LUMISSIL IS31LT3360 MR16 Demo Board User Guide
- June 3, 2024
- LUMISSIL
Table of Contents
IS31LT3360 MR16 DEMO BOARD GUIDE
DESCRIPTION
The IS31LT3360 is a continuous mode inductive step-down converter, designed
for driving a single LED or multiple series connected LEDs efficiently from a
voltage source higher than the LED voltage. The chip operates from an input
supply between 6V and 40V and provides an externally adjustable output current
of up to 1.2A.
The IS31LT3360 includes an integrated output switch and a high-side output
current sensing circuit, which uses an external resistor to set the nominal
average output current.
Output current can be adjusted linearly by applying an external control signal
to the ADJ pin. The ADJ pin will accept either a DC voltage or a PWM waveform.
This will provide either a continuous or a gated output current.
Applying a voltage of 0.2V or lower to the ADJ pin turns the output off and
switches the chip into a low current standby state.
The chip is assembled in SOT89-5 package. IS31LT3360 MR16 DEMO board is used
in MR16 lamp.
FEATURES
- Simple low parts count
- Internal 40V power switch
- Wide input voltage range: 6V to 40V
- Up to 1.2A output current
- High efficiency (up to 98% )
- Typical 1200:1 dimming rate
- Typical 3% output current accuracy
- Single pin on/off and brightness control using DC voltage or PWM
- Up to 1MHz switching frequency
- Inherent open-circuit LED protection
- Thermal shutdown protection circuitry
QUICK START
RECOMMENDED EQUIPMENT
- 30VDC power supply
- LED panel (3 WLEDs, 2 LEDs in series)
- Multi-meter
RECOMMENDED INPUT AND OUTPUT RATINGS
- Input: 12~24VDC or 12VAC
- Output: 1~3 LEDs in series/667mA
Note: The input voltage must be 2V higher than the output voltage (total VF).
ABSOLUTE MAXIMUM RATINGS
- Input voltage 25VDC
Caution: Do not exceed the conditions listed above, otherwise the board will be damaged.
PROCEDURE
The IS31LT3360 DEMO Board is fully assembled and tested. Follow the steps
listed below to verify board operation.
Caution: Do not turn on the power supply until all connections are
completed.
- Connect the terminals of the power supply to theAC1 and AC2 pin.
- Connect the negative of the LED panel (LEDarrays) to the LED- terminal.
- Connect the positive of the LED panel (LED arrays) to the LED+ terminal.
- Turn on the power supply and the LED panel(LED arrays) will light.
ORDER INFORMATION
| Part No. | Temperature Range | Package |
|---|---|---|
| IS31LT3360-SDLS3-EBMR16 | -40°C to +105°C (Industrial) | SOT89-5, Lead-free |
For pricing, delivery, and ordering information, please contacts Lumissil’s analog marketing team at analog@Lumissil.com or 408-969-6600.
DETAILED DESCRIPTION
LED Current Control
The nominal average output current in the LED(s) is determined by the value of
the external current sense resistor (RS) connected between VIN and ISENSE and
in is given by:
IOUT_NOM= 0.1/Rs [for Rs>0.082Ω] The table below gives values of nominal
average output current for several preferred values of current setting
resistor (Rs) in the typical application circuit shown on Page 1:
| Rs (Ω) | Nominal Average Output Current (mA) |
|---|---|
| 0.082 | 1200 |
| 0.1 | 1000 |
| 0.15 | 667 |
| 0.3 | 333 |
VSENSE is divided into two ranges to improve current accuracy, please refer to
bin information on Page 3.
The above values assume that the ADJ pin is floating and at a nominal voltage
of VREF =1.2V.
Note that RS=0.082Ω is the minimum allowed value of sense resistor under these
conditions to maintain switch current below the specified maximum value.
It is possible to use different values of RS if the ADJ pin is driven from an
external voltage.
Inductor selection
Recommended inductor values are in the range 47μH to 220μH.
Higher values of inductance are recommended at higher supply voltages and low
output current in order to minimize errors due to switching delays, which
result in increased ripple and lower efficiency. Higher values of inductance
also result in a smaller change in output current over the supply voltage
range. The inductor should be mounted as close to LX pin as possible with low
resistance connections to LX and VIN pins.
PCB LAYOUT CONSIDERATION
Decoupling Capacitors And Coil
It is particularly important to mount the coil and the input decoupling
capacitor close to the chip to minimize parasitic resistance and inductance,
which will degrade efficiency. The input decoupling capacitor (0.1µF fixed)
must be placed as close to the VIN and GND pins as possible. It is also
important to take account of any trace resistance in series with current sense
resistor RS.
LX Pin
The LX pin of the chip is a fast switching node, so PCB traces should be kept
as short as possible. To minimize ground ‘bounce’, the ground pin of the chip
should be soldered directly to the ground plane.
ADJ Pin
The ADJ pin is a high impedance input, so when left floating, PCB traces to
this pin should be as short as possible to reduce noise pickup. ADJ pin can
also be connected to a voltage between 1.2V~5V. In this case, the internal
circuit will clamp the output current at the value which is set by VADJ=1.2V.
High Voltage Traces
Avoid running any high voltage traces close to the ADJ pin, to reduce the risk
of leakage due to board contamination. Any such leakage may raise the ADJ pin
voltage and cause excessive output current. A ground ring placed around the
ADJ pin will minimize changes in output current under these conditions.
BILL OF MATERIALS
Name| Symbol| Description| Qty| Supplier| Part
No.
---|---|---|---|---|---
IC| U1| HBLED driver| 1| Lumissil| IS31LT3360
SMD Resistor| R1| RES,0.15R,±1%,1206| 1| |
AL Capacitor| C1| CAP,220pF,25V| 1| |
SMD Capacitor| C2| CAP.100nF.50V| 1| |
SMD Capacitor| C3| CAP,1pF,50V| 1| |
Schottky Diode| D1–D5| SS26,2A.60V| 5| |
SMD Inductor| L1| 47pH,IsAT1A| 1| |
Bill of materials refers to Figure 2 above.
Copyright © 2011 Lumissil Microsystems. All rights reserved. Lumissil
Microsystems reserves the right to make changes to this specification and its
products at any time without notice. Lumissil Microsystems assumes no
liability arising out of the application or use of any information, products
or services described herein. Customers are advised to obtain the latest
version of this device specification before relying on any published
information and before placing orders for products.
Lumissil Microsystems does not recommend the use of any of its products in
life support applications where the failure or malfunction of the product can
reasonably be expected to cause failure of the life support system or to
significantly affect its safety or effectiveness. Products are not authorized
for use in such applications unless Lumissil Microsystems receives written
assurance to its satisfaction, that:
a.) the risk of injury or damage has been minimized;
b.) the user assume all such risks; and
c.) potential liability of Lumissil Microsystems is adequately protected under
the circumstances
Lumissil Microsystems – www.lumissil.com
Rev. B, 08/26/2011
Downloaded from Arrow.com.
References
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