DC1040A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1040
QUAD DC/DC CONVERTER
LTC3544
DESCRIPTION
Demonstration circuit 1040 is a quad output regulator
consisting of four constant-frequency step-down
converters integrated into the LTC3544. DC1040 has
an input voltage range of 2.25V to 5.5V, with regulators capable of delivering 100mA, 200mA, 200mA
and 300mA of output current. The four regulators operate independently with individual RUN pins and enter pulse skipping mode at low loads to reduce output
ripple. In shutdown, the DC1040 draws less than 1uA
total. The DC1040 is a very efficient circuit with efficiency greater than 90%. The LTC3544 comes in a
16-pin QFN package, which has an exposed pad on
the bottom-side of the IC for better thermal performance. High operating frequency of 2.25MHz allows
exclusive use of small size, low profile surface mount
components. These features plus internal compensation circuits make the DC1040 demo board an ideal
circuit for use in battery-powered, hand-held applications. The DC1040 design supports both versions of
LTC3544: LTC3544EUD (burst mode of operation)
and LTC3544BEUD (pulse skip mode of operation). The label on the PCB identifies which controller is installed.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITIONS
VALUE
Minimum Input Voltage
2.25V
Maximum Input Voltage
5.5V
Output Voltage Regulation VOUT1
VIN = 2.25V to 5.5V, IOUT = 0A to 100mA
1.2V ±2%
Typical Output Ripple VOUT1
VIN = 5V, IOUT = 100mA (20 MHz BW)
<15mVP–P
Output Voltage Regulation VOUT2
VIN = 2.25V to 5.5V, IOUT = 0A to 200mA
1.5V ±2%
Typical Output Ripple VOUT2
VIN = 5V, IOUT = 200mA (20 MHz BW)
<15mVP–P
Output Voltage Regulation VOUT3
VIN = 2.25V to 5.5V, IOUT = 0A to 200mA
0.8V ±2%
Typical Output Ripple VOUT3
VIN = 5V, IOUT = 200mA (20 MHz BW)
<15mVP–P
Output Voltage Regulation VOUT4
VIN = 2.25V to 5.5V, IOUT = 0A to 300mA
1.8V ±2%
Typical Output Ripple VOUT1
VIN = 5V, IOUT = 300mA (20 MHz BW)
<15mVP–P
Nominal Switching Frequency
2.25 MHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1040
QUAD DC/DC CONVERTER
QUICK START PROCEDURE
Demonstration Circuit 1040 is easy to set up to evaluate the performance of the LTC3544. For 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
Measurement Equipment Set-up diagram in Figure 2
for proper scope probe technique.
1.
Connect the input power supply to the VIN
and GND terminals. Connect the loads between the matching VOUT and GND terminals.
Refer to Figure 1 for the proper measurement
equipment setup. Make sure that loads on
outputs VOUT1 through VOUT4 do not exceed
100mA, 200mA, 200mA and 300mA respectively.
2.
Apply 5V at VIN and place RUN jumper shunts
JP1 through JP4 in the ON positions.
3.
Measure all four outputs VOUT1 through
VOUT4; they should read 1.2V, 1.5V, 0.8V,
1.8V respectively. All output voltages should
be within +/- 2% tolerance.
4.
Vary the input voltage from 5.5V to 2.5V, all
four output voltages should be within +/- 2%
tolerance.
5.
Vary the VOUT1 load current from 0 to
100mA,. Each output voltage should be
within a tolerance of +/- 2%.
6.
Vary the VOUT2 and VOUT3 load currents
from 0 to 200mA,. Each output voltage should
be within a tolerance of +/- 2%.
7.
Vary the VOUT4 load current from 0 to
300mA. Each output voltage should be within
a tolerance of +/- 2%.
8.
To turn either output off, place corresponding
jumper in OFF position.
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 # 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.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1040
QUAD DC/DC CONVERTER
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1040
QUAD DC/DC CONVERTER
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