Datasheet

LT3844
5
3844fb
V
SENSE (CM)
(V)
0
I
(SENSE
+
+ SENSE
–
)
(μA)
400
300
200
100
0
–100
–200
0.5
1.0 1.5 2.0
3844 G10
2.5 4.53.5 5.04.03.0
TEMPERATURE (°C)
–50 25 75
3844 G12
–25 0
50 100 125
TEMPERATURE (°C)
–50 25 75
–25 0
50 100 125
TEMPERATURE (°C)
–50 25 75
–25 0
50 100 125
1.234
1.233
1.232
1.231
1.230
1.229
1.228
1.227
ERROR AMP REFERENCE (V)
3844 G14 3844 G15
4.54
4.52
4.50
4.48
4.46
4.44
4.42
4.40
V
IN
UVLO THRESHOLD, RISING (V)
V
IN
UVLO THRESHOLD, FALLING (V)
3.86
3.84
3.82
3.80
3.78
3.76
T
A
= 25°C
TEMPERATURE (°C)
–50
CURRENT SENSE THRESHOLD (mV)
102
104
106
25 75
3844 G16
100
98
–25 0
50 100 125
96
94
TEMPERATURE (°C)
–50
290
OPERATING FREQUENCY (kHz)
292
296
298
300
50
308
3844 G17
294
0
–25
75 100
25 125
302
304
306
TYPICAL PERFORMANCE CHARACTERISTICS
I
(SENSE
+
+ SENSE
–
)
vs
V
SENSE(CM)
Operating Frequency
vs Temperature
Error Amp Reference
vs Temperature
Maximum Current Sense
Threshold vs Temperature
V
IN
UVLO Threshold (Rising)
vs Temperature
V
IN
UVLO Threshold (Falling)
vs Temperature
PIN FUNCTIONS
V
IN
(Pin 1): The V
IN
pin is the main supply pin and should
be decoupled to SGND with a low ESR capacitor located
close to the pin.
SHDN (Pin 2): The SHDN pin has a precision IC enable
threshold of 1.35V (rising) with 120mV of hysteresis. It is
used to implement an undervoltage lockout (UVLO) circuit.
See Applications Information section for implementing
a UVLO function. When the SHDN pin is pulled below
a transistor V
BE
(0.7V), a low current shutdown mode
is entered, all internal circuitry is disabled and the V
IN
supply current is reduced to approximately 9μA. Typical
pin input bias current is <10μA and the pin is internally
clamped to 6V.
C
SS
(Pin 3): The soft-start pin is used to program the
supply soft-start function. Use the following formula to
calculate C
SS
for a given output voltage slew rate:
C
SS
= 2μA(t
SS
/1.231V)
The pin should be left unconnected when not using the
soft-start function.