Datasheet

LTC1644
8
1644f
TYPICAL PERFOR A CE CHARACTERISTICS
UW
3V
OUT
Discharge Resistance
vs Temperature
12V
OUT
Discharge Resistance
vs Temperature
V
EEOUT
Discharge Resistance
vs Temperature
V
OL
vs Temperature
Precharge Reference Voltage
vs Temperature
TEMPERATURE (°C)
–50
0
3V
OUT
DISCHARGE RESISTANCE (Ω)
10
30
40
50
50
90
1644 G37
20
0
–25
75
25 100
60
70
8O
TEMPERATURE (°C)
–50
0
V
EEOUT
DISCHARGE RESISTANCE (Ω)
100
300
400
500
50
900
1644 G39
200
0
–25
75
25 100
600
700
80O
TEMPERATURE (°C)
–50
700
600
500
400
300
200
100
0
25 75
1644 G38
–25 0
50 100
12V
OUT
DISCHARGE RESISTANCE (Ω)
TEMPERATURE (°C)
–50
0
V
OL
(V)
0.05
0.10
0.15
0.20
0.30
–25
02550
1644 G40
75 100
0.25
I = 3mA
FAULT
RESETOUT
PWRGD
TEMPERATURE (°C)
–50
1.002
PRECHARGE REFERENCE VOLTAGE (V)
1.003
1.004
1.005
–25
02550
1644 G41
75 100
V
5VIN
= 5V
12V
IN
(Pin 1): 12V Supply Input. A 0.5Ω switch is con-
nected between 12V
IN
and 12V
OUT
with a foldback current
limit. An undervoltage lockout circuit prevents the switches
from turning on while the 12V
IN
pin voltage is less than
8.3V. 12V
IN
also provides power to the LTC1644’s internal
circuitry.
V
EEIN
(Pin 2): –12V Supply Input. A 1Ω switch is con-
nected between V
EEIN
and V
EEOUT
with a foldback current
limit. If no V
EE
supply input is available, tie the V
EEIN
pin to
the GND pin in order to disable the V
EEOUT
power good
function.
PI FU CTIO S
UUU
5V
OUT
(Pin 3): 5V Output Sense. The PWRGD pin will not
pull low until the 5V
OUT
pin voltage exceeds 4.62V. If no 5V
input supply is available, tie the 5V
OUT
pin to the 3V
OUT
pin
in order to disable the 5V
OUT
power good function.
TIMER (Pin 4): Current Fault Inhibit Timing Input. Connect
a capacitor from TIMER to GND. With the chip turned off
(OFF/ON = HIGH), the TIMER pin is internally held at GND.
When the chip is turned on, a 21µA pull-up current source
is connected to TIMER. Current limit faults will be ignored
until the voltage at the TIMER pin rises to within 1V of
12V
IN
.