ISL97671 데이터 시트보기 (PDF) - Intersil

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ISL97671

6-Channel SMBus/I2C or PWM Dimming LED Driver with Phase Shift Control

Intersil 

ISL97671

Typical Performance Curves (Continued)

FIGURE 16. LINE REGULATION WITH VIN CHANGE

FROM 26V TO 6V FOR 6P12S AT

20mA/CHANNEL

FIGURE 17. LOAD REGULATION WITH ILED CHANGE

FROM 0% TO 100% PWM DIMMING,

VIN = 12V, 6P12S AT 20mA/CHANNEL

FIGURE 18. LOAD REGULATION WITH ILED CHANGE

FROM 100% TO 0% PWM DIMMING,

VIN = 12V, 6P12S AT 20mA/CHANNEL

Theory of Operation

PWM Boost Converter

The current mode PWM boost converter produces the

minimal voltage needed to enable the LED stack with the

highest forward voltage drop to run at the programmed

current. The ISL97671 employs current mode control

boost architecture that has a fast current sense loop and

a slow voltage feedback loop. Such architecture achieves

a fast transient response that is essential for the

notebook backlight application where the power can be a

series of drained batteries or instantly change to an

AC/DC adapter without rendering a noticeably visual

nuisance. The number of LEDs that can be driven by

ISL97671 depends on the type of LED chosen in the

application. The ISL97671 is capable of boosting up to

45V and drive 6 channels of LEDs.

FIGURE 19. ISL97671 SHUTS DOWN AND STOPS

SWITCHING ~ 30ms AFTER EN GOES LOW

Enable

The EN pin is used to enable or disable the ISL97671

operation. It is a high voltage pin that can be tied directly

to VIN up to 26.5V if the system lacks of I/O for enable

signal.

OVP and VOUT Requirement

The Overvoltage Protection (OVP) pin has a function of

setting the overvoltage trip level as well as limiting the

VOUT regulation range.

The ISL97671 OVP threshold is set by RUPPER and

RLOWER as shown in Equation 1:

VOUT_OVP = 1.21V × (RUPPER + RLOWER) ⁄ RLOWER (EQ. 1)

VOUT can only regulate between 64% and 100% of the

VOUT_OVP such that:

Allowable VOUT = 64% to 100% of VOUT_OVP

10

FN7631.0

June 24, 2010

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