BP2325A View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

BP2325A

Non-isolated Buck APFC Offline LED Driver

Unspecified 

BP2325A

Non-isolated Buck APFC Offline LED Driver

3 Feedback Network

The BP2325A senses the output current zero

crossing information through the feedback network,

the FB falling threshold voltage is set to 0.2V with

0.15V hysteresis. The FB pin is also used to detect

output OVP, the threshold voltage is 1.6V. The ratio

of FB upper resistor to lower resistor can be set as:

RFBL  1.6V

RFBL  RFBH VOVP

Where,

RFBL: The lower resistor of the feedback network

RFBH: The upper resistor of the feedback network

VOVP: Output over voltage setting point

It is recommended that the FB lower resistor set to

5KΩ--10KΩ.

4 Thermal Regulation

The BP2325A integrates thermal regulation function.

When the system is over temperature, the output

current is gradually reduced; the output power and

thermal dissipation are also reduced. The system

temperature is regulated and the system reliability is

improved. The thermal regulation temperature is set

to 150℃ internally.

5 Protection Functions

The BP2325A offers rich protection functions to

improve the system reliability.

When the LED is open circuit, the output voltage

will gradually rise up. The output voltage is sensed

by the FB pin when power MOSFET is turned off.

When FB voltage reaches the OVP threshold, it will

trigger fault logic and the system stops switching.

When the LED is shorted circuit, the system will

work under 10kHz switching frequency. Meanwhile,

the output voltage is low and the VCC pin cannot be

charged up by the output voltage, so the VCC pin

voltage will gradually decrease and finally reaches

the UVLO threshold.

After the system enters into fault condition, the VCC

voltage will decrease until it reaches UVLO

threshold. Then the system will re-start again. If the

fault condition is removed, the system will resume

normal operation.

When the output is short circuit or the inductor is

saturated, the CS peak voltage will be relatively high.

When CS voltage reaches the internal limitation (1V),

the power MOSFET will be turned off

instantaneously. This cycle by cycle current

limitation can help protecting the power MOSFET,

the inductor and the output diode.

6 PCB Layouts

The following guidelines should be followed in

BP2325A PCB layout:

Bypass Capacitor

The bypass capacitor on VCC pin should be as close

as possible to the VCC and GND pins.

Ground Path

The power ground path for current sense resistor

should be short and wide, and it should be as close as

possible to the IC ground (pin 2) , otherwise the LED

output current accuracy maybe affected. The IC

signal ground for COMP and FB components should

be connected to the IC GND pin with short traces

and should be away from the power ground path.

The Area of Power Loop

The area of main current loop should be as small as

possible to reduce EMI radiation.

FB Pin

The feedback resistor divider should be as close as

possible to the FB pin, and the trace must keeps

away from dynamic node of the inductor (DRAIN

pin trace), otherwise the FB pin OVP function might

have risk to be mis-triggered by the system noise.

DRAIN Pin

To increase the copper area of DRAIN pin for better

BP2325A_EN _DS_Rev.1.0

www.bpsemi.com

7

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