6-Channel High Efficiency Charge Pump

White LED Driver

A8434

10

Allegro MicroSystems, Inc.

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

www.allegromicro.com

Figure 7. LED disable subcircuit. Subcircuit for one LEDx pin shown. A similar block is

connected to each LEDx pin.

+

–

+

–

VBATT

A8434

CIN

COUT

D1

D2

D3

D4

D6

D5

LED1

VOUT

1×, 1.5×, 2×

Charge Pump

VIN

Current

Sink

LED Disable Block

One of six blocks

Overvoltage Protection

The A8434 is protected up to 4.9 V supply voltage, against

accidental overvoltage caused by an open LED. When any LED

to function normally. Normal operation will be resumed when the

fault is removed.

LED Disconnection

Every LEDx pin has a disable subcircuit, as shown in figure 7.

The A8434 compares the voltage on each LED pin, and if

If any WLED is not used, connect the corresponding pin to

VOUT. Never leave open any unused WLED pin. LED pins will

sink 20 μA typical when connected to VOUT and the correspond-

ing LED group (main or sub) is enabled.

Note: In shutdown mode (ENM = ENS = 0 V for > 0.5 ms), the

total leakage current is < 1μA.

Thermal Shutdown

The IC is internally protected against overtemperature. The

overtemperature limit is set to 165°C nominal. The IC shuts down

when the junction temperature exceeds 165°C and automatically

turns on again when the IC cools.

Component Selection

Ceramic capacitors with X5R or X7R dielectric are recom-

mended for the input capacitor, CIN, the output capacitor, COUT,

and the charge pump capacitors, C1 and C2.