ZXLD381
output current of the ZXLD381 is a sawtooth waveform, its peak value is substantially larger than
the DC/average value. The table also provides this data.
The internal switching transistor has a minimum collector-emitter breakdown voltage of 20V and
this sets the maximum load voltage allowable. The minimum value is set by a feature of the pulse
control circuit that requires the load voltage to be at least 0.8V greater than V
CC
. (The device will
function with load voltages smaller than this but output current regulation will be impaired.)
Higher than nominal load voltages will lower the average (DC) output current generated for a
given inductor value.
Application Examples
Standard Operating Mode
L
(uH)
VCC
I
LED
(peak)
(mA)
I
LED
(avg)
(mA)
L1
47
1.5V
35
80
120
190
260
380
510
640
6.5
15
20
30
45
55
67
76
ZXLD381
VOUT
22
15
10
LED
GND
6.8
4.7
3.3
2.2
Note: V
LED
= 3.5V
Low Ripple LED Current Mode
L
(uH)
VCC
I
LED
(mA)
L1
47
D1
1.5V
6
13.5
18
27
41
50
61
69
ZXLD381
VOUT
22
15
C1
10
LED
GND
6.8
4.7
3.3
2.2
Note: V
LED
= 3.5V, D1 = ZHCS1000, C1 = 1μF (low ESR)
© Zetex Semiconductors plc 2008
ZETEX [ ZETEX SEMICONDUCTORS ]
