1
Features
➤ Ideal for single- and dual-cell Li-Ion
packs with coke or graphite anodes
➤ Dropout voltage as low as 0.3V
➤ AutoComp™ dynamic compensa-
tion of battery pack’s internal im-
pedance
➤ Optional temperature-monitoring
before and during charge
➤ Integrated voltage and current
regulation with programmable
charge-current and high- or
low-side current sensing
➤ Integrated cell conditioning for
reviving deeply discharged cells
and minimizing heat dissipation
during initial stage of charge
➤ Better than ±1% voltage regula-
tion accuracy
➤ Charge status output for LED or
host processor interface
➤ Automatic battery-recharge feature
➤ Charge termination by minimum
current
➤ Low-power sleep mode
➤ Packaging: 8-pin SOIC, 8-pin
TSSOP
General Description
The BENCHMARQ bq2057 series
advanced Li-Ion linear charge-man-
agement ICs are designed for
cost-sensitive and compact portable
electronics. They combine high-accu-
racy current and voltage regulation,
battery conditioning, temperature
monitoring, charge termination,
charge-status indication, and
AutoComp charge-rate compen-
sation in a single 8-pin IC.
The bq2057 continuously measures
battery temperature using an exter-
nal thermistor. For safety reasons,
the bq2057 inhibits charge until the
battery temperature is within
user-defined thresholds. The bq2057
then charges the battery in three
phases: conditioning, constant cur-
rent, and constant voltage. If the
battery voltage is below the
low-voltage threshold V
MIN, the
bq2057 trickle-charges to condition
the battery. The conditioning charge
rate is set at 10% of the regulation
current. The conditioning current
also minimizes heat dissipation in
the external pass-element during
the initial stage of charge.
After conditioning, the bq2057 ap-
plies a constant current to the bat-
tery. An external sense-resistor sets
the magnitude of the current. The
sense-resistor can be on either the
low or the high side of the battery
without additional components. The
constant-current phase continues
until the battery reaches the
charge-regulation voltage.
The bq2057 then begins the con-
stant-voltage phase. The accuracy of
the voltage regulation is better than
±1% over the operating-temperature
and supply-voltage ranges. For sin-
gle and dual cells with either coke
or graphite anodes, the bq2057 is of-
fered in four fixed-voltage versions:
4.1V, 4.2V, 8.2V, and 8.4V. Charge
stops when the current tapers to the
charge termination threshold,
V
TERM. The bq2057 automatically
restarts the charge if the battery
voltage falls below the V
RCH thresh-
old.
The designer also may use the
AutoComp feature to reduce charg-
ing time. This proprietary technique
allows safe and dynamic compensa-
tion for the internal impedance of
the battery pack during charge.
bq2057
Pin Connections
Advanced Li-Ion Linear Charge
Management IC
1
PN-205701.eps
8-Pin PDIP, Narrow SOIC, or TSSOP
2
3
4
8
7
6
5
SNS
BAT
V
CC
TS
COMP
CC
VSS
STAT
Pin Names
SNS Current-sense input
BAT Battery-voltage input
V
CC Supply voltage
TS Temperature sense
input
STAT Charge status output
VSS Ground input
CC Charge control output
COMP Charge-rate
compensation input
SLUS025A – JANUARY 2000 - REVISED MAY 2000