ltc1726-5 Linear Technology Corporation, ltc1726-5 Datasheet - Page 9

• Manufacturer Part Number: ltc1726-5
• Description: Triple Supply Monitor And ?p Supervisor With Adjustable Reset And Watchdog Timer
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Selecting the Reset and Watchdog
Time-Out Capacitors
The reset time-out period is adjustable in order to accom-
modate a variety of µP applications. The reset time-out
period, t
between the RT pin and ground. The value of this capacitor
is determined as follows:
with C
capacitor should be a low leakage type. A ceramic capacitor
is recommended.
ADJUSTABLE SUPPLY
TYPICAL APPLICATIO S
OR DC/DC FEEDBACK
C
RT
RT
= t
Triple Supply Monitor (3.3V, 5V and Adjustable)
RT
in pF and t
DIVIDER
RT
, is adjusted by connecting a capacitor, C
/3.30
R1*
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
RT
U
3.3V
in µs (i.e., 1500pF ⇒ 4.95ms). The
5V
R2*
U
1
2
3
4
ADJUSTABLE
V
V
V
GND
CC3
CC5
CCA
LTC1726-5
SUPPLY
U
W
WDI
RST
WT
RT
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
THE WATCHDOG TIMER CAN BE DISABLED BY CONNECTING
THE WDI AND WT PINS TO GROUND. THE PART WILL ACT
STRICTLY AS A TRIPLE SUPPLY MONITOR WITH AN
ADJUSTABLE RESET TIME-OUT PERIOD
8
7
6
5
COMBINATION OF R1 AND R2 ≤ 66.5k
R1*
SYSTEM RESET
WDI
C
5V/2.5V
RT
Disabling the Watchdog Timer
U
R2*
3.3V
C
WT
1
2
3
4
1726 TA04
RT
LTC1726-5/2.5
V
V
V
V
GND
CC3
CC5
CC25
CCA
,
/
WDI
RST
The watchdog period is also adjustable so that the watch-
dog time-out period can be optimized for software execu-
tion. The watchdog time-out period, t
connecting a capacitor, C
ground. Once the optimum watchdog time-out period (t
is determined, the value of the capacitor is calculated as
follows:
with C
capacitor should be a low leakage type. A ceramic capacitor
is recommended.
WT
RT
C
WT
8
7
6
5
Dual Supply Monitor (3.3V and 5V, Defeat V
WT
C
SYSTEM
RESET
= t
1726 TA03
RT
in pF and t
WT
/21.8
3.3V
5V
WT
1
2
3
4
in µs (i.e., 1500pF ⇒ 32.7ms). The
V
V
V
GND
CC3
CC5
CCA
LTC1726-5
WT
, between the WT pin and
WDI
RST
WT
RT
8
7
6
5
SYSTEM RESET
WDI
WT
C
RT
, is adjusted by
LTC1726
CCA
C
WT
Input)
1726 TA05
1726fb
9
WT
)