DESCRIPTION
Demonstration circuit 1168 is a current mode
synchronous switching regulator featuring the
LTC3810-5. The circuit is configured as a synchro-
nous step-down regulator operating at 250kHz
switching frequency. Output voltage is 12V at 10A
maximum load. The input voltage range is 14V –
60V.
The operating mode can be selected with jumper
JP1. Depending on the position of this jumper, at
low load the circuit will operate in forced continu-
ous mode (for best load transient response at low
current) or in pulse skip mode (for best efficiency
at low current).
A Power Good output is provided. The PGOOD
output is normally high, with a pull up resistor to
VLOGIC. If the output voltage is not within ± 10%
of nominal value the PGOOD signal will go low.
The switching frequency can be synchronized to
an external clock signal.
Design files for this circuit board are available.
Call the LTC factory.
L
, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are
registered trademarks of Linear Technology Corporation. Adaptive Power, C-Load,
DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, µModule, Micropower
SwitcherCAD, Multimode Dimming, No Latency ∆Σ, No Latency Delta-Sigma, No
R
SENSE
, Operational Filter, PanelProtect, PowerPath, PowerSOT, SmartStart,
SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are
trademarks of Linear Technology Corporation. Other product names may be trade-
marks 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
14 60
V
OUT
Output Voltage V
IN
= 24V, I
LOAD
= 100mA 11.8 12 12.2
I
OUT
Output Current V
IN
= 24V
0 10 A
I
Q
Input Current In Shutdown V
IN
= 24V, RUN/SS
= 0V
262 622 µA
I
IN
V
IN
Current In Pulse Skip Mode
(No Load)
V
IN
= 24V, V
FCB
= INTVCC, No Load 3 mA
I
IN
V
IN
Current In Forced Continuous Mode
(No Load)
V
IN
= 24V, V
FCB
= 0V, No Load
32 mA
Efficiency
Efficiency V
IN
= 24V, I
OUT
= 6A 95.1 %
OPERATING PRINCIPLES
The LTC3810-5 is a synchronous step-down
switching regulator controller that can directly step
down voltages from up to 60V input, making it
ideal for telecom and automotive applications.
The LTC3810-5 uses a constant on-time valley
current control architecture to deliver very low duty
cycles with accurate cycle-by-cycle current limit
without requiring a current sense resistor. The cur-
rent limit is adjustable and the operating frequency
is selected by an external resistor.
The LTC3810-5 has a precise (0.5%) internal ref-
erence, a 25MHz error amplifier, large gate drivers,
programmable softstart, a shutdown pin, a Power
Good output, a Sync input and a flexible bias regu-
lator circuit that can be configured in many differ-
ent ways to fit the application.
DEMO CIRCUIT
LTC3810-5
Regu
