DC967B - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 967B
SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER
LTC3835EFE
DESCRIPTION
Demonstration circuit 967B is a single output high
frequency step-down DC/DC converter featuring
the low quiescent current LTC3835 in a 20-pin FE
package. The DC967B is designed to generate a
regulated [email protected] output from 4.5V to 36V input
voltage.
The demo board allows low dropout operation
when input voltage is close to the output voltage
to maximize battery usage. The selectable burst
mode operation reduces the IC supply current at
light loads to extend the battery life. The phaselockable frequency and clock-out signals allow
interleaving operation of multiple supplies in parallel for high output current applications. The output voltage of the LTC3835 can track an external
Table 1.
ramp voltage during power-up and power-down.
Also, the built-in current foldback prevents
MOSFET overheating during short-circuit and the
ExtVcc option reduces the IC power loss with an
external bias voltage.
All these features make the circuit an ideal solution for applications in automotive and batteryoperated systems, telecom and distributed DC
power systems.
Design files for this circuit are available.
Call the LTC Factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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
Nominal Switching Frequency
Efficiency
TYPICAL
4.5V
3.3V
3.366V
36mVP–P
400kHz
VIN = 14V, IOUT = 3.5A, 400kHz Switching Frequency
91.5%
QUICK START PROCEDURE
Demonstration circuit 967B is easy to set up to
evaluate the performance of the LTC3835EFE.
Refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
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.
NOTE:
1.
Place VOUT in OFF position, the FREQUENCY
jumper at the selected frequency and the
MODE jumper JP2 in desired Mode (Burst,
CCM or DCM) position. Table 2 shows the default setting for DC967B.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 967B
SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER
NOTE: Make sure that the input voltage is above
4.5V, but does not exceed 36V.
JP1
JP2
JP3
JP4
JP5
FREQUENCY MODE CLKOUT VOUT TRACK/SS
400kHz
BURST
O
90
ON
6.
SS
Table 2. Default Jumper Settings
2.
With power off, connect a 4.5V-36V, 6A power
supply to VIN and GND.
3.
Connect a load to VOUT and GND (maximum
load is 5A).
4.
Move the VOUT jumper to ON position.
5.
Turn on the power at the input.
Check for the proper output voltage. Vout
should measure 3.3V (could vary from 3.234V
to 3.366V).
NOTE: If
there is no output, temporarily disconnect the load to make sure that the load is not
set too high.
7.
Once the proper output voltage is established,
adjust the load within the operating range and
observe the output voltage regulation, ripple voltage, efficiency and other parameters.
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 967B
SINGLE 5A HIGH FREQUENCY STEP-DOWN DC/DC CONVERTER
3
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