LTC2942IDCB-1#PBF Linear Technology, LTC2942IDCB-1#PBF Datasheet - Page 7

• Manufacturer Part Number: LTC2942IDCB-1#PBF
• Description: IC, BATTERY FUEL GAUGE LI-ION 5.5V DFN-6
• Manufacturer: Linear Technology

Specifications of LTC2942IDCB-1#PBF

• Battery Management Function: Fuel Gauge, Charge Controller
• Battery Type: Li-Ion
• Supply Voltage Range: 2.7V To 5.5V
• Battery Ic Case Style: DFN
• No. Of Pins: 6
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

operaTion
Overview
The LTC2942 is a battery gas gauge device designed for
use with single Li-Ion cells and other battery types with a
terminal voltage at 2.7V to 5.5V. It measures battery charge
and discharge, battery voltage and chip temperature.
A precision coulomb counter integrates current through a
sense resistor between the battery’s positive terminal and
the load or charger. Battery voltage and on-chip temperature
are measured with an internal 14-bit/10-bit ADC.
Coulomb Counter
Charge is the time integral of current. The LTC2942 mea-
sures battery current by monitoring the voltage developed
across a sense resistor and then integrates this information
to infer charge. The differential voltage between SENSE
and SENSE
integrator to convert the measured current to charge.
When the integrator output ramps to REFHI or REFLO
levels, switches S1, S2, S3 and S4 toggle to reverse the
ramp direction. By observing the condition of the switches
and the ramp direction, polarity is determined.
CHARGER
BATTERY
R
SENSE
I
BAT
+
–
is applied to an auto-zeroed differential analog
LOAD
1
6
2
SENSE
SENSE
GND
+
–
V
CC
S1
S2
S3
S4
Figure 2. Coulomb Counter Section of the LTC2942
–
+
+
REFLO
REFHI
A programmable prescaler effectively increases integration
time by a factor M programmable from 1 to 128. At each
underflow or overflow of the prescaler, the accumulated
charge register (ACR) value is incremented or decremented
one count. The value of accumulated charge is read via
the I
Voltage and Temperature ADC
The LTC2942 includes a 14-bit No Latency ∆Σ analog-to-
digital converter, with internal clock and voltage reference
circuits.
The ADC can either be used to monitor the battery voltage
at SENSE
ture sensor. The sensor generates a voltage proportional to
temperature with a slope of 2.5mV/K resulting in a voltage
of 750mV at 27°C.
Conversion of either temperature or voltage is triggered
by setting the control register via the I
LTC2942 features an automatic mode where a voltage and
a temperature conversion are executed every two seconds.
At the end of each conversion the corresponding registers
are updated and the converter goes to sleep to minimize
quiescent current.
2
C interface.
+
–
+
–
–
or to convert the output of the on-chip tempera-
DETECTION
POLARITY
CONTROL
LOGIC
PRESCALER
M
LTC2942
2
C interface. The
ACR
2942 F02
2942fa