LTC1159CS datasheet(15/20 Pages) LINER

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LTC1159/LTC1159-3.3/LTC1159-5

Figure 10. High Efficiency 8V to 20V Input 2.5/5A Output Regulator

P-GATE

VIN

VCC

P-DRIVE

VCC

ITH

SENSE–

CAP

SHDN2

EXTVCC

N-GATE

P-GND

S-GND

VFB

SENSE+

LTC1159

0.15

µF

SHUTDOWN

0.1

µF

1N4148

1000pF

10k

0.047

µF

3.3

µF

1000pF

100pF

100

Ω

100

Ω

IRF7201

MBRS330

µF

WIMA

µF

25V

× 2

OS-CON

VIN

8V TO 20V

µH

RSENSE**

0.02

Ω

+ 330µF

6.3V

× 3

AVX

LTC1159 • F10

VOUT

2.5V/5A

*MAGNETICS 77120-A7 CORE, 16T 18GA. WIRE

**KRL SL-1-R020J

IRF7205

10k

3.3V

(a) CONTINUOUS MODE OPERATION

3.3V

(b) Burst Mode OPERATION

LTC1159 • F09

Figure 9. CT Pin 6 Waveforms

Troubleshooting Hints

Since efficiency is critical to LTC1159 applications it is very

important to verify that the circuit is functioning correctly

in both continuous and Burst Mode operation. The wave-

form to monitor is the voltage on the CT pin .

In continuous mode (ILOAD > IBURST) the voltage should be

a sawtooth with a 0.9VP-P swing. This voltage should never

dip below 2V as shown in Figure 9a. When the load current

is low (ILOAD < IBURST), Burst Mode operation should occur

with the CT waveform periodically falling to ground as

shown in Figure 9b.

If the CT pin is observed falling to ground at high output

currents, it indicates poor decoupling or improper ground-

ing. Refer to the Board Layout Checklist.

TYPICAL APPLICATIO S

APPLICATIONS INFORMATION

LTC1159CS Datasheet(PDF) 15 Page - Linear Technology

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