Datasheet
LT3800
5
3800fc
TYPICAL PERFORMANCE CHARACTERISTICS
V
CC
UVLO Threshold (Rising)
vs Temperature I
CC
vs V
CC
(SHDN = 0V)
Error Amp Transconductance
vs Temperature
I
(SENSE
+
+ SENSE
–
)
vs V
SENSE(CM)
Operating Frequency
vs Temperature
Error Amp Reference
vs Temperature
PIN FUNCTIONS
TEMPERATURE (°C)
–50 –25 100
3800 G07
0 50 12525 75
6.30
6.25
6.20
6.15
V
CC
UVLO THRESHOLD, RISING (V)
V
CC
(V)
0
I
CC
(µA)
15
20
25
16
3800 G12
10
5
0
246
810
12 14 18
20
T
A
= 25°C
TEMPERATURE (°C)
–50 –25 1000 50 12525 75
380
360
340
320
3800 G08
ERROR AMP TRANSCONDUCTANCE (µmho)
V
SENSE(CM)
(V)
0 0.5 1.5 2.5 3.5 4.5
I
(SENSE
+
+ SENSE
–
)
(µA)
800
600
400
200
0
–200
–400
1.0 2.0 3.0 4.0
3800 G09
5.0
T
A
= 25°C
TEMPERATURE (°C)
3800 G10
–50
220
210
200
190
180
–25
OPERATING FREQUENCY (kHz)
1000 50 12525 75
–50 –25 1000 50 12525 75
TEMPERATURE (°C)
ERROR AMP REFERENCE (V)
1.232
1.231
1.230
1.229
1.228
1.227
3800 G11
V
IN
(Pin 1): Converter Input Supply.
NC (Pin 2): No Connection.
SHDN (Pin 3): Precision Shutdown Pin. Enable threshold
is 1.35V (rising) with 120mV of input hysteresis. When
in shutdown mode, all internal IC functions are disabled.
The precision threshold allows use of the SHDN pin to
incorporate UVLO functions. If the SHDN pin is pulled
below 0.7V, the IC enters a low current shutdown mode
with I
VIN
< 10µA. In low-current shutdown, the IC will
sink 20µA from the V
CC
pin until that local supply has
collapsed. Typical pin input bias current is <10nA and the
pin is internally clamped to 6V.
C
SS
(Pin 4): Soft-Start AC Coupling Capacitor Input.
Connect capacitor (C
SS
) in series with a 200k resistor
from pin to converter output (V
OUT
). Controls converter
start-up output voltage slew rate (∆V
OUT
/∆t). Slew rate
corresponds to 2µA average current through the soft-start
coupling capacitor. The capacitor value for a desired output
startup slew rate follows the relation:
C
SS
= 2µA/(∆V
OUT
/∆t)
Shorting this pin to SGND disables the soft-start function
BURST_EN (Pin 5): Burst Mode Operation Enable Pin.
This pin also controls reverse-inhibit mode of operation.
When the pin voltage is below 0.5V, Burst Mode operation