LP3350 datasheet(6/7 Pages) POWER

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Preliminary Datasheet

LP3350

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LP3350–00 Version 0.3 NOV-2017

Application Information

The LP3350 is designed in a current mode, constant

frequency PWM boost converter. It can use dimming

input that can by external control signal with a duty

ratio of 1%-100% in 100Hz to 1kHz. LP3350 offers

protection features to protect the system such as

output

over

voltage

protection,

boost

diode

disconnection

protection,

output

short

circuit

protection and over temperature protection.

Under Voltage Lockout (UVLO)

The LP3350 had an UVLO internal circuit that enable

the device once the voltage on the VIN voltage

exceeds the UVLO threshold voltage.

Boost Controller

The LP3350 uses 200kHz fixed-frequency, current

mode architecture to fixed the output current. The

output voltage and soft start time can be adjustable by

internal register.

Boost Loop Compensation

The feedback loop can be compensated with an

external compensation network consisted of Rcomp,

Ccomp (As Figure 1). Choosing Rcomp to set high

frequency integrator gain for fast transient response

and Ccomp to set the integrator zero to maintain loop

stability.

Over Voltage Protection

The LP3350 converter has an over voltage protection

by OVP pin. When the LEDs fail open circuit or LEDs

are disconnected from the circuit, the over voltage

function will monitor the output voltage through OVP

pin to protect the converter. When LP3350 occur

OVP, it will latch off until VIN is re-startup or CTRL

input is recycled.

LED Current Setting

The LED current is specified by current sense resistor

between the FB pin to ground. In order to have

accurate

LED

current,

precision

resistors

are

preferred. The LED current can be programmed by:

ILED=0.3/RFB

Dimming Control

The LED brightness is controlled by the PWM signal

at CTRL pin which has different duty cycle. LP3350

can accept an external PWM signal to CTRL pin in the

range of 100Hz to 1 kHz.

Over Temperature Protection

The

LP3350

device

enters

over

temperature

protection(OTP) if its junction temperature exceeds

160°C (Typ.). During over temperature protection

none of the device's functions are available. To

resume normal operation the junction temperature

need cool down, and the outputs will restart.

Layout Guideline

The proper PCB layout and component placement

are critical for all circuit. The careful attention

should be prevent electromagnetic interference

(EMI) problems. Here are some suggestions to the

layout of LP3350 design.

1. Connected all

ground together

with one

uninterrupted ground plane with at least two vias .

2. The input capacitor should be located as closed

as possible to the VIN and ground plane.

3. Minimize the distance of all traces connected to

the LX node, that the traces short and wide route

to obtain optimum efficiency.

4. All output capacitor must be closed to ground

plane.

The ground terminal of COUT must be located as

closed as possible to ground plane.

5. Radiated noise can be decreased by choosing

a shielded inductor.

Diode

GND

VIN

LP3350

RComp

CComp

GND

V+

RFB

V-

Figure 4. Recommended PCB Layout Diagram

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