LTC690/LTC691
LTC694/LTC695
5
690ff
For more information www.linear.com/690
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 voltage values are with respect to GND.
Note 3: For military temperature range parts or for the LTC692 and
LTC693, consult the factory.
Note 4: The output pins of BATT ON, LOWLINE, PFO, WDO, RESET and
RESET have weak internal pull-ups of typically 3µA. However, external
pull-up resistors may be used when higher speed is required.
PARAMETER CONDITIONS MIN TYP MAX UNITS
RESET, RESET, WDO, LOWLINE
Output Short-Circuit Current (Note 4)
Output Source Current 1 3 25 µA
Output Sink Current 25 mA
WDI Input Threshold Logic Low
Logic high
3.5
0.8 V
WDI Input Current WDI = V
OUT
WDI = 0V
l
l
–50
4
–8
50 µA
Power-Fail Detector
PFI Input Threshold V
CC
= 5V
l
1.25 1.3 1.35 V
PFI Input Threshold PSRR 0.3 mV/V
PFI Input Current ±0.01 ±25 nA
PFO Output Voltage (Note 4) I
SINK
= 3.2mA
I
SOURCE
= 1µA
3.5
0.4 V
PFO Short-Circuit Source Current (Note 4) PFI = HIGH, PFO = 0V 1 3 25 µA
PFI = LOW, PFO = V
OUT
25 mA
PFI Comparator Response Time (Falling) ∆V
IN
= –20mV, V
OD
= 15mV 2 µs
PFI Comparator Response Time (Rising) (Note 4) ∆V
IN
= 20mV, V
OD
= 15mV
with 10kΩ Pull-Up
40
8
µs
Chip Enable Gating
CE IN Threshold V
IL
V
IH
2
0.8 V
CE IN Pull-Up Current (Note 7) 3 µA
CE OUT Output Voltage I
SINK
= 3.2mA
I
SOURCE
= 3.0mA
I
SOURCE
= 1µA, V
CC
= 0V
V
OUT
– 1.50
V
OUT
– 0.05
0.4 V
CE Propagation Delay V
CC
= 5V, C
L
= 20pF
l
20
20
35
45
ns
CE OUT Output Short-Circuit Current Output Source Current
Output Sink Current
30
35
mA
Oscillator
OSC IN Input Current (Note 7) ±2 µA
OSC SEL Input Pull-Up Current (Note 7) 5 µA
OSC IN Frequency Range OSC SEL = 0V
l
0 250 kHz
OSC IN Frequency with External Capacitor OSC SEL = 0V, C
OSC
= 47pF 4 kHz
elecTrical characTerisTics
The l denotes specifications which apply over the operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
= full operating range, V
BATT
= 2.8V, unless otherwise noted.
Note 5: The LTC690 and LTC691 have minimum reset active time of 35ms
(50ms typically) while the LTC694 and LTC695 have longer minimum
reset active time of 140ms (200ms typically). The reset active time of
the LTC691 and LTC695 can be adjusted (see Table 2 in Applications
Information section).
Note 6: The external clock feeding into the circuit passes through the
oscillator before clocking the watchdog timer (See Block Diagram).
Variation in the timeout period is caused by phase errors which occur
when the oscillator divides the external clock by 64. The resulting variation
in the timeout period is 64 clocks plus one clock of jitter.
Note 7: The input pins of CE IN, OSC IN and OSC SEL have weak internal
pull-ups which pull to the supply when the input pins are floating.
