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dc2215af
DEMO MANUAL DC2215A
Description
LTC3126UFD
42V, 2.5A Synchronous Step-Down
Regulator with Lossless PowerPath
Demonstration Circuit 2215A, features the
synchronous buck converter with an integrated lossless
input PowerPath™. Pin selectable (JP2) ideal diode-OR
and priority input modes, with programmable undervolt-
age lockout thresholds provide control over the transi-
tion between input sources. The unique all N-channel
architecture provides efficient operation from either of
two input sources to a programmable output voltage.
In this application the valid input voltage range is set
to be from 4.3V to 42V on V
IN1
and from 6V to 8.4V on
V
IN2
providing flexibility and voltage margin for a variety
of applications and power sources. V
IN2
can operate to
42V. Other input voltage ranges are possible by adjusting
V
SET1/2
accordingly.
The LTC3126 uses a low noise, current mode architec-
ture and a resistor programmable (R13) PWM oscillator
frequency which is also synchronizable from 200kHz to
2.2MHz. This minimizes the solution footprint while ensur-
ing high efficiency. For higher efficiency at light loads, the
user can select Burst Mode
®
operation (JP1).
Typical efficiencies for both PWM mode (JP1 = PWM)
and Burst Mode operation (JP1 = BURST) are shown
in Figure 1. Burst Mode operation allows the automatic
transition to PWM operation if the load current increases.
This is shown in Figure 5. More information on Burst Mode
operation and PWM mode can be found in the data sheet.
L
, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
In some applications the efficiency can be improved by
setting the EXTV
CC
jumper (JP3) to V
OUT
. This allows the
converter to operate from the fixed V
OUT
voltage. Typical
performance in response to a transient load is shown in
Figure 4.
The system can be monitored through
VALID1
,
VALID2
,
PRIORITY
and PGOOD indicators. There are accurate
V
SET1
and V
SET2
comparators to program independent
UVLO thresholds. Consult the data sheet for information
on start-up and shutdown thresholds. Other features
include a 1μA shut-down current (ENA pin JP4 = OFF),
short-circuit protection, soft-start, inductor current limit
and thermal overload protection.
The LTC3126 data sheet has detailed information about
the operation, specifications, and applications of the part.
The data sheet should be read in conjunction with this
Quick Start Guide.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2215A
Input Voltage Range V
IN1
4.3V to 42.0V
Input Voltage Range V
IN2
6.0V to 8.4V (Operational to 42V)
V
OUT
3.3V
I
OUT
2.5A
