LM3621 datasheet(4/14 Pages) NSC

4 / 14 page

Electrical Characteristics (Continued)

DD = 4.2V unless otherwise specified. Specifications with standard type face are for TA = 25˚C, and those with boldface type

apply over full operating temperature range.

Symbol

Parameter

Conditions

Min

Typ

Max

Units

LKG-0

Battery Load Current (Note 8)

DD = 0V

µA

LKG-MM

Battery Load Current (Note 9)

Monitor Mode

µA

BSD

Maximum Allowed Battery Self-

Discharge(Note 10)

SET = HI

110

150

SET = LO

220

260

300

CSR

Fast Charge Current Regulation

Adjustment Transfer Ratio (Notes

11, 12)

ISET = 0.5V

0.90

0.93

0.96

V/V

LED

LED1 & LED2 Driver Sink Current

LED1 = VLED2 = 1.5V

SUV

Start Up Voltage (Note 13)

3.4

UVR

Under Voltage Reset (Note 14)

2.2

PFD-MAX

Maximum PFD Output Drive

no DC load on PFD

DD−0.2

PFD-MIN

Minimum PFD Output Drive

no DC load on PFD

SS+0.1

Logic Input Low (Note 15)

0.5

Logic Input High (Note 15)

DD−0.5

DIG

Digital Input Leakage Current

(Note 15)

−1

µA

Note 1: Absolute Maximum Ratings indicates limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is in-

tended 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

Ω.

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

OUT: Voltage measured between VBAT+ and CSR.

CSR: Charging current sense voltage measured between

CSR and V

SS (Gnd).

BATTERY:

Battery terminal voltage measured between

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.

SET: External voltage applied to ISET pin, measured be-

tween I

SET and VSS, to override the default value of VCSR.

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