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 . (The device will
CC
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
I
(peak)
I
(avg)
LED
LED
(uH)
(mA)
(mA)
VCC
ZXLD381
GND
L1
47
22
35
80
6.5
15
20
30
45
55
67
76
1.5V
VOUT
15
120
190
260
380
510
640
10
LED
6.8
4.7
3.3
2.2
Note: V
= 3.5V
LED
Low Ripple LED Current Mode
L
I
LED
(uH)
(mA)
VCC
L1
47
22
6
13.5
18
D1
1.5V
VOUT
ZXLD381
15
10
27
C1
LED
6.8
4.7
3.3
2.2
41
GND
50
61
69
Note: V
= 3.5V, D1 = ZHCS1000, C1 = 1μF (low ESR)
LED
Issue 1 - April 2008
© Zetex Semiconductors plc 2008
5
www.zetex.com
ZETEX [ ZETEX SEMICONDUCTORS ]
