
MAXQ7665/MAXQ7666 User’s Guide
3-24
Table 3-6. Bipolar Code Table (PGA Gain = 1)
Table 3-7 shows the input range for various PGA settings (PGG2:PGG0) in bipolar mode. When the PGA is used (gain > 1), the differ-
ential input range at the analog multiplexer input is reduced by the gain factor:
full-scale differential input range = ±REFADC / (2 x PGA gain factor)
Table 3-7. Bipolar Input Scaling
The differential analog input voltage as a function of REFADC, PGA gain factor (PGA_GF), and the ideal (error-free) digital output code
are determined with the following equation:
ΔV
AIN
= LSB x CODE
12
± 0.5 x LSB
Where:
ΔV
AIN
= V
AIN+
- V
AIN-
LSB = REFADC / (PGA_GF x 2
12
) = REFADC / (PGA_GF x 4096)
CODE
12
= the decimal equivalent of the digital output code (see Table 3-4 and Table 3-6)
PGA_GF = PGA gain factor (1, 2, 4, 8, 16, or 32)
±0.5 x LSB represents the quantization error that is inherent to any ADC
When using a 4.096V reference and a PGA gain factor of 1, 1 LSB equals 1.0mV. When using a 5.0V reference and a PGA gain factor
of 1, 1 LSB equals 1.22mV.
BINARY DIGITAL OUTPUT CODE
ADCD11:ADCD0
HEXADECIMAL EQUIVALENT OF
ADCD11:ADCD0
DECIMAL EQUIVALENT OF
ADCD11:ADCD0 (CODE
12
)
IDEAL DIFFERENTIAL INPUT
VOLTAGE (V)
(REFADC = 5.0V)
0111 1111 1111 0x7FF +2047 +2.49878 ± 0.5 LSB
0111 1111 1110 0x7FE +2046 +2.49756 ± 0.5 LSB
0000 0000 0001 0x001 +1 +0.00122 ± 0.5 LSB
0000 0000 0000 0x000 0 0.000 ± 0.5 LSB
1111 1111 1111 0xFFF -1
-0.00122 ± 0.5 LSB
1000 0000 0001 0x801 -2047 -2.49878 ± 0.5 LSB
1000 0000 0000 0x800 -2048 -2.5 ± 0.5 LSB
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 ±REFADC/2 -2.5V to 2.5V 1.22mV
0 0 1 x2 ±REFADC/4 -1.25V to 1.25V 610.35μV
0 1 0 x4 ±REFADC/8 -0.625V to 0.625V 305.18μV
0 1 1 x8 ±REFADC/16 -0.313V to 0.313V 152.59μV
1 0 0 x16 ±REFADC/32 -0.156V to 0.156V 76.29μV
1 0 1 x32 ±REFADC/64 -0.078V to 0.078V 38.15μV
-2048 to +2047
Maxim Integrated
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