SCLK
REFSEL1 REFSEL0
VOLTAGE REFERENCE
Internal
AutoShutdown
REF- CONFIGURATION
AIN14/10/6
Reꢁerence oꢁꢁ aꢁter scan; need
wake-up delay.
0
0
1
1
0
1
0
1
External single ended
Internal
Reꢁerence oꢁꢁ; no wake-up delay.
AIN14/10/6
Reꢁerence always on; no wake-up
delay.
AIN14/10/6
External diꢁꢁerential
Reꢁerence oꢁꢁ; no wake-up delay.
REF-
DIFFSEL1 DIFFSEL0
FUNCTION
0
0
1
1
0
1
0
1
No data ꢁollows the setup byte. Unipolar mode and bipolar mode registers remain unchanged.
No data ꢁollows the setup byte. Unipolar mode and bipolar mode registers remain unchanged.
One byte oꢁ data ꢁollows the setup byte and is written to the unipolar mode register.
One byte oꢁ data ꢁollows the setup byte and is written to the bipolar mode register.
14 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Reset Register
Write to the reset register (as shown in Table 7) to clear
the FIFO or to reset all registers to their deꢁault states.
Set the RESET bit to 1 to reset the FIFO. Set the reset
bit to zero to return the MAX1226/MAX1228/MAX1230
to its deꢁault power-up state.
subtracted ꢁrom the ꢁirst at 68µA to calculate a digital
value that is proportional to absolute temperature. The
output data appearing at DOUT is the above digital
code minus an oꢁꢁset to adjust ꢁrom Kelvin to Celsius.
The reꢁerence voltage used ꢁor the temperature mea-
surements is derived ꢁrom the internal reꢁerence source
to ensure a resolution oꢁ 1/8 oꢁ a degree.
Power-Up Default State
The MAX1226/MAX1228/MAX1230 power up with all
blocks in shutdown% including the reꢁerence. All registers
power up in state 00000000% except ꢁor the setup regis-
ter% which powers up in clock mode 10 (CKSEL1 = 1).
Output Data Format
Figures 4–7 illustrate the conversion timing ꢁor the
MAX1226/MAX1228/MAX1230. The 12-bit conversion
result is output in MSB-ꢁirst ꢁormat with 4 leading zeros.
DIN data is latched into the serial interꢁace on the rising
edge oꢁ SCLK. Data on DOUT transitions on the ꢁalling
edge oꢁ SCLK. Conversions in clock modes 00 and 01
are initiated by CNVST. Conversions in clock modes 10
and 11 are initiated by writing an input data byte to the
conversion register. Data is binary ꢁor unipolar mode and
two’s complement ꢁor bipolar mode.
Temperature Measurements
The MAX1226/MAX1228/MAX1230 perꢁorm tempera-
ture measurements with an internal diode-connected
transistor. The diode bias current changes ꢁrom 68µA
to 4µA to produce a temperature-dependent bias volt-
age diꢁꢁerence. The second conversion result at 4µA is
Table 4. Unipolar Mode Register (Addressed Through Setup Register)
BIT NAME
UCH0/1
BIT
FUNCTION
7 (MSB) Set to 1 to conꢁigure AIN0 and AIN1 ꢁor unipolar diꢁꢁerential conversion.
UCH2/3
6
Set to 1 to conꢁigure AIN2 and AIN3 ꢁor unipolar diꢁꢁerential conversion.
UCH4/5
5
Set to 1 to conꢁigure AIN4 and AIN5 ꢁor unipolar diꢁꢁerential conversion.
UCH6/7
4
Set to 1 to conꢁigure AIN6 and AIN7 ꢁor unipolar diꢁꢁerential conversion.
UCH8/9
3
Set to 1 to conꢁigure AIN8 and AIN9 ꢁor unipolar diꢁꢁerential conversion (MAX1228/MAX1230 only).
Set to 1 to conꢁigure AIN10 and AIN11 ꢁor unipolar diꢁꢁerential conversion (MAX1228/MAX1230 only).
Set to 1 to conꢁigure AIN12 and AIN13 ꢁor unipolar diꢁꢁerential conversion (MAX1230 only).
Set to 1 to conꢁigure AIN14 and AIN15 ꢁor unipolar diꢁꢁerential conversion (MAX1230 only).
UCH10/11
UCH12/13
UCH14/15
2
1
0 (LSB)
Table 5. Bipolar Mode Register (Addressed Through Setup Register)
BIT NAME
BCH0/1
BIT
FUNCTION
7 (MSB) Set to 1 to conꢁigure AIN0 and AIN1 ꢁor bipolar diꢁꢁerential conversion.
BCH2/3
6
Set to 1 to conꢁigure AIN2 and AIN3 ꢁor bipolar diꢁꢁerential conversion.
BCH4/5
5
Set to 1 to conꢁigure AIN4 and AIN5 ꢁor bipolar diꢁꢁerential conversion.
BCH6/7
4
Set to 1 to conꢁigure AIN6 and AIN7 ꢁor bipolar diꢁꢁerential conversion.
BCH8/9
3
Set to 1 to conꢁigure AIN8 and AIN9 ꢁor bipolar diꢁꢁerential conversion (MAX1228/MAX1230 only).
Set to 1 to conꢁigure AIN10 and AIN11 ꢁor bipolar diꢁꢁerential conversion (MAX1228/MAX1230 only).
Set to 1 to conꢁigure AIN12 and AIN13 ꢁor bipolar diꢁꢁerential conversion (MAX1230 only).
Set to 1 to conꢁigure AIN14 and AIN15 ꢁor bipolar diꢁꢁerential conversion (MAX1230 only).
BCH10/11
BCH12/13
BCH14/15
2
1
0 (LSB)
______________________________________________________________________________________ 15
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Table 6. Averaging Register*
BIT NAME
—
BIT
FUNCTION
7 (MSB) Set to zero to select averaging register.
—
6
Set to zero to select averaging register.
Set to 1 to select averaging register.
—
5
AVGON
NAVG1
NAVG0
NSCAN1
NSCAN0
4
Set to 1 to turn averaging on. Set to zero to turn averaging oꢁꢁ.
Conꢁigures the number oꢁ conversions ꢁor single-channel scans.
Conꢁigures the number oꢁ conversions ꢁor single-channel scans.
Single-channel scan count. (Scan mode 10 only.)
3
2
1
0 (LSB)
Single-channel scan count. (Scan mode 10 only.)
*See below for bit details.
FUNCTION
Perꢁorms 1 conversion ꢁor each requested result.
AVGON
NAVG1
NAVG0
0
1
1
1
1
x
0
0
1
1
x
0
1
0
1
Perꢁorms 4 conversions and returns the average ꢁor each requested result.
Perꢁorms 8 conversions and returns the average ꢁor each requested result.
Perꢁorms 16 conversions and returns the average ꢁor each requested result.
Perꢁorms 32 conversions and returns the average ꢁor each requested result.
NSCAN1
NSCAN0
FUNCTION (APPLIES ONLY IF SCAN MODE 10 IS SELECTED)
0
0
1
1
0
1
0
1
Scans channel N and returns 4 results.
Scans channel N and returns 8 results.
Scans channel N and returns 12 results.
Scans channel N and returns 16 results.
Table 7. Reset Register
BIT NAME
BIT
FUNCTION
—
7 (MSB) Set to zero to select reset register.
—
6
Set to zero to select reset register.
Set to zero to select reset register.
Set to 1 to select reset register.
—
5
—
4
RESET
3
Set to zero to reset all registers. Set to 1 to clear the FIFO only.
Reserved. Don’t care.
x
x
x
2
1
Reserved. Don’t care.
0 (LSB)
Reserved. Don’t care.
16 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
erence needs to wake up% an additional 65µs is
required ꢁor the internal reꢁerence to power up. Iꢁ a tem-
perature measurement is being requested% reꢁerence
power-up and temperature measurement are internally
timed. In this case% hold CNVST low ꢁor at least 40ns.
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 perꢁormed automatically using the internal oscilla-
tor. Results are added to the internal FIFO to be read
out later. See Figure 4 ꢁor clock mode 00 timing.
Set CNVST high to begin a conversion. Aꢁter the con-
version 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 beꢁore pulling CS or
CNVST low.
Initiate a scan by setting CNVST low ꢁor at least 40ns
beꢁore pulling it high again. The MAX1226/MAX1228/
MAX1230 then wake up% scan all requested channels%
store the results in the FIFO% and shut down. Aꢁter the
scan is complete% EOC is pulled low and the results are
available in the FIFO. Wait until EOC goes low beꢁore
pulling CS low to communicate with the serial interꢁace.
EOC stays low until CS or CNVST is pulled low again. A
temperature measurement result% iꢁ requested% pre-
cedes all other FIFO results.
Iꢁ averaging is turned on% multiple CNVST pulses need
to be perꢁormed beꢁore a result is written to the FIFO.
Once the proper number oꢁ conversions has been per-
ꢁormed to generate an averaged FIFO result% as speci-
ꢁied by the averaging register% the scan logic
automatically switches the analog input multiplexer to
the next-requested channel. Iꢁ a temperature measure-
ment is programmed% it is perꢁormed aꢁter the ꢁirst rising
edge oꢁ CNVST ꢁollowing the input data byte written to
the conversion register. The result is available on DOUT
once EOC has been pulled low.
Do not initiate a second CNVST beꢁore EOC goes low;
otherwise the FIFO can become corrupted.
Externally Timed Acquisitions and
Internally Timed Acquisitions and
Internally Timed Conversions with CNVST
Conversions Using the Serial Interface
Performing Conversions in Clock Mode 01
In clock mode 01% conversions are requested one at a
time using CNVST and perꢁormed automatically using the
internal oscillator. See Figure 5 ꢁor clock mode 01 timing.
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 per-
ꢁormed automatically using the internal oscillator. This
is the deꢁault clock mode upon power-up. See Figure 6
ꢁor clock mode 10 timing.
Setting CNVST low begins an acquisition% wakes up the
ADC% and places it in track mode. Hold CNVST low ꢁor
at least 1.4µs to complete the acquisition. Iꢁ internal reꢁ-
CNVST
(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)
CS
SCLK
DOUT
EOC
MSB1
LSB1
MSB2
SET CNVST LOW FOR AT LEAST 40ns TO BEGIN A CONVERSION.
Figure 4. Clock Mode 00
______________________________________________________________________________________ 17
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
CNVST
(CONVERSION2)
(ACQUISITION1)
(ACQUISITION2)
CS
(CONVERSION1)
SCLK
DOUT
EOC
MSB1
LSB1
MSB2
REQUEST MULTIPLE CONVERSIONS BY SETTING CNVST LOW FOR EACH CONVERSION.
Figure 5. Clock Mode 01
(CONVERSION BYTE)
(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)
DIN
CS
SCLK
DOUT
EOC
MSB1
LSB1
MSB2
THE CONVERSION BYTE BEGINS THE ACQUISITION. CNVST IS NOT REQUIRED.
Figure 6. Clock Mode 10
Initiate a scan by writing a byte to the conversion regis-
ter. The MAX1226/MAX1228/MAX1230 then power up%
scan all requested channels% store the results in the
FIFO% and shut down. Aꢁter the scan is complete% EOC
is pulled low and the results are available in the FIFO. Iꢁ
a temperature measurement is requested% the tempera-
ture result precedes all other FIFO results. 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 ini-
tiated by writing to the conversion register and are per-
ꢁormed 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 con-
version. See Figure 7 ꢁor clock mode 11 timing.
18 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
(CONVERSION BYTE)
DIN
(ACQUISITION1)
(CONVERSION1)
(ACQUISITION2)
CS
SCLK
DOUT
EOC
MSB1
LSB1
MSB2
EXTERNALLY TIMED ACQUISITION, SAMPLING AND CONVERSION WITHOUT CNVST.
Figure 7. Clock Mode 11
Initiate a conversion by writing a byte to the conversion
register ꢁollowed by 16 SCLK cycles. Iꢁ CS is pulsed
high between the eighth and ninth cycles% the pulse
width must be less than 100µs. To continuously con-
vert at 16 cycles per conversion% alternate 1 byte oꢁ
zeros between each conversion byte.
Transfer Function
Figure 8 shows the unipolar transꢁer ꢁunction ꢁor single-
ended or diꢁꢁerential inputs. Figure 9 shows the bipolar
transꢁer ꢁunction ꢁor diꢁꢁerential inputs. Code transitions
occur halꢁway between successive-integer LSB values.
Output coding is binary% with 1 LSB = V
/ 4096V ꢁor
REF
unipolar and bipolar operation% and 1 LSB = 0.125°C
Iꢁ reꢁerence mode 00 is requested% or iꢁ an external reꢁ-
erence is selected but a temperature measurement is
being requested% wait 65µs with CS high aꢁter writing
the conversion byte to extend the acquisition and allow
the internal reꢁerence to power up. To perꢁorm a tem-
perature measurement% write 24 bytes (192 cycles) oꢁ
zeros aꢁter the conversion byte. The temperature result
appears on DOUT during the last 2 bytes oꢁ the
192 cycles.
ꢁor temperature measurements.
Layout, Grounding, and Bypassing
For best perꢁormance% use PC boards. Do not use wire-
wrap boards. Board layout should ensure that digital
and analog signal lines are separated ꢁrom each other.
Do not run analog and digital (especially clock) signals
parallel to one another or run digital lines underneath the
MAX1226/MAX1228/MAX1230 package. High-ꢁrequen-
cy noise in the V
power supply can aꢁꢁect perꢁor-
DD
Partial Reads and Partial Writes
Iꢁ the ꢁirst byte oꢁ an entry in the FIFO is partially read
(CS is pulled high aꢁter ꢁewer than eight SCLK cycles)%
the second byte oꢁ data that is read out contains the
next 8 bits (not b7–b0). The remaining bits are lost ꢁor
that entry. Iꢁ the ꢁirst byte oꢁ an entry in the FIFO is read
out ꢁully% but the second byte is read out partially% the
rest oꢁ the entry is lost. The remaining data in the FIFO
is uncorrupted and can be read out normally aꢁter tak-
ing CS low again% as long as the 4 leading bits (nor-
mally 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 oꢁ the register that is not written
contains previously written values. Iꢁ CS is pulled low
beꢁore EOC goes low% a conversion cannot be com-
pleted and the FIFO is corrupted.
mance. Bypass the V
supply with a 0.1µF capacitor
pin. Minimize capacitor lead
DD
to GND% close to the V
DD
lengths ꢁor best supply-noise rejection. Iꢁ the power sup-
ply is very noisy% connect a 10Ω resistor in series with
the supply to improve power-supply ꢁiltering. For the
QFN package% connect its exposed pad to ground.
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation oꢁ the values
on an actual transꢁer ꢁunction ꢁrom a straight line. This
straight line can be either a best-straight-line ꢁit or a
line drawn between the end points oꢁ the transꢁer ꢁunc-
tion% once oꢁꢁset and gain errors have been nulliꢁied.
INL ꢁor the MAX1226/MAX1228/MAX1230 is measured
using the end-point method.
______________________________________________________________________________________ 19
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
OUTPUT CODE
OUTPUT CODE
V
FULL-SCALE
TRANSITION
REF
2
FS
+ V
COM
=
011 . . . 111
011 . . . 110
11 . . . 111
11 . . . 110
ZS = COM
-V
2
REF
+ V
REF
11 . . . 101
-FS =
COM
000 . . . 010
000 . . . 001
000 . . . 000
V
4096
1 LSB =
FS = V + V
REF
COM
111 . . . 111
111 . . . 110
111 . . . 101
ZS = V
COM
V
REF
1 LSB =
4096
00 . . . 011
00 . . . 010
100 . . . 001
100 . . . 000
00 . . . 001
00 . . . 000
0
1
2
3
FS
COM*
- FS
+FS - 1 LSB
(COM)
FS - 3/2 LSB
INPUT VOLTAGE (LSB)
INPUT VOLTAGE (LSB)
*V
≥ V / 2
REF
COM
Figure 8. Unipolar Transfer Function, Full Scale (FS) = V
Figure 9. Bipolar Transfer Function, Full Scale ( FS) =
V
REF
/ 2
REF
In reality% there are other noise sources besides quanti-
zation noise% including thermal noise% reꢁerence noise%
clock jitter% etc. Thereꢁore% SNR is calculated by taking
the ratio oꢁ the RMS signal to the RMS noise% which
includes all spectral components minus the ꢁundamen-
tal% the ꢁirst ꢁive harmonics% and the DC oꢁꢁset.
Differential Nonlinearity
Diꢁꢁerential nonlinearity (DNL) is the diꢁꢁerence between
an actual step width and the ideal value oꢁ 1 LSB. A
DNL error speciꢁication oꢁ less than 1 LSB guarantees
no missing codes and a monotonic transꢁer ꢁunction.
Aperture Jitter
Signal-to-Noise Plus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio oꢁ the
ꢁundamental input ꢁrequency’s RMS amplitude to the
RMS equivalent oꢁ all other ADC output signals:
Aperture jitter (t ) is the sample-to-sample variation in
AJ
the time between the samples.
Aperture Delay
Aperture delay (t ) is the time between the rising
AD
edge oꢁ the sampling clock and the instant when an
actual sample is taken.
SINAD (dB) = 20 x log (Signal
/ Noise
)
RMS
RMS
Effective Number of Bits
Eꢁꢁective number oꢁ bits (ENOB) indicates the global
accuracy oꢁ an ADC at a speciꢁic input ꢁrequency and
sampling rate. An ideal ADC error consists oꢁ quantiza-
tion noise only. With an input range equal to the ꢁull-
scale range oꢁ the ADC% calculate the eꢁꢁective number
oꢁ bits as ꢁollows:
Signal-to-Noise Ratio
For a waveꢁorm perꢁectly reconstructed ꢁrom digital
samples% signal-to-noise ratio (SNR) is the ratio oꢁ the
ꢁull-scale analog input (RMS value) to the RMS quanti-
zation error (residual error). The ideal% theoretical mini-
mum analog-to-digital noise is caused by quantization
error only and results directly ꢁrom the ADC’s resolution
(N bits):
ENOB = (SINAD - 1.76) / 6.02
SNR = (6.02 x N + 1.76)dB
20 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Total Harmonic Distortion
Ordering Information (continued)
Total harmonic distortion (THD) is the ratio oꢁ the RMS
sum oꢁ the ꢁirst ꢁive harmonics oꢁ the input signal to the
ꢁundamental itselꢁ. This is expressed as:
PART
TEMP RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
MAX1226BCEE-T
MAX1226BEEE-T
MAX1228ACEP-T*
MAX1228AEEP-T*
MAX1228BCEP-T
MAX1228BEEP-T
MAX1230ACEG-T*
MAX1230AEEG-T*
MAX1230BCEG-T
MAX1230BEEG-T
MAX1230BCGI-T*
MAX1230BEGI-T*
16 QSOP
2
2
2
2
20 QSOP
THD = 20 x log
V
+ V3 + V4 + V5 / V
(
)
2
1
20 QSOP
20 QSOP
where V1 is the ꢁundamental amplitude% and V2–V5 are
the amplitudes oꢁ the ꢁirst ꢁive harmonics.
20 QSOP
24 QSOP
Spurious-Free Dynamic Range
Spurious-ꢁree dynamic range (SFDR) is the ratio oꢁ the
RMS amplitude oꢁ the ꢁundamental (maximum signal
component) to the RMS value oꢁ the next-largest distor-
tion component.
24 QSOP
24 QSOP
24 QSOP
28 QFN-EP**
28 QFN-EP**
*Future product—contact factory for availability.
**EP = Exposed paddle (connect to GND).
Chip Information
TRANSISTOR COUNT: 30%889
PROCESS: BiCMOS
Pin Configurations (continued)
TOP VIEW
AIN0
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
1
2
3
4
5
6
7
8
9
24 EOC
23 DOUT
22 DIN
21 CS
N.C.
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
1
2
3
4
5
6
7
21 CS
20 SCLK
19 N.C.
MAX1230
20 SCLK
MAX1230
18
V
DD
19
V
DD
17 N.C.
16 GND
15 REF+
18 GND
17 REF+
16 CNVST/AIN15
15 REF-/AIN14
14 AIN13
AIN9 10
AIN10 11
AIN11 12
13 AIN12
QSOP
QFN
______________________________________________________________________________________ 21
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Package Information
(The package drawing(s) in this data sheet may not reꢁlect the most current speciꢁications. For the latest package outline inꢁormation
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
1
21-0055
E
1
22 ______________________________________________________________________________________
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Package Information (continued)
(The package drawing(s) in this data sheet may not reꢁlect the most current speciꢁications. For the latest package outline inꢁormation
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, 16,20,28,32L QFN,
5x5x0.90 MM
1
21-0091
I
2
______________________________________________________________________________________ 23
12-Bit 300ksps ADCs with FIFO,
Temp Sensor, Internal Reference
Package Information (continued)
(The package drawing(s) in this data sheet may not reꢁlect the most current speciꢁications. For the latest package outline inꢁormation
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, 16,20,28,32L QFN,
5x5x0.90 MM
2
21-0091
I
2
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.
24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2003 Maxim Integrated Products
Printed USA
is a registered trademark oꢁ Maxim Integrated Products.
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