Datasheet
6
LT1375/LT1376
13756fd
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
INPUT VOLTAGE (V)
0
CURRENT (A)
1.50
1.25
1.00
0.75
0.50
0.25
0
5101520
1375/76 G13
25
L = 20µH
L = 10µH
L = 5µH
V
OUT
= 10V
INPUT VOLTAGE (V)
0
CURRENT (A)
1.50
1.25
1.00
0.75
0.50
0.25
0
5101520
1375/76 G14
25
L = 20µH
L = 10µH
L = 5µH
V
OUT
= 3.3V
Maximum Load Current
at V
OUT
= 10V
Maximum Load Current
at V
OUT
= 3.3V
Maximum Load Current
at V
OUT
= 5V
INPUT VOLTAGE (V)
0
CURRENT (A)
1.50
1.25
1.00
0.75
0.50
0.25
0
5101520
1375/76 G15
25
L = 20µH
L = 10µH
L = 5µH
V
OUT
= 5V
PIN FUNCTIONS
UUU
BOOST: The BOOST pin is used to provide a drive voltage,
higher than the input voltage, to the internal bipolar NPN
power switch. Without this added voltage, the typical
switch voltage loss would be about 1.5V. The additional
boost voltage allows the switch to saturate and voltage
loss approximates that of a 0.3Ω FET structure, but with
much smaller die area. Efficiency improves from 75% for
conventional bipolar designs to > 87% for these new parts.
V
SW
: The switch pin is the emitter of the on-chip power
NPN switch. It is driven up to the input pin voltage during
switch on time. Inductor current drives the switch pin
negative during switch off time. Negative voltage is clamped
with the external catch diode. Maximum negative switch
voltage allowed is –0.8V.
SHDN: The shutdown pin is used to turn off the regulator
and to reduce input drain current to a few microamperes.
Actually, this pin has two separate thresholds, one at
2.38V to disable switching, and a second at 0.4V to force
complete micropower shutdown. The 2.38V threshold
functions as an accurate undervoltage lockout (UVLO).
This is sometimes used to prevent the regulator from
operating until the input voltage has reached a predeter-
mined level.
SWITCH CURRENT (A)
0
BOOST PIN CURRENT (mA)
12
10
8
6
4
2
0
0.25 0.50 0.75 1.00
1375/76 G16
1.25
T
J
= 25°C
BOOST Pin Current
V
C
Pin Shutdown Threshold
SWITCH CURRENT (A)
0
SWITCH VOLTAGE (V)
0.8
0.6
0.4
0.2
0
0.25 0.50 0.75 1.00
1375/76 G18
1.25 1.50
T
J
= 25°C
Switch Voltage Drop
JUNCTION TEMPERATURE (°C)
–50
1.4
1.2
1.0
0.8
0.6
0.4
100
1375/76 G11
–25 0 25 50 75 125
THRESHOLD VOLTAGE (V)
SHUTDOWN