[ AP2200]
OPERATION DETAILS
1. Operation overview
When the output voltage is entered into V
IN
from the solar cell(s), the low voltage startup circuit
starts to step up the output voltage (V
OUT
). When V
OUT
reaches the voltage required for operation of
the step-up converter, the low voltage startup circuit stops and the step-up converter starts. After that,
the step-up converter increases V
OUT
to the target voltage (V
TGT
) and controls V
OUT
so that it will be
stabilized at V
TGT
. Also, when V
OUT
reaches V
TGT
, the step-up converter decreases the LC pin to a low
level. For the application where an external PMOS load switch is connected to the LC pin, when the
LC pin becomes a low level, the external switch is turned ON to start the power supply to the
equipment. However, if one of the conditions below is met, the external load switch is turned OFF to
stop the power supply:
The STBY pin is set to a high level:
The AP2200 has a standby function. When the STBY pin is set to a high level (V
IHSTB
) by
applying voltage, the external load switch is turned OFF to stop the power supply. The step-up
converter is still running even in a standby state. When the STBY pin is set to a low level
(V
ILSTB
) by applying voltage, the standby mode is released to start the power supply.
The VB pin voltage is less than or equal to V
BLOW
:
The AP2200 has a battery monitoring function. When the VB pin voltage deceases to V
BLOW
or
lower, a battery is assumed to be removed and the external load switch is turned OFF to stop
the power supply. When the VB pin voltage increases to V
BLOW
or higher, a battery is assumed
to be reinserted and the external load switch in turned ON to start the power supply.
To disable this function, connect the VB pin to the VOUT pin.
The VOUT pin voltage is less than or equal to V
OL
:
When the VOUT pin voltage decreases to V
OL
and lower, the external load switch is turned OFF
to stop the power supply. The step-up converter is still running. When V
OUT
reaches V
TGT
again,
the power supply is restarted.
When sampling the open circuit voltage (V
OC
) of the solar cell(s) per the cycle t
SH
,
The AP2200 turns OFF the external load switch as well as pausing the voltage step-up
operation. When the sampling of the open circuit voltage comes to an end, the voltage step-up
operation resumes. Unless V
OUT
reaches V
TGT
again, the external load switch is not turned ON.
This prevents back flow from the battery to V
OUT
to minimize the battery consumption when the
power supply from the solar cell(s) decreases, and the step-up converter cannot increase the
voltage sufficiently.
MS1462-E-00
6
AKM [ ASAHI KASEI MICROSYSTEMS ]
