DC1013A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1013
DUAL MONOLITHIC SYNCHRONOUS, 300MA, 2.25 MHZ BUCK REGULATORS
LTC3547
DESCRIPTION
Demonstration circuit 1013 is a dual output regulator
consisting of two constant-frequency step-down converters, based on the LTC3547 monolithic dual synchronous buck regulator IC. The DC1013 has an input voltage range of 2.5V to 5.5V, and both outputs are capable
of delivering up to 300 mA of output current at a minimum input voltage of 3V. In Burst Mode operation,
which is the mode of the LTC3547 during light load current operation, the DC supply current of the DC1013 is
typically only 40 uA (per channel) at no load, and less
than 1 uA in shutdown. The DC1013 is a very efficient
circuit: over 95% for either circuit. The LTC3547 comes
in a tiny 8-lead 3x2 mm DFN package, which has an ex-
posed pad on the bottom-side of the IC for better thermal performance. These features, plus the nominal operating frequency of 2.25 MHz (allowing the exclusive
use of low profile surface mount components), make the
DC1013 demo board an ideal circuit for use in batterypowered, hand-held applications.
Design files for this circuit board are available. Call
the LTC factory.
TM - Burst Mode is a trademark of Linear Technology Corporation
Table 1.
Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
2.5V
Maximum Input Voltage
5.5V
1.2V ±4% (1.152V – 1.248V)
Output Voltage VOUT1
VIN = 2.5V to 5.5V, IOUT1 = 0A to 300 mA
1.5V ±4% (1.44V – 1.56V)
1.8V ±4% (1.728V – 1.872V)
Typical Output Ripple VOUT1
Output Regulation
VIN = 5V, IOUT1 = 300 mA (20 MHz BW)
< 20mVP–P
Line
±1%
Load
±1%
2.5V ±4% (2.4V – 2.6V)
Output Voltage VOUT2
VIN = 2.5V to 5.5V, IOUT2 = 0A to 300 mA
Typical Output Ripple VOUT2
VIN = 5V, IOUT2 = 300 mA (20 MHz BW)
< 20mVP–P
Line
±1%
Load
±1%
Output Regulation
Nominal Switching Frequency
3.3V ±4% (3.168V – 3.432V)
2.25 MHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1013
DUAL MONOLITHIC SYNCHRONOUS, 300MA, 2.25 MHZ BUCK REGULATORS
QUICK START PROCEDURE
The DC1013 is easy to set up to evaluate the performance of the LTC3547. For a proper measurement
equipment configuration, set up the circuit according
to the diagram in Figure 1.
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 probe measurement diagram in Figure 2 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 loads between
the Vout and GND terminals. Refer to Figure
1 for the proper measurement equipment
setup.
2.
Before proceeding to operation, insert shunts
JP1 and JP2 into the OFF positions. Also inserts shunts into JP5, the 1.8V Vout1 voltage
option, and into JP7, the 3.3V Vout2 voltage
option.
3.
Apply 5V at Vin, and turn on Vout1 and Vout2
by changing shunts JP1 and JP2 from the
OFF positions to the ON positions. Both output voltages should be within a tolerance of
+/- 2%.
4.
Vary the input voltage from 5V to 0.5V above
the output voltage (If Vout2 is off, then the
minimum input voltage limit is 2.5V.). Both
output voltages should be within +/- 3% tolerance.
5.
Vary the load current, of each output, from 0
to 300mA. Each output voltage should be
within a tolerance of +/- 4%.
6.
Set the load current of both outputs at 300 mA
and measure the output ripple voltage of each
regulator (Refer to Figure 2 for proper measurement technique); they should measure less
than 20 mVAC each. Also, observe the voltage
waveform at either switch node (pins 4 – reg.1
and 6 – reg.2) of each regulator. The switching
frequencies should be between 1.8 MHz and 2.7
MHz (T = 555 ns and 370 ns).
7.
When finished, insert shunts into the OFF position(s) of JP1 and JP2. To test and evaluate
the other voltage options, move the shunts in
JP5 and JP7 into any of the remaining output
voltage options – 1.2V (JP3) or 1.5V (JP4) for
Vout1 and 2.5V (JP6) for Vout2. Just as in
the 1.8V, Vout1, or 3.3V, Vout2, voltage options, the new output voltages should measure +/- 2% tolerance for static line and load
conditions and +/- 2% tolerance under dynamic line and load conditions (4% total).
When finished, turn off the circuits by inserting shunts JP1 and JP2 into the OFF positions, and disconnect the power.
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 (which, of
course, may damage the IC). To eliminate the ringing, a
small tantalum capacitor (AVX part # TAJW476M010)
has been inserted on the pads between the input power
and return terminals on the bottom of the demo board.
The (greater) ESR of the tantalum capacitor 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.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1013
DUAL MONOLITHIC SYNCHRONOUS, 300MA, 2.25 MHZ BUCK REGULATORS
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1013
DUAL MONOLITHIC SYNCHRONOUS, 300MA, 2.25 MHZ BUCK REGULATORS
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