SC801
POWER MANAGEMENT
Applications Information (Cont.)
selection of an adjustable voltage see the section titled,
Configuring the Output Voltage to the Battery. Note, only
one of these jumpers JP2 or JP7 should be inserted at
any given time. Jumper JP8 should be left open and is
used only for testing SC801M operation. Connector J1
is used for connecting the evaluation board to a demon-
stration platform to exemplify the SC801 operation. Other
components on the eval board consist of Semtechs
SD12 and SD05 ESD clamp diodes which should be part
of any system requiring ESD protection. LEDs for status
information and TP3 which will allow the current through
the battery to be monitored. The input capacitor C1 is
chosen to be 10uF to decouple any inductance from a
laboratory supply when evaluation is taking place.
Using the SC801 With a Charge Controller IC
The SC801 can also be used with numerous charge con-
troller ICs on the market. In many instances the charge
controller will control the charging and termination of the
SC801. The best method of interfacing the SC801 with
such a device is to place the SC801 in LDO mode, and
monitor the current to the battery by an ADC that
samples the voltage on the IPRGM pin. Slow and fast
charge can be controlled by placing two resistors in se-
ries from IPRGM to GND and adding a transistor switch
across one of the resistors. This way the current can be
monitored for proper termination by the charge control-
ler. In LDO mode the STAT LED will not light. When charg-
ing the battery in LDO mode the charge profile will be the
same as in charge mode except there will be no precharge
or termination current function. Meanwhile, the maxi-
mum current the battery will see is set by the battery
equivalent circuit or the fast-charge current limit. The
battery will still charge in this mode, albeit a slightly dif-
ferent approach than placing the charger in the charge
mode.
Complete Charge Cycle
The complete charge cycle of the SC801 is shown on
page 15. The pre-charge current will be under control
until the precharge threshold of 2.8V is reached. At this
time the device enters the fast-charge mode and the
output voltage continues to increase as the constant
current is applied to the battery. Eventually constant volt-
age is reached and the current begins to decrease until
the termination current threshold is reached at which
time the SC801 will turn off. Many Lithium-Ion batteries
have a built in under-voltage detect circuit. This makes
the battery pack open circuited when the battery volt-
age falls below 3V typically. With these batteries the
SC801 will unlikely enter pre-charge operation because
the battery voltage will always be above 2.8V.
Evaluation Board
The evaluation board is shown on Page 10. The evalua-
tion board was designed to test the complete operation
of the SC801 and the SC801M. Note the minimum parts
requirement is shown within the dotted rectangle on the
schematic. The adaptor voltage of 5V is applied to TP1
and TP2 which supplies power to the SC801. The output
charger voltage or LDO output voltage is taken off of
TP4 and TP5. Jumper JP5 will set the device in LDO mode
when inserted or charge mode when left open. Jumper
JP6 will enable the device when inserted or disable the
device when left open. Note as long as power is applied
to VCC the CP LED will light, regardless of the EN pin
level. Jumper JP4 is used to measure the bias current of
the SC801 and should always be in place except when
measuring bias current. JP1 and JP3 set the charge limit
voltage to 4.2V or 4.1V respectively. Only one of these
jumpers JP1 or JP3 should be in place at any given time.
If you expect VCC to exceed 6V (testing breakdown of
the SC801) and you want to set the output voltage to
4.2V you should remove any jumper on JP1 and manu-
ally tie pin 2 of JP1 to the CP pin, because the absolute
maximum voltage on the VPRGM input pin is 6V. Jumper
JP7 when inserted will short the BSEN line to Vout for
charging Lithium-Ion batteries. Jumper JP2 should be in-
serted when an adjustable voltage is required, with the
addition of R1, R2 & C2. For more information about
2002 Semtech Corp.
8
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