LTC1265 LINER [Linear Technology], LTC1265 Datasheet - Page 11

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

Troubleshooting Hints
Since efficiency is critical to LTC1265 applications, it is
very important to verify that the circuit is functioning
correctly in both continuous and Burst Mode operation. As
the LTC1265 is highly tolerant of poor layout, the output
voltage will still be regulated. Therefore, monitoring the
output voltage will not tell you whether you have a good or
bad layout. The waveform to monitor is the voltage on the
timing capacitor Pin 5.
In continuous mode the voltage on the C
with approximately 0.9V
never dip below 2V as shown in Figure 6a.
APPLICATIONS
3.3V
2.4V
0V
(a) POORLY DECOUPLED LTC1265
U
(a) CONTINUOUS MODE OPERATION
P-P
INFORMATION
U
swing. This voltage should
TIME
W
T
pin is a sawtooth
Figure 7. Inductor Waveforms
U
LTC1265 F06a
Figure 6. C
T
Waveforms
LTC1265/LTC1265-3.3/LTC1265-5
When the load currents are low (I
Mode operation occurs. The voltage on C
ground for periods of time as shown in Figure 6b. During
this time the LTC1265 is in sleep mode with quiescent
current reduced to 160 A.
The inductor current should also be monitored. If the
circuit is poorly decoupled, the peak inductor current will
be haphazard as in Figure 7a. A well decoupled LTC1265
has a clean inductor current as in Figure 7b.
3.3V
2.4V
0V
(b) WELL DECOUPLED LTC1265
(b) Burst Mode OPERATION
SLEEP MODE
TIME
LOAD
T
< I
pin now falls to
BURST
LTC1265 F06b
11
) Burst