MAX8901AETA(2007) Ver la hoja de datos (PDF) - Maxim Integrated

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MAX8901AETA
(Rev.:2007)

Highest Efficiency Supply for 2 to 6 Series WLEDs in a 2mm x 2mm TDFN Package

Maxim Integrated 

Highest Efficiency Supply for 2 to 6

Series WLEDs in a 2mm x 2mm TDFN Package

MAX8901B

THERMAL

SHUTDOWN

INTERNAL

750kHz OSC

SHUTDOWN

TIMER

REF

BOOST

CONTROL

LOGIC

GND

IC

IN

POWER

LX

PGND

OVP

Gm

0.5V

PULSE

DIMMING

CS

COMP

ON

EP

Figure 3. MAX8901B Block Diagram

The MAX8901_ features:

• Internal soft-start that gradually illuminates the

WLEDs to eliminate inrush current during startup.

• Input overvoltage protection (6.5V max) that

prevents IC switching when exceeded.

• WLED overvoltage protection (25V typ) that latches

off the IC.

• Shutdown mode that reduces current to 0.01µA (typ).

No WLED current is present in shutdown or during an

overvoltage condition if the WLED forward voltage is

greater than the input supply voltage. Figures 2 and 3

show the block diagrams for the MAX8901A and

MAX8901B, respectively.

Input Overvoltage Lockout

When VIN exceeds 6.2V (min), input overvoltage

lockout (OVLO) is engaged to protect the MAX8901_

from high-input voltage conditions. Once input OVLO

occurs, the MAX8901_ stops switching and no WLED

current flows, provided the forward voltage of the

WLED string is greater than VIN. When VIN falls below

6V (min), the input OVLO condition is cleared, and the

IC is enabled and enters soft-start.

WLED Overvoltage Protection

WLED overvoltage protection (OVP) occurs when the

WLED output voltage rises above the WLED OVP

threshold. The WLED OVP protection circuitry latches

off the IC and the IC enters shutdown when the WLED

OVP threshold is exceeded. After OVP is engaged,

cycle VIN or toggle ON to reenable the IC and enter

soft-start.

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