
Electrical Characteristics (Continued)
V
DD = 4.2V unless otherwise specified. Specifications with standard type face are for TA = 25C, and those with boldface type
apply over full operating temperature range.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
I
LKG-MM
Monitor Mode
1
10
A
V
BSD
Maximum Allowed Battery Self-
V
SET = HI
70
110
150
mV
V
SET = LO
220
260
300
mV
G
CSR
Fast Charge Current Regulation
Adjustment Transfer Ratio (Notes
V
ISET = 0.5V
0.90
0.93
0.96
V/V
I
LED
LED1 & LED2 Driver Sink Current
V
LED1 =VLED2 = 1.5V
20
mA
V
SUV
3.4
V
UVR
2.2
V
PFD-MAX
Maximum PFD Output Drive
no DC load on PFD
V
DD0.2
V
PFD-MIN
Minimum PFD Output Drive
no DC load on PFD
V
SS+0.1
V
IL
0.5
V
IH
V
DD0.5
V
I
DIG
Digital Input Leakage Current
1
A
Note 1: Absolute Maximum Ratings indicates limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is
intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see
the Electrical Characteristics.
Note 2: ESD rating is based on the human body model, 100 pF discharged through 1.5 k
.
Note 3: LM3621 requires a minimum VDD of 3.4V to start-up. After start-up, the operating range is 3.0V to 5.5V.
Note 4: VOUT is measured between VBAT+ and CSR.
Note 5: VCSR is measured between CSR and VSS (across the current sense resistor).
Note 6: VBAT-Det is measured between VBAT+ and VBAT.
Note 7: VCSR-Det is measured between CSR and VSS (across the current sense resistor).
Note 8: This is the current drawn from the battery by the LM3621 when VDD =0V.
Note 9: This is the current drawn from the battery by the LM3621 when the charger is in Monitor Mode.
Note 10: This is the maximum battery voltage droop that is allowed before the charger initiates a fast charge mode to refresh the battery to its full charge capacity.
Note 11: The current regulation and detection levels can be set by applying a dc voltage adjusting between 0.1V to 1V to the ISET pin without changing the value
of the current sense resistor. To ensure proper operation, if the default current regulation and detection values are desired, then a capacitor of at least 100 pF should
be connected from ISET to VSS (GND).
Note 12: Transfer ratio of VCSR/VISET to adjust the fast charge current regulation level. See application section.
Note 13: Minimum VDD supply voltage required at start-up.
Note 14: The LM3621 goes to a shutdown or reset state during “brown out” (i.e., when VDD < VUVR)
Note 15: Digital inputs are Enable, Boost, Chgint and VSET. To ensure proper operation, never allow any unused input pin to be left open.
Note 16: No external voltage applied to Iset pin; a 100 pF capacitor is connected across Iset and VSS.
Definition of Terms
V
OUT: Voltage measured between VBAT+ and CSR.
V
CSR: Charging current sense voltage measured between
CSR and V
SS (Gnd).
V
BATTERY:
Battery terminal voltage measured between
V
BAT+ and VBAT.
ESR: The equivalent series resistance of a battery. The ESR
is the purely resistive component of a battery’s impedance.
Its value is usually determined by the battery construction.
RFV: The RFV (resistance free voltage, often called the float
voltage) is the open circuit terminal voltage of a battery
which is free from the ESR voltage drop error.
VI
SET: External voltage applied to ISET pin, measured be-
tween I
SET and VSS, to override the default value of VCSR.
LM3621
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