RT4539AWSC datasheet(31/39 Pages) RICHTEK

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RT4539A

is a registered trademark of Richtek Technology Corporation

DS4539A-01

December 2022

www.richtek.com

MTP Function

The RT4539A integrates Multiple-Time Programmable

(MTP) non-volatile memory. During power-on, the

contents of the MTP are transferred to the DAC register.

Users can write and read MTP or DAC via I2C interface.

If users want to change data of MTP, it is needed to

write all desired data to DAC first. Finally, write address

0xFFh [7: 7] = 1, and it will write all data of DAC into

MTP. Users also can read data from DAC or MTP via

address 0xFFh [0: 0]. When 0xFFh = 0, I2C interface

reads data from DAC. Otherwise, 0xFFh = 1, I2C

interface reads data from MTP. The detailed

description is shown in Table 19.

Table 19. MTP Function

Address Bit

Name

Default Value

Description

R/W

FFh

[0: 0]

MTP Read

I2C read data from DAC

(B0)

MTP Read

B0: I2C reads data from DAC

B1: I2C reads data from MTP

R/W

FFh

[7: 7] MTP Programming

Normal operation

(B0)

MTP Programming

B0: Normal operation

B1: Start MTP programming sequence

R/W

LED OVP level

The LED OVP level can be controlled by address 0x0Ah

[6: 5] and LED OVP level range is from 2.1V to 3.5V.

When the minimum FBx voltage rises above the LED

OVP level setting, the internal switch will be turned off.

Once the minimum FBx voltage drops below the LED

OVP level setting, the internal switch will be turned on

again. The minimum FBx voltage can be clamped at the

LED OVP level setting

LED Connection

The LED strings are connected from the output of the

boost converter to pin FBx (x = 1 to 6) respectively. If

one of the current sink channels is not used, the FBx pin

should be connected toGND. If the un- used channel is

not connected to GND, it will be considered as a

LED string open. Once the channel is accounted as

string open, the un-used channel can be turned on

again when the LED string is reconnected.

LED String Open Protection

If the voltage at FBx pin is lower than 100mV, this

channel is defined as open channel. The Minimum LED

Selection function will discard this channel and regulate

other used channels in proper voltage. Once the

channel is accounted as string open, the FBx pin

voltage will not be regulated and not latched, until the

FBx pin is reconnected, the FBx pin will work normally

again. If all FBx pins are open (floating), the output

voltage will be clamped to the setting voltage of OVP

(VOUT(OVP)).

LED String Short Protection

If CHx pin voltages exceeds the threshold of

approximately 5.6V during normal operation, the

channels will be turned off and it can be reset by EN or

VIN UVLO.

Over Temperature Protection

The RT4539A has over-temperature protection function

to prevent the IC from overheating due to excessive

power dissipation. The OTP function will shut down the

IC when junction temperature exceeds 150°C (typ.).

When junction temperature cools down to 130°C

(TOTP_hys = 20°C), the LED driver will return to normal

operation.

Input Capacitor Selection

Low ESR ceramic capacitors are recommended for input

capacitor applications. Low ESR will effectively reduce

the input ripple voltage caused by the switching operation.

Two 2.2µF low ESR ceramic capacitors are sufficient for

most applications. Nevertheless, this value can be

decreased for applications with lower output current

requirement.

Another consideration is the voltage rating of the input

capacitor, which must be greater than the maximum input

voltage.

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