MAX11612_11 Datasheet, PDF (19/22 Pages) Maxim Integrated Products – Low-Power, 4-/8-/12-Channel, I2C, 12-Bit ADCs in Ultra-Small Packages

Low-Power, 4-/8-/12-Channel, I²C,
OUTPUT CODE
011 . . . 111
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
111 . . . 101
FS = ^VREF
2
ZS = 0
-FS = ^-VREF
2
1 LSB = ^VREF
4096
MAX11612–
MAX11617
100 . . . 001
100 . . . 000
*V_COM
V_REF/2
- FS
0
INPUT VOLTAGE (LSB)
*V_IN = (AIN+) - (AIN-)
Figure 13. Bipolar Transfer Function
+FS - 1 LSB
Transfer Functions
Output data coding for the MAX11612–MAX11617 is
binary in unipolar mode and two’s complement in bipo-
lar mode with 1 LSB = (V_REF/2N) where N is the number
of bits (12). Code transitions occur halfway between
successive-integer LSB values. Figures 12 and 13
show the input/output (I/O) transfer functions for unipo-
lar and bipolar operations, respectively.
Layout, Grounding, and Bypassing
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-
age. Use separate analog and digital PCB ground sec-
tions with only one star point (Figure 14) connecting the
two ground systems (analog and digital). For lowest
noise operation, ensure the ground return to the star
ground’s power supply is low impedance and as short
as possible. Route digital signals far away from sensi-
tive analog and reference inputs.
High-frequency noise in the power supply (V_DD) could
influence the proper operation of the ADC’s fast com-
parator. Bypass V_DD to the star ground with a network of
two parallel capacitors, 0.1µF and 4.7µF, located as
close as possible to the MAX11612–MAX11617 power-
3V OR 5V
SUPPLIES
V_LOGIC = 3V/5V GND
R* = 5Ω
4.7µF
0.1µF
V_DD
GND
3V/5V DGND
MAX11612–
MAX11617
DIGITAL
CIRCUITRY
*OPTIONAL
Figure 14. Power-Supply Grounding Connection
supply pin. Minimize capacitor lead length for best sup-
ply noise rejection, and add an attenuation resistor (5Ω)
in series with the power supply if it is extremely noisy.
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values on
an actual transfer function from a straight line. This straight
line can be either a best straight-line fit or a line drawn
between the endpoints of the transfer function, once offset
and gain errors have been nullified. The MAX11612–
MAX11617’s INL is measured using the endpoint.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1 LSB. A
DNL error specification of less than 1 LSB guarantees
no missing codes and a monotonic transfer function.
Aperture Jitter
Aperture jitter (t_AJ) is the sample-to-sample variation in
the time between the samples.
Aperture Delay
Aperture delay (t_AD) is the time between the falling
edge of the sampling clock and the instant when an
actual sample is taken.
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