DC1157A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1157A
DUAL MONOLITHIC STEP-DOWN DC/DC CONVERTER
LT3510EFE
DESCRIPTION
Demo circuit 1157A is a dual monolithic step-down
DC/DC converter featuring LT®3510. The demo circuit is designed for 3.3V and 1.8V outputs from a
4.5V to 24V input. The current capability of each
channel is up to 2A. Independent input voltage, feedback, soft-start and power good pins for each channel simplify complex power supply tracking/sequencing requirements.
Both converters are synchronized to either a common external clock input or a resistor programmable
250kHz to 1.5MHz internal oscillator. At all frequencies, a 180° phase shift between channels is maintained, reducing voltage ripple and component size.
Programmable frequency allows for optimization between efficiency and external component size.
multiple clock cycles, only switching off when the
boost capacitor needs recharging, resulting in about
95% maximum duty cycle.
Each output can be independently disabled using its
own soft-start pin, or by using the SHDN pin the entire part can be placed in a low quiescent current
shutdown mode.
The LT3510 datasheet gives a complete description
of the part, operation and application information.
The datasheet must be read in conjunction with this
quick start guide for demo circuit 1157A.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Minimum input-to-output voltage ratios are improved by allowing the switch to stay on through
Table 1. Performance Summary ( TA = 25oC )
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
4.5V
Maximum Input Voltage
24V
Output Voltage VOUT1
3.3V ±4%
Output Voltage VOUT2
1.8V ±4%
Switching Frequency
500kHz ±20%
Maximum Output Current Iout1 and Iout2
2.0A
Voltage Ripple VOUT1
VIN=12V, Iout1=2A
10mV
Voltage Ripple VOUT2
VIN=12V, Iout2=2A
10mV
QUICK START PROCEDURE
Demo circuit 1157A is easy to set up to evaluate the
performance of the LT3510. Refer to Figure 1 for
proper measurement equipment setup and follow the
procedure below:
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1157A
DUAL MONOLITHIC STEP-DOWN DC/DC CONVERTER
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 JP1 on the COMBINED position.
2. With power off, connect the input power supply to VIN1 and GND. (Connect another input
power supply to VIN2 and GND if
INDEPENDENT is selected.)
3. Turn on the power at the input.
NOTE: Make sure that the input voltage does
not exceed 24V.
4. Check for the proper output voltages.
NOTE: If there is no output, temporarily
disconnect the load to make sure that the load is
not set too high.
5. 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.
ADDITIONAL NOTES
1. Install a 10k resistor at R22 if the board is synchronized from an external signal generator.
2. Different tracking and sequencing schemes can be
exercised. However, the Vout1 should stay on for
proper operation of Vout2.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1157A
DUAL MONOLITHIC STEP-DOWN 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 1157A
DUAL MONOLITHIC STEP-DOWN DC/DC CONVERTER
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