LTC1265 LINER [Linear Technology], LTC1265 Datasheet - Page 4

• Manufacturer Part Number: LTC1265
• Description: 1.2A, High Efficiency Step-Down DC/DC Converter
• Manufacturer: LINER [Linear Technology]

LTC1265/LTC1265-3.3/LTC1265-5
PIN
PWR V
its Driver. Must decouple this pin properly to ground. Must
always tie Pins 1 and 13 together.
V
LTC1265.
LB
Comparator. This pin will sink current when Pin 4 (LB
goes below 1.25V. During shutdown, this pin is high
impedance.
LB
The (+) input is connected to a reference voltage of 1.25V.
C
the switch off time. The operating frequency is dependent
on the input voltage and C
I
current comparator threshold is proportional to Pin 6
voltage.
SENSE
comparator. For LTC1265-3.3 and LTC1265-5, it also
connects to an internal resistive divider which sets the
output voltage.
TYPICAL PERFORMANCE CHARACTERISTICS
4
TH
IN
T
2.1
1.8
1.5
1.2
0.9
0.6
0.3
OUT
IN
(Pin 5): External capacitor C
U
0
(Pin 2): Main Supply for All the Control Circuitry in the
(Pin 6): Feedback Amplifier Decoupling Point. The
(Pin 4): The (–) Input of the Low-Battery Comparator.
0
DC Supply Current
DOES NOT INCLUDE
GATE CHARGE
FUNCTIONS
IN
(Pin 3): Open-Drain Output of the Low-Battery
–
(Pin 7): Connect to the (–) input of the current
2
(Pins 1, 13): Supply for the Power MOSFET and
U
4
INPUT VOLTAGE (V)
6
ACTIVE MODE
SLEEP MODE
U
8
10
T
.
W
12
T
from Pin 5 to ground sets
1265 G07
U
14
8
7
6
5
4
3
2
1
0
Supply Current in Shutdown
3
SHUTDOWN = 3V
T
A
4
= 25C
5
IN
INPUT VOLTAGE (V)
6
)
7
8
SENSE
built-in offset between Pins 7 and 8 in conjunction with
R
N/C,V
pin serves as the feedback pin from an external resistive
divider used to set the output voltage. On the LTC1265-3.3
and LTC1265-5 versions, this pin is not used.
SHDN (Pin 10): Pulling this pin HIGH keeps the internal
switch off and puts the LTC1265 in micropower shut-
down. Do not float this pin.
SGND (Pin 11): Small-Signal Ground. Must be routed
separately from other grounds to the (–) terminal of C
PGND (Pin 12): Switch Driver Ground. Connects to the
(–) terminal of C
connected close to this pin.
SW (Pin 14): Drain of the P-Channel MOSFET Switch.
Cathode of the Schottky diode must be connected close to
this pin.
SENSE
9
10
FB
+
sets the current trip threshold.
11
(Pin 8): The (+) Pin to the Current Comparator. A
(Pin 9): For the LTC1265 adjustable version, this
12
1265 G08
13
IN
. Anode of the Schottky diode must be
1.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
0.5
0
0
Gate Charge Losses
200
FREQUENCY (kHz)
400
600
V
V
V
800
IN
IN
IN
= 12V
= 9V
= 6V
1265 G09
OUT
1000
.