zxld1352 Zetex Semiconductors plc., zxld1352 Datasheet - Page 13

• Manufacturer Part Number: zxld1352
• Description: 350ma Led Driver With Internal Switch And Enhanced Pwm Dimming Range
• Manufacturer: Zetex Semiconductors plc.

Application notes
Setting nominal average output current with external resistor R
The nominal average output current in the LED(s) is determined by the value of the external
current sense resistor (R
I
The table below gives values of nominal average output current for several preferred values of
current setting resistor (R
The above values assume that the ADJ pin is floating and at a nominal voltage of V
Note that R
maintain switch current below the specified maximum value.
It is possible to use different values of R
next section).
Output current adjustment by external DC control voltage
The ADJ pin can be driven by an external dc voltage (V
to a value above or below the nominal average value defined by R
The nominal average output current in this case is given by:
I
Note that 100% brightness setting corresponds to V
1.25V, R
The input impedance of the ADJ pin is 50k
Issue 1 - August 2008
© Diodes Incorporated 2008
OUTnom
OUTdc
DC
R
0.27
0.33
0.39
S
0.3
GND
+
= 0.08*V
( )
S
= 0.1/R
must be increased in proportion to prevent I
S
=0.27
ADJ
ADJ
S
[for R
output current (mA)
/R
Nominal average
S
is the minimum allowed value of sense resistor under these conditions to
[for 0.3< V
S
ZXLD1352
>0.27 ]
S
S
) connected between V
370
333
300
256
GND
) in the typical application circuit shown on page 1:
ADJ
<2.5V]
S
if the ADJ pin is driven from an external voltage. (See
±25%.
13
IN
and I
ADJ
ADJ
OUTdc
SENSE
= V
), as shown, to adjust the output current
REF
exceeding 370mA maximum.
and is given by:
. When driving the ADJ pin above
S
S
.
ZXLD1352
www.diodes.com
www.zetex.com
REF
(=1.25V).