19-0464; Rev 2; 5/98
KIT
ATION
EVALU
BLE
AVAILA
+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
General Description
____________________________Features
o
8-Channel Single-Ended or 4-Channel
Differential Inputs
o
Single-Supply Operation: +2.7V to +5.25V
o
Internal 2.5V Reference (MAX149)
o
Low Power: 1.2mA (133ksps, 3V supply)
54µA (1ksps, 3V supply)
1µA (power-down mode)
o
SPI/QSPI/MICROWIRE/TMS320-Compatible
4-Wire Serial Interface
o
Software-Configurable Unipolar or Bipolar Inputs
o
20-Pin DIP/SSOP Packages
MAX148/MAX149
The MAX148/MAX149 10-bit data-acquisition systems
combine an 8-channel multiplexer, high-bandwidth
track/hold, and serial interface with high conversion
speed and low power consumption. They operate from a
single +2.7V to +5.25V supply, and sample to 133ksps.
Both devices’ analog inputs are software configurable for
unipolar/bipolar and single-ended/differential operation.
The 4-wire serial interface connects directly to SPI™/
QSPI™ and MICROWIRE™ devices without external
logic. A serial-strobe output allows direct connection to
TMS320-family digital signal processors. The MAX148/
MAX149 use either the internal clock or an external serial-
interface clock to perform successive-approximation
analog-to-digital conversions.
The MAX149 has an internal 2.5V reference, while the
MAX148 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 pro-
grammed to automatically shut down at the end of a con-
version. Accessing the serial interface automatically
powers up the MAX148/MAX149, and the quick turn-on
time allows them to be shut down between all conver-
sions. This technique can cut supply current to under
60µA at reduced sampling rates.
The MAX148/MAX149 are available in a 20-pin DIP and a
20-pin SSOP.
For 4-channel versions of these devices, see the
MAX1248/MAX1249 data sheet.
Ordering Information
PART
†
MAX148ACPP
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
20 Plastic DIP
INL
(LSB)
±1/2
±1
MAX148BCPP
0°C to +70°C
20 Plastic DIP
±1/2
MAX148ACAP
0°C to +70°C
20 SSOP
MAX148BCAP
0°C to +70°C
20 SSOP
±1
Ordering Information continued at end of data sheet.
†
Contact factory for availability of alternate surface-mount
packages.
__________Typical Operating Circuit
+3V
CH0
0V TO
+2.5V
ANALOG
INPUTS
V
DD
DGND
V
DD
0.1µF
________________________Applications
Portable Data Logging
Medical Instruments
Pen Digitizers
Data Acquisition
Battery-Powered Instruments
Process Control
MAX149
AGND
CH7
VREF
COM
CS
SCLK
DIN
REFADJ
DOUT
SSTRB
SHDN
V
SS
I/O
SCK (SK)
MOSI (SO)
MISO (SI)
CPU
4.7µF
0.01µF
Pin Configuration appears at end of data sheet.
SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
MAX148/MAX149
ABSOLUTE MAXIMUM RATINGS
V
DD
to AGND, DGND................................................. -0.3V to 6V
AGND to DGND ...................................................... -0.3V to 0.3V
CH0–CH7, COM to AGND, DGND ............ -0.3V to (V
DD
+ 0.3V)
VREF, REFADJ 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
= +70°C)
Plastic DIP (derate 11.11mW/°C above +70°C) ......... 889mW
SSOP (derate 8.00mW/°C above +70°C) ................... 640mW
CERDIP (derate 11.11mW/°C above +70°C) .............. 889mW
Operating Temperature Ranges
MAX148_C_P/MAX149_C_P .............................. 0°C to +70°C
MAX148_E_P/MAX149_E_P............................ -40°C to +85°C
MAX148_MJP/MAX149_MJP ........................ -55°C to +125°C
Storage Temperature Range ............................ -60°C to +150°C
Lead Temperature (soldering, 10sec) ............................ +300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
V
DD
= +2.7V to +5.25V; COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle); 15 clocks/conversion cycle (133ksps);
MAX149—4.7µF capacitor at VREF pin; MAX148—external reference, VREF = 2.500 V applied to VREF pin; T
A
= T
MIN
to T
MAX
; unless
otherwise noted.)
PARAMETER
DC ACCURACY
(Note 1)
Resolution
Relative Accuracy (Note 2)
Differential Nonlinearity
Offset Error
Gain Error (Note 3)
Gain Temperature Coefficient
Channel-to-Channel Offset
Matching
Signal-to-Noise + Distortion Ratio
Total Harmonic Distortion
Spurious-Free Dynamic Range
Channel-to-Channel Crosstalk
Small-Signal Bandwidth
Full-Power Bandwidth
CONVERSION RATE
Internal clock,
SHDN
= FLOAT
Conversion Time (Note 5)
Track/Hold Acquisition Time
Aperture Delay
Aperture Jitter
t
CONV
t
ACQ
30
<50
Internal clock,
SHDN
= V
DD
External clock = 2MHz, 12 clocks/conversion
5.5
35
6
1.5
µs
ns
ps
7.5
65
µs
SINAD
THD
SFDR
65kHz, 2.500V
p-p
(Note 4)
-3dB rolloff
Up to the 5th harmonic
INL
DNL
MAX14_A
MAX14_B
No missing codes over temperature
MAX14_A
MAX14_B
MAX14_A
MAX14_B
±0.15
±0.15
10
±0.5
±1.0
±1
±1
±2
±1
±2
Bits
LSB
LSB
LSB
LSB
ppm/°C
LSB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
±0.25
±0.05
DYNAMIC SPECIFICATIONS
(10kHz sine-wave input, 0V to 2.500Vp-p, 133ksps, 2.0MHz external clock, bipolar input mode)
66
-70
70
-75
2.25
1.0
dB
dB
dB
dB
MHz
MHz
2
_______________________________________________________________________________________
+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
ELECTRICAL CHARACTERISTICS (continued)
V
DD
= +2.7V to +5.25V; COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle); 15 clocks/conversion cycle (133ksps);
MAX149—4.7µF capacitor at VREF pin; MAX148—external reference, VREF = 2.500 V applied to VREF pin; T
A
= T
MIN
to T
MAX
; unless
otherwise noted.)
PARAMETER
CONVERSION RATE (continued)
Internal Clock Frequency
External Clock Frequency
ANALOG/COM INPUTS
Input Voltage Range, Single-
Ended and Differential (Note 6)
Multiplexer Leakage Current
Input Capacitance
INTERNAL REFERENCE
(MAX149 only, reference buffer enabled)
VREF Output Voltage
VREF Short-Circuit Current
VREF Temperature Coefficient
Load Regulation (Note 8)
Capacitive Bypass at VREF
Capacitive Bypass at REFADJ
REFADJ Adjustment Range
EXTERNAL REFERENCE AT VREF
(Buffer disabled)
VREF Input Voltage Range
(Note 9)
VREF Input Current
VREF Input Resistance
Shutdown VREF Input Current
REFADJ Buffer-Disable Threshold
EXTERNAL REFERENCE AT REFADJ
Capacitive Bypass at VREF
Reference Buffer Gain
REFADJ Input Current
Internal compensation mode
External compensation mode
MAX149
MAX148
MAX149
MAX148
0
4.7
2.06
2.00
±50
±10
µF
V/V
µA
V
DD
-
0.5
VREF = 2.500V
18
1.0
100
25
0.01
10
V
DD
+
50mV
150
V
µA
kΩ
µA
V
MAX149
0mA to 0.2mA output load
Internal compensation mode
External compensation mode
0
4.7
0.01
±1.5
±30
0.35
T
A
= +25°C (Note 7)
2.470
2.500
2.530
30
V
mA
ppm/°C
mV
µF
µF
%
Unipolar, COM = 0V
Bipolar, COM = VREF / 2
On/off leakage current, V
CH_
= 0V or V
DD
±0.01
16
0 to VREF
±VREF / 2
±1
V
µA
pF
SHDN
= FLOAT
SHDN
= V
DD
0.1
Data transfer only
0
1.8
0.225
2.0
2.0
MHz
MHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX148/MAX149
_______________________________________________________________________________________
3
+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
MAX148/MAX149
ELECTRICAL CHARACTERISTICS (continued)
V
DD
= +2.7V to +5.25V; COM = 0V; f
SCLK
= 2.0MHz; external clock (50% duty cycle); 15 clocks/conversion cycle (133ksps);
MAX149—4.7µF capacitor at VREF pin; MAX148—external reference, VREF = 2.500 V applied to VREF pin; T
A
= T
MIN
to T
MAX
; unless
otherwise noted.)
PARAMETER
SYMBOL
V
DD
≤
3.6V
V
DD
> 3.6V
CONDITIONS
MIN
2.0
3.0
0.8
0.2
V
IN
= 0V or V
DD
(Note 10)
V
DD
- 0.4
1.1
SHDN
= 0V or V
DD
SHDN
= FLOAT
SHDN
= FLOAT
V
DD
/ 2
±100
V
DD
- 1.1
0.4
±4.0
±0.01
±1
15
TYP
MAX
UNITS
DIGITAL INPUTS
(DIN, SCLK,
CS, SHDN)
DIN, SCLK,
CS
Input High Voltage
DIN, SCLK,
CS
Input Low Voltage
DIN, SCLK,
CS
Input Hysteresis
DIN, SCLK,
CS
Input Leakage
DIN, SCLK,
CS
Input Capacitance
SHDN
Input High Voltage
SHDN
Input Mid Voltage
SHDN
Input Low Voltage
SHDN
Input Current
SHDN
Voltage, Floating
SHDN
Maximum Allowed
Leakage, Mid Input
DIGITAL OUTPUTS
(DOUT, SSTRB)
Output Voltage Low
Output Voltage High
Three-State Leakage Current
Three-State Output Capacitance
POWER REQUIREMENTS
Positive Supply Voltage
V
DD
Operating mode,
full-scale input (Note 11)
Positive Supply Current
I
DD
I
DD
I
DD
Supply Rejection (Note 12)
PSR
Full power-down
Fast power-down (MAX149)
Full-scale input, external reference = 2.500V,
V
DD
= 2.7V to 5.25V
V
DD
= 5.25V
V
DD
= 3.6V
V
DD
= 5.25V
V
DD
= 3.6V
2.70
1.6
1.2
3.5
1.2
30
±0.3
5.25
3.0
2.0
15
10
70
mV
µA
V
mA
V
OL
V
OH
I
L
C
OUT
I
SINK
= 5mA
I
SINK
= 16mA
I
SOURCE
= 0.5mA
CS
= V
DD
CS
= V
DD
(Note 10)
V
DD
- 0.5
±0.01
±10
15
0.4
0.8
V
V
µA
pF
V
IH
V
IL
V
HYST
I
IN
C
IN
V
SH
V
SM
V
SL
I
S
V
FLT
V
V
V
µA
pF
V
V
V
µA
V
nA
4
_______________________________________________________________________________________
+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
TIMING CHARACTERISTICS
(V
DD
= +2.7V to +5.25V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Acquisition Time
DIN to SCLK Setup
DIN to SCLK Hold
SCLK Fall to Output Data Valid
CS
Fall to Output Enable
CS
Rise to Output Disable
CS
to SCLK Rise Setup
CS
to SCLK Rise Hold
SCLK Pulse Width High
SCLK Pulse Width Low
SCLK Fall to SSTRB
CS
Fall to SSTRB Output Enable
CS
Rise to SSTRB Output Disable
SSTRB Rise to SCLK Rise
SYMBOL
t
ACQ
t
DS
t
DH
t
DO
t
DV
t
TR
t
CSS
t
CSH
t
CH
t
CL
t
SSTRB
t
SDV
t
STR
t
SCK
Figure 1
External clock mode only, Figure 1
External clock mode only, Figure 2
Internal clock mode only (Note 7)
0
Figure 1
Figure 1
Figure 2
100
0
200
200
240
240
240
MAX14_ _C/E
MAX14_
Figure 1
_M
CONDITIONS
MIN
1.5
100
0
20
20
200
240
240
240
TYP
MAX
UNITS
µs
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
MAX148/MAX149
Note 1:
Tested at V
DD
= 2.7V; COM = 0V; unipolar single-ended input mode.
Note 2:
Relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has
been calibrated.
Note 3:
MAX149—internal reference, offset nulled; MAX148—external reference (VREF = +2.500V), offset nulled.
Note 4:
Ground “on” channel; sine wave applied to all “off” channels.
Note 5:
Conversion time defined as the number of clock cycles multiplied by the clock period; clock has 50% duty cycle.
Note 6:
The common-mode range for the analog inputs is from AGND to V
DD
.
Note 7:
Sample tested to 0.1% AQL.
Note 8:
External load should not change during conversion for specified accuracy.
Note 9:
ADC performance is limited by the converter’s noise floor, typically 300µVp-p.
Note 10:
Guaranteed by design. Not subject to production testing.
Note 11:
The MAX148 typically draws 400µA less than the values shown.
Note 12:
Measured as
|
V
FS
(2.7V) - V
FS
(5.25V)
|
.
__________________________________________Typical Operating Characteristics
(V
DD
= 3.0V, VREF = 2.500V, f
SCLK
= 2.0MHz, C
LOAD
= 20pF, T
A
= +25°C, unless otherwise noted.)
INTEGRAL NONLINEARITY
vs. CODE
MAX148/9-01
INTEGRAL NONLINEARITY
vs. SUPPLY VOLTAGE
MAX148/9-02
INTEGRAL NONLINEARITY
vs. TEMPERATURE
V
DD
= 2.7V
0.100
MAX148/9-03
0.125
0.125
0.10
0.100
0.05
INL (LSB)
INL (LSB)
0.075
MAX149
INL (LSB)
0.075
MAX149
0
0.050
MAX148
0.025
0.050
MAX148
0.025
-0.05
-0.10
0
256
512
CODE
768
1024
0
2.25
0
2.75
4.25
3.25
3.75
SUPPLY VOLTAGE (V)
4.75
5.25
-60
-20
20
60
100
140
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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