Datasheet

Operation description STNS01
16/29 DocID024654 Rev 2
8 Operation description
The STNS01 is a power management IC integrating a battery charger with power path
function, battery protection circuitry, battery temperature monitoring and a 3.1 V 100 mA
LDO.
When a valid input voltage (V
IN
) is present on the IN pin, after security checks are
performed, the battery charger starts charging the battery using a constant-current/constant-
voltage charging algorithm.
The input voltage (V
IN
) is considered to be valid if it is higher than V
UVLO
and lower than
V
INOVP
.
The power path architecture allows charging the battery and supplying the system at the
same time. When the input voltage is not valid, the LDO (and every external IC connected to
SYS) is supplied by the battery through a low resistance path.
The device also provides protection to the battery against the following fault conditions:
– overcharge
– overdischarge
– charge overcurrent
– discharge overcurrent
If a fault condition is detected while the input voltage is valid (V
UVLO
< V
IN
< V
INOVP
), the
CHG pin starts toggling to inform the control logic that an error occurred.
The device can also be put in reduced battery drain mode (shutdown, I
BAT
< 500 nA) to
maximize battery life during end-product shipping and shelf time.
8.1 Power-on
When the device is in shutdown mode, the pins LDO and SYS are not supplied. In order to
turn the device on a valid input voltage must be connected (V
IN
).
The CEN pin must be floating or tied high during power-on for proper operation.
8.2 Battery charger
The STNS01's battery charger is designed to charge single cell Li-Ion batteries up to 4.2 V
using a CC-CV charging algorithm (see Figure 6). When a valid input voltage is detected,
the STNS01 starts the charge cycle and the CHG pin switches from high impedance to low
level.
The charging process starts if the battery voltage is higher than V
BATMIN
. If the battery is
deeply discharged (the battery voltage is lower than V
PRE
and higher than V
BATMIN
) the
charger enters the pre-charge phase and starts charging in constant-current mode using a
low current (I
PRE
= 20% I
FAST
). If the battery voltage does not reach the V
PRE
threshold
within t
PRE
, the charging process is stopped and a fault is signaled.
When the battery voltage reaches the V
PRE
threshold, the constant-current fast-charge
phase is entered and the charging current is increased to I
FAST
. The value of I
FAST
can be
programmed from 15 mA to 200 mA using an external resistor as described in the I
SET
pin
description (Section 7).