LTC1148LCS データシートの表示（PDF） - Linear Technology

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LTC1148LCS

High Efficiency Synchronous Step-Down Switching Regulators

Linear Technology 

TYPICAL PERFOR A CE CHARACTERISTICS

LTC1148

LTC1148-3.3/LTC1148-5

Gate Charge Supply Current

28

24

20

QN + QP = 100nC

16

12

8

QN + QP = 50nC

4

0

20

80

140

200

260

OPERATING FREQUENCY (kHz)

LTC1148 • TPC07

Off Time vs VOUT

80

70

VSENSE– = VOUT

60

50

40

30

20

10

LTC1148-5

LTC1148-3.3

0

0

1

2

3

4

5

OUTPUT VOLTAGE (V)

LTC1148 • TPC08

Current Sense Threshold Voltage

175

MAXIMUM

150

THRESHOLD

125

100

75

50

MINIMUM

THRESHOLD

25

0

0

20

40

60

80 100

TEMPERATURE (°C)

LTC1148 • TPC09

PI FU CTIO S

P-DRIVE (Pin 1): High Current Drive for Top P-Channel

MOSFET. Voltage swing at this pin is from VIN to ground.

NC (Pin 2): No Connection. Can connect to power ground.

VIN (Pin 3): Main Supply Pin. Must be closely decoupled

to power ground Pin 12.

CT (Pin 4): External capacitor CT from Pin 4 to ground sets

the operating frequency. The actual frequency is also

dependent upon the input voltage.

INTVCC (Pin 5): Internal Supply Voltage, Nominally 3.3V.

Can be decoupled to signal ground. Do not externally load

this pin.

ITH (Pin 6): Gain Amplifier Decoupling Point. The current

comparator threshold increases with the Pin 6 voltage.

SENSE – (Pin 7): Connects to internal resistive divider

which sets the output voltage in LTC1148-3.3 and

LTC1148-5 versions. Pin 7 is also the (–) input for the

current comparator.

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

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

RSENSE sets the current trip threshold.

VFB (Pin 9): For the LTC1148 adjustable version, Pin 9

serves as the feedback pin from an external resistive

divider used to set the output voltage. On LTC1148-3.3

and LTC1148-5 versions this pin is not used.

SHUTDOWN (Pin 10): When grounded, the LTC1148

series operates normally. Pulling Pin 10 high holds both

MOSFETs off and puts the LTC1148 series in micropower

shutdown mode. Requires CMOS logic signal with tR,

tF < 1µs, should not be left floating.

SGND (Pin 11): Small-Signal Ground. Must be routed

separately from other grounds to the (–) terminal of COUT.

PGND (Pin 12): Driver Power Ground. Connects to source

of N-channel MOSFET and the (–) terminal of CIN.

NC (Pin 13): No Connection. Can connect to power ground.

N-DRIVE (Pin 14): High Current Drive for Bottom

N-Channel MOSFET. Voltage swing at Pin 14 is from

ground to VIN.

5

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