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RC4391
PRODUCT SPECIFICATION
15
I
LX
-I
MAX
Time
I
LX
-I
MAX
Time
I
LX
-I
MAX
Time
Troubleshooting Chart
Symptom
Possible Problems
Draws excessive supply current on star-up.
Inductance value too low.
Output frequency (F
O
) too low.
Combination of low resistance inductor and high
value filter capacitor — needs current limiting circuit
(Figure 13).
Inductance value too high for F
O
or core saturating.
Not potted well or bolted loosely.
Normal operating condition.
Inductor is saturating:
1. Core too small.
2. Core too hot.
3. Operating frequency too low.
Output voltage is low.
Inductor "sings" with audible hum.
L
X
pin appears noisy — scope will not synchronize.
Inductor current shows nonlinear waveform.
Waveform has resistive component:
1. Wire size too small.
2. Power transistor lacks base drive.
3. Components not rated high enough.
4. Battery has high series resistance.
Inductor current shows nonlinear waveform.
External transistor lacks base drive or beta is too
low.
Inductor current is linear until high current is reached.
Poor efficiency.
Core saturating.
Diode or transistor:
1. Not fast enough.
2. Not rated for current level (high V
CE
SAT).
High series resistance.
Operating frequency too high.
Loop stability problem — needs feedback from
V
OUT
to V
FB
(pin 8), 100pF to 1000pF
Motorboating (erratic current pulses).