m41st85w STMicroelectronics, m41st85w Datasheet - Page 26

• Manufacturer Part Number: m41st85w
• Description: 3.0/3.3v I 2c Combination Serial Rtc, Nvram Supervisor And Microprocessor Supervisor
• Manufacturer: STMicroelectronics

3.8
Figure 17. RSTIN1 & RSTIN2 timing waveforms
Note:
Table 5.
1. Valid for Ambient Operating Temperature: T
2. Pulse width less than 50ns will result in no RESET (for noise immunity).
3. Pulse width less than 20ms will result in no RESET (for noise immunity).
4. Programmable (see
3.9
26/41
t
t
t
t
Symbol
R1HRH
R2HRH
RLRH1
RLRH2
RSTIN1
RSTIN2
RST
(2)
(3)
(4)
(4)
Reset inputs (RSTIN1 & RSTIN2)
The M41ST85W provides two independent inputs which can generate an output reset. The
duration and function of these resets is identical to a reset generated by a power cycle.
Table 5
than t
internally pulled up to V
With pull-up resistor
Reset AC characteristics
Power-fail input/output
The Power-Fail Input (PFI) is compared to an internal reference voltage (1.25V). If PFI is
less than the power-fail threshold (V
function is intended for use as an undervoltage detector to signal a failing power supply.
Typically PFI is connected through an external voltage divider (see
either the unregulated DC input (if it is available) or the regulated output of the V
regulator. The voltage divider can be set up such that the voltage at PFI falls below V
several milliseconds before the regulated V
microprocessor drops below the minimum operating voltage.
During battery back-up, the power-fail comparator turns off and PFO goes (or remains) low.
This occurs after V
irrespective of V
inputs are recognized. At the end of this time, the power-fail comparator is enabled and PFO
(1)
RLRH1
Table 6 on page
RSTIN1 Low to RSTIN1 High
RSTIN2 Low to RSTIN2 High
RSTIN1 High to RST High
RSTIN2 High to RST High
and
Figure 17
and t
PFI
RLRH2
CC
for the write protect time (t
Parameter
28).
drops below V
illustrate the AC reset characteristics of this function. Pulses shorter
tRLRH1
CC
will not generate a reset condition. RSTIN1 and RSTIN2 are each
A
tR1HRH
through a 100k
= –40 to 85°C; V
(1)
PFI
PFD
tRLRH2
), the Power-Fail Output (PFO) will go low. This
(min). When power returns, PFO is forced high,
CC
= 2.7 to 3.6V (except where noted).
CC
resistor.
rec
input to the M41ST85W or the
), which is the time from V
Min
200
100
40
40
tR2HRH
Figure 5 on page
Max
200
200
PFD
AI03665
(max) until the
CC
Unit
ms
ms
ms
ns
11) to
PFI