LTC1265I データシートの表示（PDF） - Linear Technology

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LTC1265I

1.2A, High Efficiency Step-Down DC/DC Converter

Linear Technology 

LTC1265/LTC1265-3.3/LTC1265-5

TYPICAL PERFORMANCE CHARACTERISTICS

DC Supply Current

2.1

DOES NOT INCLUDE

GATE CHARGE

1.8

1.5

ACTIVE MODE

1.2

0.9

0.6

0.3

SLEEP MODE

0

0 2 4 6 8 10 12 14

INPUT VOLTAGE (V)

1265 G07

Supply Current in Shutdown

8

SHUTDOWN = 3V

7 TA = 25C

6

5

4

3

2

1

0

3 4 5 6 7 8 9 10 11 12 13

INPUT VOLTAGE (V)

1265 G08

Gate Charge Losses

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

VIN = 12V

VIN = 9V

VIN = 6V

0.5

0

0

200 400 600 800

FREQUENCY (kHz)

1000

1265 G09

PIN FUNCTIONS

PWR VIN (Pins 1, 13): Supply for the Power MOSFET and

its Driver. Must decouple this pin properly to ground. Must

always tie Pins 1 and 13 together.

VIN (Pin 2): Main Supply for All the Control Circuitry in the

LTC1265.

LBOUT (Pin 3): Open-Drain Output of the Low-Battery

Comparator. This pin will sink current when Pin 4 (LBIN)

goes below 1.25V. During shutdown, this pin is high

impedance.

LBIN (Pin 4): The (–) Input of the Low-Battery Comparator.

The (+) input is connected to a reference voltage of 1.25V.

CT (Pin 5): External capacitor CT from Pin 5 to ground sets

the switch off time. The operating frequency is dependent

on the input voltage and CT.

ITH (Pin 6): Feedback Amplifier Decoupling Point. The

current comparator threshold is proportional to Pin 6

voltage.

SENSE – (Pin 7): Connect to the (–) input of the current

comparator. For LTC1265-3.3 and LTC1265-5, it also

connects to an internal resistive divider which sets the

output voltage.

SENSE+ (Pin 8): The (+) Pin to the Current Comparator. A

built-in offset between Pins 7 and 8 in conjunction with

RSENSE sets the current trip threshold.

N/C,VFB (Pin 9): For the LTC1265 adjustable version, this

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 COUT.

PGND (Pin 12): Switch Driver Ground. Connects to the

(–) terminal of CIN. Anode of the Schottky diode must be

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.

4

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