Datasheet

LTC1235
4
1235fa
PARAMETER CONDITIONS MIN TYP MAX UNITS
RESET, RESET, WDO, LOW LINE
Output Short Circuit Current (Note 6)
Output Source Current
Output Sink Current
13
25
25 μA
mA
WDI Input Threshold Logic Low
Logic High 2.0
0.8 V
V
WDI Input Current WDI = V
OUT
WDI = 0V
l
l
–50
4
–8
50 μA
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 6) I
SINK
= 3.2mA
I
SOURCE
= 1A 3.5
0.4 V
V
PFO Short Circuit Source Current
(Note 6)
PFI = HIGH, PFO = 0V
PFI = LOW, PFO = V
OUT
13
30
25 μA
mA
PFI Comparator Response Time (falling) ΔV
IN
= –20mV, V
OD
= 15mV 2 μs
PFI Comparator Response Time (rising)
(Note 6)
ΔV
IN
= 20mV, V
OD
= 15mV
with 10kΩ Pullup
40
8
μs
μs
Chip Enable Gating
CE IN Threshold V
IL
V
IH
2.0
0.8 V
V
CE IN Pullup Current (Note 4) 3μA
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
V
V
CE Propagation Delay V
CC
= 5V, CL = 20pF
l
20
20
35
45
ns
ns
CE OUT Output Short Circuit Current Output Source Current
Output Sink Current
30
35
mA
mA
ELECTRICAL CHARACTERISTICS
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, consult the factory.
Note 4: The input pins of PB RST, BACKUP and CE IN, have weak internal
pullups which pull to the supply when the input pins are fl oating.
Note 5: The LTC1235 can be programmed either to provide or not to
provide battery backup power to the V
OUT
pin during power failure.
The power down condition of V
OUT
is selected by the logic level of the
BACKUP pin which is latched internally when V
CC
falls through the reset
voltage threshold. If the latched logic level of the BACKUP pin is high,
V
OUT
will be in Battery Backup Mode and will be switched to V
BATT
when
V
CC
falls below V
BATT
. If the latched logic level of the BACKUP pin is low,
V
OUT
will be in Battery Saving Mode when V
CC
falls below V
BATT
.
Note 6: The output pins of BATT ON, LOW LINE, PFO, WDO, RESET and
RESET have weak internal pullups of typically 3A. However, external
pullup resistors may be used when higher speed is required.
Note 7: The push-button reset input requires an active low signal.
Internally, this input signal is debounced and timed for a minimum of
40ms. When this condition is satisfi ed, the reset outputs go to the active
states. The reset outputs will remain in active states for a minimum of
140ms from the moment the push-button reset input is released from
logic low level.
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
CC
= Full Operating Range, V
BATT
= 2.8V, Backup = No Connection,
T
A
= 25°C, unless otherwise noted.