Internal reference, Transfer function – Rainbow Electronics MAX1111 User Manual

Page 17

MAX1110/MAX1111

+2.7V, Low-Power, Multichannel,

Serial 8-Bit ADCs

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Internal Reference

To use the MAX1110/MAX1111 with the internal refer-
ence, connect REFIN to REFOUT. The full-scale range
of the MAX1110/MAX1111 with the internal reference is
typically 2.048V with unipolar inputs, and ±1.024V with
bipolar inputs. The internal reference should be
bypassed to AGND with a 1µF capacitor placed as
close to the REFIN pin as possible.

Transfer Function

Table 4 shows the full-scale voltage ranges for unipolar
and bipolar modes. Figure 15 depicts the nominal, unipo-
lar I/O transfer function, and Figure 16 shows the bipolar
I/O transfer function when using a 2.048V reference.
Code transitions occur at integer LSB values. Output cod-
ing is binary, with 1LSB = 8mV (2.048V/256) for unipolar
operation and 1LSB = 8mV [(2.048V/2 - -2.048V/2)/256]
for bipolar operation.

POWERED UP

POWER-

DOWN

POWERED
UP

POWERED UP

DATA VALID

DATA

INVALID

EXTERNAL

INTERNAL

S X X X X X 1 1

0 1

X X X X X

1 1

POWER-

DOWN

MODE

DOUT

DIN

CLOCK

MODE

SHDN

SETS EXTERNAL
CLOCK MODE

SETS EXTERNAL

CLOCK MODE

SETS POWER-
DOWN MODE

Figure 14a. Power-Down Modes, External Clock Timing Diagram

POWER-DOWN

POWERED

POWERED UP

DATA VALID

INTERNAL CLOCK MODE

S X X X X X 1 0

0 0

MODE

DOUT

DIN

SETS INTERNAL
CLOCK MODE

SETS POWER-DOWN MODE

CONVERSION

SSTRB

Figure 14b. Power-Down Modes, Internal Clock Timing Diagram