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________________General Description
The MAX125/MAX126 are high-speed, multichannel,
14-bit data-acquisition systems (DAS) with simultane-
ous track/holds (T/Hs). These devices contain a 14-bit,
3s, successive-approximation analog-to-digital con-
verter (ADC), a +2.5V reference, a buffered reference
input, and a bank of four simultaneous-sampling T/H
amplifiers that preserve the relative phase information
of the sampled inputs. The MAX125/MAX126 have two
multiplexed inputs for each T/H, allowing a total of eight
inputs. In addition, the converter is overvoltage tolerant
to 17V; a fault condition on any channel will not harm
the IC. Available input ranges are 5V (MAX125) and
2.5V (MAX126).
An on-board sequencer converts one to four channels
per CONVST pulse. In the default mode, one T/H output
(CH1A) is converted. An interrupt signal (INT) is pro-
vided after the last conversion is complete. Convert
two, three, or four channels by reprogramming the
MAX125/MAX126 through the bidirectional parallel
interface. Once programmed, the MAX125/MAX126
continue to convert the specified number of channels
per CONVST pulse until they are reprogrammed. The
channels are converted sequentially, beginning with
CH1. The INT signal always follows the end of the last
conversion in a conversion sequence. The ADC con-
verts each assigned channel in 3s and stores the
result in an internal 14x4 RAM. Upon completion of the
conversions, data can be accessed by applying suc-
cessive pulses to the RD pin. Four successive reads
access four data words sequentially.
The parallel interface's data-access and bus-release
timing specifications are compatible with most popular
digital signal processors and 16-bit/32-bit microproces-
sors, so the MAX125/MAX126 conversion results can
be accessed without resorting to wait states.
________________________Applications
Multiphase Motor Control
Power-Grid Synchronization
Power-Factor Monitoring
Digital Signal Processing
Vibration and Waveform Analysis
____________________________Features
o
Four Simultaneous-Sampling T/H Amplifiers with
Two Multiplexed Inputs (eight single-ended inputs
total)
o
3s Conversion Time per Channel
o
Throughput: 250ksps (1 channel)
142ksps (2 channels)
100ksps (3 channels)
76ksps (4 channels)
o
Input Range: 5V (MAX125)
2.5V (MAX126)
o
Fault-Protected Input Multiplexer (17V)
o
5V Supplies
o
Internal +2.5V or External Reference Operation
o
Programmable On-Board Sequencer
o
High-Speed Parallel DSP Interface
MAX125/MAX126
2x4-Channel, Simultaneous-Sampling
14-Bit DAS
________________________________________________________________
Maxim Integrated Products
1
19-1319; Rev 1; 1/98
PART
MAX125
ACAX
MAX125BCAX
0C to +70C
0C to +70C
TEMP. RANGE
PIN-PACKAGE
36 SSOP*
36 SSOP*
EVALUATION KIT
AVAILABLE
______________Ordering Information
*
Contact factory for availability.
Typical Operating Circuit appears at end of data sheet.
Pin Configuration appears at end of data sheet.
INL
(LSB)
2
4
MAX125AEAX
-40C to +85C
36 SSOP*
2
MAX125BEAX
-40C to +85C
36 SSOP*
4
MAX125CCAX
0C to +70C
36 SSOP
4
MAX125CEAX
-40C to +85C
36 SSOP
4
MAX126
ACAX
MAX126BCAX
MAX126CCAX
0C to +70C
0C to +70C
0C to +70C
36 SSOP*
36 SSOP*
36 SSOP
2
4
4
MAX126AEAX
-40C to +85C
36 SSOP*
2
MAX126BEAX
-40C to +85C
36 SSOP*
4
MAX126CEAX
-40C to +85C
36 SSOP
4
MAX125
MAX125/MAX126
2x4-Channel, Simultaneous-Sampling
14-Bit DAS
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(AV
DD
= +5V 5%, AV
SS
= -5V 5%, DV
DD
= +5V 5%, V
REFIN
= 2.5V, AGND = DGND = 0V, 4.7F capacitor from REFOUT to
AGND, 0.1F capacitor from REFIN to AGND, f
CLK
= 16MHz, external clock, 50% duty cycle, 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.
AV
DD
to AGND ...........................................................-0.3V to 6V
AV
SS
to AGND ............................................................0.3V to -6V
DV
DD
to DGND ...........................................................-0.3V to 6V
AGND to DGND .......................................................-0.3V to 0.3V
CH_ _ to AGND....................................................................17V
REFIN, REFOUT to AGND ..........................................-0.3V to 6V
Digital Inputs/Outputs to DGND ..............-0.3V to (DV
DD
+ 0.3V)
Continuous Power Dissipation (T
A
= +70C)
SSOP (derate 11.8mW/C above +70C) .....................941mW
Operating Temperature Ranges
MAX125_CAX/MAX126_CAX ...............................0C to +70C
MAX125_EAX/MAX126_EAX ............................-40C to +85C
Storage Temperature Range .............................-65C to +150C
Lead Temperature (soldering, 10sec)................................300C
CONDITIONS
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
All channels
14
N
Resolution
MAX125A/MAX126A
Bits
2
INL
Integral Nonlinearity
(Note 2)
MAX12_B/C
LSB
2
4
MAX12_A/B, guaranteed monotonic to 14 bits
1
T
A
= +25C
mV
5
15
Bipolar Zero Error
T
A
= T
MIN
to T
MAX
25
Bipolar Zero-Error Match
Between all channels
mV
1.2
5
5
ppm/C
Zero-Code Tempco
5
10
mV
Gain Error
15
T
A
= T
MIN
to T
MAX
T
A
= +25C
1.2
5
mV
Gain Error Match
5
Between all channels
Gain Error Tempco
ppm/C
72
75
SINAD
Single-channel mode,
channel 1A, 250ksps
Signal-to-Noise Plus
Distortion (Note 4)
dB
-89
-80
THD
Single-channel mode, channel 1A, 250ksps
Total Harmonic
Distortion (Notes 4, 5)
dB
80
90
SFDR
Single-channel mode, channel 1A, 250ksps
Spurious-Free Dynamic
Range (Note 4)
dB
80
Single-channel mode, channel 1A, 250ksps
Channel-to-Channel
Isolation (Note 6)
dB
MAX125C/MAX126C,
guaranteed monotonic to 13 bits
LSB
2
DNL
Differential Nonlinearity
DC ACCURACY
(Note 1)
DYNAMIC PERFORMANCE
(f
CLK
= 16MHz, f
IN
= 10.06kHz) (Notes 1, 3)
70
72
MAX125
MAX126
A
MAX125/MAX126
2x4-Channel, Simultaneous-Sampling
14-Bit DAS
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(AV
DD
= +5V 5%, AV
SS
= -5V 5%, DV
DD
= +5V 5%, V
REFIN
= 2.5V, AGND = DGND = 0V, 4.7F capacitor from REFOUT to
AGND, 0.1F capacitor from REFIN to AGND, f
CLK
= 16MHz, external clock, 50% duty cycle, T
A
= T
MIN
to T
MAX
, unless otherwise
noted.)
CONDITIONS
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
MAX125
V
5
V
IN
Input Voltage Range
MAX125, V
IN
= 5V
A
667
I
IN
Input Current
(Note 7)
pF
16
C
IN
Input Capacitance
s
1
t
ACQ
Acquisition Time
MHz
8
Small-Signal Bandwidth
MHz
0.5
Full-Power Bandwidth
mV/ms
2
Droop Rate
ns
5
Aperture Delay
ps
RMS
30
Aperture Jitter
ps
500
Aperture-Delay Matching
T
A
= +25C
V
2.475
2.500
2.525
V
REFOUT
Output Voltage
0mA < I
LOAD
< 1mA
%
1
External Load Regulation
(Note 9)
ppm/C
30
REFOUT Tempco
F
0.1
External Capacitive
Bypass at REFIN
V
2.50 10%
Input Voltage Range
F
4.7
22
External Capacitive
Bypass at REFOUT
REFIN = 2.5V
A
10
Input Current
(Note 10)
k
10
Input Resistance
(Note 7)
pF
10
Input Capacitance
MHz
0.1
16
External Clock Frequency
V
2.4
V
IH
Input High Voltage
V
0.8
V
IL
Input Low Voltage
CONVST, RD, WR, CS, CLK
1
(Note 7)
pF
15
C
IN
Input Capacitance
A0A3
A
10
I
IN
Input Current
MAX126
2.5
MAX126, V
IN
= 2.5V
ANALOG INPUT
TRACK/HOLD
REFERENCE OUTPUT
(Note 8)
REFERENCE INPUT
EXTERNAL CLOCK
DIGITAL INPUTS
(CONVST, RD, WR, CS, CLK, A0A3) (Note 1)
MAX125/MAX126
2x4-Channel, Simultaneous-Sampling
14-Bit DAS
4
_______________________________________________________________________________________
CONDITIONS
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
I
OUT
= 1mA
V
4
V
OH
Output High Voltage
I
OUT
= -1.6mA
V
0.4
V
OL
Output Low Voltage
D0D13
A
10
Three-State Leakage Current
(Note 7)
pF
10
Three-State Output
Capacitance
V
4.75
5
5.25
AV
DD
Positive Supply Voltage
V
-5.25
-5
-4.75
AV
SS
Negative Supply Voltage
V
4.75
5
5.25
DV
DD
Digital Supply Voltage
mA
17
25
I(AV
DD
)
Positive Supply Current
mA
-17
-13
I(AV
SS
)
Negative Supply Current
mA
3
5
I(DV
DD
)
Digital Supply Current
mA
3
Shutdown Positive Current
mA
-1
Shutdown Negative Current
mA
3
Shutdown Digital Current
(Note 11)
LSB
1
2
PSRR+
Positive Supply Rejection
(Note 11)
LSB
2
PSRR-
Negative Supply Rejection
(Note 12)
mW
165
250
Power Dissipation
DIGITAL OUTPUTS
(D0D13, INT) (Note 1)
POWER REQUIREMENTS
ELECTRICAL CHARACTERISTICS (continued)
(AV
DD
= +5V 5%, AV
SS
= -5V 5%, DV
DD
= +5V 5%, V
REFIN
= 2.5V, AGND = DGND = 0V, 4.7F capacitor from REFOUT to
AGND, 0.1F capacitor from REFIN to AGND, f
CLK
= 16MHz, external clock, 50% duty cycle, T
A
= T
MIN
to T
MAX
, unless otherwise
noted.)
MAX125/MAX126
2x4-Channel, Simultaneous-Sampling
14-Bit DAS
_______________________________________________________________________________________
5
CONDITIONS
ns
30
t
CW
CONVST Pulse Width
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
TIMING CHARACTERISTICS
(Figure 4)
(AV
DD
= +5V, AV
SS
= -5V, DV
DD
= +5V, AGND = DGND = 0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
ns
0
t
CWS
CS to WR Setup Time
ns
0
t
CWH
CS to WR Hold Time
ns
30
t
WR
WR Low Pulse Width
ns
125
t
CSD
CS to CONVST Delay
ns
30
t
AS
Address Setup Time
ns
0
t
AH
Address Hold Time
25pF load
ns
30
t
ID
RD to INT Delay
ns
40
t
RD
Delay Time Between Reads
ns
0
t
CRS
CS to RD Setup Time
ns
0
t
CRH
CS to RD Hold Time
ns
30
t
RD
RD Low Pulse Width
25pF load (Note 13)
ns
30
t
DA
Data-Access Time
25pF load (Note 14)
ns
5
45
t
DH
Bus-Relinquish Time
Mode 1, 1 channel
s
3
Mode 2, 2 channel
6
Mode 3, 3 channel
9
Mode 4, 4 channel
12
t
CONV
Exiting shutdown
s
5
Start-Up Time
Note 1:
AV
DD
= +5V, AV
SS
= -5V, DV
DD
= +5V, V
REFIN
= 2.500V (external), V
IN
= 5V (MAX125) or 2.5V (MAX126).
Note 2:
Relative accuracy is the analog value's deviation at any code from its theoretical value after the full-scale range has been
calibrated.
Note 3:
CLK synchronized with CONVST.
Note 4:
f
IN
= 10.06kHz, V
IN
= 5V (MAX125) or 2.5V (MAX126).
Note 5:
First five harmonics.
Note 6:
All inputs except CH1A driven with 5V (MAX125) or 2.5V (MAX126) 10kHz signal; CH1A connected to AGND and digitized.
Note 7:
Guaranteed by design. Not production tested.
Note 8:
AV
DD
= +5V, AV
SS
= -5V, DV
DD
= +5V, V
IN
= 0V (all channels).
Note 9:
Temperature drift is defined as the change in output voltage from +25C to T
MIN
or T
MAX
. It is calculated as
TC = [
REFOUT/REFOUT] /
T.
Note 10:
See Figure 2.
Note 11:
Defined as the change in positive full scale caused by a 5% variation in the nominal supply voltage. Tested with one input
at full scale and all others at AGND. V
REFIN
= 2.5V (internal).
Note 12:
Tested with V
IN
= AGND on all channels, V
REFIN
= 2.5V (internal).
Note 13:
The data-access time is defined as the time required for an output to cross 0.8V or 2.0V. It is measured using the circuit of
Figure 1. The measured number is then extrapolated back to determine the value with a 25pF load.
Note 14:
The bus-relinquish time is derived from the measured time taken for the data outputs to change 0.5V when loaded with the
circuit of Figure 1. The measured number is then extrapolated back to remove the effects of charging/discharging the 120pF
capacitor. Thus, the time given is the part's true bus-relinquish time, independent of the external bus loading capacitance.
Conversion Time
Mode 1, 1 channel
ksps
250
Conversion Rate/Channel
Mode 2, 2 channel
142
Mode 3, 3 channel
100
Mode 4, 4 channel
76
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