DC882A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 882
SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
LTC3809EDD-1
DESCRIPTION
Demonstration circuit 882 is a small size, low profile,
low cost and high efficiency synchronous step-down
DC/DC converter featuring the LTC3809EDD-1 controller.
The demo board is capable of providing 2A output current with 2.75V to 9.8V input range. Burst mode/Pulse
skipping/Forced continuous operation is selectable. The
constant frequency current mode architecture with
MOSFET VDS sensing eliminates the need for a sense resistor and improves efficiency. The maximum peak cur-
rent sense threshold can be easily selected with IPRG
pin. Switching frequency is internally set at 550KHz.
The demo board has optional power component footprints to deliver higher output current and a tracking
function, allowing Vout to track an external voltage signal at the TRACK terminal (JP4: Track).
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
CONDITION
VALUE
Input Voltage Range
2.75V to 9.8V
VOUT
VIN = 2.75V-9.8V, IOUT = 0A to 2A
1.8V ±2.5%
Maximum load current IOUT
VIN = 2.75V-9.8V
2A
Typical Output Ripple Voltage
VIN = 3.3V, IOUT = 2A (20MHz BW)
8mVP–P
Typical Switching Frequency
550kHz
QUICK START PROCEDURE
Demonstration circuit 882 is easy to set up to evaluate
the performance of the LTC3809-1. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below: (Initial jumper positions: JP1 selected; JP4: Soft Start)
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 Figure 2 for
proper scope probe technique.
2.
Connect the 1.8V load between Vout and GND (Initial
load: 0 A).
3.
Connect the DVMs to the input and output.
4.
Turn on the input power supply and check for the
proper output voltage. Vout should be 1.8V+/-2.5%.
5.
Once the proper output voltage is established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage and other parameters.
NOTE: When
1.
With power off, connect the input power supply to Vin
(2.75V-9.8V) and GND (input return).
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 882
SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 882
SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
10000
100
Vo=1.8V
1000
80
100
Loss
70
10
POWER LOSS (mW)
EFFICIENCY (%)
Efficiency
90
1
60
Vin=3.3V
0.1
50
1
10
100
1k
10k
LOAD CURRENT (mA)
Figure 3. Efficiency and Loss vs Load Current (Burst Mode)
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 882
SYNCHRONOUS STEP-DOWN CONVERTER WITH OUTPUT TRACKING
4
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