7
LTC3729
sn3729 3729fas
RUN/SS (Pin 1/Pin 28):
Combination of Soft-Start, Run
Control Input and Short-Circuit Detection Timer. A capaci-
tor to ground at this pin sets the ramp time to full current
output. Forcing this pin below 0.8V causes the IC to shut
down all internal circuitry. All functions are disabled in
shutdown.
SENSE1
+
, SENSE2
+
(Pins 2,14/Pins 30, 12):
The (+)
Input to the Differential Current Comparators. The I
TH
pin
voltage and built-in offsets between SENSE
–
and SENSE
+
pins in conjunction with R
SENSE
set the current trip thresh-
old.
SENSE1
–
, SENSE2
–
(Pins 3, 13/Pins 31, 11):
The (–)
Input to the Differential Current Comparators.
EAIN (Pin 4/Pin 1):
Input to the Error Amplifier that
compares the feedback voltage to the internal 0.8V refer-
ence voltage. This pin is normally connected to a resistive
divider from the output of the differential amplifier
(DIFFOUT).
PI FU CTIO S
U
U
U
Current Sense Pin Input Current
vs Temperature
EXTV
CC
Switch Resistance
vs Temperature
Oscillator Frequency
vs Temperature
Undervoltage Lockout
vs Temperature
Shutdown Latch Thresholds
vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
TEMPERATURE (
°
C)
–50
–25
0
SHUTDOWN LATCH THRESHOLDS (V) 0.5
1.5
2.0
2.5
75
100
50
4.5
3729
G27
1.0
0
25
125
3.0
3.5
4.0
LATCH ARMING
LATCHOFF
THRESHOLD
TEMPERATURE (
°
C)
–50
UNDERVOLTAGE LOCKOUT (V)
3.40
3.45
3.50
25
75
3729
G26
3.35
3.30
–25
0
50
100
125
3.25
3.20
TEMPERATURE (
°
C)
– 50
400
500
700
25
75
3729
G25
300
200
– 25
0
50
100
125
100
0
600
FREQUENCY (kHz)
V
PLLFLTR
= 2.4V
V
PLLFLTR
= 1.2V
V
PLLFLTR
= 0V
TEMPERATURE (
°
C)
–50
–25
0
EXTV
CC
SWITCH RESISTANCE (
Ω
)
4
10
0
50
75
3729
G24
2
8
6
25
100
125
TEMPERATURE (
°
C)
–50
–25
25
CURRENT SENSE INPUT CURRENT (
µ
A)
29
35
0
50
75
3729
G23
27
33
31
25
100
125
V
OUT
= 5V
G Package/UH Package
