IS31LT3352-V2GRLS2-TR ISSI, IS31LT3352-V2GRLS2-TR Datasheet - Page 13

• Manufacturer Part Number: IS31LT3352-V2GRLS2-TR
• Description: LED Lighting Drivers 40V LED Drvr w/ External Switch
• Manufacturer: ISSI

Specifications of IS31LT3352-V2GRLS2-TR

• Input Voltage: 6 V to 40 V
• Operating Frequency: 154 kHz
• Maximum Supply Current: 80 uA
• Output Current: 750 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-8
• Factory Pack Quantity: 2500

IS31LT3352
LAYOUT CONSIDERATIONS
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.
Coil and decoupling capacitors
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. It is also important to take account of any trace
resistance in series with current sense resistor RS.
High voltage traces
Avoid running any high voltage traces close to the ADJI
pin, to reduce the risk of leakage due to board
contamination. Any such leakage may raise the ADJI pin
voltage and cause excessive output current. A ground
ring placed around the ADJI pin will minimize changes in
output current under these conditions
ADJI pin
The ADJI 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. The ADJI 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. ADJI 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
ADJI=1.2V.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 09/01/2011
RTH, RNTC pin
The PCB trace from R1 to RTH pin should be as short as
possible to reduce noise pickup. Because NTC thermistor
R2 is mounted close to the LEDs and remote from
IS31LT3352, the PCB trace from R2 to R
longer and pick up noise more easily. A 0.1uF capacitor
from R
recommended to filter the frequency noise and provide
protection against high voltage transients.
ADJO pin
Because ADJO pin drives next stages, ADJI pins and the
PCB trace may be longer which picks up noise easily. In
this case 200pF (max) capacitor is needed to connect
from ADJO trace to ground to filter out the noise. Best
practice is to connect one capacitor respectively close to
ADJO output pin and the next stage ADJI input pins, but
the total capacitance besides the parasitic capacitance
from ADJO pin to ground must be less than 200pF.
Please refer to the connection as below.
NTC
pin to ground and close to the R
NTC
NTC
pin will be
pin is
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