A8434
Overvoltage Protection
6-Channel High Efficiency Charge Pump
White LED Driver
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.
The A8434 is protected up to 4.9 V supply voltage, against
accidental overvoltage caused by an open LED. When any LED
opens, V
OUT
will increase till 6 V. Remaining LEDs will continue
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
the voltage on the pin is greater than either V
OUT
– 0.4 V or
V
IN
– 0.4 V, then the corresponding LED pin is disabled.
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.
A8434
VBATT
CIN
VIN
1×, 1.5×, 2×
Charge Pump
VOUT
COUT
LED Disable Block
One of six blocks
–
+
–
+
V
OUT
– 0.4
Current
Sink
V
IN
– 0.4
LED1
D1
D2
D3
D4
D5
D6
Figure 7. LED disable subcircuit. Subcircuit for one LEDx pin shown. A similar block is
connected to each LEDx pin.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
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ALLEGRO [ ALLEGRO MICROSYSTEMS ]
