BQ2203A Datasheet, PDF (2/12 Pages) Texas Instruments – NV Controller With Battery Monitor

bq2203A
As the supply continues to fall past VPFD, an internal
switching device forces VOUT to the external backup en-
ergy source. CECON1 and CECON2 are held high by the
VOUT energy source.
During power-up, VOUT is switched back to the 5V sup-
ply as VCC rises above the backup cell input voltage
sourcing VOUT. Outputs CECON1 and CECON2 are held
inactive for time tCER (120ms maximum) after the
power supply has reached VPFD, independent of the CE
input, to allow for processor stabilization.
During power-valid operation, the CE input is passed
through to one of the two CECON outputs with a propaga-
tion delay of less than 10ns. The CE input is output on
one of the two CECON output pins depending on the level
of bank select input A, as shown in the Truth Table.
Bank select input A is usually tied to a high-order ad-
dress pin so that a large nonvolatile memory can be de-
signed using lower-density memory devices. Nonvolatil-
ity and decoding are achieved by hardware hookup as
shown in Figure 1.
The reset output (RST) goes active within tPFD (150µs
maximum) after VPFD, and remains active for a mini-
mum of 40ms (120ms maximum) after power returns
valid. The RST output can be used as the power-on re-
set for a microprocessor. Access to the external RAM
may begin when RST returns inactive.
Energy Cell Inputs—BC_P, BC_S
Two backup energy source inputs are provided on the
bq2203A—a primary cell BC_P and a secondary cell BC_S.
The primary cell input is designed to accept any 3V pri-
mary battery (non-rechargeable), typically some type of
lithium chemistry. If a primary cell is not to be used, the
BCP pin should be tied to VSS. The secondary cell input
BCS is designed to accept constant-voltage current-
limited rechargeable cells.
During normal 5V power valid operation, 3.3V typical is out-
put on the BCS pin and is current-limited internally. Al-
though this charging method can be used with various 3V
secondary cells, it is specifically designed for a Panasonic VL
(vanadium-lithium) series of rechargeable cells.
5V
bq2203A
VCC VOUT
From Address
Decoder
3V Primary
Cell
BCF
BCL
A
CECON1
CE CECON2
BCP
THS
VSS
RST
BCS
VCC
CMOS
SRAM
CE
VCC
CMOS
SRAM
CE
To Microprocessor
3V Secondary
Cell
FG220301.eps
Figure 1. Hardware Hookup (5% Supply Operation)
Nov. 1994 B
2