DN66
An OLED bias supply for a clamshell handset sub display
Description
Portable applications such as cell phones are becoming increasingly complex with more and
more features designed into every generation. One popular feature is to replace the STN sub
display with an OLED sub display. OLED displays have infinite contrast ratio and are self-
illuminating. This gives the handset manufacturer two key advantages, the first is lower power
consumption and the second is a slimmer display. One disadvantage with OLED sub displays over
LCD sub displays is the higher leakage current when not in use, which is the majority of the time.
The way to overcome this issue is to disconnect the OLED sub display when the handset is
dormant.
The ZXLB1600 is a boost converter that can provide the power requirements for OLED sub display
with the additional feature of a fully integrated isolation switch which disconnects the input from
output when the ZXLB1600 is shutdown, making it ideally suited to OLED biasing.
The schematic diagram in Figure 1 shows a full color OLED bias supply for clamshell handset sub
display.
L1
U2
BAT54S
OUTPUT
U1
VBATT
V
IN
C3
SW
LX
SENSE
FB
ADJ
R1
N/C
N/C
R2
C2
C1
N/C
N/C
LBF
EN
LBT
GND
ZXLB1600
Figure 1
Schematic diagram
Note:
For applications where OLED leakage is not an issue and the ZXLB1600 isolation switch is not
needed, the SW pin can be shorted to the V
IN
pin, giving a further 3% to 5% improvement in
efficiency.
Issue 4 - July 2006
© Zetex Semiconductors plc 2006
1
www.zetex.com
DN66
The materials list and associated performance characteristics provide an OLED biasing solution
for the following sub display specification:
•
•
•
•
Input voltage:
Output voltage:
Output current:
Output ripple:
4.2V to 3.0V
12V
20mA (max.)
50mVpk-pk (max.)
Part number
Manufacturer Contact details
www.zetex.com
www.zetex.com
Comments
OLED bias IC
Dual Schottky diode
Reference Value
U1
U2
L1
R1
R2
C1
C2
(1)
ZXLB1600X10 Zetex
BAT54S
22 H
715k
82k
10 F/6V3
10 F/16V
82pF/16V
Zetex
CMD4D11-220 Sumida
Generic
Generic
GRM series
GRM series
Generic
Generic
Generic
Murata
Murata
Generic
Table 1
www.sumida.com 1mm height profile
NA
NA
0603 size
0603 size
www.murata.com 0805 size
www.murata.com 1206 size
NA
0603 size
C3
Bill of materials
NOTES:
(1) For a lower profile, two 4.7 F 0805 capacitors can be used by connecting in parallel.
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2
Issue 4 - July 2006
© Zetex Semiconductors plc 2006
DN66
Typical operating characteristics
(For typical application circuit where V
IN
= 3V, V
OUT
= 12V, I
OUT
= 20mA unless otherwise stated)
Figure 2
Performance graphs
Issue 4 - July 2006
© Zetex Semiconductors plc 2006
3
www.zetex.com
DN66
Typical operating waveforms
(For typical application circuit where V
IN
= 3V, V
OUT
= 12V, I
OUT
= 20mA unless otherwise stated)
Figure 3
Typical operating waveforms
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4
Issue 4 - July 2006
© Zetex Semiconductors plc 2006
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