RT4832AWSC datasheet(20/26 Pages) RICHTEK

20 / 26 page

RT4832A

is a registered trademark of Richtek Technology Corporation.

www.richtek.com

DS4832A-00

January

2017

Figure 4. LED Current vs Brightness Code

Ramp Rate

There are 16 programmable ramp rates available in the

RT4832A. These ramp rates are programmable as a

time. Therefore, the ramp time from one current

set-point to the next, depends on the register 0x03[6:3].

Over-Voltage Protection (Open LED, Open Circuit)

The RT4832A provides an internal over voltage

protection to limit its output voltage. The OVP function

prevents the RT4832A from damaging while open LED

or open circuit condition occurs. Once the open circuit

condition is removed, and the RT4832A will return to

normal operation.

Over-Current Protection

The RT4832A features a 1.2A OCP. The driver

provides cycle-by-cycle current limit function to control

the current on power switch. The boost switch turns off

when

the

inductor

current

reaches

this

current

threshold and it remains off until the beginning of the

next switching cycle. This protects the RT4832A and

external component under overload conditions.

Flash LED

The RT4832A FLED provides a current regulated

output to drive high current white LEDs for camera

flash applications. The output current provides up to

375mA for torch and 1.5A for strobe per channel white

LEDs for camera flash applications. It adopts two

channels to provide accurately regulated current flow

through two separate white LEDs.

The RT4832A FLED can be set in Flash or Torch mode

by the register and the STRB pin. Figure 5 shows the

RT4832A FLED operation and Table 6 contains the

FLED operation control table.

Flash Mode

In Flash Mode, FLED provides 15 different current

levels from 100mA to 1500mA in step of 100mA. The

flash currents are adjusted via the register 0x06[3:0] for

flash brightness. RT4832A provides 32 steps timeout

from 32ms to 1024ms in step of 32ms for flash mode

only. The Flash mode can be set via the register

0x0A[1] = 1 and 0x0A[2] = 1.

Timeout

To avoid the thermal increase from flash current,

RT4832A provides 32 steps timeout from 32ms to

1024ms in step of 32ms for flash mode only. The

timeout can be set via the register 0x07[4:0]. Once a

flash event is completed, the Flash Timeout flag in

the Flash Enable bit is not cleared. If a Flash event is

activated via the STROBE pin and STROBE transitions

low after the end of the programmed flash timeout, the

Flash event is terminated at the programmed Flash

11 bit LED Current vs. Linearty

Brightness Code

0.000

0.005

0.010

0.015

0.020

0.025

256

512

768

1024 1280 1536 1792 2048

Brightness Code (LSB)

11 bit LED Current vs. Exponential

Brightness Code

0.000

0.005

0.010

0.015

0.020

0.025

256

512

768

1024 1280 1536 1792 2048

Brightness Code (LSB)

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