SMB139 SUMMIT Microelectronics, Inc:, SMB139 Datasheet - Page 10

• Manufacturer Part Number: SMB139
• Description: ? Summit Microelectronics, Inc. 2005 ? 757 N. Mary Avenue ? Sunnyvale Ca 94085 ? Phone [phone] ? Fax [phone] Http //www.summitmicro.com/ 2121 3.0 6/19/2008 1 Programmable Linear Battery Charger
• Manufacturer: SUMMIT Microelectronics, Inc:

DEVICE OPERATION
The SMB139 is a fully programmable battery charger
for single-cell Li-Ion and Li-Polymer battery packs. The
device’s simple, linear-mode operation and ultra-small
package significantly reduce component count and
required board space. The SMB139 provides four main
charging phases: trickle-charge, pre-conditioning (pre-
charge), constant (fast-charge) current and constant
voltage. The overall system accuracy of the SMB139 is
1%, allowing for a higher capacity utilization versus
other conventional solutions. The main battery charging
parameters are programmable, allowing for high design
flexibility
Furthermore, the SMB139 offers many advanced
protection features, allowing applications to meet strict
safety standards without the need for additional cost
and components.
Power Supply
The SMB139 can be powered from an input voltage
between +4.35 and +6.5 Volts applied between the IN
pin and ground. The voltage on the IN pin is monitored
by an Under-Voltage (UVLO) circuit, which prevents the
charger from turning on when the voltage at this node is
less than the UVLO threshold (+3.5V). The IN pin also
supplies an internal +2.5V VDD regulator, filtered by an
external capacitor attached between the VDDCAP pin
and ground; this filtered voltage is then used as an
internal VDD supply. When the input supply is
removed, the SMB139 enters a low-power shutdown
mode, exhibiting a very low discharge leakage current
(2µA), thereby extending battery life.
Pre-qualification Mode
When an external wall adaptor or another type of power
source is connected, the SMB139 performs a series of
pre-qualification tests before initiating the first charge
cycle. The input voltage level needs to be higher than
the UVLO threshold, and 130mV greater than the
battery voltage; the ENABLE input needs to be
asserted or the appropriate I2C command needs to be
asserted; and the cell temperature needs to be within
the specified temperature limits for the charging cycle
to
continuously monitored and charge cycle is suspended
when one of them is outside the limits.
Trickle-charge Mode
Once all pre-qualification conditions are met, the device
checks the battery voltage to decide if trickle-charging
is required. If the battery voltage is below approximately
2.0V, a charging current of 3mA (typical) is applied on
the battery cell. This allows the SMB139 to reset the
protection circuit in the battery pack and bring the
Summit Microelectronics, Inc
APPLICATIONS INFORMATION
start.
and
The
sophisticated
pre-qualification
battery
parameters
management.
2121 3.0 6/19/2008
are
battery voltage to a higher level without compromising
safety.
Pre-charge Mode
Once the battery voltage crosses the 2.0V level, the
SMB139 pre-charges the battery to safely charge the
deeply discharged cells (Figure 3). The pre-charge
(pre-conditioning) current is programmable from 23mA
to 90mA (Register 00h). The SMB139 remains in this
mode until the battery voltage reaches the pre-charge
to fast-charge voltage threshold (programmable from
+2.4V to +3.1V in 100mV steps). If the pre-charge to
fast-charge voltage threshold is not exceeded before
the pre-charge timer expires, the charge cycle is
terminated and a corresponding timeout fault signal is
asserted (“Pre-charge Timeout” in register 36h).
Constant Current Mode
When the battery voltage exceeds the pre-charge to
fast-charge voltage threshold, the device enters the
constant current (fast charge) mode. During this mode,
the fast charge current level is set by the corresponding
register. The fast charge current is programmable from
33mA to 212mA (Register 00h).
Constant Voltage Mode
When the battery voltage reaches the pre-defined float
voltage, the fast-charge current starts diminishing. The
float voltage is programmable from +4.020V to +4.40V
in 20mV steps and is ±1% accurate over the +10°C to
+50°C temperature range. The higher float voltage
settings of the SMB139 enable the charging of modern
battery packs with a required float voltage of 4.3V, and
4.4V. Furthermore, the ability to dynamically adjust the
float voltage allows the implementation of sophisticated
battery charging and control algorithms.
Charge Completion
The charge cycle is considered complete when the
charge current reaches the programmed termination
current
programmable from 10mA to 89mA (Register 01h). If
the termination current threshold is not met before the
fast-charge
terminated and a corresponding timeout fault signal is
asserted (“Fast-charge Timeout” in register 36h).
threshold.
timer
expires,
The
termination
the
charge
SMB139
current
cycle
10
is
is