LT1375/ LT1376
TYPICAL PERFORMANCE CHARACTERISTICS
W
U
Maximum Load Current
at VOUT = 5V
Maximum Load Current
at VOUT = 3.3V
Maximum Load Current
at VOUT = 10V
1.50
1.25
1.00
0.75
0.50
0.25
0
1.50
1.25
1.00
0.75
0.50
0.25
0
1.50
1.25
1.00
0.75
0.50
0.25
0
L = 20µH
V
OUT
= 10V
L = 20µH
L = 10µH
L = 20µH
L = 10µH
L = 10µH
L = 5µH
L = 5µH
L = 5µH
V
OUT
= 5V
5
V
OUT
= 3.3V
5
0
10
15
20
25
0
5
10
15
20
25
0
10
15
20
25
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1375/76 G15
1375/76 G13
1375/76 G14
BOOST Pin Current
V Pin Shutdown Threshold
C
Switch Voltage Drop
1.4
1.2
1.0
0.8
0.6
0.4
0.8
0.6
0.4
0.2
0
12
10
8
SHUTDOWN
T = 25°C
T = 25°C
J
J
6
4
2
0
–25
0
25
50
75
125
–50
100
0
0.25
0.50
0.75
1.00
1.25
0
0.25 0.50 0.75 1.00 1.25 1.50
SWITCH CURRENT (A)
JUNCTION TEMPERATURE (°C)
SWITCH CURRENT (A)
1375/76 G11
1375/76 G16
1375/76 G18
U
U
U
PIN FUNCTIONS
BOOST: The BOOST pin is used to provide a drive voltage,
with the external catch diode. Maximum negative switch
higher than the input voltage, to the internal bipolar NPN voltage allowed is –0.8V.
power switch. Without this added voltage, the typical
SHDN: The shutdown pin is used to turn off the regulator
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
conventionalbipolardesigns to>87%forthesenewparts.
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.
V : The switch pin is the emitter of the on-chip power
SW
NPN switch. It is driven up to the input pin voltage during
switch on time. Inductor current drives the switch pin
negativeduringswitchofftime.Negativevoltageis clamped
6
Linear [ Linear ]
