T6316B Taiwan Memory Technology, T6316B Datasheet - Page 4

• Manufacturer Part Number: T6316B
• Description: Constant-Current White LED Bias Supply
• Manufacturer: Taiwan Memory Technology

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bias supply for white LED designs. The
T6316A uses a single resistor to set the bias
current for up to four LEDs. LED bias
currents are matched to 3%. The T6316B
build in internal resistor to set the bias current
for four LED. The T6316A/B offers several
advantages over using ballast resistors, such
as improved LED to LED brightness
matching, lower bias variation with supply
voltage changes, significantly lower dropout
voltage,
significantly improved efficiency.
Enable Input
Drive EN high (> 2.0V) to enable the device;
drive EN low (< 0.8V) to disable the device.
Driving EN low forces LED1, LED2, LED3,
LED4 and SET into a high-impedance state.
Setting the Output Current
flowing into LED1, LED2, LED3 and LED4
is 270/250 times greater than the current
flowing
into SET. Set the output current as follows:
T6316A
T6316B
TM Technology Inc. reserves the right
to change products or specifications without notice.
Functional Description
EN powers the input of the T6316A/B.
SET controls the LED bias current. Current
I
I
The T6316A/B provides constant current
LED
LED
= 270 (0.306V / R
= 250 (0.306V / R
and
CH
TE
in
SET
SET
some
)
)
applications,
P. 4
Applications Information
A battery (single Li+ or three NiMH cells)
powers the LEDs directly. This is the least
expensive and most efficient architecture. Due
to the high forward voltage of white LEDs,
the LED brightness may dim slightly at the
end of battery life. The T6316A/B current
regulating architecture and low dropout
greatly minimize this effect compared to
using simple ballast resistors. The enable
function of the T6316A/B turns on and off the
LEDs.
Very Low-Cost, High-Efficiency Solution .
Preliminary T6316A/B
Publication Date: JUN. 2006
Revision: B