MAX807N Maxim Integrated Products, MAX807N Datasheet - Page 13

• Manufacturer Part Number: MAX807N
• Description: Full-Featured P Supervisory Circuit with 1.5eset Accuracy
• Manufacturer: Maxim Integrated Products

Table 1. Input and Output Status in Battery-Backup Mode
Figure 12. V
Battery backup preserves the contents of RAM in the
event of a brownout or power failure. With a backup
battery installed at BATT, the MAX807 automatically
switches RAM to backup power when V
conditions are required for switchover to battery-back-
up mode: 1) V
V
inputs and outputs during battery-backup mode.
CC
PIN
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
BATT
V
CC
must be below V
LOW LINE
CC
BATT ON
BATT OK
CE OUT
NAME
RESET
RESET
CE IN
CIRCUITRY
WDO
BATT
GND
CONTROL
OUT
PFO
V
WDI
MR
PFI
and BATT-to-OUT Switch
CC
CC
Full-Featured µP Supervisory Circuit with
must be below the reset threshold; 2)
______________________________________________________________________________________
BATT
The power-fail comparator remains active in battery-backup mode for V
The power-fail comparator remains active in battery-backup mode for V
Battery switchover comparator monitors V
WDI is ignored and goes high impedance.
Ground—0V reference for all signals.
MR is ignored.
Logic low.
Logic high; the open-circuit output voltage is equal to V
Logic low.
Logic high. The open-circuit output voltage is equal to V
Logic high. The open-circuit output voltage is equal to V
High impedance.
Logic high. The open-circuit output voltage is equal to V
Supply current is 1µA maximum for V
Logic high when V
OUT is connected to BATT through two internal PMOS switches in series.
P
Battery-Backup Mode
. Table 1 lists the status of
P
MAX807
P
BATT
CC
exceeds 2.285V. Valid for V
falls. Two
0.1 F
OUT
BATT
CC
≤ 2.8V.
The BATT input is similar to V
switch is much smaller. This input is designed to con-
duct up to 20mA to OUT during battery backup. The
on-resistance of the PMOS switch is approximately
13Ω. Figure 12 shows the two series pass elements
between the BATT input and OUT that facilitates UL
approval. V
tion without causing a reset.
The output supply (OUT) transfers power from V
BATT to the µP, RAM, and other external circuitry. At
the maximum source current of 250mA, V
cally be 260mV below V
a 0.1µF capacitor.
The battery on (BATT ON) output indicates the status of
the internal battery switchover comparator, which con-
trols the internal V
greater than V
effect), BATT ON typically sinks 3.2mA at 0.4V. In bat-
tery-backup mode, this output sources approximately
5mA. Use BATT ON to indicate battery switchover sta-
tus, or to supply gate or base drive for an external pass
transistor for higher current applications (see Typical
Operating Circuit ).
±1.5% Reset Accuracy
for active switchover.
FUNCTION
CC
≥ 4V. Below 4V, BATT OK is forced low.
CC
BATT
CC
BATT
BATT
.
.
.
.
BATT
can exceed V
CC
CC
(ignoring the small hysteresis
and BATT switches. For V
CC
≥ 4V. Below 4V, PFO is forced low.
CC
. Decouple this terminal with
≥ 4V.
CC
Output Supply Voltage
CC
Backup-Battery Input
BATT ON Output
during normal opera-
, except the PMOS
OUT
will typi-
CC
CC
13
or