Datasheet

LTC2917/LTC2918
5
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SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Reset Output (RST)
t
RST(INT)
Internal Reset Timeout Period V
RT
= V
CC
●
150 200 260 ms
t
RST(EXT)
Adjustable Reset Timeout Period C
RT
= 2.2nF
●
16 20 25 ms
t
UV
VM Undervoltage Detect to RST
Asserted
VM Less Than Reset Threshold
V
MTX
by More Than 5%
●
10 80 150 μs
V
OL
Output Voltage Low RST V
CC
= 3.3V, I
RST
= 2.5mA
V
CC
= 1V, I
RST
= 100μA
V
CC
= 0.8V, I
RST
= 15μA
●
●
●
0.15
0.15
0.05
0.4
0.3
0.2
V
V
V
I
OH(RST)
RST Output Voltage High Leakage RST = V
CC
●
±1 μA
Watchdog Timer Control (WT)
I
WT(UP)
WT Pull-Up Current V
WT
= 0.25V
●
–2 –3 –4 μA
I
WT(DOWN)
WT Pull-Down Current V
WT
= 1.1V
●
234μA
V
WT(INT, LH)
WT Internal Timer Threshold V
WT
Rising, Referenced to V
CC
●
–100 –160 –300 mV
I
WT(INT)
Internal WT V
CC
Detect Current V
WT
= V
CC
●
18μA
I
WT(DIS)
Watchdog Disable Hold Current V
WT
= 0V –3.5 μA
Watchdog Input (WDI)
t
WDU(INT)
Internal Watchdog Upper Boundary V
WT
= V
CC
●
1.3 1.6 2 s
t
WDL(INT)
Internal Watchdog Lower Boundary
(Note 5)
B Versions, V
WT
= V
CC
●
37.5 50 62.5 ms
t
WDU(EXT)
External Watchdog Upper Boundary C
WT
= 2.2nF
●
130 160 200 ms
t
WDL(EXT)
External Watchdog Lower Boundary
(Note 5)
B Versions, C
WT
= 2.2nF
●
t
WDU(EXT)
/32 ms
V
IL(WDI)
Input Low Voltage
●
0.4 V
V
IH(WDI)
Input High Voltage
●
1.1 V
t
PW(WDI)
Input Pulsewidth
●
400 ns
WDI Leakage Current
●
±1 μA
Manual Reset Input (LTC2918)
V
IL(MR)
Input Low Voltage
●
0.2 • V
CC
V
V
IH(MR)
Input High Voltage
●
0.8 • V
CC
V
R
PU
Pull-Up Resistance
●
50 100 150
kΩ
t
PW(MR)
Pulsewidth
●
250 ns
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 3: V
CC
maximum pin voltage is limited by input current. Since the
V
CC
pin has an internal 6.2V shunt regulator, a low impedance supply
which exceeds 5.7V may exceed the rated terminal current. Operation
ELECTRICAL CHARACTERISTICS
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
CC
= 2.5V, unless otherwise noted. (Note 2)
from higher voltage supplies requires a series dropping resistor. See
Applications Information.
Note 4: Input impedance is dependent on the confi guration of the SEL
pins.
Note 5: In the LTC2917-B/LTC2918-B, edges must occur on WDI with a
period between the lower and upper boundary or RST is invoked. For the
LTC2917-A/LTC2918-A, the edges must simply occur before the upper
boundary. See Applications Information.