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dc1781af
DEMO MANUAL DC1781A
DESCRIPTION
LT3507A
Triple Monolithic Step-Down
Regulator with LDO
Demo circuit 1781A is a Triple Monolithic Step-Down Regu-
lator with LDO featuring the LT3507A. The demo circuit
is designed for 1.8V, 3.3V, 5.0V and 2.5V outputs from a
7V to 36V input. The current capability of each channel
is 2.7A, 1.5A, 1.8A and 0.3A respectively. Independent
input voltage, feedback, soft-start and power good pins
for each channel simplify complex power supply tracking/
sequencing requirements.
All three converters are either synchronized to a common
external clock input or single-resistor programmable from
250kHz to 2.5MHz using internal oscillator. At all frequen-
cies, a 180° phase shift between V
OUT1
and the other two
outputs is maintained, reducing input voltage ripple and
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
component size. Programmable frequency allows for opti-
mization between efficiency and external component size.
Each output can be independently disabled using its own
soft-start pin, or by using the
SD
terminal the entire part
can be placed in a low quiescent current shutdown mode.
The LT3507A data sheet gives a complete description of
the part, operation and application information. The data
sheet must be read in conjunction with this quick start
guide for demo circuit 1781A.
Design files for this circuit board are available at
http://www.linear.com/demo
(T
A
= 25°C)
PARAMETER
CONDITIONS
VALUE
Minimum Input Voltage
7V
Maximum Input Voltage
36V
Output Voltage V
OUT1
V
IN
= 7~36V
1.80V ±3%
Output Voltage V
OUT2
V
IN
= 7~36V
3.33V ±3%
Output Voltage V
OUT3
V
IN
= 7~36V
5.0V ±3%
Output Voltage V
OUT4
V
IN
= 7~36V
2.52V ±3%
Switching Frequency
450kHz ±10%
Maximum Output Current I
OUT1
V
IN
= 7~36V
2.7A
Maximum Output Current I
OUT2
V
IN
= 7~36V
1.5A
Maximum Output Current I
OUT3
V
IN
= 7~36V
1.8A
Maximum Output Current I
OUT4
V
IN
= 7~36V
0.3A
Voltage Ripple V
OUT1
V
IN
= 12V, I
OUT1
= 2.7A
<20mV
Voltage Ripple V
OUT2
V
IN
= 12V, I
OUT2
= 1.5A
<20mV
Voltage Ripple V
OUT3
V
IN
= 12V, I
OUT3
= 1.8A
<20mV
Voltage Ripple V
OUT4
V
IN
= 12V, I
OUT4
= 0.3A
<10mV
