LTC6803 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC6803' PDF : 40 Pages View PDF
LTC6803-1/LTC6803-3
APPLICATIONS INFORMATION
the LTC6803-1 and LTC6803-3 were chosen to facilitate
this physical separation. There is no more than 5.5V
between any two adjacent pins. The package body is used
to separate the highest voltage (e. g., 43.2V) from the low-
est voltage (0V). As an example, Figure 27 shows the DC
voltage on each pin with respect to V– when twelve 3.6V
battery cells are connected to the LTC6803-3.
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.
For a given sample rate, a delta-sigma converter can
achieve excellent noise rejection while settling completely
in a single conversion—something that a filtered SAR con-
verter cannot do. Noise rejection is particularly important
in high voltage switching controllers, where switching
noise will invariably be present in the measured voltage.
42.5V
42.5V
42.5V
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
CSBO
CSBI
SDOI
SDO
SCKO
SDI
V+
SCKI
C12
VMODE
S12
GPIO2
C11
GPIO1
S11
WDTB
C10 LTC6803-3 TOS
S10
VREG
C9
VREF
S9
VTEMP2
C8
VTEMP1
S8
NC
C7
V–
S7
C0
C6
S1
S6
C1
C5
S2
S5
C2
C4
S3
S4
C3
680313 F27
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
7.2V
10.8V
10.8V
Figure 27. Typical Pin Voltages for Twelve 3.6V Cells
680313f
37
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