MAX8830EWET(2007) View Datasheet(PDF) - Maxim Integrated

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MAX8830EWET
(Rev.:2007)

LED Light Management IC in 2.5mm x 2.5mm UCSP

Maxim Integrated 

LED Light Management IC in

2.5mm x 2.5mm UCSP

Flash Current-Sink Regulator

(FLED, MVON, FLEN)

A low-dropout linear current regulator from FLED to

PGND sinks current from an external flash LED cathode

terminal. The FLED current is regulated to I2C-program-

mable levels for movie mode (up to 200mA) and flash

mode (up to 200mA). The movie mode provides contin-

uous lighting when enabled through I2C (see Table 1).

The flash mode is enabled only when FLEN goes high.

A flash maximum timer, programmable from 0.5s to

2.0s through I2C, limits the duration of the flash mode in

case FLEN remains high. The flash mode has priority

over the movie mode.

Current-Sink Regulators (LED1–LED4)

Four low-dropout linear current regulators from LED_ to

GND sink current from external LED cathode terminals.

The LED_ currents are individually regulated to an I2C-

programmable level from off to 10mA in 32 steps, inde-

pendently set for each LED_.

Undervoltage Lockout

The IC contains undervoltage lockout (UVLO) circuitry

that disables the device until VIN is greater than 2.45V

(typ). Once VIN rises above 2.45V (typ), the UVLO cir-

cuitry does not disable the IC until VIN falls below the

UVLO threshold hysteresis.

Soft-Start

The MAX8830 soft-starts by charging CCOMP with a

100µA current source. During this time, the internal

MOSFET is switching at the minimum duty cycle. Once

VCOMP rises above 1V, the duty cycle increases until the

output voltage reaches the desired regulation level.

COMP is pulled to GND with a 80Ω internal resistor dur-

ing UVLO or shutdown. See the Typical Operating

Characteristics for an example of soft-start operation.

Shutdown and Standby

The MAX8830 is in shutdown when VDD = 0. In shut-

down, supply current is reduced to 0.1µA (typ). The

MAX8830 is in standby when the step-up converter and

all LED outputs are turned off through I2C (and by

keeping MVON and FLEN at logic 0). During this time,

the I2C port remains in standby (ready) state as long as

logic-high voltage is supplied to VDD.

CCOMP is discharged whenever the step-up converter is

turned off, allowing the device to reinitiate soft-start when

it is enabled. The internal MOSFET and synchronous rec-

tifier are also high impedance when the step-up converter

is off; however, OUT is one diode drop below the input.

FLED and LED_ are high impedance in shutdown, so the

external LEDs are all off, but any external circuitry on OUT

(such as an audio amplifier) is not disconnected, and

therefore, should include its own shutdown capability.

Parallel Connection of

Current-Sink Regulators

The LED current-sink regulators (FLED and LED_) can

be connected in parallel in any combination to allow the

use of higher current LEDs or any other desired effects.

Unused current regulators may be left unconnected or

shorted to ground. The LED regulators must be dis-

abled through I2C to avoid a fault detection from an

open or short.

Open/Short LED Detection

The MAX8830 includes 10 comparators to detect open

or shorted LEDs on the FLED and LED1–LED4 pins.

One comparator on each pin detects when the voltage

falls below 100mV, indicating an open LED fault.

Another comparator on each pin detects when the volt-

age rises above VOUT - 1V, indicating a shorted LED

fault. The fault-detection comparators are enabled only

when the corresponding current sink is enabled (and

not set to zero current). Once a fault is detected the two

comparators provide a single bit output (1 = fault, 0 =

no fault) corresponding to the appropriate pin. When a

read command (address 0x95) is issued to the

MAX8830, the status of each pin is latched into the sta-

tus register (see Table 6) and subsequently written to

the I2C bus by the MAX8830.

Thermal Shutdown

Thermal shutdown limits total power dissipation in the

MAX8830. When the junction temperature exceeds

+160°C, the device turns off, allowing the IC to cool.

The IC turns on and begins soft-start after the junction

temperature cools by 20°C. This results in a pulsed out-

put during continuous thermal-overload conditions.

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