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General Description
The MAX1246/MAX1247 12-bit data-acquisition systems
combine a 4-channel multiplexer, high-bandwidth
track/hold, and serial interface with high conversion
speed and low power consumption. The MAX1246 oper-
ates from a single +2.7V to +3.6V supply; the MAX1247
operates from a single +2.7V to +5.25V supply. Both
devices' analog inputs are software configurable for
unipolar/bipolar and single-ended/differential operation.
The 4-wire serial interface connects directly to SPITM/
QSPITM and MICROWIRETM devices without external
logic. A serial strobe output allows direct connection to
TMS320-family digital signal processors. The MAX1246/
MAX1247 use either the internal clock or an external seri-
al-interface clock to perform successive-approximation
analog-to-digital conversions.
The MAX1246 has an internal 2.5V reference, while the
MAX1247 requires an external reference. Both parts have
a reference-buffer amplifier with a 1.5% voltage-
adjustment range. These devices provide a hard-wired
SHDN pin and a software-selectable power-down, and
can be programmed to automatically shut down at the
end of a conversion. Accessing the serial interface auto-
matically powers up the MAX1246/MAX1247, and the
quick turn-on time allows them to be shut down between
all conversions. This technique can cut supply current to
under 60A at reduced sampling rates. The MAX1246/
MAX1247 are available in a 16-pin DIP and a small QSOP
that occupies the same board area as an 8-pin SO.
For 8-channel versions of these devices, see the
MAX146/MAX147 data sheet.
________________________Applications
Portable Data Logging
Medical Instruments
Pen Digitizers
Data Acquisition
Battery-Powered Instruments
Process Control
Features
o 4-Channel Single-Ended or 2-Channel
Differential Inputs
o Single-Supply Operation:
+2.7V to +3.6V (MAX1246)
+2.7V to +5.25V (MAX1247)
o Internal 2.5V Reference (MAX1246)
o Low Power: 1.2mA (133ksps, 3V supply)
54A (1ksps, 3V supply)
1A (power-down mode)
o SPI/QSPI/MICROWIRE/TMS320-Compatible
4-Wire Serial Interface
o Software-Configurable Unipolar or Bipolar Inputs
o 16-Pin QSOP Package (same area as 8-pin SO)
MAX1246/MAX1247
+2.7V, Low-Power, 4-Channel,
Serial 12-Bit ADCs in QSOP-16
________________________________________________________________ Maxim Integrated Products
1
V
DD
I/O
SCK (SK)
MOSI (SO)
MISO (SI)
V
SS
SHDN
SSTRB
DOUT
DIN
SCLK
CS
COM
AGND
DGND
V
DD
CH3
4.7
F
0.1
F
CH0
0V TO
+2.5V
ANALOG
INPUTS
MAX1246
CPU
+3V
VREF
0.047
F
REFADJ
__________Typical Operating Circuit
19-1071; Rev 2; 10/01
PART
MAX1246ACPE
MAX1246BCPE
MAX1246ACEE
0C to +70C
0C to +70C
0C to +70C
TEMP RANGE
PIN-PACKAGE
16 Plastic DIP
16 Plastic DIP
16 QSOP
EVALUATION KIT
AVAILABLE
Ordering Information
Ordering Information continued at end of data sheet.
MAX1246BCEE
0C to +70C
16 QSOP
INL
(LSB)
1/2
1
1/2
1
SPI and QSPI are registered trademarks of Motorola, Inc.
MICROWIRE is a registered trademark of National
Semiconductor Corp.
Pin Configuration appears at end of data sheet.
MAX1246/MAX1247
+2.7V, Low-Power, 4-Channel,
Serial 12-Bit ADCs in QSOP-16
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
DD
= +2.7V to +3.6V (MAX1246); V
DD
= +2.7V to +5.25V (MAX1247); COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle);
15 clocks/conversion cycle (133ksps); MAX1246--4.7F capacitor at VREF pin; MAX1247--external reference, VREF = 2.5V applied
to VREF pin; T
A
= T
MIN
to T
MAX
; unless otherwise noted.)
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.
V
DD
to AGND, DGND................................................. -0.3V to 6V
AGND to DGND ...................................................... -0.3V to 0.3V
CH0CH3, COM to AGND, DGND ............ -0.3V to (V
DD
+ 0.3V)
VREF to AGND........................................... -0.3V to (V
DD
+ 0.3V)
Digital Inputs to DGND .............................................. -0.3V to 6V
Digital Outputs to DGND ........................... -0.3V to (V
DD
+ 0.3V)
Digital Output Sink Current .................................................25mA
Continuous Power Dissipation (T
A
= +70C)
Plastic DIP (derate 10.53mW/C above +70C) ......... 842mW
QSOP (derate 8.36mW/C above +70C) ................... 667mW
CERDIP (derate 10.00mW/C above +70C) .............. 800mW
Operating Temperature Ranges
MAX1246_C_E/MAX1247_C_E .......................... 0C to +70C
MAX1246_E_E/MAX1247_E_E........................ -40C to +85C
MAX1246_MJE/MAX1247_MJE .................... -55C to +125C
Storage Temperature Range ............................ -60C to +150C
Lead Temperature (soldering, 10s) ................................ +300C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC ACCURACY (Note 1)
Resolution
12
Bits
MAX124_A
0.5
MAX124_B
1.0
Relative Accuracy (Note 2)
INL
MAX1247C
2.0
LSB
No Missing Codes
NMC
12
Bits
MAX124_A/MAX124_B
1
Differential Nonlinearity
DNL
MAX124_C
0.8
LSB
MAX124_A
0.5
3
Offset Error
MAX124_B
0.5
4
LSB
Gain Error (Note 3)
0.5
4
LSB
Gain Temperature Coefficient
0.25
ppm/C
Channel-to-Channel Offset
Matching
0.25
LSB
DYNAMIC SPECIFICATIONS (10kHz sine-wave input, 0V to 2.500Vp-p, 133ksps, 2.0MHz external clock, bipolar input mode)
MAX124_A/MAX124_B
70
73
Signal-to-Noise + Distortion
Ratio
SINAD
MAX1247C
73
dB
MAX124_A/MAX124_B
-88
-80
Total Harmonic Distortion
THD
Up to the 5th
harmonic
MAX1247C
-88
dB
MAX124_A/MAX124_B
80
90
Spurious-Free Dynamic Range
SFDR
MAX1247C
90
dB
Channel-to-Channel Crosstalk
65kHz, 2.500V
P-P
(Note 4)
-85
dB
Small-Signal Bandwidth
-3dB rolloff
2.25
MHz
Full-Power Bandwidth
1.0
MHz
MAX1246/MAX1247
+2.7V, Low-Power, 4-Channel,
Serial 12-Bit ADCs in QSOP-16
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +2.7V to +3.6V (MAX1246); V
DD
= +2.7V to +5.25V (MAX1247); COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle);
15 clocks/conversion cycle (133ksps); MAX1246--4.7F capacitor at VREF pin; MAX1247--external reference, VREF = 2.5V applied
to VREF pin; T
A
= T
MIN
to T
MAX
; unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CONVERSION RATE
Internal clock, SHDN = FLOAT
5.5
7.5
Internal clock, SHDN = V
DD
35
65
Conversion Time (Note 5)
t
CONV
External clock = 2MHz, 12 clocks/
conversion
6
s
Track/Hold Acquisition Time
t
ACQ
1.5
s
Aperture Delay
30
ns
Aperture Jitter
<50
ps
SHDN = FLOAT
1.8
Internal Clock Frequency
SHDN = V
DD
0.225
MHz
0.1
2.0
External Clock Frequency
Data transfer only
0
2.0
MHz
ANALOG/COM INPUTS
Unipolar, COM = 0V
0 to VREF
Input Voltage Range, Single-
Ended and Differential (Note 6)
Bi p ol ar , C OM = V RE F / 2
VREF / 2
V
Multiplexer Leakage Current
On/off leakage current, V
CH
_ = 0V or V
DD
0.01
1
A
Input Capacitance
16
pF
INTERNAL REFERENCE (MAX1246 only, reference buffer enabled)
VREF Output Voltage
T
A
= +25C
2.480
2.500
2.520
V
VREF Short-Circuit Current
30
mA
MAX1246_C
30
50
MAX1246_E
30
60
VREF Temperature Coefficient
MAX1246_M
30
80
ppm/C
Load Regulation (Note 8)
0mA to 0.2mA output load
0.35
mV
Internal compensation mode
0
Capacitive Bypass at VREF
External compensation mode
4.7
F
Capacitive Bypass at REFADJ
0.047
F
REFADJ Adjustment Range
V
BST
= V
LX
= V
IN
= 28V, V
FB
= 1.5V
1.5
%
EXTERNAL REFERENCE AT VREF (Buffer disabled)
VREF Input Voltage Range
(Note 9)
1.0
VDD +
50mV
V
VREF Input Current
VREF = 2.5V
100
150
V
VREF Input Resistance
18
25
k
Shutdown VREF Input Current
0.01
100
A
REFADJ Buffer Disable
Threshold
VDD -
0.5
V
MAX1246/MAX1247
+2.7V, Low-Power, 4-Channel,
Serial 12-Bit ADCs in QSOP-16
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +2.7V to +3.6V (MAX1246); V
DD
= +2.7V to +5.25V (MAX1247); COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle);
15 clocks/conversion cycle (133ksps); MAX1246--4.7F capacitor at VREF pin; MAX1247--external reference, VREF = 2.5V applied
to VREF pin; T
A
= T
MIN
to T
MAX
; unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
EXTERNAL REFERENCE AT REFADJ
Internal compensation mode
0
Capacitive Bypass at VREF
External compensation mode
4.7
F
MAX1246
2.06
Reference Buffer Gain
MAX1247
2.00
V/V
MAX1246
50
REFADJ Input Current
MAX1247
10
A
MAX1246/MAX1247
+2.7V, Low-Power, 4-Channel,
Serial 12-Bit ADCs in QSOP-16
_______________________________________________________________________________________
5
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +2.7V to +3.6V (MAX1246); V
DD
= +2.7V to +5.25V (MAX1247); COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle);
15 clocks/conversion cycle (133ksps); MAX1246--4.7F capacitor at VREF pin; MAX1247--external reference, VREF = 2.5V applied
to VREF pin; T
A
= T
MIN
to T
MAX
; unless otherwise noted.)
V
3.0
V
IH
V
DD
= 3.6V
DIN, SCLK, CS Input High Voltage
V
DD
> 3.6V, MAX1247 only
mV
0.3
PSR
Supply Rejection (Note 10)
V
DD
= 2.7V to V
DD(MAX)
, full-scale input,
external reference = 2.500V
pF
15
C
IN
DIN, SCLK, CS Input Capacitance
A
0.01
1
I
IN
DIN, SCLK, CS Input Leakage
V
0.2
V
HYST
DIN, SCLK, CS Input Hysteresis
V
0.8
V
IL
DIN, SCLK, CS Input Low Voltage
2.0
A
4.0
I
S
SHDN Input Current
V
0.4
V
SL
SHDN Input Low Voltage
V
V
DD
- 0.4
V
SH
SHDN Input High Voltage
SHDN = 0V or V
DD
nA
100
SHDN Maximum Allowed
Leakage, Mid Input
V
V
DD
/ 2
V
FLT
SHDN Voltage, Floating
SHDN = FLOAT
SHDN = FLOAT
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
(Note 7)
V
IN
= 0V or V
DD
V
DD
3.6V
I
DD
CONDITIONS
Positive Supply Current, MAX1246
A
1.2
2.0
A
0.01
10
I
L
Three-State Leakage Current
V
V
DD
- 0.5
V
OH
Output Voltage High
V
0.8
V
OL
Output Voltage Low
0.4
2.70
3.60
pF
15
C
OUT
Three-State Output Capacitance
MAX1246
CS = V
DD
(Note 7)
CS = V
DD
I
SOURCE
= 0.5mA
I
SINK
= 16mA
I
SINK
= 5mA
V
2.70
5.25
V
DD
Positive Supply Voltage
MAX1247
0.9
1.5
Operating mode,
full-scale input
30
70
V
DD
= 5.25V
V
DD
= 3.6V
3.5
15
V
DD
= 5.25V
V
DD
= 3.6V
1.2
10
Full power-down
mA
1.8
2.5
30
70
1.2
10
Operating mode, full-scale input
Fast power-down
Full power-down
mA
V
1.1
V
DD
- 1.1
V
SM
SHDN Input Mid Voltage
Fast power-down
I
DD
A
Positive Supply Current, MAX1247
DIGITAL INPUTS (DIN, SCLK, CS, SHDN)
DIGITAL OUTPUTS (DOUT, SSTRB)
POWER REQUIREMENTS
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