BQ2058T Datasheet, PDF (4/18 Pages) Texas Instruments – Lithium Ion Pack Supervisor For 2-Cell Packs

bq2058T
Functional Description
Figure 1 is a block diagram outlining the major compo-
nents of the bq2058T. Figure 2 shows a low-side control
connection diagram. The following sections detail the
various functional aspects of the bq2058T.
Thresholds
The bq2058T monitors the lithium ion pack for the con-
ditions listed below. Shown with these conditions are
the respective thresholds used to determine if that con-
dition exists:
s Overvoltage (VOV)
s Undervoltage (VUV)
s Overcurrent (VOCH, VOCL)
s Charge Enable (VCE)
s Charge Detect (VCD)
The bq2058T samples a cell every 60ms (typical). Every
sample is a fully differential measurement of each cell.
During this sample period, the bq2058T compares the
measurements with these thresholds to determine if any
of the these conditions exist: V_OV, V_UV, and V_CE.
Overcurrent and charge detect are conditions that are
not sampled, but are continuously monitored.
Initialization
On initial power-up, such as connecting the battery pack
for the first time to the bq2058T, the bq2058T enters the
low-power sleep mode, disabling the DSG output. It is
recommended that a top to bottom cell connection
be made at pack assembly for proper initializa-
tion. A charging supply must be applied to the bq2058T
circuit to enable the pack. See Low-Power Sleep Mode
and Charge Detect sections.
POS
R2
CHG
DSG
CTL
VCC
VSS
UVD
CSL
OVD
BAT2N OCD
BAT2N VCC
BAT2N CSH
BAT1N BAT1P
bq2058T
C1
C2
C3
R1
NEG
C7
Q1
Q2
C6
BAT1
C4
BAT2
C5
FG2058T1.eps
Figure 2. 2-Cell Connection Diagram, Low-Side Control
4
July 1997