Rainbow Electronics MAX17047 - Manual (Page 13)

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MAX17047
ModelGauge m3 Fuel Gauge
Figure 7. Proper Board Layout
Recommended Layout
Proper circuit layout (see Figure 7 ) is essential for
measurement accuracy when using the MAX17047
ModelGauge m3 IC. The recommended layout guide-
lines are as follows:
1) Mount R
SNS
as close as possible to PACK-. The
device shares both voltage and current measure-
ments on the CSP pin. Therefore, it is important to limit
the amount of trace resistance between the current-
sensing resistor and PACK-.
2) V
BATT
trace should make a Kelvin connection to
PACK+. The device shares the V
BATT
pin for both
voltage measurement and IC power. Limiting the
voltage loss through this trace is important to voltage-
measurement accuracy. PCB resistance that cannot
be removed can be compensated for during charac-
terization of the application cell.
3) CSN and CSP traces should make Kelvin connections
to R
SNS
. The device measures current differentially
through the CSN and CSP pins. Any shared high-
current paths on these traces will affect current-
measurement gain accuracy. PCB resistance that
cannot be removed can be compensated for during
characterization of the application cell.
4) V
BATT
capacitor trace loop area should be minimized.
The device shares the V
BATT
pin for both voltage mea-
surement and IC power. Limiting noise at the V
BATT
pin is important to current-measurement accuracy.
5) REG capacitor trace loop area should be minimized.
The helps filter any noise from the internal regulated
supply.
6) There are no limitations on any other IC connection.
Connections to THRM, ALRT, SDA, SCL, V
TT
, and
AIN, as well as any external components mounted to
these pins, have no special layout requirements.
C VBATT
C REG
R SNS
PACK +
CONTACT
PACK -
CONTACT
NEGATIVE POWER BUS
POSITIVE POWER BUS
CSN
AIN
V TT
SDA
SCL
EP
CSP
ALRT
V BATT
THRM
REG
MAX17047