Linear Technology LT3740EDHC, Быстрый старт

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LT3740EDHC
1
DESCRIPTION
Demonstration circuit 947 is a Wide Operating
Range, Valley Mode, No R
SENSE
™ Synchronous
Step-Down Controller featuring the LT3740EDHC.
It produces 1.8VDC for loads up to 10A from an
input range of 3-15VDC, switching at a fixed fre-
quency of 300KHz.
In order to operate from an input voltage as low as
3V, the circuit must provide adequate voltage to
drive the external power MOSFETs. To this end,
the LT3740 includes an on-chip step-up converter
to provide a bias about 7V above the input voltage
to power the top MOSFET gate driver. The stock
configuration of DC947 also uses this bias to
power the bottom gate drive circuit, but pads have
been added to the circuit board to power the bot-
tom gate drive from another source.
The LT3740 is equipped with an external reference
input that allows the user to override the 0.8V in-
ternal reference with any lower value, allowing full
control of the output voltage during operation, out-
put voltage tracking or soft-start.
In addition, the LT3740 has three current limit lev-
els that can be chosen by connecting the RANGE
pin to ground, leaving it open circuit, or tying to the
input.
DC947 is equipped with jumpers that allow the
user to select among soft-start options and refer-
ence voltage sources. Unpopulated pads have
been added to DC947 in order to facilitate input
voltages higher than 15V and No R
SENSE
™ opera-
tion.
Design files for this circuit board are available.
Call the LTC factory.
and LT are registered trademarks of Linear Technology Corporation. No R
SENSE
is a trademark of Linear Technology Corporation. Other product names may be
trademarks of the companies that manufacture the products.
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Input Supply Range 3.0 15.0 V
V
OUT
Output Voltage Range V
IN
= 3.0 – 15.0V, I
LOAD
= 0-10A 1.76 1.84 V
I
OUT
Output current V
IN
= 3.0 – 15.0V, V
OUT
= 1.8V 0 10.0 A
V
RIPPLE
Output Ripple V
IN
= 3.0 – 15.0V, I
LOAD
= 0-10A 20 mV
QUICK START PROCEDURE
Demonstration circuit 947 is easy to set up to
evaluate the performance of the LT3740EDHC.
Refer to Figure 1 for proper measurement equip-
ment setup and follow the procedure below:
DEMO CIRCUIT 947
QUICK START GUIDE
LT3740EDHC
Wide Operating Range, Valley Mode,
No R
SENSE
™ Synchronous Step-Down Controller