IS31LT3354 datasheet(8/12 Pages) ISSI

Part #	IS31LT3354

Description	40V LED DRIVER WITH EXTERNAL SWITCH

Download	12 Pages

Scroll/Zoom	100%

Manufacturer	ISSI [Integrated Silicon Solution, Inc]

Direct Link	http://www.issi.com

Logo

8 / 12 page

IS31LT3354

Integrated Silicon Solution, Inc. – www.issi.com

Rev. A, 09/01/2011

8

Inherent open-circuit LED protection

If the connection to the LED(s) is open-circuited, the

coil is isolated from the switch, so neither the chip nor

the switch will be damaged, unlike in many boost

converters, where the back EMF may damage the

switch by forcing the drain above its breakdown

voltage.

Capacitor selection

A low ESR capacitor should be used for input

decoupling, as the ESR of this capacitor appears in

series with the supply source impedance and lowers

overall efficiency. This capacitor has to supply the

relatively high peak current to the coil and smooth the

current ripple on the input supply.

If the source is DC supply, the capacitor is decided by

ripple of the source, the value is given by:

MAX

on

F

U

T

I

C





*

min

IF is the value of output current,

MAX

U



is the ripple

of power supply. Ton is the “ON” time of MOSFET the

value is normally 2 times of the minimum value.

If the source is an AC supply, typical output voltages

ripple from a nominal 12V AC transformer can be

±10%.If the input capacitor value is lower than 200μF,

the AC input waveform is distorted, sometimes the

lowest value will be lower than the forward voltage of

LED strings. This lower the average current of the

LEDs. So it is recommended to set the value of the

capacitor bigger than 200uF.

For maximum stability over temperature and voltage,

capacitors with X7R, X5R, or better dielectric are

recommended. Capacitors with Y5V dielectric are not

suitable for decoupling in this application and should

not be used.

Switch MOSFET selection

The IS31LT3354 demands a power N-MOSFET as a

switch. The voltage and current rating of the MOSFET

must be higher than the application output voltage and

the inductor peak current. The VGS(th) of MOSFET

should be lower than 3V and the RDSon should be as

low as possible for maximum efficiency and

performance. AP2306 and AP2310 are recommended.

NOTE: For the recommended MOSFETs, the

maximum load current is about 2A. For high current

applications, the operating input voltage, the LED

current, and the switching frequency will determine the

operating temperature of the MOSFET. Switching

frequency can be lowered by choosing a larger value

of inductance, however, the MOSFET specifications

must be carefully analyzed first. The key

specifications to consider are RDSON and CDS, both

should be as low as possible.

Inductor selection

Recommended inductor values for the IS31LT3354

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. (See

graphs). The inductor should be mounted as close to

the chip as possible with low resistance connections to

the GATE and VIN pins.

The chosen coil should have a saturation current

higher than the peak output current and a continuous

current rating above the required mean output current.

It is recommended to use an inductor with saturation

current bigger than 1.2A for 700mA output current and

inductor with saturation current bigger than 500mA for

350mA output current.

The inductor value should be chosen to maintain

operating duty cycle and switch 'on/off' times within the

specified limits over the supply voltage and load

current range.

The following equations can be used as a guide.

Switch 'On' time

)

(

LX

S

AVG

LED

IN

ON

R

rL

R

I

V

I

L

T









Note:

TONmin>200ns

Switch 'Off' time

)

(

S

AVG

D

LED

OFF

R

rL

I

V

I

L

T







Note:

TOFFmin>200ns

Where:

L is the coil inductance (H)

rL is the coil resistance (Ω)

Iavg is the required LED current (A)

∆I is the coil peak-peak ripple current (A) {Internally set

to 0.3 × Iavg}

VIN is the supply voltage (V)

VLED is the total LED forward voltage (V)

RLX is the switch resistance (Ω)

VD is the diode forward voltage at the required load

current (V)

Similar Part No. - IS31LT3354

Manufacturer	Part #	Datasheet	Description
Integrated Silicon Solu...	IS31LT3354-STLS2	301Kb / 12P	40V LED DRIVER WITH EXTERNAL SWITCH
Integrated Silicon Solu...	IS31LT3354-STLS2-TR	301Kb / 12P	40V LED DRIVER WITH EXTERNAL SWITCH

More results

Similar Description - IS31LT3354

Manufacturer	Part #	Datasheet	Description
Integrated Silicon Solu...	IS31LT3354-STLS2	301Kb / 12P	40V LED DRIVER WITH EXTERNAL SWITCH
	IS31LT3354-STLS2-TR	301Kb / 12P	40V LED DRIVER WITH EXTERNAL SWITCH
	IS31LT3350-V1SDLS2-TR	421Kb / 12P	40V LED DRIVER WITH INTERNAL SWITCH
List of Unclassifed Man...	ZLED7000	706Kb / 20P	40V LED Driver with Internal Switch
Unisonic Technologies	L4075	174Kb / 5P	40V LED DRIVER WITH INTERNAL SWITCH
Renesas Technology Corp	ZLED7000	739Kb / 19P	40V LED Driver with Internal Switch April 20, 2016
Integrated Silicon Solu...	IS31LT3350	421Kb / 12P	40V LED DRIVER WITH INTERNAL SWITCH
Unisonic Technologies	L4075	188Kb / 5P	40V LED DRIVER WITH INTERNAL SWITCH
Integrated Device Techn...	ZLED7000	564Kb / 18P	40V LED Driver with Internal Switch
Integrated Silicon Solu...	IS31LT3360-SDLS3-TR	438Kb / 15P	40V/1.2A LED DRIVER WITH INTERNAL SWITCH

More results

IS31LT3354 Datasheet(PDF) 8 Page - Integrated Silicon Solution, Inc

IS31LT3354 Datasheet(HTML) 8 Page - Integrated Silicon Solution, Inc

Similar Part No. - IS31LT3354

Similar Description - IS31LT3354

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12

Datasheet Download

Link URL