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dc2598af
DEMO MANUAL DC2598A
DESCRIPTION
LT8390A
60V 2MHz Synchronous
Buck-Boost Controller
Demonstration circuit 2598A is a 60V 2MHz synchronous
buck-boost controller featuring the
LT
®
8390A
. It accepts
an input voltage from 4V to 24V (with transient to 60V) and
regulates 12V output at up to 4A. DC2598A features high
efficiency and 2MHz switching frequency, a high speed
for a 4-switch buck-boost controller. It has a PGOOD flag,
short-circuit fault protection, ISMON current-monitoring
output signal, and spread spectrum frequency modulation
(SSFM) or frequency synchronization.
The LT8390A has a wide input voltage range from 4V to
60V. It can regulate an output as a boost, a buck, or a
4-switch boost-buck controller. It has adjustable switch-
ing frequency between 600kHz and 2MHz. It has an option
for external frequency synchronization or spread spec-
trum frequency modulation. Its high switching frequency
is unique to buck-boost controller ICs. Because of this, it
can be used for high power when the input may be above,
below, or equal to the output.
DC2598A features an option to turn on spread spectrum
by simply changing the position of a jumper from “NO
SSFM/SYNC” to “SSFM” (or to ”SYNC”).
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Analog
Devices, Inc. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
Small ceramic input and output capacitors are used to
save space and cost. There is a protection diode from
LED+ to GND to prevent negative ringing during a short-
circuit with long wires. Optional EMI input, output, and
gate resistor component placeholders exist when a low
EMI application is needed.
Under voltage lockout can be adjusted with a few resistors
and output voltage can be changed from 12V with FB resis-
tors changes. Please note that higher voltage outputs may
require higher voltage MOSFETs and output capacitors.
The LT8390A data sheet gives a complete description of the
part, operation and applications information. The data sheet
must be read in conjunction with this demo manual for
demonstration circuit 2598A. The LT8390AEUFD is assem-
bled in a 28-lead 4mm × 5mm plastic QFN package with a
thermally enhanced ground pad. LT8390A is also available
in a 28-Lead plastic TSSOP (FE) package. Proper board
layout is essential for maximum thermal performance. See
the data sheet section “Layout Considerations”.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2598A
Specifications are at T
A
= 25°C
PARAMETER
CONDITION
MIN
TYP
MAX
Input Voltage Range
Operating
4V
60V
Full Load (4A) Input Voltage Range
Component Temp Rise <60°C with No Airflow
7V
23V
Typical Efficiency
12V Input, 12V 4A Output, 2MHz
90%
Switching Frequency
R3 = 59.0k
2MHz
Peak Switch Current Limit
R1 = 0.005Ω
10A
(AC) Output Ripple
12V Input, 12V 4A Output
70mV
P-P
Input Under Voltage Lockout (Falling Turn-Off)
R7 = 383k, R8 = 165k
4.0V
Input Under Voltage Lockout (Rising Turn-On)
R7 = 383k, R8 = 165k
5.0V
V
ISMON
12V 4A Output
1.0V
Maximum Load Current
12V Input, 12V Output
4
4.5A
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