Maxim Integrated MAXQ7666 - Manual (Page 113)

MAXQ7665/MAXQ7666 User’s Guide
3-23
Table 3-5 shows the input range for various PGA settings (PGG2:PGG0) in unipolar mode. When the PGA is used (gain > 1), the dif-
ferential input range at the analog multiplexer input is reduced by the gain factor. The maximum PGA output value is limited to 3.2V.
For gain > 1, differential input range x PGA gain
≤ 3.2V and the ADC output code range is limited to 0–2621 (decimal).
Table 3-5. Unipolar Input Scaling
The MAXQ7665/MAXQ7666 ADC output is two’s complement in bipolar mode. Figure 3-6 shows the MAXQ7665/MAXQ7666 ADC bipo-
lar transfer function for PGA gain = 1. Table 3-6 shows the bipolar relationship between the differential analog input voltage and the
digital output code for PGA gain = 1. In bipolar mode, the inputs are measured in a truly differential fashion where either input can
exceed the other by up to REFADC/2 (for gain = 1, but limited for gain > 1).
PGG2 PGG1 PGG0
GAIN
FACTOR
DIFFERENTIAL INPUT
RANGE AT MUX
INPUTS
DIFFERENTIAL INPUT
RANGE WITH 5.0V
EXTERNAL REFERENCE
LSB SIZE WITH 5.0V
EXTERNAL
REFERENCE
OUTPUT CODE RANGE
(DECIMAL)
0 0 0 x1 0 to +REFADC 0 to 4.99878V 1.22mV 0–4095
0 0 1 x2
0 to +REFADC/2
(1.6V max)
0 to 1.6V 610.35
V
0 1 0 x4
0 to +REFADC/4
(0.8V max)
0 to 0.8V 305.18
V
0 1 1 x8
0 to +REFADC/8
(0.4V max)
0 to 0.4V 152.59
V
1 0 0 x16
0 to +REFADC/16
(0.2V max)
0 to 0.2V 76.29
V
1 0 1 x32
0 to +REFADC/32
(0.1V max)
0 to 0.1V 38.15
V
0–2621
(REFADC = +5V)
Figure 3-6. Bipolar Transfer Function (PGA Gain = 1)
800
801
FFE
001
000
FFF
7FE
7FF
-FS 0 +FS
OUTPUT CODE (hex)
DIFFERENTIAL INPUT VOLTAGE (LSB)
+FS - 1.5 LSB
FULL-SCALE
TRANSITION
+FS = REFADC / 2
ZS = 0
-FS = -REFADC / 2
1 LSB = REFADC / 4096
-FS + 0.5 LSB
Maxim Integrated