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dc2117af
DEMO MANUAL DC2117A
Description
LTC3895EFE
High Input Voltage
Synchronous Buck Converter
Demonstration circuit 2117A is a single output high volt-
age nonisolated synchronous step-down converter that
drives all N-channel MOSFET power stage. It features the
LTC3895EFE, a high voltage step-down DC/DC controller
housed in a TSSOP-38 package with several pins removed
for high voltage spacing.
This DC2117A operates over an input voltage range from
14V to 130V, while the
can operate up to 150V.
This demo board produces a 12V output voltage with up to
a 5A output current, and is configured with a sense resistor
for over current protection and has optional DCR sensing.
To prevent high on-chip power dissipation in high input
voltage applications, the LTC3895 includes an NDRV pin
which drives the gate of an optional external N-channel
MOSFET acting as a low dropout linear regulator to supply
IC power and is an option on this board.
An internal charge pump allows for 100% duty cycle op-
eration in dropout, a useful feature when powered from
a battery during discharge. The LTC3895’s powerful 1Ω
L
, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
performance summary
N-channel MOSFET gate drivers can be adjusted from
5V to 10V to enable the use of logic- or standard-level
MOSFETs to maximize efficiency. The EXTV
CC
pin permits
the LTC3895 to be powered from the output of the switch-
ing regulator or other available source, reducing power
dissipation and improving efficiency.
A mode selector allows the DC2117A to operate in forced
continuous operation, pulse-skipping or low ripple Burst
Mode
®
operation during light loads. Additional features
include a power good output signal, a PLLIN, PHASEMD
and CLKOUT for multiphase operation.
The LTC3895 data sheet gives a complete description of
the part, operation and application information and must
be read in conjunction with this demo board manual.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2117A
Specifications are at T
A
= 25°C
Table 1.
PARAMETER
CONDITIONS
UNITS
Input Voltage Range
DC Up to 150V
PK
Transient
14V ~ 130V
Output Voltage V
OUT
V
IN
= 14~130V, I
OUT
= 0~5A, JP4: FCM
12V ± 2% (11.76V ~ 12.24V)
Maximum Output Current I
OUT(MAX)
V
IN
= 14~130V
5A
Default Operating Frequency (Typical)
150kHz
External Clock Sync Frequency Range
75kHz to 850kHz
Typical Full Load Efficiency (See Figure 4)
V
IN
= 48V, V
OUT
= 12V, I
OUT
= 5A, f
SW
= 150kHz
94.9%
*Important Note: 60V or higher voltage can result in an electric shock if care is not taken. Also, hot plugging the circuit to a power supply that has more
than 40V present at its output can produce a high voltage transient exceeding the absolute maximum input voltage which can damage the DC2117A
board.