Operation
The SE9016 is a single cell lithium-ion battery
charger using a constant-current/constant-voltage
algorithm. It can deliver up to 800mA of charge
current (using a good thermal PCB layout) with a
final float voltage accuracy of ±1%. The SE9016
includes an internal P-channel power MOSFET and
thermal regulation circuitry. No blocking diode or
external current sense resistor is required; thus, the
basic charger circuit requires only two external
components. Furthermore, the SE9016 is capable
of operating from a USB power source.
current are calculated using the following equations:
R
PROG
=
1100
V
1100
V
,
I
CHG
=
,
I
CHG
R
PROG
The charge current out of the BAT pin can be
determined at any time by monitoring the PROG pin
voltage using the following equation:
I
BAT
=
V
PROG
•
1100
R
PROG
Charge Termination
A charge cycle is terminated when the charge current
falls to 1/10th the programmed value after the final
float voltage is reached. This condition is detected by
using an internal, filtered comparator to monitor the
PROG pin. When the PROG pin voltage falls below
100mV for longer than t
TERM
(typically 1ms), charging
is terminated. The charge current is latched off and
the SE9016 enters standby mode, where the input
supply
current
drops
to
200mA.
(Note:
C/10
termination is disabled in trickle charging and thermal
limiting modes).
When charging, transient loads on the BAT pin can
cause the PROG pin to fall below 100mV for short
periods of time before the DC charge current has
dropped to 1/10th the programmed value. The 1ms
filter time (t
TERM
) on the termination comparator
ensures that transient loads of this nature do not
result in premature charge cycle termination. Once
the average charge current drops below 1/10th the
programmed value, the SE9016 terminates the
charge cycle and ceases to provide any current
through the BAT pin. In this state, all loads on the
BAT pin must be supplied by the battery.
The SE9016 constantly monitors the BAT pin voltage
in standby mode. If this voltage drops below the
4.05V recharge threshold (V
RECHRG
), another charge
cycle begins and current is once again
supplied to the
Normal Charge Cycle
A charge cycle begins when the voltage at the VCC
pin rises above the UVLO threshold level and a 1%
program resistor is connected from the PROG pin to
ground or when a battery is connected to the
charger output. If the BAT pin is less than 2.8V, the
charger enters trickle charge mode. In this mode,
the SE9016 supplies approximately 1/10 the
programmed charge current to bring the battery
voltage up to a safe level for full current charging.
When the BAT pin voltage rises above 2.8V, the
charger enters constant-current mode, where the
programmed charge current is supplied to the
battery. When the BAT pin approaches the final
float
voltage
(4.2V),
the
SE9016
enters
constant-voltage mode and the charge current
begins to decrease. When the charge current drops
to 1/10 of the programmed value, the charge cycle
ends.
Programming Charge Current
The charge current is programmed using a single
resistor from the PROG pin to ground. The battery
charge current is 1100 times the current out of the
PROG pin. The program resistor and the charge
Revision 6/7/2007
Preliminary and all contents are subject to change without prior notice
© Seaward Electronics Inc., 2007. • www.seawardinc.com • Page 5
SEAWARD [ Seaward Electronics Inc. ]
