DC1168A - Demo Manual

DEMO CIRCUIT 1168
LTC3810-5
QUICK START
GUIDE
LTC3810-5 Current Mode
Synchronous Switching
Regulator Controller
DESCRIPTION
Demonstration circuit 1168 is a current mode
synchronous switching regulator featuring the
LTC3810-5. The circuit is configured as a synchronous 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 continuous mode (for best load transient response at low
current) or in pulse skip mode (for best efficiency
at low current).
PERFORMANCE SUMMARY
SYMBOL
VIN
VOUT
IOUT
IQ
IIN
PARAMETER
Input Supply Range
Output Voltage
Output Current
Input Current In Shutdown
VIN Current In Pulse Skip Mode
(No Load)
IIN
VIN Current In Forced Continuous Mode
(No Load)
Efficiency Efficiency
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
RSENSE, 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 trademarks of the companies that manufacture the products.
Specifications are at TA = 25°C
CONDITIONS
VIN = 24V, ILOAD = 100mA
VIN = 24V
VIN = 24V, RUN/SS = 0V
VIN = 24V, VFCB = INTVCC, No Load
VIN = 24V, VFCB = 0V, No Load
VIN = 24V, IOUT = 6A
MIN
14
11.8
0
TYP
12
262
3
MAX
60
12.2
10
622
UNITS
V
V
A
µA
mA
32
mA
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 reference, a 25MHz error amplifier, large gate drivers,
programmable softstart, a shutdown pin, a Power
Good output, a Sync input and a flexible bias regulator circuit that can be configured in many different ways to fit the application.
1
LTC3810-5
The 5.5V bias regulator circuit controls an external
series transistor which helps to reduce internal
power dissipation when the bias voltage is generated from the input voltage. LTC3810-5 also contains an internal low dropout regulator that can be
used when an external voltage source in the range
4.7V…15V is available. Demonstration Circuit
1168 uses this internal regulator to generate the
bias voltage from the 12V output during normal
operation, while the external series transistor is
used for startup.
Demonstration Circuit 1168 is configured to use
current sense resistor, but can easily be modified
to sense current without sense resistor by moving
zero ohm resistor R20 to R21, adjusting the current limit for the increased sense voltage by moving R5 to R4, and replacing the current sense resistor (R22, R23) with a short circuit.
EQUIPMENT
4 DMMs
1 DC Supply 0-60V capable of delivering at least 150W
1 Adjustable load 0-10A
QUICK START PROCEDURE
Demonstration circuit 1168 is easy to set up to evaluate the performance of the LTC3810-5. Refer to
Figure 1 for proper measurement equipment setup and follow the procedure below:
1. Place jumpers in the following positions:
JP1 Forced continuous mode operation
JP2 ON
2. With power off, connect the input power supply to Vin and GND.
3. Set the power supply to 24V and turn on the power at the input.
NOTE. Make sure that the input voltage does not exceed 60V.
4. Check for the proper output voltage. Vout = 11.8V to 12.2V.
NOTE. If there is no output, temporarily disconnect the load to make sure that the load is not set too high.
5. Once the proper output voltages are established, adjust input voltage and load within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
2
LTC3810-5
Figure 1. Proper Measurement Equipment Setup
3
LTC3810-5
4
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