M41ST95WMH6TR STMICROELECTRONICS [STMicroelectronics], M41ST95WMH6TR Datasheet - Page 22

• Manufacturer Part Number: M41ST95WMH6TR
• Description: 5.0 or 3.0V, 512 bit (64 bit X 8) Serial RTC (SPI) SRAM and NVRAM Supervisor
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M41ST95Y*, M41ST95W
Power-fail INPUT/OUTPUT
The Power-Fail Input (PFI) is compared to an in-
ternal reference voltage (1.25V). If PFI is less than
the power-fail threshold (V
Output (PFO) will go low. This function is intended
for use as an under-voltage detector to signal a
failing power supply. Typically PFI is connected
through an external voltage divider (see Figure 17)
to either the unregulated DC input (if it is available)
or the regulated output of the V
voltage divider can be set up such that the voltage
at PFI falls below V
the regulated V
microprocessor drops below the minimum operat-
ing voltage.
Figure 17. Power-Fail Comparator Hookup
Note: 1. Available only in 28-pin, 300mil SOIC (MX) package.
22/35
Unregulated
Voltage
CC
input to the M41ST95Y/W or the
PFI
R1
R2
several milliseconds before
PFI
V
Pushbutton
Regulator
IN
), the Power-Fail
CC
Reset
regulator. The
V
CC
During battery back-up, the power-fail comparator
turns off and PFO goes (or remains) low. This oc-
curs after V
er returns, PFO is forced high, irrespective of V
for the write protect time (t
from V
the end of this time, the power-fail comparator is
enabled and PFO follows PFI. If the comparator is
unused, PFI should be connected to V
left unconnected.
V
EX
SDI
SCL
WDI
RSTIN1
RSTIN2
PFI
V
V
E
CC
BAT
SS
M41ST95Y/W
PFD
IRQ/FT/OUT
(max) until the inputs are recognized. At
CC
V
E
SQW
CON
OUT
SDO
PFO
RST
drops below V
To RST
To LED Display
To NMI
To INT
F
32k
REC
E
V
CC
PFD
(1)
V
), which is the time
CC
(min). When pow-
AI06373
SS
and PFO
PFI