LTC1726_15 Datasheet, PDF (6/14 Pages) Linear Technology – Triple Supply Monitor and P Supervisor with Adjustable Reset and Watchdog Timer

LTC1726
Pin Functions
V_CC3 (Pin 1): 3.3V Sense Input. This pin also supplies
power to the part when the voltage on this pin is greater
than the voltage on V_CC25/V_CC5. Bypass this pin to ground
with a 0.1µF or larger ceramic capacitor.
V_CC5 (Pin 2): 5V Sense Input (LTC1726-5). This pin also
supplies power to the part when the voltage on this pin is
greater than the voltage on V_CC3. Bypass this pin to ground
with a 0.1µF or larger ceramic capacitor.
V_CC25 (Pin 2): 2.5V Sense Input (LTC1726-2.5). This pin
also supplies power to the part when the voltage on this
pin is greater than the voltage on V_CC3. Bypass this pin to
ground with a 0.1µF or larger ceramic capacitor.
V_CCA (Pin 3): 1V Sense, High Impedance Input. If unused
it can be tied to either V_CC3, V_CC5 or V_CC25.
GND (Pin 4): Ground.
WDI (Pin 5): Watchdog Input. A logic input whose rising
or falling edge must occur on this pin within the selected
watchdog time-out period or a reset pulse will occur.
The watchdog time-out period is set by the value of the
capacitor that is placed on the WT pin. The rising or falling
edge of this pin clears the voltage on the WT capacitor,
preventing a reset pulse from occurring. If the watchdog
timer is not cleared, a reset pulse will occur. The watchdog
timer is cleared during a reset and restarts when the reset
is deasserted. When disabling the watchdog function, this
pin should be connected to either V_CC3 or ground and WT
must be grounded.
RST (Pin 6): Reset Logic Output. Active low, open-drain
logic output with weak pull-up to V_CC3. Asserted when one
or more of the supplies are below trip thresholds. After all
supplies become valid, the reset remains asserted for the
period set by the capacitor on the RT pin. The watchdog
timer can also trigger the reset whenever the watchdog
time-out period is exceeded. This pin can be pulled up
greater than V_CC3 when interfacing to 5V logic.
WT (Pin 7): Watchdog Time-Out Input. Place a capacitor
between this pin and ground to adjust the watchdog time-
out period. To determine the watchdog time-out period:
t_WT = 21.8 • C_WT
with t_WT in µs and C_WT in pF. As an example, a 47nF
capacitor will generate a 1s watchdog time-out period.
The watchdog function can be disabled by connecting
this pin to ground.
RT (Pin 8): Reset Time-Out Input. Place a capacitor between
this pin and ground to adjust the reset time-out period.
To determine the reset time-out period:
t_RT = 3.30 • C_RT
with t_RT in µs and C_RT in pF. As an example, a 47nF capaci-
tor will generate a 155ms reset time-out period.
1726fd
6
For more information www.linear.com/LTC1726