DC965A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 965A
SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER
LTC3835EGN-1
DESCRIPTION
Demonstration circuit 965A is a single output high
frequency step-down DC/DC converter featuring the
low quiescent current LTC®3835 in a 16-pin GN
package. The DC965A is programmed to generate a
regulated [email protected] output from a 4.5V to 36V input
voltage.
To maximize battery usage, the demo circuit allows
low dropout operation when the input voltage is close
to the output voltage. Its selectable burst mode operation reduces the IC supply current at light loads to
extend battery life. The phase-lockable frequency allows the LTC3835 to be synchronized by an external
signal. The output voltage of the LTC3835 can track
an external ramp voltage signal during power-up and
power-down. Also, the built-in current foldback prevents the overheating of output MOSFETs during
short-circuit.
All these features make the circuit a high performance
solution for applications in automotive and batteryoperated systems, telecom and distributed DC power
systems.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a registered trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITION
MINIMUM
Input Voltage Range
Maximum Output Current
4.5V < VIN < 36V
Output Voltage VOUT
0A < IOUT < 5A
Output Ripple VOUT
IOUT = 5A (20MHz BW) VIN = 36V, FSW = 400kHz
MAXIMUM
36V
5A
3.234V
3.3V
3.366V
36mVP–P
Nominal Switching Frequency
Efficiency
TYPICAL
4.5V
400kHz
VIN = 14V, IOUT = 3.5A, 400kHz Switching Frequency
91.5%
QUICK START PROCEDURE
Demonstration circuit 965A is easy to set up to evaluate the performance of the LTC3835EGN-1. Refer to
Figure 1 for proper measurement equipment setup
and follow the procedure below:
MODE jumper (JP3) in desired Mode (Burst, CCM
or DCM) position. Table 2 shows the default setting
for DC965A.
JP1
TRACK/SS
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
Figure 2 for proper scope probe technique.
1.
Place VOUT jumper in the OFF position, the PLLPF
jumper (JP2) at the selected frequency and the
SS
JP2 PLLPF JP3 MODE JP4
400kHz
DCM
VOUT
ON
Table 2. Default Jumper Settings
2.
With power off, connect a 4.5V-36V, 6A power
supply to VIN and GND.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 965A
SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER
3.
Connect a load to VOUT and GND (maximum load
is 5A).
4.
Move the VOUT jumper to the ON position.
5.
Turn on the power at the input.
7.
NOTE: Make sure that the input voltage is above
4.5V, but does not exceed 36V.
6.
NOTE: If there is no output, temporarily disconnect
the load to make sure that the load is not set too
high.
Once proper output voltages are established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage, efficiency
and other parameters.
Check for proper output voltages. VOUT should
measure 3.3V (could vary from 3.234V to 3.366V).
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 965A
SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER
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