DESCRIPTION
Demonstration circuit 952 is a current mode syn-
chronous switching regulator featuring the
LTC3810. The circuit is configured as a synchro-
nous step-down regulator operating at 230kHz
switching frequency. Output voltage is 12V at 6A
maximum load. The input voltage range is 13V –
80V.
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). With jumper JP1 in the mid position
the circuit can synchronize to an external clock
signal on the Mode/Sync pin.
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 circuit 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
13 80
V
OUT
Output Voltage V
IN
= 24V, I
LOAD
= 100mA 11.8 12 12.2
I
OUT
Output Current V
IN
= 24V
0 6 A
I
Q
Input Current In Shutdown V
IN
= 24V, RUN/SS
= 0V
288 648 µA
I
IN
V
IN
Current In Pulse Skip Mode
(No Load)
V
IN
= 24V, V
FCB
= INTVCC, No Load 3.5 mA
I
IN
V
IN
Current In Forced Continuous Mode
(No Load)
V
IN
= 24V, V
FCB
= 0V, No Load
26 mA
Efficiency
Efficiency V
IN
= 24V, I
OUT
= 6A 96.4 %
OPERATING PRINCIPLES
The LTC3810 is a synchronous step-down switch-
ing regulator controller that can directly step down
voltages from up to 100V input, making it ideal for
telecom and automotive applications.
The LTC3810 uses a constant on-time valley cur-
rent 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 has a precise (0.5%) internal refer-
ence, a 25MHz error amplifier, large gate drivers,
DEMO CIRCUIT
LTC3810
Syn
Regula
