DC1313A - Demo Manual

DEMO C IR C U IT 1 3 1 3
Q U IC K S TA R T GLT1912
U IDE
L T 1 9 1 2 EDD
2 A ,3 6V, 5 0 0 k H z S te p -d o w n S w itc h in g R e g u lato r
DESCRIPTION
Demonstration circuit 1313 is a monolithic step-dow n
DC/DC sw itching regulator featuring LT1912. The demo
board is designed for 5V output from a 6.3V to 36V input. The w ide input range of the LT1912 allow s a variety
of input sources. The typical sources are automotive batteries,w all adaptors and industrial supplies.
The current mode control scheme creates fast transient
response and good loop stability. The gate drive of the
internal sw itch is boosted to a voltage that is higher than
the Vin to ensure saturation of the sw itch. The LT1912’s
integrated boost diode reduces the parts count. The
RUN/SS pin can be used to set the part in micropow er
shutdow n mode,reducing the supply current to less than
1uA. The RUN/SS pin can also be used to program soft
start. In this mode, the RUN/SS pin is driven through an
external RC filter to create a voltage ramp on this pin.
The soft start function reduces the input current surge
during start-up.
The LT1912 datasheet gives a complete description of
the part,operation and application information. The datasheet must be read in conjunction w ith this quick start
guide for demo circuit 1313.
Note:It is best to ground the SYNC pin ifthe SYNC function is not being used.
Design files for this circuit board are available. Call
the LTC factory.
,LTC and LT are registered trademarks ofLinear Technology Corporation. ThinSOT and
Pow erPath are trademarks ofLinear Technology Corporation.
Perform ance Sum m ary for Step-dow n Sw itching R egulator ( TA = 25oC )
PAR AM ETER FO R BU CK R EG ULATO R
M inimum Input Voltage
M aximum Input Voltage
O utput Voltage VOUT
M aximum O utput Current
Typical Sw itching Frequency
CO N DITIO N
VALU E
6.3V
36V
5V +/- 4%
2A
500kH z
Q U ICK STA RT PROCEDU RE
Demonstration circuit 1313 is easy to set up to evaluate
the performance of the LT1912. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below :
NOTE. W hen measuring the input or output voltage ripple,care must be
taken to avoid a long ground lead on the oscilloscope probe. M easure the
input or output voltage ripple by touching the probe tip directly across the
Vin or Vout and GND terminals. See Figure 2 for proper scope probe
technique.
1. Place JP1 on the R U N position.
2. W ith pow er off,connect the input pow er supply to Vin
and GND.
3. Turn on the pow er at the input.
4. Check for the proper output voltage.
NOTE. Ifthere is no output,temporarily disconnect the load to make sure
that the load is not set too high.
5. Once the proper output voltage is established, adjust
the load w ithin the operating range and observe the
output voltage regulation, ripple voltage, efficiency
and other parameters.
1
LT1912
6. An external clock can be added to the SYNC pin w hen
SYNC function is used. See synchronization section in
the datasheet for details.
+
A
+
+
+
V
+ _
_
_
V
_
Figure 1. Proper M easurem ent Equipm ent Setup
GND
VIN
Figure 2. M easuring Input or Output R ipple
2
+
Load
_
A
_
LT1912
3
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