LT1371 Linear Technology, LT1371 Datasheet - Page 5

• Manufacturer Part Number: LT1371
• Description: 500kHz High Efficiency 3A Switching Regulator
• Manufacturer: Linear Technology

TYPICAL PERFORMANCE CHARACTERISTICS
PIN
V
sation, current limiting and soft start. It is the output of the
error amplifier and the input of the current comparator.
Loop frequency compensation can be performed with an
RC network connected from the V
FB: The Feedback pin is used for positive output voltage
sensing and oscillator frequency shifting. It is the invert-
ing input to the error amplifier. The noninverting input of
this amplifier is internally tied to a 1.245V reference. Load
on the FB pin should not exceed 250 A when NFB pin is
used. See Applications Information.
NFB: The Negative Feedback pin is used for negative
output voltage sensing. It is connected to the inverting
input of the negative feedback amplifier through a 100k
source resistor.
S/S (R and T7 Packages Only): Shutdown and Synchroni-
zation Pin. The S/S pin is logic level compatible. Shutdown
is active low and the shutdown threshold is typically 1.3V.
For normal operation, pull the S/S pin high, tie it to V
C
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.4
0.6
: The Compensation pin is used for frequency compen-
U
–50
V
Clamp Voltage vs Temperature
C
FUNCTIONS
–25
Pin Threshold and High
U
0
TEMPERATURE ( C)
V
C
25
HIGH CLAMP
V
C
THRESHOLD
50
U
75
100 125 150
W
LT1371 • G10
U
C
pin to ground.
800
700
600
500
400
300
200
100
0
–50
Feedback Input Current
vs Temperature
V
–25
FB
=V
REF
IN
0
TEMPERATURE ( C)
or
25
50
leave it floating. To synchronize switching, drive the S/S
pin between 600kHz and 800kHz.
SHDN: (SW Package Only): The Shutdown pin is active
low and the shutdown threshold is typically 1.3V. For
normal operation, pull the SHDN pin high, tie it to V
leave it floating.
SYNC (SW Package Only): To synchronize switching,
drive the SYNC pin between 600kHz and 800kHz. If not
used, the SYNC pin can be tied high, low or left floating.
V
10 F or more. The regulator goes into undervoltage lock-
out when V
stops switching and pulls the V
V
and has large currents flowing through it. Keep the traces
to the switching components as short as possible to
minimize radiation and voltage spikes.
GND: Tie all Ground pins to a good quality ground plane.
IN
SW
75
: Bypass Input Supply pin with a low ESR capacitor,
: The Switch pin is the collector of the power switch
100
LT1371 • G11
125
IN
150
drops below 2.5V. Undervoltage lockout
–20
–50
–10
–30
–40
0
–50
Negative Feedback Input Current
vs Temperature
V
–25
NFB
C
=V
0
NFR
pin low.
TEMPERATURE ( C)
25
50
75
LT1371
100 125 150
LT1371 • G12
IN
5
or