MAX1238EEE+ Maxim Integrated Products, MAX1238EEE+ Datasheet - Page 18

• Manufacturer Part Number: MAX1238EEE+
• Description: IC ADC 12-BIT 94KSPS 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1238EEE+

• Number Of Bits: 12
• Sampling Rate (per Second): 94.4k
• Data Interface: I²C, Serial
• Number Of Converters: 1
• Power Dissipation (max): 666.7mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Number Of Adc Inputs: 12
• Architecture: SAR
• Conversion Rate: 94.4 KSPs
• Resolution: 12 bit
• Interface Type: I2C
• Voltage Reference: Internal 4.096 V
• Supply Voltage (max): 5 V
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Wake-up is invisible when using an external reference
or V
Automatic shutdown results in dramatic power savings,
particularly at slow conversion rates and with internal
clock. For example, at a conversion rate of 10ksps, the
average supply current for the MAX1237 is 60µA (typ) and
drops to 6µA (typ) at 1ksps. At 0.1ksps the average sup-
ply current is just 1µA, or a minuscule 3µW of power con-
sumption, see Average Supply Current vs. Conversion
Rate in the Typical Operating Characteristics section.
SEL[2:0] of the setup byte (Table 1) control the reference
and the AIN_/REF configuration (Table 6). When
AIN_/REF is configured to be a reference input or refer-
ence output (SEL1 = 1), differential conversions on
AIN_/REF appear as if AIN_/REF is connected to GND
(see Note 2 and Table 4). Single-ended conversion in
scan mode AIN_/REF is ignored by the internal limiter,
which sets the highest available channel at AIN2 or
AIN10.
The internal reference is 4.096V for the MAX1236/
MAX1238 and 2.048V for the MAX1237/MAX1239. SEL1 of
the setup byte controls whether AIN_/REF is used for an
analog input or a reference (Table 6). When AIN_/REF is
configured to be an internal reference output (SEL[2:1] =
11), decouple AIN_/REF to GND with a 0.1µF capacitor
and a 2kΩ series resistor (see the Typical Operating
Circuit ). Once powered up, the reference always remains
on until reconfigured. The internal reference requires 10ms
to wake up and is accessed using SEL0 (Table 6). When
in shutdown, the internal reference output is in a high-
impedance state. The reference should not be used to
supply current for external circuitry. The internal reference
does not require an external bypass capacitor and works
best when not connected to the pin (SEL1 = 0).
The external reference can range from 1V to V
maximum conversion accuracy, the reference must be
2.7V to 3.6V and 4.5V to 5.5V, Low-Power,
4-/12-Channel, 2-Wire Serial, 12-Bit ADCs
Table 6. Reference Voltage and AIN_/REF Format
18
SEL2
DD
0
0
1
1
1
1
______________________________________________________________________________________
as the reference.
SEL1
0
1
0
0
1
1
SEL0
X
X
0
1
0
1
Reference Voltage
REFERENCE VOLTAGE
External Reference
Internal Reference
External Reference
Internal Reference
Internal Reference
Internal Reference
Internal Reference
V
DD
DD
. For
able to deliver up to 40µA and have an output imped-
ance of 500Ω or less. If the reference has a higher out-
put impedance or is noisy, bypass it to GND as close to
AIN_/REF as possible with a 0.1µF capacitor.
Output data coding for the MAX1236–MAX1239 is bina-
ry in unipolar mode and two’s complement in bipolar
mode with 1 LSB = (V
bits (12). Code transitions occur halfway between suc-
cessive-integer LSB values. Figures 12 and 13 show
the input/output (I/O) transfer functions for unipolar and
bipolar operations, respectively.
Only use PC boards. Wire-wrap configurations are not
recommended since the layout should ensure proper
separation of analog and digital traces. Do not run ana-
log and digital lines parallel to each other, and do not
layout digital signal paths underneath the ADC pack-
Figure 12. Unipolar Transfer Function
Reference Output
Reference Output
11 . . . 111
11 . . . 110
Reference Input
11 . . . 101
00 . . . 011
00 . . . 010
00 . . . 001
00 . . . 000
Analog Input
Analog Input
Analog Input
AIN_/REF
OUTPUT CODE
Layout, Grounding, and Bypassing
0
1
2
INPUT VOLTAGE (LSB)
REF
3
/2
N
) where “N” is the number of
FULL-SCALE
TRANSITION
INTERNAL REFERENCE
Transfer Functions
FS - 3/2 LSB
Always Off
Always Off
Always Off
Always On
Always Off
Always On
STATE
MAX1236–
MAX1239
1 LSB =
FS = V
ZS = GND
FS
REF
4096
V
REF