LM3621M-3.0 National Semiconductor, LM3621M-3.0 Datasheet - Page 12

• Manufacturer Part Number: LM3621M-3.0
• Description: Single Cell Lithium-Ion Battery Charger Controller
• Manufacturer: National Semiconductor

www.national.com
Application Information
Fault Protection
LM3621 provides redundant fault protection for a Li-Ion bat-
tery pack. If the charger’s control loop is accidentally
opened, the regulation voltage will begin to increase beyond
the level that are safe for the battery. In order to protect the
battery from a fault condition, PFD goes low to turn off the
series pass FET whenever the voltage across the battery ex-
ceeds the over voltage detection threshold (V
whenever V
both of the LED drivers to pulse at 0.8 Hz. Enable must go
low to cause the LM3621 to transition from the Fault State to
Standby mode.
Low Current Drain of Battery
If power is inadvertently removed from the battery charger,
the voltage at the V
as the V
of the LM3621 from the V
(typical) of leakage current will be drawn from the battery.
SS
pin. An internal switch will disconnect the circuitry
CSR
exceeds 1V. A fault condition also causes
DD
pin will collapse to the same potential
BAT
+ pin so that no more than 1µA
FIGURE 6. Adjusting V
(Continued)
BAT
FIGURE 5. Battery Refresh
-Det) or
CSR
12
by applying V
Adjustable Charge Current
The current sense resistor (Rcs) converts the charging cur-
rent to a voltage level, V
source (V
Fast Charge current regulation. Simultaneously the regula-
tion level for Boost mode, Hi-Z Charge mode, End-of-Charge
threshold and over current detect threshold will also be ad-
justed accordingly. The voltage at I
the range of 1V
V
Fast Charge Mode, V
Hi-Z Mode, V
Boost Mode, V
Over Current Threshold, V
End-Of-Charge, V
CSR
to V
DS100107-16
EXT
ISET
EXT
) to the I
CSR
to I
are:
CSR
= 0.083·V
SET
CSR
= 0.48·V
V
SET
ISET
CSR
pin
DS100107-5
= 0.07·V
pin will adjust the value of V
CSR
= 0.933·V
CSR
ISET
ISET
0.1V. The transfer functions of
. Applying an external voltage
= 0.36·V
ISET
+0.65
SET
ISET
pin should be within
ISET
+0.79
CSR
for