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 cur-
rent 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 V
DS
sensing eliminates the need for a sense re-
sistor 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 foot-
prints to deliver higher output current and a tracking
function, allowing Vout to track an external voltage sig-
nal 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 (T
A
= 25°C)
PARAMETER
Input Voltage Range
V
OUT
Maximum load current I
OUT
Typical Output Ripple Voltage
Typical Switching Frequency
V
IN
= 2.75V-9.8V, I
OUT
= 0A to 2A
V
IN
= 2.75V-9.8V
V
IN
= 3.3V, I
OUT
= 2A (20MHz BW)
CONDITION
VALUE
2.75V to 9.8V
1.8V ±2.5%
2A
8mV
P–P
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 se-
lected; JP4: Soft Start)
measuring the input or output voltage rip-
ple, 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.
1.
NOTE:
When
2.
3.
4.
5.
Connect the 1.8V load between Vout and GND (Initial
load: 0 A).
Connect the DVMs to the input and output.
Turn on the input power supply and check for the
proper output voltage. Vout should be 1.8V+/-2.5%.
Once the proper output voltage is established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage and other pa-
rameters.
With power off, connect the input power supply to Vin
(2.75V-9.8V) and GND (input return).
1
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