AS3833 datasheet(11/21 Pages) AMSCO

Part #	AS3833

Description	6 channel high-precision LED cont rol ler for 3D-LCD backl ight with integrated step-up cont rol ler

PDF	21 Pages

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Manufacturer	AMSCO [ams AG]

Direct Link	http://www.ams.com

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11 / 21 page

Revision 1.8

10 - 20

AS3833

Datasheet - D e t a i l e d D e s c r i p t i o n

8 Detailed Description

8.1 Precision current output

Figure 9. Current output stage

The LED-current is derived from either Rset using the following equation

Iset is protected against a short to ground. In the case of a ground short the current Iset is limited to 660uA and the LED-current to 330mA.

Iset has a lower limit of 6uA with a 1uA hysteresis.This sets the lower limit of the LED-current to 3mA with Rset=200kΩ. If Rset is large than

200k

Ω, the LED-current is set to 0mA.

8.1.1

Phase shift

The outputs are controlled by the PWM-input and a built in phase shift generator. All outputs are phase shifted by 1/6 of the PWM-period. In

order to calculate the phase shift timing, two PWM-periods are needed. This means that after changing the PWM-frequency, the phase shift is

updated after the second period. The PWM-frequency must be in the range from 60Hz to 1kHz.

Figure 10. Phase shift

LED

RATIO

se t

RATIO

s et

---------

500

1.2V

SET

------------

(EQ 1)

AS3833 Datasheet(PDF) 11 Page - ams AG