Linear Technology DC1496B Demo Manual

DESCRIPTION
Demonstration circuit 1496B-A (Figure 1) features the
LTC ® 2941. Demonstration circuit 1496B-B features the
LTC2942. Demonstration circuit 1496B-C features the
LTC2941-1. Demonstration circuit 1496B-D features the
LTC2942-1. The C, D options have parts that use an internal
sense resistor while the A, B options rely on an external
precision sense resistor. All four devices measure battery
charge state in handheld PC and portable product applica-
tions. The operating range is perfectly suited for single
cell Li-Ion batteries. A precision analog coulomb counter
integrates current through a sense resistor between the
battery's positive terminal and the load or charger. The
LTC2942 adds battery voltage and on-chip temperature
measurement with an internal 14-bit No Latency ∆Σ™
ADC. The three measured quantities (charge, voltage and
temperature) are stored in internal registers accessible via
the onboard SMBus/I
The LTC2941/LTC2941-1 has programmable high and
low thresholds for accumulated charge. The LTC2942/
LTC2942-1 has programmable high and low thresholds for
all three measured quantities. If a programmed threshold
is exceeded, the device reports an alert using either the
Arrow.com.
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C interface.
DEMO MANUAL DC1496B
Battery Gas Gauge with I
Interface and 14-Bit ADC
SMBus alert protocol or by setting a fl ag in the internal
status register.
The LTC2941 and LTC2942 require only a single low value
sense resistor to set the measured current range. The
LTC2941-1 and the LTC2942-1 have their own 50mΩ inter-
nal resistor. The default value assembled on the DC1496 is
100mΩ for a maximum current measurement of 500mA.
Both parts have a software-confi gurable charge complete/
alert pin. When the pin is set for charge complete, a jumper
connects the pushbutton which simulates a logic high input
to indicate a full battery. When the pin is confi gured for
alert, the same jumper is used to connect a red LED that
indicates an alert is present. A change was made between
DC1496A and DC1496B to fl oat the exposed pad under
the LTC2941/LTC2942 in accordance with the data sheet
recommendations.
The DC1496B is a part of the QuikEval system for quick
evaluation with a host controller through a PC.
Design fi les for this circuit board are available at
http://www.linear.com/demo.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No Latency ∆Σ is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
Figure 1. DC1496B
LTC2941/LTC2942:
2
C
dc1496fa
1