BQ2902 Datasheet, PDF (2/12 Pages) Texas Instruments – Rechargeable Alkaline Charge/Discharge Controller IC

bq2902
Pin Descriptions
DC
CHG
VSEL
DC supply input
This input is used to charge the rechargeable
alkaline cells and power the bq2902 during
charge. To charge the batteries, this input
should be connected to a current-source lim-
ited to 300 mA. If the DC input current is
greater than 300mA, the power dissipation
limits of the package may be exceeded. The
DC input should also be capable of supplying
a minimum of 3.3V and should not exceed
5.5V.
Charge status
This open-drain output is used to signify the
battery charging status and is valid only
when DC is applied.
End-of-discharge select input
This three-level input selects the desired
end-of-discharge cut-off voltage for the
bq2902. VSEL = BAT1P selects an EDV of
1.10V. VSEL floating selects EDV = 1.0V. VSEL
= VSS selects EDV = 0.9.V
BAT1P
BAT1N
VSS
LRTN
Battery 1 positive input
This input connects to the positive terminal
of the battery designated BAT1 (see Figure
3). This pin also provides power to the bq2902
when DC is not present.
Battery 1 negative input
This input connects to the negative terminal
of the battery designated BAT1 (see Figure 3).
Battery 2 negative input/IC ground
This input connects to the negative terminal
of the battery designated BAT2 (see Figure 3).
Load return
This open-drain pull-down output is typi-
cally used as a low-side switch. High-side
load switching is also possible with the addi-
tion of an external P-FET.
Functional Description
Figure 1 is a block diagram outlining the major compo-
nents of the bq2902.
Figure 2 illustrates the charge control and display
status during a bq2902 cycle. Table 1 outlines the vari-
4
DC
VSEL ¹
CHG ⁸
3 _BAT1P
Control/Status
Logic
2 _BAT1N
5
LRTN
6 _VSS
7
VSS
BD290201.eps
Figure 1. Functional Block Diagram
2