DC1340A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1340
TRIPLE DC/DC CONVERTER
LTC3569
DESCRIPTION
Demonstration circuit 1340 is a triple output regulator
consisting of three constant-frequency step-down
converters integrated into LTC3569. DC1340 has an
input voltage range of 2.5V to 5.5V, with regulators
capable of delivering 1.2A or 600mA of load current
on corresponding output. The three regulators operate independently with individual Enable pins and enter pulse skipping or burst mode at low loads for increasing efficiency. The DC1340 is a very efficient
circuit with efficiency reading above 90%. The
LTC3569 comes in a 20-pin QFN or 16-LEAD TSSOP
package, which has an exposed pad on the bottomside of the IC for better thermal performance. High
operating frequency of 2.25MHz allows exclusive use
of the small size, low profile surface mount components. These features plus internal compensation circuits and extremely low quiescent current make the
DC1340 demo board an ideal circuit for use in battery-powered, hand-held applications. DC1340 supports reference voltage programming for each regulator. This value is programmed in -25mV steps by
toggling the respective Enable pin.
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
2.5V
Maximum Input Voltage
5.5V
Output Voltage Regulation VOUT1
VIN = 2.5V to 5.5V, IOUT = 0A to 1.2A
1.8V ±2%
Typical Output Ripple VOUT1
VIN = 4V, IOUT = 1.2A (20 MHz BW)
<15mVP–P
Output Voltage Regulation VOUT2
VIN = 2.5V to 5.5V, IOUT = 0A to 600mA
1.2V ±2%
Typical Output Ripple VOUT2
VIN = 4V, IOUT = 600mA (20 MHz BW)
<15mVP–P
Output Voltage Regulation VOUT3
VIN = 2.5V to 5.5V, IOUT = 0A to 600mA
1.5V ±2%
Typical Output Ripple VOUT3
VIN = 4V, IOUT = 600mA (20 MHz BW)
<15mVP–P
Nominal Switching Frequency
2.25 MHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1340
TRIPLE DC/DC CONVERTER
QUICK START PROCEDURE
Demonstration Circuit 1340 is easy to set up to evaluate the performance of the LTC3569. 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 VOUT 1 does not exceed 1.2A and
VOUT2, VOUT3 do not exceed 600mA, on
each output (all three outputs can be loaded
at the same time)
2.
Apply 5V at VIN and than insert RUN jumper
shunts JP1 through JP3 into the ON positions.
3.
Measure all three outputs VOUT1 through
VOUT3; they should read 1.8V, 1.2V and 1.5V
correspondingly. All output voltages should
be within +/- 2% tolerance.
4.
Vary the input voltage from 5.5V to 2.25V; all
four output voltages should be within +/- 2%
tolerance.
5.
Vary the VOUT1 load current from 0 to 1.2A.
Each output voltage should be within a tolerance of +/- 2%.
6.
Vary the VOUT2 load currents from 0 to
600mA. Each output voltage should be within
a tolerance of +/- 2%.
7.
Vary the VOUT3 load current from 0 to
600mA. Each output voltage should be within
a tolerance of +/- 2%.
8.
To turn either output off set corresponding
jumper into OFF position.
To synchronize converter to external clock move
jumper J4 to Sync position (contacts 1 and 2) and
apply synchronization pulses in 1MHz to 3MHz frequency range to SYNC pin, see datasheet LTC3569
for details. For converter to operate in Pulse skipping
mode move jumper J4 to Pulse Skip position (contacts 2 and 3). For converter to operate in Burst mode
move jumper J4 into Burst position (contacts 1 and
2).
For reference voltage programming apply toggling
pulses on corresponding PRG_VOUT terminals as it
described in LTC3569 datasheet.
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 converter. 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 1340
TRIPLE 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 1340
TRIPLE DC/DC CONVERTER
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