DC964A - Demo Manual

DEMO CIRCUIT 964A
LT3501
QUICK START GUIDE
LT3501
3A Dual Monolithic
Step-Down DC/DC Converter
DESCRIPTION
Demo circuit 964A is a dual monolithic step-dow n DC/DC
converter featuring LT3501. 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 3A. Independent input voltage, feedback, soft-start and pow er good
pins for each channel simplify complex pow er supply
tracking/sequencing requirements.
Both converters are synchronized to either a common
external clock input or a resistor programmable 250kH z
to 1.5M H z internal oscillator. At all frequencies, a 180°
phase shift betw een channels is maintained, reducing
voltage ripple and component size. Programmable frequency allow s for optimization betw een efficiency and
external component size.
cles, only sw itching off w hen the boost capacitor needs
recharging,resulting in ~95% maximum duty cycle.
Each output can be independently disabled using its ow n
soft-start pin, or by using the SH DN pin the entire part
can be placed in a low quiescent current shutdow n
mode.
The LT3501 datasheet gives a complete description of
the part,operation and application information. The datasheet must be read in conjunction w ith this quick start
guide for demo circuit 964A.
Design files for this circuit board are available. Call
the LTC factory.
,LTC and LT are registered trademarks ofLinear Technology Corporation.
M inimum input-to-output voltage ratios are improved by
allow ing the sw itch to stay on through multiple clock cy-
Performance Summary ( TA = 25oC )
PAR AM ETER
M inimum Input Voltage
M aximum Input Voltage
O utput Voltage VOUT1
O utput Voltage VOUT2
Sw itching Frequency
M aximum O utput Current Iout1 and Iout2
Voltage R ipple VOUT1
Voltage R ipple VOUT2
CO N DITIO N
VIN=4.5~16V
VIN=16~24V
VIN=12V,Iout1=3A
VIN=12V,Iout2=3A
VALU E
4.5V
24V
3.3V ±4%
1.8V ±4%
500kH z ±20%
3.0A
2.8A
<10mV
<10mV
1
LT3501
QUICK START PROCEDURE
Demo circuit 964A is easy to set up to evaluate the performance of the LT3501. R efer to Figure 1 for proper
measurement equipment setup and follow the procedure
below :
NOTE. W hen measuring the input or output voltage ripple,care must be
taken to avoid a long ground lead on the oscilloscope probe. M easure the
input or output voltage ripple by touching the probe tip directly across the
VIN or VO U T and GND terminals. See Figure 2 for proper scope probe
technique.
1.
Place JP1 on the CO M BINED position.
2.
W ith pow er off, connect the input pow er supply to
VIN1 and G ND. (Connect another input pow er supply
to VIN2 and G ND ifINDEPENDENT is selected.)
3.
Turn on the pow er at the input.
NOTE. M ake sure that the input voltage does not exceed 24V.
4.
Check for the proper output voltages.
NOTE. Ifthere is no output,temporarily disconnect the load to make
sure that the load is not set too high.
5.
O nce the proper output voltage is established, adjust
the load w ithin the operating range and observe the
output voltage regulation,ripple voltage,efficiency and
other parameters.
Figure 1. Proper M easurem ent Equipm ent Setup
2
LT3501
GND
VIN
Figure 2. M easuring Input or Output Ripple
ADDITIONAL NOTES
1. Install a 10k resistor at R 22 if the board is synchronized from an external signal generator.
2. Different tracking and sequencing schemes can be
exercised. H ow ever, the Vout1 should stay on for
proper operation ofVout2.
3
LT3501
4
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