Linear Technology LT1374CFE Quick Start Manual page 2

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 474
To turn the circuit off, ground the
4.
terminal labeled SHDN
To test the synchronization feature
5.
of the demo board apply a sync sig-
nal to the sync terminal and note
the shift in
quency. The Sync signal should have
an amplitude
duty cycle of between 10% and 90%
and a frequency of 580kHz–1000kHz
MEASUREMENT NOTES
Voltage measurements
The correct way to measure voltage is
at the terminal of the demo board.
Attempts to measure output voltage at
the load will result in a too low
output voltage due to wiring loss.
the operating
greater than 2.2V,
+
+
–
+
–
LOAD
–
Figure 3. Proper Measurement Equipment Setup
4A, 500KHZ STEP DOWN SWITCHING REGULATOR
This is especially true at high cur-
rent. Needless to say any efficiency
calculation should be made using demo
circuit terminal voltages as opposed
to load
voltages.
fre-
Ripple Voltage Measurements
The ceramic capacitors used in this
demo board have almost no ESR and are
extremely effective filters. In order
to correctly measure output ripple
voltage correct technique is impor-
tant. The
sheath should be removed and the out-
put ripple measured by placing the
scope probe directly across the out-
put Vout and GND pins as illustrated
in Figure 4.
or power source
scope ground
–
+
+
+
–
–
5V TO 25V
SUPPLY
25W
terminal
lead and
2