Datasheet

LTC1235
3
1235fa
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Battery Backup Switching
Operating Voltage Range
V
CC
V
BATT
4.75
2.00
5.50
4.25
V
V
V
OUT
Output Voltage I
OUT
= 1mA
I
OUT
= 50mA
l
V
CC
– 0.05
V
CC
– 0.1
V
CC
– 0.5
V
CC
– 0.005
V
CC
– 0.005
V
CC
– 0.25
V
V
V
BACKUP Input Threshold V
CC
> Reset Voltage Threshold
Logic Low
Logic High 2.0
0.8 V
V
BACKUP Pullup Current (Note 4) 3μA
V
OUT
in Battery Backup Mode (Note 5) I
OUT
= 250μA, V
CC
< V
BATT
V
BATT
– 0.1 V
BATT
– 0.02 V
V
OUT
in Battery Saving Mode (Note 5) V
CC
< V
BATT
1MΩ Pulldown on V
OUT
0V
V
V
CC
Supply Current (excluding I
OUT
)I
OUT
≤ 50mA
l
0.6
0.6
1.5
2.5
mA
mA
Battery Supply Current in Battery Backup Mode
and Battery Saving Mode (Note 5)
V
CC
= 0V, V
BATT
= 2.8V
l
0.04
0.04
1
5
μA
μA
Battery Standby Current
(+ = Discharge, – = Charge)
5.5 > V
CC
> V
BATT
+ 0.2V
l
–0.1
–1.0
+0.02
+0.10
μA
μA
Battery Switchover Threshold
V
CC
– V
BATT
Power-Up
Power-Down
70
50
mV
mV
Battery Switchover Hysteresis 20 mV
BATT ON Output Voltage (Note 6) I
SINK
= 3.2mA 0.4 V
BATT ON Output Short Circuit Current (Note 6) BATT ON = V
OUT
Sink Current
BATT ON = 0V Source Current 0.5
35
125
mA
μA
Push-Button Reset
PB RST Input Threshold Logic Low
Logic High 2.0
0.8 V
V
PB RST Input Low Time (Notes 4, 7)
l
40 ms
Reset and Watchdog Timer
Reset Voltage Threshold
l
4.5 4.65 4.75 V
Reset Threshold Hysteresis 40 mV
Reset Active Time V
CC
= 5V
l
60
140
200
200
240
280
ms
ms
Watchdog Time-out Period V
CC
= 5V
l
1.2
1.0
1.6
1.6
2.00
2.25
sec
sec
Reset Active Time PSRR 1ms/V
Watchdog Time-out Period PSRR 8ms/V
Minimum WDI Input Pulse Width V
IL
= 0.4V, V
IH
= 3.5V
l
200 ns
RESET Output Voltage At V
CC
= 1V I
SINK
= 10μA, V
CC
= 1V 4 200 mV
RESET and LOW LINE Output Voltage
(Note 6)
I
SINK
= 1.6mA, V
CC
= 4.25V
I
SOURCE
= 1μA, V
CC
= 5V 3.5
0.4 V
V
RESET and WDO Output Voltage
(Note 6)
I
SINK
= 1.6mA, V
CC
= 5V
I
SOURCE
= 1μA, V
CC
= 4.25V 3.5
0.4 V
V
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.