LT4254
6
4254fb
OPEN Output Voltage vs I
LOAD
OPEN Pin Threshold Voltage
vs Temperature PWRGD Output Voltage vs I
LOAD
TYPICAL PERFOR A CE CHARACTERISTICS
UW
OV Threshold Voltage (High-to-
Low) vs Temperature OV Hysteresis vs Temperature
PI FU CTIO S
UUU
V
CC
: Input Supply Voltage. The positive supply input
ranges from 10.8V to 36V for normal operation. I
CC
is
typically 1.9mA. An internal circuit disables the LT4254 for
inputs less than 9.8V (typ).
GND: Device Ground. This pin must be tied to a ground
plane for best performance.
FB: Power Good Comparator Input. FB monitors the
output voltage through an external resistive divider. When
the voltage on the FB pin is lower than the high-to-low
threshold of 4V, the PWRGD pin is pulled low and released
when the FB pin is pulled above the 4.45V low-to-high
threshold.
The FB pin also affects foldback current limit (see Figure 7
and related discussion). To disable PWRGD monitoring,
connect FB to the output voltage and float the PWRGD pin.
TIMER: Timing Input. An external timing capacitor from
TIMER to GND programs the maximum time the part is
allowed to remain in current limit. When the part goes into
current limit, a 120µA pull-up current starts to charge the
timing capacitor. When the voltage on the TIMER pin
TEMPERATURE (°C)
–50
3.50
OV THRESHOLD VOLTAGE (HIGH-TO-LOW) (V)
3.55
3.60
3.65
3.70
–25 0 25 50
4254 G22
75 100 125
TEMPERATURE (°C)
–50
OV HYSTERESIS (mV)
400
450
500
25 75
4254 G23
350
300
–25 0
50 100 125
250
200
I
LOAD
(mA)
0
0
OPEN V
OL
(V)
2
4
6
8
10
2
468
4254 G24
10 12
T
A
= 25°C
TEMPERATURE (°C)
–50
3.0
OPEN THRESHOLD VOLTAGE (mV)
3.5
4.0
4.5
5.0
–25 0 25 50
4254 G25
75 100 125
I
LOAD
(mA)
0
0
PWRGD V
OL
(V)
1
2
3
4
6
2
468
4254 G26
10 12
5
T
A
= 25°C
