DC870A-B - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B
HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR
LTC3410B
DESCRIPTION
Demonstration circuit 870A-B is a high efficiency,
high frequency buck converter, incorporating the
LTC3410B monolithic synchronous regulator. The
DC870 has an input voltage range of 2.25V to 5.5V,
and is capable of delivering up to 300 mA of output
current. It has an output voltage range from 0.8V to
5V, and an operating frequency range of 2.25 MHz
(allowing the exclusive use of low profile surface
mount components). In low load current operation,
the LTC3410B operates in pulse-skip mode. The
DC870 is a very efficient circuit: up to 96%. These
features, plus the LTC3410B coming in a tiny, lowprofile 6-Pin SC70 package, make the DC870 demo
board an ideal circuit for use in battery-powered,
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
Minimum Input Voltage
CONDITION
VALUE
2.25V
Maximum Input Voltage
Output Voltage VOUT
Typical Output Ripple VOUT
Output Regulation
5.5V
VIN = 2.25V to 5.5V, IOUT = 0A to 0.3A
1.8V ±4%
VIN = 5V, IOUT = 0.3A (20 MHz BW)
20mVP–P
Line
±1%
Load
±1%
Nominal Switching Frequency
2.25 MHz
QUICK START PROCEDURE
The DC870A-B is easy to set up to evaluate the performance of the LTC3410B. For proper measurement
equipment configuration, set up the circuit according
to the diagram in Figure 1. Before proceeding to test,
insert jumper JP1 shunt into the off position, connecting the RUN pin to ground (GND), which shuts
down the circuit.
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 out-
put 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.
Connect the input power supply and the load to the
board. Do not hot-plug Vin or increase Vin over
the rated maximum supply voltage of 5.5V, or the
part may be damaged. Refer to figure 1 for the
proper measurement equipment setup.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B
HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR
2.
Apply 3.3V 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 approximately 1 uA in shutdown.
3.
Turn on the circuit by inserting the shunt in jumper
JP1 into the ON position. The output voltage
should be regulating. Measure Vout - it should
measure 1.8V +/- 2%.
4.
Vary the input voltage from 2.25V to 5.5V and adjust the load current from 0 to 0.3A. Vout should
read between 1.8V +/- 3%.
5.
Measure the output ripple voltage at any output
current level; it usually will measure less than 20
mVAC.
6.
Observe the voltage waveform at the switch node
(one pin of the inductor). Verify the switching frequency is between 1.8 MHz and 2.7 MHz (T = 0.56
us and 0.37 us), and that the switch node waveform is rectangular in shape.
When finished, turn off the circuit by inserting the
shunt in jumper JP1 into the OFF position.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B
HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B
HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR
Figure 3. Load Step Response
Vin = 3.3V, Vout = 1.8V, Iout Step = 0.2A
Trace 1: Output Voltage (50 mV/div AC)
Trace 2: Output Current (0.1A/div)
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B
HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR
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