LTC6803-2/LTC6803-4
APPLICATIONS INFORMATION
As an example, Figure 24 shows the DC voltage on each
pin with respect to V– when twelve 3.6V battery cells are
connected to the LTC6803.
ADVANTAGES OF DELTA-SIGMA ADCS
The LTC6803 employs a delta-sigma analog-to-digital
converter for voltage measurement. The architecture of
delta-sigma converters can vary considerably, but the
common characteristic is that the input is sampled many
times over the course of a conversion and then filtered or
averaged to produce the digital output code. In contrast,
a SAR converter takes a single snapshot of the input
voltage and then performs the conversion on this single
sample. For measurements in a noisy environment, a
delta-sigma converter provides distinct advantages over
a SAR converter.
While SAR converters can have high sample rates, the full-
power bandwidth of a SAR converter is often greater than
1MHz, which means the converter is sensitive to noise out
to this frequency. And many SAR converters have much
higher bandwidths—up to 50MHz and beyond. It is pos-
sible to filter the input, but if the converter is multiplexed
to measure several input channels a separate filter will be
required for each channel. A low frequency filter cannot
reside between a multiplexer and an ADC and achieve a
high scan rate across multiple channels. Another conse-
quence of filtering a SAR ADC is that any noise reduction
gained by filtering the input cancels the benefit of having
a high sample rate in the first place, since the filter will
take many conversion cycles to settle.
43.2V
43.2V
43.2V
39.6V
39.6V
36V
36V
32.4V
32.4V
28.8V
28.8V
25.2V
25.2V
21.6
21.6
18V
18V
14.4V
14.4V
10.8
10.8
7.2
V+
CSBI
C12
SDO
S12
SDI
C11
SCKI
S11
A3
C10
A2
S10
A1
C9 LTC6803-4 A0
S9
GPIO2
C8
GPIO1
S8
WDTB
C7
TOS
S7
VREG
C6
VREF
S6
VTEMP2
C5
VTEMP1
S5
NC
C4
V–
S4
C0
C3
S1
S3
C1
C2
S2
680324 F24
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
0V TO 5.5V
5V
3.1V
1.5V
1.5V
0V
0V
0V
3.6V
3.6V
7.2V
Figure 24. Typical Pin Voltages for Twelve 3.6V Cells
680324f
37