DC1343A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1343A
2.25MHZ, 1.25A MONOLITHIC SYNCHRONOUS BUCK REGULATOR
LTC3564
DESCRIPTION
Demonstration circuit DC1343A is a high efficiency
monolithic synchronous buck regulator using a
constant frequency, current mode architecture featuring LTC3564. Its high switching frequency of
2.25MHz allows the use of small surface mount
inductors and capacitors. Supply current during
operation is typically only 20uA, and drops to below 1uA in shutdown. The 2.5V to 5.5V input voltTable 1.
age range makes the LTC3564 ideally suited for
single Li-Ion battery-powered or 3.3V to 5V input
voltage applications. 100% duty cycle provides
low dropout operation, extending battery life in
portable systems. Automatic Burst Mode® operation increases efficiency at light loads, further extending battery runtime. Gerber files for this circuit are available. Call the LTC Factory.
Performance Summary (TA = 25ºC)
PARAMETER
CONDITION
VALUE
Input Voltage
Output Voltage VOUT
2.5V to 5.5V
IOUT=0A to 1.25A
VOUT ± 1%
Maximum Output Current
1.25A
DC Supply Current
VIN = 3.3V, VOUT = 1.8V, IOUT = 0A
<40µA
Nominal Switching Frequency
VIN = 3.3V, VOUT = 1.8V, IOUT = 1.25A
2.25MHz
QUICK START PROCEDURE
The DC1343A is easy to set up to evaluate the
performance of the LTC3564. Refer to Figure 2
for the proper measurement equipment setup.
NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long
ground lead on the oscilloscope probe. Measure
the input or output voltage ripple by touching the
probe tip directly across the VIN or VOUT and GND
terminals. See the measurement example diagram in Figure 1 for proper scope probe technique.
Please follow the procedure outlined below for
proper operation.
1. Connect the input power supply to the VIN
and GND terminals. Connect the load between
the VOUT and GND terminals.
2. Before proceeding to operation, insert
jumper shunt XJP1 into the OFF position and
insert one jumper shunt into XJP2, XJP3 or
XJP4 for voltages of 1.2V, 1.5V, or 1.8V respectively. Set the load output current to less than
1.25A. An optional output voltage can be set by
populating resistor RFB6, removing RFB5, and
moving the shunt to JP5.
3. Apply 5V at VIN. Measure VOUT; it should
read 0V. If desired, one can measure the shutdown supply current at this point. The supply current will be about 1 µA in shutdown.
4. Turn on VOUT by changing shunt XJP1 from
the OFF position to the ON position. The output voltage should measure according to the
voltage set by the shunt in JP2, JP3, or JP4.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1343A
2.25MHZ, 1.25A MONOLITHIC SYNCHRONOUS BUCK REGULATOR
5. Vary the input voltage between 2.5V and
5.5V and the output voltage should be within +/1% tolerance.
Warning - If the power for the demo board is carried in long leads, the input voltage at the part
could “ring”, which could affect the operation of
the circuit or even exceed the maximum voltage
rating of the IC. To eliminate the ringing, insert a
small tantalum capacitor (for instance, AVX part
6. Vary the VOUT load current from 0 to 1.25A,
and the output voltage should be within a tolerance of +/- 1%.
# TAJW686M010) on the pads between the input power and return terminals on the bottom of
the demo board. The (greater) ESR of the tantalum will dampen the (possible) ringing voltage
due to the use of long input leads. On a normal,
typical PCB, with short traces, the capacitor is
not needed.
Figure 1. Measuring Input or Output Ripple
Figure 2. Proper Measurement Equipment Setup
Load Step Response
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1343A
2.25MHZ, 1.25A MONOLITHIC SYNCHRONOUS BUCK REGULATOR
Figure 3. Load Step Response
Vin = 3.3V, Vout = 1.8V, 1A Load Step (250mA <-> 1.25A), Fsw = 2.25 MHz
Trace 3: Output Voltage (100mV/div – AC coupled)
Trace 4: Output Current (500mA/div)
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1343A
2.25MHZ, 1.25A MONOLITHIC SYNCHRONOUS BUCK REGULATOR
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